Gobi soil fine particle hydration consolidation enhancement method

Abstract

The application discloses a kind of gobi soil fine particle hydration consolidation enhancement method, it is related to gobi soil in-place consolidation enhancement technical field, including attached hydration powder body: calcium aluminate and slag powder are mixed into hydration powder body by slaked lime, hydration powder body is added to gobi soil fine particle through sieve hole, under the condition that water is not supplemented, gobi soil fine particle and hydration powder body are turned, make hydration powder body attach to gobi soil fine particle surface;It can not destroy the embedded structure of skeleton particle, and make hydration powder body enter subsequent compaction process under the premise of attached state, improve the filling and cementing degree of particle contact area, make the local area of load transfer in consolidation layer form relatively stable hydration consolidation structure, to improve the overall compactness of gobi soil consolidation layer, contact interface stability and strength development uniformity after maintenance.

Description

Technical Field

[0001] This invention relates to the field of in-situ consolidation and reinforcement technology for Gobi soil, and in particular to a method for hydration consolidation and reinforcement of fine-particle Gobi soil. Background Technology

[0002] With the development of transportation engineering, site leveling engineering, and temporary construction road construction in arid and semi-arid regions, the on-site use of Gobi soil to prepare consolidation layers has become an important direction for reducing the consumption of transported materials and improving construction adaptability. Gobi soil is usually composed of skeleton particles, sand, silt, and a small amount of clay particles. Among them, coarse particles form an interlocking skeleton, while fine particles participate in pore filling and contact interface stability, which has an important influence on the later consolidation strength. Existing Gobi soil reinforcement technologies mostly use cement, lime, slag, fly ash, or alkaline activating materials for overall mixing, mainly relying on cementitious products to improve the overall strength.

[0003] Existing Gobi soil consolidation technologies typically employ dry mixing, wet mixing, or slurry infiltration of cement, lime, slag, fly ash, or alkaline activating materials with the soil. Their strengthening effect primarily relies on the overall dispersion of cementitious components within the soil and subsequent hydration and hardening. However, these methods lack step-by-step process control based on the gradation characteristics of Gobi soil, where coarse particles form the framework and fine particles fill the pores. Especially during compaction, fine particles are prone to deviating from the stress-bearing area where the framework particles meet due to pre-mixing agglomeration, localized mud formation, or liquid phase migration. This results in hydration reaction products being distributed more in ordinary pores or surface areas, making it difficult to form a stable cemented structure in the particle contact area. Therefore, existing technologies still lack a process method that enables Gobi soil fine particles to carry hydration components and form in-situ hydration and consolidation within the framework particle contact area. Summary of the Invention

[0004] This invention provides a method for strengthening fine-particle hydration consolidation of Gobi soil, comprising:

[0005] S1. Soil separation: The Gobi soil is crushed and screened to separate fine particles and skeleton particles.

[0006] S2. Pre-wetting fine particles: Spray the first stage of water into the Gobi soil fine particles, while simultaneously turning the Gobi soil fine particles.

[0007] After stopping the water spraying, the fine particles of Gobi soil were allowed to stand. The fine particles of Gobi soil that had stood were then screened again. Aggregates that did not pass through the sieve holes were loosened and screened again.

[0008] S3, Adhesive hydration powder: Hydrated lime, calcium aluminate and slag powder are mixed to form hydration powder;

[0009] Add the hydrated powder to the fine Gobi soil particles that have passed through the sieve, and turn the fine Gobi soil particles and the hydrated powder over without adding water, so that the hydrated powder adheres to the surface of the fine Gobi soil particles.

[0010] S4. Mixed laying: The fine particles of Gobi soil obtained in S3 are mixed with the skeleton particles obtained in S1 to obtain the soil material to be consolidated, and the soil material to be consolidated is laid into the layer to be consolidated.

[0011] S5. Initial compaction without water replenishment: Initial compaction is performed on the layer to be consolidated. During the initial compaction, no water is added to the layer to be consolidated, nor is any water-containing slurry added.

[0012] S6. Contact area water replenishment and repressurization: The second stage of water is sprayed into the layer to be consolidated after the initial pressurization. After the second stage of water is sprayed in, the layer to be consolidated is stopped, and then the layer to be consolidated is repressurized.

[0013] S7. Sealing and curing: After the re-pressurization is completed, the layer to be consolidated is covered and sealed for curing. The surface of the layer to be consolidated is not rinsed before covering and sealing. During the covering and sealing process, the covering layer is in contact with the surface of the layer to be consolidated.

[0014] As a preferred embodiment of the hydration consolidation and reinforcement method for fine Gobi soil particles described in this invention, wherein: in S1, the fine Gobi soil particles are the undersize material collected separately after screening;

[0015] The skeleton particles are the sieve material collected separately after screening;

[0016] The secondary screening in S2 uses a sieve with the same mesh size as that used in S1 to separate fine particles of Gobi soil.

[0017] As a preferred embodiment of the hydration consolidation and reinforcement method for fine particles of Gobi soil described in this invention, wherein: in S2, the first stage of water is added before the fine particles of Gobi soil are mixed with the skeleton particles;

[0018] The amount of water added in the first stage is less than the amount of water added in the second stage;

[0019] After the first water is sprayed in, the fine particles of Gobi soil are left to stand before being sieved again.

[0020] As a preferred embodiment of the fine-particle hydration consolidation and reinforcement method for Gobi soil described in this invention, in S2, the agglomerates that did not pass through the sieve holes during the re-sieving process are loosened and then re-sieved.

[0021] Aggregates that fail to pass through the sieve openings after a second sieve will not proceed to S3.

[0022] As a preferred embodiment of the hydration consolidation and reinforcement method for fine-particle Gobi soil described in this invention, wherein: in S3, quicklime, calcium aluminate and slag powder are dry-mixed before being added to the fine-particle Gobi soil;

[0023] After the hydrated powder is added to the fine particles of Gobi soil, no additional water is added to the mixture.

[0024] As a preferred embodiment of the method for hydration consolidation and reinforcement of fine Gobi soil particles according to the present invention, in S3, the fine Gobi soil particles after hydration powder adhesion are sieved before entering S4, and the sieve residue is returned to S3 for re-tumbling.

[0025] Fine particles of Gobi soil passing through the sieve are mixed with the skeleton particles.

[0026] As a preferred embodiment of the fine-particle hydration consolidation and reinforcement method for Gobi soil described in this invention, in step S4, the soil to be consolidated is leveled first after being laid.

[0027] The leveled layer to be consolidated proceeds directly to S5;

[0028] After leveling and before initial compaction, do not spray the second stage of water into the layer to be consolidated.

[0029] As a preferred embodiment of the fine-particle hydration consolidation and reinforcement method for Gobi soil described in this invention, wherein: in S6, the second stage of water is added after the initial pressure is completed;

[0030] After the second stage of water injection, wait for the solidified layer to stop before repressurizing;

[0031] No more hydration powder is added to the layer to be consolidated after the re-pressing is completed.

[0032] As a preferred embodiment of the fine-particle hydration consolidation and reinforcement method for Gobi soil described in this invention, in step S7, the sealing curing is carried out by covering and sealing.

[0033] The surface of the layer to be consolidated should not be rinsed before the cover is sealed.

[0034] After the cover is sealed, the cover layer comes into contact with the surface of the layer to be consolidated.

[0035] As a preferred embodiment of the fine-particle hydration consolidation and reinforcement method for Gobi soil described in this invention, wherein: after the S7 sealing curing is completed, a profile sample is taken from the layer to be consolidated;

[0036] The contact area is defined as the point where adjacent skeletal particles abut against each other and the surrounding pores.

[0037] The interparticle pore area in the profile sample, excluding the particle contact area, is taken as the non-particle contact area. The location where the skeleton particles abut each other and the surrounding pores in the profile sample are selected as the observation location.

[0038] Record the proportion of fine particles retained in the Gobi soil within the observation location, and the proportion of the area of ​​hydrated powder reaction products in the non-particle contact zone to the total area of ​​the profile reaction products.

[0039] When the proportion of fine particles retained in the Gobi soil at the observation location is lower than the fine particle retention judgment value, when re-executing the Gobi soil fine particle hydration consolidation enhancement method, extend the time for loosening the agglomerates before the S2 re-screening, or increase the number of compaction passes of the initial compaction described in S5, and correspondingly reduce the number of compaction passes of the re-compaction in S6 when increasing the number of initial compaction passes, so as to keep the total number of compaction passes unchanged.

[0040] When the proportion of the area of ​​hydrated powder reaction products in the non-particle contact zone to the total area of ​​reaction products in the profile is higher than the reaction product distribution judgment value, when re-implementing the Gobi soil fine particle hydration consolidation enhancement method, the time for turning over the Gobi soil fine particles and hydrated powder in S3 should be increased, or the dwell time after the second stage of water injection in S6 should be extended.

[0041] The beneficial effects of this invention are as follows: This invention does not use the conventional whole wet mixing or grouting method, but first pre-wets, lets stand and screens the fine particles of Gobi soil separately, so that the fine particles remain in a dispersible state before entering the skeleton particle system, reducing the mud phenomenon caused by dry mixing agglomeration and one-time water addition.

[0042] Subsequently, the hydrated powder formed by quicklime, calcium aluminate and slag powder is attached to the surface of fine particles without additional water, so that the fine particles not only exist as ordinary gap filler, but can also carry the hydration reaction components into the subsequent compaction process.

[0043] By coordinating the sequence of initial compaction without water replenishment, pausing after the second stage of water injection, and re-compaction, it is beneficial for the fine particles of Gobi soil carrying hydration powder to enter the position where the skeleton particles abut against each other and the surrounding pores during the subsequent compaction process, and to enable the second stage of water to form the conditions for subsequent hydration reaction in this area.

[0044] Therefore, this invention can improve the filling and bonding degree of the particle contact area without destroying the interlocking structure of the skeleton particles and allowing the hydrated powder to enter the subsequent compaction process in an attached state. This enables the local area in the consolidated layer that bears the load transfer to form a more stable hydrated consolidation structure, thereby improving the overall compactness, contact interface stability and uniformity of strength development after curing of the Gobi soil consolidated layer. Attached Figure Description

[0045] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the following description of the embodiments will be briefly introduced. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 This is a flowchart of the fine-particle hydration consolidation enhancement method for Gobi soil in Example 1.

[0047] Figure 2 This is a schematic diagram of the positioning of fine powder particles in the particle contact area and the replenishment and repressurization in Example 1. Detailed Implementation

[0048] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0049] Example 1, referring to Figure 1 and Figure 2 This is the first embodiment of the present invention;

[0050] This embodiment provides a method for enhancing the hydration consolidation of fine-particle Gobi soil, including the following steps:

[0051] This embodiment illustrates the specific implementation method of fine-particle hydration consolidation reinforcement of Gobi soil in Gobi soil base consolidation materials.

[0052] The Gobi soil used was taken from the same Gobi engineering soil extraction point. After sampling, it was naturally air-dried until the mass change between two consecutive weighings did not exceed 0.5%. Plant roots, boulders and non-soil debris were removed.

[0053] The air-dried Gobi soil is crushed to a size that can pass through a 20mm square hole sieve, and then screened using a 5mm square hole sieve.

[0054] The material passing through a 5mm square-hole sieve is used as fine particles of Gobi soil, while the material that cannot pass through a 5mm square-hole sieve but can pass through a 20mm square-hole sieve is used as skeleton particles.

[0055] The fine particles of Gobi soil refer to the fine particles that can be pre-wetted, carry hydrated powder, and enter the pores between the skeleton particles in subsequent processes.

[0056] The skeleton particles refer to the coarse particles that can form an abutting relationship after being laid and compacted;

[0057] The contact area between adjacent skeleton particles and the surrounding pores is called the particle contact area. This area is where the force transmission between particles is more concentrated after compaction.

[0058] Based on 100 parts of dry weight of soil to be consolidated, weigh out 28 parts of fine Gobi soil particles and 72 parts of skeleton particles.

[0059] First, pre-wet the fine particles of Gobi soil. Spray 3 parts of water into the fine particles of Gobi soil. During the water spraying process, turn the fine particle layer over for 5 minutes to make the first part of water and the fine particles of Gobi soil come into uniform contact.

[0060] After stopping the water spraying, let the fine particles of Gobi soil stand for 15 minutes, and then re-sieve them using the same 5mm square hole sieve as the previous sieve.

[0061] Fine particles of Gobi soil passed through the sieve holes are collected for later use.

[0062] Aggregates that do not pass through the sieve holes are returned, loosened for 2 minutes, and then re-sieved using the same 5mm square hole sieve as before.

[0063] The material that passes through the sieve holes in the second screening is combined with the material that passes through the first screening and enters the subsequent hydration powder adhesion step together.

[0064] Aggregates that remain on the sieve surface after the second sieving are temporarily stored separately and do not proceed to the hydration powder adhesion step.

[0065] The above-mentioned screening and re-screening steps are used to control the state of particles after pre-wetting, so that the fine particles of Gobi soil entering the hydration powder adhesion step remain in a dispersible granular shape, and avoid large agglomerates only having hydration powder attached to the outer layer while the interior does not fully participate in the subsequent hydration reaction.

[0066] Mix 3 parts quicklime, 2 parts calcium aluminate and 3 parts slag powder in a dry state for 3 minutes to obtain hydrated powder;

[0067] Quicklime serves as a calcium source in subsequent hydration reactions, calcium aluminate provides aluminate reaction components, and slag powder provides a source of calcium silicate gel.

[0068] Add the hydrated powder to the fine particles of Gobi soil that have been screened multiple times, and stir for 4 minutes;

[0069] No water is added during this process, and the hydrated powder is not made into a slurry. The hydrated powder adheres to the surface of the pre-wetted Gobi soil fine particles.

[0070] After the agitation is completed, the hydrated powder is distributed on the surface of the fine particles of Gobi soil in an adhered state, and the mixture still maintains a sieveable and agitable particle state.

[0071] Subsequently, the fine particles of Gobi soil with attached hydration powder are mixed with the skeleton particles and laid into a 100mm thick layer to be consolidated, and the surface of the layer to be consolidated is leveled.

[0072] After leveling, the layer to be consolidated is subjected to initial compaction without water replenishment. The initial compaction is carried out by compacting twice with a small vibratory compactor. During the initial compaction, no water is added to the layer to be consolidated, nor is any water-containing slurry added.

[0073] This step is used to allow the fine particles of Gobi soil with attached hydrated powder to enter the particle contact area between the skeleton particles under pressure.

[0074] After the initial pressure is completed, 7 parts of the second stage water are sprayed into the layer to be consolidated. The second stage water enters the particle contact area along the pores of the layer to be consolidated.

[0075] After spraying water, let it stand for 20 minutes, then repeat the compaction three times using the same compactor.

[0076] After the re-pressing is completed, the surface of the layer to be consolidated is not rinsed. Instead, a polyethylene film is used to cover the surface of the layer to be consolidated, and the film is kept in contact with the surface of the layer to be consolidated. The layer is then sealed and cured at 20℃±2℃ for 7 days and 28 days.

[0077] To evaluate the technical effectiveness of this method, four comparative examples were set up;

[0078] All groups used the same small vibratory compactor, with a total of 5 compaction passes, and maintained the same source of original soil, the same total amount of hydrated powder, the same total amount of water added, the same laying thickness, and the same closed curing conditions.

[0079] Example 1 uses a compaction process of two initial compactions without water addition and three subsequent compactions after water addition;

[0080] Comparative Example 1 is a single wet-mix compaction, that is, the fine particles of Gobi soil, the skeleton particles, the hydrated powder and all the water are mixed at one time, laid out and then compacted 5 times in succession.

[0081] Comparative Example 2 involved laying the soil first and then spraying and compacting it with slurry. This involved mixing fine particles and skeleton particles of Gobi soil and laying them first, then spraying and infiltrating the soil with slurry made from hydrated powder and water. The water in the slurry was included in the total amount of water added. After spraying and infiltrating, the soil was compacted five times.

[0082] Comparative Example 3 omitted the initial compaction without water replenishment. After laying, the second stage of water was sprayed directly, and after stopping, it was compacted 5 times in a row.

[0083] Comparative Example 4 only omits the secondary screening. The fine particles of Gobi soil after pre-wetting and settling directly enter the hydration powder adhesion step. After that, the compaction steps of two initial compaction without water replenishment and three secondary compaction after water replenishment are still adopted.

[0084] After 7 days of curing, a cross-sectional sample was cut from each group of layers to be consolidated. The position where the skeleton particles abutted each other and the surrounding pores were selected as the particle contact area. The cross-section was magnified and photographed. Image analysis was used to calculate the ratio of the area of ​​hydration products in the particle contact area to the total area of ​​hydration products in the cross-section, which was taken as the concentration ratio of hydration products in the particle contact area.

[0085] In the unconfined compressive strength test, three cylindrical specimens were prepared for each group, with a diameter of 50 mm and a height of 50 mm. The test result was the average value of the three specimens.

[0086] The strength retention rate after immersion in water for 48 hours is the ratio of the unconfined compressive strength after immersion in water to the unconfined compressive strength without immersion in water at the same age.

[0087] In the wet-dry cycle test, each cycle includes immersion in water for 12 hours and placement in an indoor environment at 20℃±2℃ for 12 hours, for a total of 5 cycles. After the cycle, the mass of the specimen is weighed and the mass loss rate is calculated.

[0088] The maximum thickness of the identifiable pulping zone on the surface was obtained by cross-sectional observation, and the maximum depth of the pulping zone extending from the surface inward in the cross-section was recorded.

[0089] It should be noted that before image analysis, the hydration product areas that appear as light-colored cementitious structures and are located in the interparticle pores in the cross-sectional image were marked, and statistical analysis was performed under the same magnification and illumination conditions.

[0090] The reflective areas of light-colored skeleton particles, the cutting dust areas, and isolated powder spots are not included in the hydration product areas. Suspected areas are reviewed according to the same judgment rules.

[0091] The test results are shown in Table 1;

[0092] Table 1: Process conditions and performance test results of Example 1 and Comparative Examples 1-4

[0093] Parameter name Example 1: Pre-wetting - Re-screening - Dry powder adhesion - Initial pressing without water addition - Re-pressing with water addition Comparative Example 1: One-time wet mixing and compaction Comparative Example 2: Laying first, then spraying and compacting grout. Comparative Example 3: Initial pressure without water replenishment omitted Comparative Example 4: Rescreening omitted Dosage of fine particles of Gobi soil (per part) 28 28 28 28 28 Dosage of skeleton particles / part 72 72 72 72 72 quicklime / part 3 3 3 3 3 Calcium aluminate / part 2 2 2 2 2 Slag powder / part 3 3 3 3 3 First section water / portion 3 — — 3 3 Second section water / portion 7 — — 7 7 Total water added / serving 10 10 10 10 10 When to add water The first stage of water is used for pre-wetting of fine particles; the second stage of water is added after initial pressing. Add all the water at once during the wet mixing process. All water was poured in along with the hydrated powder slurry. The first section is pre-wetted with water; after laying, water is added and the surface is compacted. The first stage involves pre-wetting with water, and the second stage involves adding water after initial pressure. Secondary screening Pre-wetting and then sieving Not set Not set Pre-wetting and then sieving Not set Compaction process Two initial pressure tests without water replenishment, followed by three more pressure tests after the second water test. After wet mixing and laying, compact continuously for 5 times. After grouting, compact continuously for 5 times. After the second stage of watering, compact the soil five times consecutively. Two initial pressure tests without water replenishment, followed by three more pressure tests after the second water test. Total number of compaction passes / passes 5 5 5 5 5 Concentration ratio of hydration products in the particle contact zone / % 63.8 34.2 40.5 44.6 47.8 7d unconfined compressive strength / MPa 2.18 1.68 1.73 1.82 1.88 28-day unconfined compressive strength / MPa 3.46 2.56 2.67 2.85 2.96 Strength retention rate after immersion in water for 48 hours / % 86.7 66.8 71 74.3 76.5 Mass loss rate after 5 wet-dry cycles / % 2.8 6.9 6.1 5.2 4.8 Maximum thickness of the identifiable slurry zone on the surface / mm 0.6 3.9 3 2.1 1.8

[0094] As shown in Table 1, under the conditions that the amount of fine particles, skeleton particles, total amount of hydration powder, total amount of water added, laying thickness, curing conditions and total number of compaction passes of Gobi soil are all the same, the concentration ratio of hydration products in the particle contact area of ​​Example 1 is 63.8%, which is higher than that of Comparative Examples 1 to 4.

[0095] The results show that the advantage of Example 1 does not come from the increase in the number of compaction passes, but from the sequential combination of pre-wetting, re-screening, dry powder adhesion, initial compaction without water replenishment and re-compaction with water replenishment.

[0096] Although Comparative Example 1 also involved compaction five times, all the water was added at once during wet mixing, and the hydrated powder was dispersed throughout the soil material, with some of the hydrated powder being consumed in the non-particle contact area.

[0097] Comparative Example 2 also used 5 compaction passes, but the hydrated powder entered the layer to be consolidated along with the slurry, and the slurry migrated along the larger pores, making it difficult to stay stably near the contact position of the skeleton particles.

[0098] Comparative Example 3 also had a total of 5 compaction passes, but no initial compaction without water was set. Water was added and compacted before the fine particles were pressed into the particle contact area, resulting in a more dispersed hydration reaction location.

[0099] Comparative Example 4 uses the same two initial pressing and three secondary pressing as Example 1, but omits the secondary sieving. The pre-wetted agglomerates directly enter the powder adhesion step, resulting in some agglomerates carrying hydrated powder on the outer layer while the internal reaction is insufficient.

[0100] The 7-day unconfined compressive strength of Example 1 was 2.18 MPa, the 28-day unconfined compressive strength was 3.46 MPa, the strength retention rate after immersion in water for 48 hours was 86.7%, and the mass loss rate after 5 wet-dry cycles was 2.8%.

[0101] The above results indicate that there is a continuous coordination relationship between pre-wetting, re-screening, dry powder adhesion, initial pressing without water replenishment, and re-pressing with water replenishment:

[0102] Pre-wetting and re-screening limit the particle state of fine particles when they enter the powder adhesion step;

[0103] Dry powder adhesion causes the hydrated powder to move along with the fine particles of Gobi soil;

[0104] The initial pressure without water replenishment allows fine particles of the attached hydrated powder to enter the particle contact zone;

[0105] The second stage of water enters the particle contact zone after initial pressure and participates in the hydration reaction;

[0106] Compared with the one-time wet mixing grouting method, this method reduces the dispersion consumption of hydrated powder in non-contact pores, and also reduces the mass loss after surface slurrying and dry-wet cycles.

[0107] Compared with schemes that omit initial pressure without water replenishment or omit secondary screening, this method further demonstrates that the secondary screening state control and initial pressure positioning steps have a direct impact on the distribution of hydration products in the particle contact zone.

[0108] Example 2 is the second embodiment of the present invention;

[0109] This embodiment provides a method for enhancing the hydration consolidation of fine-particle Gobi soil, including the following steps:

[0110] This embodiment is used to illustrate the specific implementation of the following steps in the preparation of Gobi soil base consolidation materials: double sieving of Gobi soil fine particles through the same sieve, rework of agglomerates, and sieving after powdering.

[0111] The Gobi soil used was taken from the same Gobi engineering soil extraction point, and was naturally air-dried until the mass change between two consecutive weighings did not exceed 0.5%. Plant roots, boulders and non-soil debris were then removed.

[0112] The air-dried Gobi soil is crushed to a size that can pass through a 20mm square hole sieve, and then screened using a 5mm square hole sieve.

[0113] The material passing through a 5mm square hole sieve is collected separately as fine particles of Gobi soil, while the material passing through a 20mm square hole sieve but not through a 5mm square hole sieve is collected separately as skeleton particles.

[0114] The screened material refers to the portion of Gobi soil particles with a particle size smaller than the 5mm square hole screen size that are collected separately.

[0115] The sieve feed refers to the portion of particles that do not pass through a 5mm square hole sieve but can pass through a 20mm square hole sieve;

[0116] By collecting undersize and oversize materials separately, fine particles can play the role of pre-wetting and carrying hydrated powders in subsequent processes, while skeleton particles can play the role of forming particle contact relationships.

[0117] Based on a total dry weight of 100 parts for fine Gobi soil particles and skeleton particles, weigh out 28 parts for fine Gobi soil particles and 72 parts for skeleton particles.

[0118] Take 3 parts quicklime, 2 parts calcium aluminate and 3 parts slag powder as hydration powder, and prepare a total of 10 parts water, of which 3 parts are water for the first stage and 7 parts are water for the second stage.

[0119] First, spray the first stage of water into the fine particles of Gobi soil. During the spraying process, stir the fine particle layer for 5 minutes to disperse the first stage of water into contact with the fine particles of Gobi soil.

[0120] After stopping the water spraying, let it stand for 15 minutes, and then re-sieve it using the same 5mm square hole sieve as the one used to separate fine particles of Gobi soil.

[0121] During the secondary screening, the fine particles of Gobi soil that pass through the sieve holes enter the hydration powder adhesion step;

[0122] Aggregates that do not pass through the sieve holes are returned to the loosening process for 2 minutes and then screened again using a 5mm square hole sieve.

[0123] Material that passes through the sieve again enters the hydration powder adhesion step, while agglomerates that remain on the sieve surface are temporarily stored separately and do not enter the hydration powder adhesion step.

[0124] In this embodiment, the aggregates are not the coarse particles that naturally exist in the original soil before sieving, but rather temporary aggregates formed by the adhesion of multiple fine Gobi soil particles after pre-wetting.

[0125] If such agglomerates directly enter the hydration powder adhesion step, problems such as outer layer hydration powder adhesion, insufficient internal water entry, or insufficient internal hydration reaction are likely to occur.

[0126] Quicklime, calcium aluminate and slag powder were dry-mixed for 3 minutes to obtain hydrated powder.

[0127] Add the hydrated powder to the fine Gobi soil particles that have passed the double sieving, and stir for 4 minutes to allow the hydrated powder to adhere to the surface of the fine Gobi soil particles.

[0128] Before entering the skeleton particle mixing step, the fine particles of Gobi soil after hydration powder adhesion are sieved through a 5mm square hole sieve.

[0129] The fine particles of Gobi soil passing through the sieve are mixed with the skeleton particles, and the residue on the sieve surface is returned to the hydration powder adhesion step and turned over again for 2 minutes.

[0130] The material after being turned over is sieved again through a 5mm square hole sieve. The material passing through the sieve holes is mixed with the skeleton particles, and the material that is still stuck on the sieve surface is returned to be turned over again or temporarily stored separately.

[0131] After powdering, sieving is used to check the particle dispersion state after the hydrated powder is attached, so that the fine Gobi soil particles entering the skeleton particle mixing step remain in a dispersible and powder-carrying state.

[0132] After the fine particles of Gobi soil that have been sieved through powdering are mixed with the skeleton particles, they are laid as a 100mm thick layer to be consolidated.

[0133] After leveling, use the same small vibratory compactor to perform two initial compactions without water replenishment, then spray in 7 parts of water for the second stage, let stand for 20 minutes, and then perform three re-compactions.

[0134] After the re-pressing is completed, the surface of the layer to be consolidated is not rinsed. Instead, a polyethylene film is used to cover the surface of the layer to be consolidated, and the film is kept in contact with the surface of the layer to be consolidated. The layer is then sealed and cured at 20℃±2℃ for 7 days and 28 days.

[0135] To evaluate the effects of repeated sieving with the same sieve aperture, repeated sieving after loosening agglomerates, and sieving after powder adsorption on the powder-carrying state of fine particles, three comparative examples were set up.

[0136] The only difference between Comparative Example 1 and Example 2 is that the fine particles of Gobi soil that have been pre-wetted and allowed to stand are not screened again, but directly enter the hydration powder adhesion step.

[0137] After the hydrated powder adheres, it is still sieved through a 5mm square hole sieve, and the residue on the sieve surface is returned and turned over again.

[0138] The only difference between Comparative Example 2 and Example 2 is that the agglomerates that failed to pass through the sieve holes in the first re-screening were loosened for 2 minutes and then not subjected to a second re-screening. Instead, they were put into the hydration powder adhesion step together with the fine Gobi soil particles that passed through the first re-screening.

[0139] The only difference between Comparative Example 3 and Example 2 is that the fine particles of Gobi soil after the hydrated powder adheres are not subjected to process sieving and are directly mixed with the skeleton particles.

[0140] To evaluate the particle agglomeration state after powdering, another sample was taken from the fine particles of Gobi soil after powdering and the retention rate on the sieve surface was tested using a 5mm square hole sieve.

[0141] All groups used the same source of original soil, the same total amount of hydrated powder, the same total amount of water added, the same laying thickness, the same total number of compaction passes, and the same closed curing conditions;

[0142] The retention rate on the sieve surface after powdering was determined as follows: fine particles of Gobi soil after hydration powdering was attached were taken, sieved through a 5mm square hole sieve for 2 minutes, the mass of material retained on the sieve surface was weighed, and the result was calculated as: mass of material retained on the sieve surface / total mass of fine particles of Gobi soil after powdering × 100%.

[0143] For comparative examples where sieving after powdering is not used as a process step, but only a separate sample is taken from the fine particles of Gobi soil after powdering for this test, the test does not change the process flow.

[0144] The proportion of aggregated inclusions in the cross-section was determined as follows: After 7 days of curing, a cross-sectional sample was cut and the cross-section was magnified and photographed.

[0145] In the cross-sectional image, the area formed by the adhesion of multiple fine particles, with continuous boundaries and no obvious hydration products inside is marked as an agglomeration and inclusion area;

[0146] The proportion of aggregated and mixed areas in the cross-section is the percentage of the area of ​​the aggregated and mixed regions to the total area of ​​the cross-section observation area;

[0147] The concentration ratio of hydration products in the particle contact zone was determined as follows: the positions where the skeleton particles abutted each other and the surrounding pores were marked in the cross-sectional image as the particle contact zone. The area of ​​hydration products in the particle contact zone and the total area of ​​hydration products in the cross-section were counted, and the ratio was calculated as (area of ​​hydration products in the particle contact zone / total area of ​​hydration products in the cross-section) × 100%.

[0148] In the unconfined compressive strength test, three cylindrical specimens were prepared for each group, with a diameter of 50 mm and a height of 50 mm. The test result was the average value of the three specimens.

[0149] The strength retention rate after immersion in water for 48 hours is the ratio of the unconfined compressive strength after immersion in water to the unconfined compressive strength without immersion in water at the same age.

[0150] In the wet-dry cycle test, each cycle includes immersion in water for 12 hours and placement in an indoor environment at 20℃±2℃ for 12 hours, for a total of 5 cycles. After the cycle, the mass of the specimen is weighed and the mass loss rate is calculated.

[0151] The test results are shown in Table 2;

[0152] Table 2: Effects of sieving, secondary sieving, and sieving after powdering on the hydration and consolidation properties of fine particles in Gobi soil.

[0153] Parameter name Example 2: Sieve again through the same sieve opening and after adding powder. Comparative Example 1: Cancellation of S2 rescreening Comparative Example 2: Cancellation of rescreening for agglomerates Comparative Example 3: Screening process after removing S3 Basic screening conditions 5mm square hole sieve for separating undersize and oversize material 5mm square hole sieve for separating undersize and oversize material 5mm square hole sieve for separating undersize and oversize material 5mm square hole sieve for separating undersize and oversize material Secondary screening conditions 5mm square hole sieve double sieve No secondary screening was set up 5mm square hole sieve double sieve 5mm square hole sieve double sieve The secondary screening failed the agglomerate treatment. After loosening, sieve again; those that still fail to pass will not proceed to the powdering step. not applicable After loosening, the material is not sieved again and enters the powdering step together with the material that passed the first sieve. After loosening, sieve again; those that still fail to pass will not proceed to the powdering step. After powdering, the powder is sieved. After powdering, sieve through a 5mm square-hole sieve; any retained material is returned, turned over, and sieved again. After powdering, sieve through a 5mm square-hole sieve; any retained material is returned, turned over, and sieved again. After powdering, sieve through a 5mm square-hole sieve; any retained material is returned, turned over, and sieved again. Not included as a process step, but instead sampled and tested for screen retention rate. Dosage of fine particles of Gobi soil (per part) 28 28 28 28 Dosage of skeleton particles / part 72 72 72 72 quicklime / part 3 3 3 3 calcium aluminate / part 2 2 2 2 Slag powder / part 3 3 3 3 Total water added / serving 10 10 10 10 Total number of compaction passes / passes 5 5 5 5 Powder retention rate on sieve surface / % 4.6 11.8 9.7 16.4 Sectional aggregate area ratio / % 1.8 6.4 5.1 7.9 Concentration of hydration products in the particle contact zone / % 65.2 54.8 57.6 50.8 7d unconfined compressive strength / MPa 2.21 1.95 2.02 1.88 28-day unconfined compressive strength / MPa 3.51 3.08 3.19 2.96 Strength retention rate after immersion in water for 48 hours / % 87.4 79.8 81.6 76.9 Mass loss rate after 5 wet-dry cycles / % 2.6 4.1 3.7 4.9

[0154] As shown in Table 2, under the same conditions of original soil source, hydration powder composition, total water addition, laying thickness, total number of compaction passes and curing conditions, the sieve retention rate of powder after adsorption in Example 2 was 4.6%, which was lower than that of Comparative Examples 1 to 3.

[0155] Comparative Example 1 was not pre-wetted and was sieved again through the same sieve. The pre-wetted agglomerates directly entered the hydration powder adhesion step.

[0156] Although subsequent sieving was still performed after powdering, the agglomerates at the front end had already participated in the powdering process, resulting in a higher retention rate on the sieve surface and a higher proportion of agglomerates mixed in the cross section than in Example 2.

[0157] In Comparative Example 2, the agglomerates were not re-sieved after being loosened. Some of the agglomerates that were not redispersed entered the hydration powder adhesion step along with the fine particles that passed the first re-sieve. The agglomerate inclusion area ratio in Comparative Example 2 was 5.1%, which was higher than the 1.8% in Example 2.

[0158] Comparative Example 3 eliminated the sieving process after the hydration powder adhered, and the residue on the sieve surface formed after the powder adhered directly entered the skeleton particle mixing step, resulting in a higher proportion of cross-sectional aggregated area and a lower strength retention rate after soaking in water for 48 hours than in Example 2.

[0159] In Example 2, basic screening determined the particle size boundaries between fine particles and skeleton particles in Gobi soil;

[0160] After pre-wetting, the same sieve size is used for re-sieving to prevent agglomerates that do not pass through the sieve from directly entering the hydration powder adhesion step;

[0161] Aggregates that fail the second screening are loosened and then screened again to prevent undispersed aggregates from entering the powdering step.

[0162] After the hydrated powder adheres, it is sieved again so that the residue on the sieve surface formed after powder adhesion is returned and turned over again.

[0163] The above steps correspond to raw material boundary, pre-wetting agglomeration control, and powder adsorption state verification, respectively, so that the fine particles of Gobi soil entering the skeleton particle mixing step maintain a relatively stable powder-carrying state.

[0164] This powder-carrying state is conducive to the subsequent entry of fine Gobi soil particles into the particle contact area between skeleton particles, and to their participation in hydration reactions during water replenishment, repressurization, and closed curing processes.

[0165] Based on the performance results, the concentration ratio of hydration products in the particle contact zone of Example 2 was 65.2%, which was higher than that of Comparative Examples 1 to 3.

[0166] The 28-day unconfined compressive strength was 3.51 MPa, the strength retention rate after immersion in water for 48 hours was 87.4%, and the mass loss rate after 5 wet-dry cycles was 2.6%.

[0167] The results indicate that the repeated screening with the same sieve opening, the repeated screening after loosening the agglomerates, and the screening after powder adsorption are not repetitions of ordinary screening actions, but rather a continuous screening control path established around the fine particles of Gobi soil carrying hydrated powder into the particle contact zone.

[0168] Compared to processes that eliminate any screening step, this approach reduces the amount of agglomerated impurities entering the subsequent mixing process, lowers the retention rate on the screen surface after powder adsorption, and improves the distribution concentration of hydration products in the particle contact zone, thereby improving strength retention after immersion and quality stability after wet-dry cycles.

[0169] Example 3 is the third embodiment of the present invention;

[0170] This embodiment provides a method for enhancing the hydration consolidation of fine-particle Gobi soil, including the following steps:

[0171] This embodiment is used to illustrate the effects of water addition sequence, dry adhesion of hydrated powder, direct initial compaction after leveling, and second-stage watering followed by re-compaction on the hydration and consolidation effect of fine particles in Gobi soil.

[0172] This embodiment is applicable to the consolidation construction of the base layer or subbase layer of construction access roads in the Gobi region, which utilizes fine particles of Gobi soil on-site.

[0173] The Gobi soil used was taken from the same Gobi engineering soil extraction point, and was naturally air-dried until the mass change between two consecutive weighings did not exceed 0.5%. Plant roots, boulders and non-soil debris were then removed.

[0174] The air-dried Gobi soil is crushed to a size that can pass through a 20mm square hole sieve, and then screened using a 5mm square hole sieve.

[0175] The material passing through a 5mm square hole sieve is used as fine particles of Gobi soil, while the material passing through a 20mm square hole sieve but not through a 5mm square hole sieve is used as skeleton particles.

[0176] Based on a total dry weight of 100 parts for fine Gobi soil particles and skeleton particles, weigh out 28 parts for fine Gobi soil particles and 72 parts for skeleton particles; and take 3 parts for quicklime, 2 parts for calcium aluminate and 3 parts for slag powder as hydration powder.

[0177] In this embodiment, the first section of water consists of 3 parts, and the second section of water consists of 7 parts;

[0178] The first stage of water is added before the fine particles and skeleton particles of Gobi soil are mixed, and the second stage of water is added after the initial compaction is completed.

[0179] The amount of water added in the first stage is less than the amount of water added in the second stage, so that the fine particles of Gobi soil remain in a pre-wetted state that can be screened again before entering the powder adhesion step, and do not form water-containing slurry in this stage.

[0180] First, spray 3 parts of water into the fine particles of Gobi soil. During the water spraying process, stir the fine particle layer for 5 minutes. After stopping the water spraying, let it stand for 15 minutes.

[0181] After settling, the fine particles of Gobi soil are screened again using a 5mm square hole sieve. The fine particles that pass through the sieve holes enter the hydration powder adhesion step, while the agglomerates that do not pass through the sieve holes are returned for loosening.

[0182] Quicklime, calcium aluminate, and slag powder were dry-mixed for 3 minutes without adding water to obtain hydrated powder.

[0183] Add the hydrated powder to the fine particles of Gobi soil that have been screened multiple times, and stir for 4 minutes;

[0184] No water is added to the mixture during this process, nor is the hydrated powder made into an aqueous slurry;

[0185] The dry mixing refers to the homogenization of quicklime, calcium aluminate and slag powder in a dry powder state before adding fine particles of Gobi soil.

[0186] This step keeps the hydrated powder in a dispersed state before it adheres to the surface of fine Gobi soil particles, reducing local agglomeration during the powder adhesion stage.

[0187] Subsequently, the fine particles of Gobi soil with attached hydration powder were mixed with the skeleton particles and laid as a 100mm thick layer to be consolidated.

[0188] After laying, the unconsolidated layer should be leveled.

[0189] After leveling, the layer to be consolidated is not sprayed with a second stage of water; it is directly subjected to initial pressure without water replenishment.

[0190] The initial compaction without water replenishment is carried out twice using a small vibratory compactor.

[0191] No water or water-containing slurry is added to the layer to be consolidated during the initial compaction period;

[0192] After the initial pressure is completed, spray 7 parts of water into the layer to be consolidated in the second stage.

[0193] After the second stage of water is injected, it is left to stand for 20 minutes to allow the second stage of water to seep into the pores of the layer to be consolidated and into the contact position of the skeleton particles and the surrounding pores.

[0194] After the resting period, the same small vibratory compactor was used to compact the material three times.

[0195] After the secondary compaction is completed, no more quicklime, calcium aluminate, slag powder or their mixtures shall be added to the layer to be consolidated.

[0196] After re-pressing, the layer to be consolidated was covered with a polyethylene film, and the film was made to contact the surface of the layer to be consolidated. It was then sealed and cured at 20℃±2℃ for 7 days and 28 days.

[0197] To evaluate the effects of the timing of water addition, no water addition during the powder adsorption stage, direct initial compaction after leveling, pause and re-compacting after the second water stage, and no water addition after re-compacting to hydrate the powder, five comparative groups were set up.

[0198] The difference between Comparative Example 1 and this embodiment is that the first section contains 7 parts water and the second section contains 3 parts water.

[0199] The difference between Comparative Example 2 and this embodiment is that: after adding fine particles of Gobi soil to the hydrated powder, 2 parts of water are added, and the water in the second stage is adjusted to 5 parts accordingly, while the total amount of water added remains at 10 parts.

[0200] The difference between Comparative Example 3 and this embodiment is that: after the consolidation layer is leveled, 7 parts of the second stage of water are sprayed in before the first compaction, and after standing for 20 minutes, it is compacted 5 times in a row.

[0201] The difference between Comparative Example 4 and this embodiment is that: after the second water spray is injected, there is no 20-minute pause time, but the water is repressurized 3 times immediately after the water spray ends;

[0202] The difference between Comparative Example 5 and this embodiment is that the total amount of hydrated powder is still 8 parts, of which 6 parts are added during the fine particle powdering stage of Gobi soil, and the remaining 2 parts are added after the re-compression is completed;

[0203] The powder added after re-compression consists of 0.75 parts quicklime, 0.50 parts calcium aluminate, and 0.75 parts slag powder;

[0204] All groups used the same source of original soil, the same amount of fine Gobi soil particles, the same amount of skeleton particles, the same total amount of hydrated powder, the same total amount of water added, the same laying thickness, the same total number of compaction passes, and the same closed curing conditions.

[0205] The retention rate on the sieve surface after powder coating was determined by sampling and testing.

[0206] After the hydrated powder adheres, take an equal amount of sample from the fine particles of Gobi soil after powder adhesion in each group, sieve it for 2 minutes using a 5mm square hole sieve, weigh the mass of the residue on the sieve surface, and calculate it as sieve surface residue mass / sample material mass × 100%.

[0207] This test is only used to evaluate the agglomeration state after powder adsorption, and the tested sample is not returned to the layer to be consolidated.

[0208] The proportion of the identifiable water film area on the surface before initial compaction is the percentage of the area of ​​the continuous reflective water film region to the total area of ​​the photographed area in the image taken vertically from the surface of the layer to be consolidated before the first compaction.

[0209] Three surface areas were measured in each group and the average value was taken, with the shooting distance and lighting conditions kept consistent.

[0210] The concentration ratio of hydration products in the particle contact zone was determined as follows: After 7 days of curing, a cross-sectional sample was cut, and the contact position of adjacent skeleton particles and the surrounding pores were marked in the cross-sectional image as the particle contact zone.

[0211] The hydration product area was marked according to the continuous cemented light-colored area in the interparticle pores. The area was counted using image analysis software under the same magnification and illumination conditions, and calculated as the area of ​​hydration products in the particle contact area / the total area of ​​hydration products in the profile × 100%.

[0212] The maximum thickness of the identifiable slurry zone on the surface is the maximum depth of the mud-like or fine powder-rich area extending inward from the surface of the layer to be consolidated in the profile.

[0213] Take 3 profile samples for each group, select 3 points on each profile for measurement, and record the maximum value;

[0214] In the unconfined compressive strength test, three cylindrical specimens were prepared for each group, with a diameter of 50 mm and a height of 50 mm. The test result was the average value of the three specimens.

[0215] The strength retention rate after immersion in water for 48 hours is the ratio of the unconfined compressive strength after immersion in water to the unconfined compressive strength without immersion in water at the same age.

[0216] In the wet-dry cycle test, each cycle includes immersion in water for 12 hours and placement in an indoor environment at 20℃±2℃ for 12 hours, for a total of 5 cycles. After the cycle, the mass of the specimen is weighed and the mass loss rate is calculated.

[0217] The test results are shown in Table 3;

[0218] Table 3: Effects of moisture time sequence and dry dust adsorption control on the hydration and consolidation properties of fine-particle Gobi soil

[0219] Parameter name Example 3: Moisture Sequencing Control Comparative Example 1: The amount of water added in the early stage was too large. Comparative Example 2: Hydration during the powdering stage Comparative Example 3: Water was added in advance before initial pressure. Comparative Example 4: The second water stage was not stopped. Comparative Example 5: Adding powder after re-compression Dosage of fine particles of Gobi soil (per part) 28 28 28 28 28 28 Dosage of skeleton particles / part 72 72 72 72 72 72 Quicklime in powdering stage / portion 3 3 3 3 3 2.25 Calcium aluminate in powdering stage / part 2 2 2 2 2 1.5 Slag powder in the powdering stage / part 3 3 3 3 3 2.25 Add quicklime / part after re-compression 0 0 0 0 0 0.75 Add calcium aluminate per part after recompression 0 0 0 0 0 0.5 Add slag powder / part after recompression 0 0 0 0 0 0.75 Total amount of hydrated powder / part 8 8 8 8 8 8 First section water / portion 3 7 3 3 3 3 Hydration during powdering stage / serving 0 0 2 0 0 0 Second section water / portion 7 3 5 7 7 7 Total water added / serving 10 10 10 10 10 10 Timing of adding water in the second stage After initial compression After initial compression After initial compression Before the first compaction After initial compression After initial compression Second water retention time / min 20 20 20 20 0 20 Total number of compaction passes / passes 5 5 5 5 5 5 Powder retention rate on sieve surface / % 4.9 13.8 15.6 5.2 5 6.4 Percentage of identifiable surface water film area before initial pressure / % 0.7 4.6 3.8 8.9 0.9 0.8 Concentration of hydration products in the particle contact zone / % 64.7 49.5 47.8 43.6 55.4 51.9 7d unconfined compressive strength / MPa 2.15 1.82 1.76 1.68 1.93 1.87 28-day unconfined compressive strength / MPa 3.43 2.91 2.84 2.7 3.08 2.96 Strength retention rate after immersion in water for 48 hours / % 86.1 76.8 75.4 72.6 80.3 78.7 Mass loss rate after 5 wet-dry cycles / % 2.9 4.8 5.1 5.7 3.9 4.4 Maximum thickness of the identifiable slurry zone on the surface / mm 0.6 2.4 2.7 3.6 1.5 1.9

[0220] As shown in Table 3, under the same conditions of original soil source, amount of fine Gobi soil particles, amount of skeleton particles, total amount of hydration powder, total amount of water added, laying thickness, total number of compaction passes and closed curing conditions, the concentration ratio of hydration products in the particle contact area of ​​Example 3 is 64.7%, which is higher than that of Comparative Examples 1 to 5.

[0221] The 28-day unconfined compressive strength was 3.43 MPa, the strength retention rate after immersion in water for 48 hours was 86.1%, and the mass loss rate after 5 wet-dry cycles was 2.9%.

[0222] Compared with Comparative Example 1, Example 3 used less water for pre-wetting of fine Gobi soil particles and reserved more water for addition after initial compaction.

[0223] In Comparative Example 1, the first stage water content was 7 parts. After powder adsorption, the sieve retention rate increased to 13.8%. The proportion of the surface identifiable water film area before initial pressing was 4.6%, and the maximum thickness of the surface identifiable pulping zone was 2.4 mm.

[0224] The results indicate that when the amount of water added in the early stage is too large, fine particles of Gobi soil are prone to local agglomeration or surface water film during the dusting stage.

[0225] In Example 3, the first stage of water was 3 parts and the second stage of water was 7 parts. The retention rate on the sieve surface after powdering was 4.9%, indicating that the amount of water in the first stage was less than that in the second stage, which helped to maintain the pre-wetting of fine particles without premature slurrying.

[0226] Compared with Comparative Example 2, in Example 3, no water was added after the hydrated powder was mixed with fine Gobi soil particles;

[0227] In Comparative Example 2, after adding 2 parts of water during the powder adsorption stage, the retention rate on the sieve surface after powder adsorption increased to 15.6%, the concentration ratio of hydration products in the particle contact area decreased to 47.8%, and the 28-day unconfined compressive strength was 2.84 MPa.

[0228] This result indicates that water replenishment during the powdering stage will cause some hydrated powders to be wetted and aggregated prematurely, weakening their ability to enter the particle contact zone with fine Gobi soil particles.

[0229] Compared with Comparative Example 3, Example 3 did not spray the second stage of water in advance after leveling, but directly entered the initial pressure without water replenishment;

[0230] Comparative Example 3 had the second stage of water sprayed in before the first compaction. Before the initial compaction, the identifiable water film area on the surface was 8.9%, the maximum thickness of the identifiable slurry zone on the surface was 3.6 mm, and the concentration ratio of hydration products in the particle contact zone was 43.6%.

[0231] The results indicate that adding water in the second stage in advance will cause water and powder to migrate or react before fine particles enter the particle contact zone, which is not conducive to the concentrated formation of hydration products in the subsequent contact zone.

[0232] Compared with Comparative Example 4, Example 3 had a 20-minute pause after the second water injection.

[0233] In Comparative Example 4, after the second stage of water injection, the pressure was immediately restored, and the concentration ratio of hydration products in the particle contact zone was 55.4%, which was lower than 64.7% in Example 3.

[0234] After immersion in water for 48 hours, the strength retention rate was 80.3%, which is lower than the 86.1% in Example 3;

[0235] The results indicate that the pause step after the second water injection helps water to penetrate along the pores into the contact position of the skeleton particles and the surrounding pores, making the hydration reaction conditions in the particle contact area more sufficient during repressurization.

[0236] Compared with Comparative Example 5, in Example 3, no additional hydration powder was added after the re-pressing was completed;

[0237] Although the total powder amount of Comparative Example 5 was still 8 parts, 2 parts were added after re-compression. The concentration ratio of hydration products in the particle contact area was 51.9%, and the strength retention rate after soaking in water for 48 hours was 78.7%.

[0238] The results indicate that the powder added after recompression is difficult to enter the particle contact zone with the fine particles of Gobi soil and tends to remain on the surface or in non-contact pores.

[0239] Example 3: No hydrated powder is added after the repressing is completed, which is beneficial to maintaining the continuous process of dry powder adsorption, no water replenishment during the initial press, water stoppage in the second stage, and repressing.

[0240] The above results indicate that the following processes are all aimed at achieving the same goal: less water in the first stage than in the second stage; dry mixing of quicklime, calcium aluminate, and slag powder; addition of fine Gobi soil particles; no water replenishment during the powder adsorption stage; no premature injection of the second stage of water after leveling; stopping and re-compacting after the second stage of water; and no addition of hydration powder after re-compacting. Even if the fine Gobi soil particles carry hydration powder into the contact area of ​​the skeleton particles, the second stage of water will then participate in the hydration and consolidation reaction in that area.

[0241] This process reduces powder agglomeration during the powder attachment stage, surface water film before initial pressing, and ineffective powder retention after repressing. It also increases the distribution ratio of hydration products in the particle contact area and improves the consolidation stability after immersion and wet-dry cycles.

[0242] Example 4 is the fourth embodiment of the present invention;

[0243] This embodiment provides a method for enhancing the hydration consolidation of fine-particle Gobi soil, including the following steps:

[0244] This embodiment is used to illustrate the effects of the second stage of water injection followed by a pause and re-pressurization, the absence of additional hydration powder after re-pressurization, and the covering and sealing curing method on the hydration and consolidation effect of fine particles in Gobi soil.

[0245] This embodiment is applicable to the construction process of preparing a consolidation layer in situ using fine particles and skeleton particles of Gobi soil in the base layer or subbase layer of construction access roads in the Gobi region.

[0246] This embodiment uses the same source of Gobi soil, screening method, amount of fine Gobi soil particles, amount of skeleton particles, composition of hydrated powder, first stage water pre-wetting method, dry powdering method, thickness of the layer to be consolidated, leveling method, and no water replenishment initial pressure method as in embodiment 3.

[0247] Specifically, based on a total dry weight of 100 parts for fine particles and skeleton particles of Gobi soil, the fine particles of Gobi soil are 28 parts and the skeleton particles are 72 parts.

[0248] The hydrated powder is composed of 3 parts quicklime, 2 parts calcium aluminate and 3 parts slag powder;

[0249] The first section contains 3 parts water, and the second section contains 7 parts water.

[0250] The thickness of the consolidation layer to be laid is 100mm;

[0251] The initial compaction without water replenishment is carried out twice using a small vibratory compactor.

[0252] After the initial pressure is completed, spray 7 parts of water into the layer to be consolidated in the second stage.

[0253] The second stage of water refers to the water added after the initial pressure without water replenishment, which is used to enter the pores of the layer to be consolidated and participate in the subsequent hydration reaction;

[0254] The term "stopping" refers to keeping the layer to be consolidated static after the second stage of water is injected and before repressurization, so that the second stage of water can seep into the pores of the layer to be consolidated and into the contact position of the skeleton particles and the surrounding pores.

[0255] In this embodiment, after the second water is sprayed in, it is left to stand for 20 minutes, and then the same small vibratory compactor is used to compact it three times.

[0256] After the secondary compaction is completed, no more quicklime, calcium aluminate, slag powder or their mixtures shall be added to the layer to be consolidated.

[0257] The layer to be consolidated after re-compression enters a closed curing process;

[0258] The term "covering and sealing" refers to using a covering layer to cover the surface of the layer to be consolidated, thereby reducing water loss from the surface of the layer to be consolidated and external water flow disturbance.

[0259] In this embodiment, a polyethylene film is used as the covering layer;

[0260] Do not rinse the surface of the consolidation layer before covering and sealing;

[0261] When covering and sealing, a polyethylene film is laid on the surface of the layer to be solidified and the polyethylene film is made to adhere to the surface of the layer to be solidified. The edges of the film are pressed with pressure strips to keep the covering layer closed.

[0262] The closed curing was carried out at 20℃±2℃ for 7 days and 28 days, respectively.

[0263] To evaluate the effects of the second stage of water injection followed by a pause and repressurization, the absence of additional hydration powder after repressurization, the absence of rinsing before sealing, and the contact between the cover layer and the surface of the layer to be consolidated, five comparative examples were set up.

[0264] The difference between Comparative Example 1 and this embodiment is that: after the second water is sprayed in, there is no 20-minute pause, and the water is repressurized 3 times immediately after the spraying is finished; the rest of the steps are the same as in this embodiment.

[0265] The difference between Comparative Example 2 and this embodiment is that the total amount of hydrated powder is still 8 parts, of which 6 parts are added during the fine particle powdering stage of Gobi soil, and the remaining 2 parts are added after the re-compression is completed;

[0266] In the powdering stage, 2.25 parts of quicklime, 1.50 parts of calcium aluminate and 2.25 parts of slag powder are added. After re-compression, 0.75 parts of quicklime, 0.50 parts of calcium aluminate and 0.75 parts of slag powder are added.

[0267] The difference between Comparative Example 3A and this embodiment is that: the second water volume is 6 parts, and no rinsing is performed before covering and sealing, which is used to evaluate the effect of the reduction in the second water volume on the consolidation performance;

[0268] The difference between Comparative Example 3B and Comparative Example 3A is that: before covering and sealing, the surface of the layer to be consolidated is rinsed with a low-pressure spray using 1 part water.

[0269] The rinsing water is included in the total water volume, so the total water volume for this group is still 10 parts;

[0270] The difference between Comparative Example 4 and this embodiment is that: when covering and sealing, spacer pads are set on the surface of the layer to be consolidated so that the covering layer does not contact the surface of the layer to be consolidated.

[0271] The edges of the film are still sealed using the same pressure strip method as in this embodiment;

[0272] In Comparative Example 3B, low-pressure spray rinsing was carried out using a nozzle with a spray pressure of 0.05 MPa. The nozzle was 300 mm away from the surface of the layer to be consolidated. The spray was carried out at a constant speed and went back and forth once along the surface of the layer to be consolidated. The rinsing water volume was 1 part.

[0273] In Comparative Example 4, the height of the spacer support is 5 mm, and the support is placed at the edge of the surface of the layer to be consolidated, so that an air gap of about 5 mm is formed between the polyethylene film and the surface of the layer to be consolidated.

[0274] Except for the fact that the covering layer does not contact the surface, the other methods of pressing the covering edge, the sealing curing temperature, and the sealing curing time are the same as in this embodiment;

[0275] All groups used the same source of original soil, the same amount of fine Gobi soil particles, the same amount of skeleton particles, the same laying thickness, the same total number of compaction passes, and the same closed curing conditions.

[0276] Except for Comparative Example 3A, the total amount of water added to each group was 10 portions;

[0277] The total water addition for Comparative Example 3A was 9 parts, used to separately evaluate the impact of water reduction in the second stage.

[0278] The mass loss rate after 24 hours of closed curing was determined as follows: the initial mass was the mass of the sample before the end of the re-pressing and the completion of the covering. After 24 hours of closed curing, the covering layer was removed and the sample mass was weighed immediately. The mass loss rate was calculated as the ratio of the initial mass minus the mass after 24 hours to the initial mass. The mass of the covering layer was not included in the sample mass.

[0279] The concentration ratio of hydration products in the particle contact zone was determined as follows: After 7 days of curing, a cross-sectional sample was cut, and the contact position of adjacent skeleton particles and the surrounding pores were marked in the cross-sectional image as the particle contact zone.

[0280] Cross-sectional photographs were taken under the same lighting conditions, at the same magnification, and at the same shooting distance.

[0281] The continuous, cemented, light-colored area within the pores between particles is marked as the hydration product area. The reflective areas of light-colored skeleton particles and the cutting dust areas are not included in the hydration product area. Suspected areas are reviewed according to the same judgment rule.

[0282] The concentration ratio of hydration products in the particle contact zone is calculated as follows: (Area of ​​hydration products in the particle contact zone / Total area of ​​hydration products in the cross-section) × 100%.

[0283] The proportion of surface powdering area was determined as follows: After 7 days of curing, a 100mm×100mm observation area was selected on the surface of the layer to be consolidated. A nylon soft brush with a bristle length of 20mm and a brush width of 30mm was used. A load of 100g was applied above the brush body to make the bristles contact the surface of the layer to be consolidated.

[0284] Brush 5 times in the same direction, with each brush stroke being 100mm.

[0285] After brushing, take a picture of the observation area, mark the loose powdery areas exposed after brushing, and calculate the percentage of the observation area to the total area of ​​the area.

[0286] Three observation areas were selected for each group, and the average value was taken.

[0287] In the unconfined compressive strength test, three cylindrical specimens were prepared for each group, with a diameter of 50 mm and a height of 50 mm. The test result was the average value of the three specimens.

[0288] The strength retention rate after immersion in water for 48 hours is the ratio of the unconfined compressive strength after immersion in water to the unconfined compressive strength without immersion in water at the same age.

[0289] In the wet-dry cycle test, each cycle includes immersion in water for 12 hours and placement in an indoor environment at 20℃±2℃ for 12 hours, for a total of 5 cycles. After the cycle, the mass of the specimen is weighed and the mass loss rate is calculated.

[0290] The test results are shown in Table 4;

[0291] Table 4: Effects of the second stage water cessation, no powder replenishment after repressurization, and covering / sealing method on consolidation performance

[0292] Parameter name Example 4: Stop and repressurize and contact the cover Comparative Example 1: Immediately after the second stage of water pressure was restored Comparative Example 2: Adding powder after re-compression Comparative Example 3A: Second stage water volume reduced, no rinsing Comparative Example 3B: Rinsing before covering Comparative Example 4: The coating layer does not contact the surface Dosage of fine particles of Gobi soil (per part) 28 28 28 28 28 28 Dosage of skeleton particles / part 72 72 72 72 72 72 Quicklime in powdering stage / portion 3 3 2.25 3 3 3 Calcium aluminate in powdering stage / part 2 2 1.5 2 2 2 Slag powder in the powdering stage / part 3 3 2.25 3 3 3 Add quicklime / part after re-compression 0 0 0.75 0 0 0 Add calcium aluminate per part after recompression 0 0 0.5 0 0 0 Add slag powder / part after recompression 0 0 0.75 0 0 0 Total amount of hydrated powder / part 8 8 8 8 8 8 First section water / portion 3 3 3 3 3 3 Second section water / portion 7 7 7 6 6 7 Rinse with water before covering / serving 0 0 0 0 1 0 Total water added / serving 10 10 10 9 10 10 Second water retention time / min 20 0 20 20 20 20 Pre-coverage flushing conditions Unrinsed Unrinsed Unrinsed Unrinsed 0.05MPa, 300mm distance, one round trip Unrinsed Coverage method Film bonding surface, edge pressing Film bonding surface, edge pressing Film bonding surface, edge pressing Film bonding surface, edge pressing Film bonding surface, edge pressing A 5mm support pad creates an air gap, and the edges are pressed tightly. Total number of compaction passes / passes 5 5 5 5 5 5 Quality loss rate after 24 hours of closed curing / % 0.82 0.91 0.88 0.94 1.35 2.18 Concentration of hydration products in the particle contact zone / % 66.3 57.8 53.6 61.5 50.2 59.4 Percentage of surface powdery area / % 1.2 2.3 3.4 2 4.7 3.1 7d unconfined compressive strength / MPa 2.23 2.02 1.96 2.07 1.89 2.05 28-day unconfined compressive strength / MPa 3.49 3.17 3.05 3.24 2.94 3.16 Strength retention rate after immersion in water for 48 hours / % 87 81.7 79.6 83.2 76.9 80.9 Mass loss rate after 5 wet-dry cycles / % 2.7 3.8 4.3 3.6 5.3 4.1

[0293] As shown in Table 4, under the same conditions of fine particle dosage, skeleton particle dosage, laying thickness, total number of compaction passes, and closed curing conditions, the concentration ratio of hydration products in the particle contact zone of Example 4 was 66.3%, the 28-day unconfined compressive strength was 3.49 MPa, the strength retention rate after immersion in water for 48 hours was 87.0%, and the mass loss rate after 5 dry-wet cycles was 2.7%.

[0294] Compared with Comparative Example 1, Example 4 retained the 20-minute pause after the second water injection;

[0295] In Comparative Example 1, the hydration product concentration ratio in the particle contact zone was 57.8% immediately after the second stage of water injection, which was lower than that in Example 4.

[0296] The 28-day unconfined compressive strength was 3.17 MPa, which is lower than the 3.49 MPa of Example 4;

[0297] The results show that setting a pause time after the second stage of water injection is beneficial for the second stage of water to penetrate into the pores of the layer to be consolidated and into the contact position of the skeleton particles and the surrounding pores, so that the particle contact area has more stable hydration reaction conditions during re-pressurization.

[0298] Compared with Comparative Example 2, in Example 4, no hydration powder was added after the re-pressing was completed;

[0299] Although the total amount of hydrated powder in Comparative Example 2 was still 8 parts, 2 parts were added after recompression. This part of the powder did not enter the contact area of ​​the skeleton particles along with the fine particles of Gobi soil, and was easy to stay on the surface or in non-contact pores.

[0300] The concentration ratio of hydration products in the particle contact area of ​​Comparative Example 2 was 53.6%, the proportion of surface powdery area was 3.4%, and the strength retention rate after immersion in water for 48 hours was 79.6%, all of which were lower than those of Example 4.

[0301] The results indicate that not adding hydrated powder after recompression helps maintain the powder-carrying position of fine particles formed before recompression and reduces the ineffective retention of added powder.

[0302] Compared with Example 4, Comparative Example 3A reduced the amount of water in the second stage from 7 parts to 6 parts but did not perform pre-coverage rinsing. The concentration ratio of hydration products in the particle contact area was 61.5%, and the 28-day unconfined compressive strength was 3.24 MPa.

[0303] Comparative Example 3B is based on Comparative Example 3A, with 1 part of water used for low-pressure flushing before covering, so that the total water volume is restored to 10 parts.

[0304] However, the proportion of hydration products concentrated in the particle contact area decreased to 50.2%, the proportion of surface pulverization area increased to 4.7%, and the mass loss rate increased to 5.3% after 5 dry-wet cycles;

[0305] The results show that pre-covering flushing does not simply change the water volume, but rather disturbs the distribution of fine particles and hydrated powders on the surface after re-compaction, causing some hydrated powders and fine particles to deviate from the already compacted area.

[0306] Not rinsing before sealing helps maintain the particle arrangement and hydration position of the contact area after repressurization;

[0307] Compared with Comparative Example 4, Example 4 adopts a covering and sealing method in which the covering layer contacts the surface of the layer to be consolidated;

[0308] In Comparative Example 4, an air gap of approximately 5 mm was formed between the polyethylene film and the surface of the layer to be solidified. Although the edges of the film were still compressed, the mass loss rate after 24 hours of sealed curing increased to 2.18%, which was higher than the 0.82% in Example 4.

[0309] Its strength retention rate after immersion in water for 48 hours was 80.9%, which was also lower than that of Example 4;

[0310] The results show that the adhesion between the cover layer and the surface of the layer to be consolidated can reduce local water loss caused by surface air gaps, and keep the hydration reaction involving the second stage of water under relatively stable water content conditions during the closed curing stage.

[0311] The above comparison results show that adding water after the initial pressing and then repressurizing after a period of rest, not adding hydrated powder after repressurization, not rinsing before covering and sealing, and contact between the covering layer and the surface of the layer to be solidified correspond to the time control of the second stage water entering the particle contact zone, the spatial position control of the powder, the surface disturbance control after repressurization, and the water loss control during the sealing and curing stage, respectively.

[0312] These measures, in conjunction with the preceding fine particle carrying and non-water-replenishing initial pressing steps, enable the hydrated powder and the second stage of water to undergo a hydration reaction near the particle contact zone, thereby increasing the concentration ratio of hydration products in the particle contact zone and improving the consolidation stability after immersion and wet-dry cycles.

[0313] Example 5 is the fifth embodiment of the present invention;

[0314] This embodiment provides a method for enhancing the hydration consolidation of fine-particle Gobi soil, including the following steps:

[0315] This embodiment is used to illustrate the method of profile verification after the completion of closed curing, and the specific way to adjust the process of subsequent layers to be consolidated in the same batch based on the profile verification results;

[0316] This embodiment follows the steps of raw material screening, Gobi soil fine particle pre-wetting, hydration powder dry adhesion, initial pressure without water replenishment, second stage water stop and re-pressure, and covering and sealing curing disclosed in Embodiments 1 to 4.

[0317] This embodiment focuses on how the cross-sectional observation results are fed back to the subsequent pre-screening loosening process, initial compaction process, hydration powder turning process, and second water cessation process of the layer to be consolidated, without repeating the complete construction steps already disclosed in the previous embodiment.

[0318] In this embodiment, the subsequent consolidation layers of the same batch refer to the consolidation layers prepared using the same soil sampling point, the same natural air drying and sieving conditions, the same hydrated powder composition, and within the same construction cycle.

[0319] The verification layer is only used for cross-sectional verification and will not be reworked.

[0320] The judgment results obtained from the verification layer are only used for process adjustments of subsequent layers to be consolidated.

[0321] The aforementioned subsequent layers A1, A2, B1 and B2 serve as verification implementation methods for determining the direction of the pre-screening loosening process of S2, the initial pressing process of S5, the turning process of S3, and the stopping process after the second stage of water injection in S6, respectively, based on the profile verification results.

[0322] The process adjustments are only made within the range of the agglomerate loosening time before secondary screening, the number of initial pressing passes without water replenishment and the number of secondary pressing passes, the agitation time after the addition of hydrated powder, and the dwell time after the second stage of water injection, which have been disclosed in this embodiment.

[0323] After the sealing and curing is completed, a cross-sectional sample with dimensions of 50mm×50mm×30mm is cut from the middle of the layer to be consolidated, with a dimensional deviation not exceeding ±2mm;

[0324] The cross-section is not washed with water during the cutting process;

[0325] Take photos immediately after cutting the cross-sectional sample;

[0326] When there is free water on the profile surface, use absorbent paper to gently touch the edge of the profile to absorb the free water, without wiping the profile observation area;

[0327] The cross-sectional images were acquired under the same lighting conditions, magnification, and shooting distance.

[0328] In the cross-sectional image, with the contact point of adjacent skeleton particles as the center, a pore area extending outward within 5 mm and connected to the contact point is selected as the observation position;

[0329] When the extended areas of adjacent contact points overlap, the midpoint of the line connecting the two contact points shall be used as the boundary.

[0330] The retention state of the fine particles of Gobi soil is expressed as the proportion of the area where the fine particles of Gobi soil are retained within the observation location.

[0331] Among them, identifiable fine particles of Gobi soil refer to the particle area located in the pores between skeleton particles, with a particle size of less than 5 mm and a boundary that can be distinguished from the skeleton particles. The floating powder formed by cutting and the dust that is not continuous with the pore structure are not included in the fine particle area.

[0332] The distribution of the hydrated powder reaction products is expressed as the ratio of the reaction product area in the particle contact area to that in the non-particle contact area.

[0333] In the profile verification after the S7 closed curing is completed, the retention state of the fine particles of Gobi soil and the distribution state of the hydration powder reaction products are preferably represented by the proportion of fine particle retention area and the proportion of reaction product area in the particle contact area and non-particle contact area, respectively.

[0334] Among them, the hydrated powder reaction product area is marked by the light-colored area in the cross section that is located in the interparticle pores, is continuously cemented, and has a different boundary from the loose fine particles. The reflective area of ​​the skeleton particles, the cutting dust area, and the isolated powder spots are not included in the reaction product area. Suspected areas are reviewed according to the same judgment rule.

[0335] In this embodiment, in order to transform the cross-sectional observation results into a basis for subsequent process adjustments, the following judgment criteria are adopted:

[0336] In this embodiment, the determination value of the fine particle retention area ratio and the determination value of the reaction product distribution are engineering discrimination thresholds selected based on the results of the profile verification test;

[0337] The basis for this setting is that the abnormal distribution results of the verification layer and the unadjusted subsequent layer are located on one side of the judgment value, while the subsequent layer after the corresponding process adjustment has cross-sectional observation results that cross the judgment value and are accompanied by improvements in the concentration ratio of hydration products in the particle contact area, unconfined compressive strength and strength retention rate after immersion.

[0338] Therefore, the judgment value is used to classify the cross-sectional observation results into two categories: those that require adjustment of process parameters and those that do not require adjustment of process parameters.

[0339] When the proportion of fine particle retention area in the Gobi soil within the observation location is less than 25% of the fine particle retention judgment value, it is judged as insufficient fine particle retention.

[0340] When the area of ​​hydrated powder reaction products in the non-particle contact zone exceeds 35% of the total area of ​​reaction products in the profile, it is determined that the reaction products are concentrated in the non-particle contact zone.

[0341] The above judgment criteria are only used for process adjustments of subsequent layers to be consolidated in the same batch as described in this embodiment;

[0342] The judgment criteria are used to classify the cross-sectional observation results into process situations that require adjustment of S2, S3, S5 or S6.

[0343] If the observation results do not meet the above-mentioned judgment conditions, the process parameters of the subsequent consolidation layer shall remain unchanged as in Example 4.

[0344] When the observation results meet the judgment conditions, during the process of continuing to prepare the consolidation layer, steps S1 to S7 are re-executed according to the adjusted process parameters, so that the distribution of hydration products and strength development of the subsequently prepared consolidation layer in the particle contact area are improved.

[0345] In this embodiment, the subsequent consolidation layers of the same batch refer to the consolidation layers that are laid continuously within the same construction period, using the same original soil from the same soil sampling point, the same air drying and sieving conditions, the same ratio of fine particles to skeleton particles of Gobi soil, the same hydration powder composition, the same total water addition.

[0346] The verification layer is only used to obtain cross-sectional observation results and determine the direction of subsequent process adjustments, and is not the object of adjustment itself;

[0347] Check layer A and check layer B are profile anomalies caused by differences in the degree of local fine particle agglomeration, uniformity of hydrated powder adhesion, or compaction distribution in the same batch of projects.

[0348] The raw material sources, hydration powder composition, total water addition, laying thickness and curing conditions of verification layer A and verification layer B are the same as those in Example 4, but different distribution anomalies appear in the cross-sectional verification after closed curing.

[0349] In the first set of experiments, the verification layer A was prepared first;

[0350] After 7 days of closed curing, profile samples were taken for observation. The proportion of fine particles retained in the Gobi soil at the observation location was 19.4%, which was lower than the 25% judgment value used in this embodiment, and was judged to be insufficient fine particle retention.

[0351] In response to this situation, three sets of subsequent layers are set up in the same batch of subsequent layers to be consolidated: the process of subsequent layer A0 is not adjusted, and the process conditions of the verification layer A are still used;

[0352] In subsequent layer A1, the loosening process before re-screening was adjusted. The loosening time of agglomerates that did not pass through the 5mm square hole sieve after pre-wetting and standing was adjusted from 2 minutes to 4 minutes before re-screening.

[0353] In the subsequent A2 layer, the initial compaction process was adjusted from 2 to 3 times without water replenishment, and the secondary compaction was adjusted from 3 to 2 times, so that the total number of compaction passes remained at 5.

[0354] Except for the above adjustments, the original soil source, hydration powder composition, total water addition, laying thickness and sealing curing conditions of the subsequent layers A0, A1 and A2 are the same;

[0355] In the second set of experiments, the verification layer B was prepared;

[0356] After 7 days of closed curing, a cross-sectional sample was taken for observation. The area ratio of hydrated powder reaction products in the non-particle contact area was 39.8%, which exceeded the 35% judgment value used in this embodiment. Therefore, it was determined that the hydrated powder reaction products were concentrated in the non-particle contact area.

[0357] In response to this situation, three sets of subsequent layers are set in the same batch of subsequent layers to be consolidated: the process of subsequent layer B0 is not adjusted, and the process conditions of the verification layer B are still used.

[0358] In subsequent layer B1, the turning process after the addition of hydration powder was adjusted, and the turning time between the Gobi soil fine particles and the hydration powder was adjusted from 4 minutes to 6 minutes.

[0359] The subsequent layer B2 will adjust the pause process after the second water injection, changing the pause time after the second water injection from 20 minutes to 30 minutes;

[0360] Except for the above adjustments, the original soil source, hydration powder composition, total water addition, laying thickness, total number of compaction passes and sealing curing conditions of subsequent layers B0, B1 and B2 are the same.

[0361] In the unconfined compressive strength test, three cylindrical specimens were prepared for each group, with a diameter of 50 mm and a height of 50 mm. The test result was the average value of the three specimens.

[0362] The strength retention rate after immersion in water for 48 hours is the ratio of the unconfined compressive strength after immersion in water to the unconfined compressive strength without immersion in water at the same age.

[0363] In the wet-dry cycle test, each cycle includes immersion in water for 12 hours and placement in an indoor environment at 20℃±2℃ for 12 hours, for a total of 5 cycles. After the cycle, the mass of the specimen is weighed and the mass loss rate is calculated.

[0364] The test results are shown in Table 5;

[0365] Table 5: Cross-sectional verification and the effect of subsequent process adjustments for the consolidation layer in the same batch

[0366] Parameter name Check layer A: Insufficient retention of fine particles Subsequent layer A0: Not adjusted Subsequent layer A1: Adjust the loosening process before re-screening Subsequent layer A2: Initial pressure adjustment process Check layer B: Concentration of reaction products in non-contact areas Subsequent layer B0: Unadjusted Subsequent layer B1: Adjust the S3 flipping process Subsequent layer B2: Adjust the second stage of water cessation process. Time to loosen agglomerates before secondary screening (min) 2 2 4 2 2 2 2 2 No initial pressure pass without water replenishment / passes 2 2 2 3 2 2 2 2 Number of re-pressing passes / passes 3 3 3 2 3 3 3 3 Total number of compaction passes / passes 5 5 5 5 5 5 5 5 Agitation time after adding hydrated powder / min 4 4 4 4 4 4 6 4 Second water jet injection pause time / min 20 20 20 20 20 20 20 30 Percentage of fine particle retention area at observation location / % 19.4 20.7 28.6 30.1 27.8 28.3 29.4 29.1 Non-particle contact area reaction product area ratio / % 32.6 31.9 29.5 30.8 39.8 38.7 31.6 32.4 Concentration of hydration products in the particle contact zone / % 55.2 56.4 63.7 62.8 52.9 53.8 61.9 62.4 7d unconfined compressive strength / MPa 1.91 1.94 2.13 2.16 1.88 1.9 2.09 2.11 28-day unconfined compressive strength / MPa 3.03 3.08 3.38 3.34 2.98 3.02 3.31 3.36 Strength retention rate after immersion in water for 48 hours / % 78.9 79.4 85.2 84.6 77.6 78.2 84.1 84.8 Mass loss rate after 5 wet-dry cycles / % 4.4 4.2 3.1 3.2 4.7 4.5 3.3 3.2

[0367] As shown in Table 5, the proportion of fine particles retained at the observation location in the verification layer A is 19.4%, which is lower than the 25% judgment value used in this embodiment, indicating that the fine particles of Gobi soil in the pores around the contact location of the skeleton particles are not retained enough.

[0368] No process adjustments were made to subsequent layer A0 in the same batch. The proportion of fine particle retention area at its observation location was 20.7%, and the concentration of hydration products in the particle contact area was 56.4%. The changes were small compared with the verification layer A, indicating that if the process is not adjusted according to the profile verification results when the material conditions in the same batch are similar, subsequent layers may still retain the same type of distribution defects.

[0369] In subsequent layer A1, the time for loosening agglomerates before rescreening was adjusted from 2 min to 4 min;

[0370] After adjustment, the proportion of fine particle retention area at the observation location increased to 28.6%, the concentration of hydration products in the particle contact area increased to 63.7%, and the 28-day unconfined compressive strength increased to 3.38 MPa.

[0371] The results indicate that when profile observation shows insufficient retention of fine particles, extending the agglomerate loosening time before secondary screening can reduce the entry of undispersed agglomerates into subsequent steps, allowing more Gobi soil fine particles to enter the contact position of skeleton particles and the surrounding pores during the initial and secondary compaction processes.

[0372] The subsequent layer A2 will have its initial compaction without water replenishment increased from 2 times to 3 times, and its secondary compaction increased from 3 times to 2 times, maintaining a total of 5 compaction passes.

[0373] After this adjustment, the proportion of fine particle retention area at the observation location increased to 30.1%, the concentration ratio of hydration products in the particle contact area was 62.8%, and the strength retention rate after immersion in water for 48 hours was 84.6%.

[0374] Since the total number of compaction passes did not increase, the above improvement mainly corresponds to the promoting effect of the initial compaction stage on the entry of fine powder-carrying particles into the particle contact zone, rather than the increase in compaction energy.

[0375] The area ratio of reaction products in the non-particle contact area of ​​the verification layer B is 39.8%, which exceeds the 35% judgment value used in this embodiment, indicating that the reaction products of the hydrated powder deviate from the particle contact area and are concentrated in the non-particle contact area.

[0376] The subsequent layer B0 of the same batch did not undergo process adjustments, and the area ratio of reaction products in the non-particle contact zone was still 38.7%, while the concentration ratio of hydration products in the particle contact zone was 53.8%, indicating that this type of distribution problem may continue even without process adjustments.

[0377] The agitation time after adding the hydrated powder in subsequent layer B1 will be adjusted from 4 min to 6 min;

[0378] After this adjustment, the area ratio of reaction products in the non-particle contact zone decreased to 31.6%, the concentration ratio of hydration products in the particle contact zone increased to 61.9%, and the 28-day unconfined compressive strength increased to 3.31 MPa.

[0379] The results indicate that when profile observation shows that the reaction products are concentrated in the non-particle contact area, adjusting the agitation process between the hydrated powder and the fine particles of Gobi soil can help improve the uniformity of the adhesion of the hydrated powder on the surface of the fine particles and reduce the concentration of powder in the subsequent non-contact area.

[0380] The subsequent layer B2 will adjust the dwell time after the second water jet is injected from 20 minutes to 30 minutes;

[0381] After this adjustment, the area ratio of reaction products in the non-particle contact zone decreased to 32.4%, the concentration ratio of hydration products in the particle contact zone increased to 62.4%, and the strength retention rate after immersion in water for 48 hours was 84.8%.

[0382] The results indicate that when the hydration powder reaction products are biased towards the non-particle contact area, extending the dwell time after the second stage water injection helps the second stage water to penetrate into the pores of the unconsolidated layer at the front of the repressurization front into the contact position of the skeleton particles and the surrounding pores, so that the subsequent hydration reaction occurs more near the particle contact area.

[0383] The test results of subsequent layers A1, A2, B1 and B2 show that the profile verification results can correspond to the adjustment of the loosening time before re-screening, the number of initial pressing passes without water replenishment, the turning time after adding hydrated powder, and the dwell time after the second stage of water injection.

[0384] Compared with the unadjusted subsequent layers A0 and B0, the adjusted subsequent layers showed improvements in the concentration ratio of hydration products in the particle contact zone, the 28-day unconfined compressive strength, and the strength retention rate after immersion in water for 48 hours.

[0385] The results indicate that the observation of profile samples after closed curing is not simply a result check, but can concentrate the insufficient retention of fine particles and the reaction products of hydration powder in the non-particle contact area, and respectively transform them into specific process adjustment actions for the subsequent consolidation layer, thereby further stabilizing the construction effect of the Gobi soil fine particle hydration consolidation reinforcement method.

[0386] Verification Example 1

[0387] This verification example illustrates the comprehensive effect of the fine-particle hydration consolidation reinforcement method for Gobi soil under complete process conditions, compared with the conventional one-time wet mixing and compaction process and the pre-laying followed by grout spraying and infiltration compaction process.

[0388] This verification example is applicable to the process verification of preparing a consolidation layer in the base layer or subbase layer of construction access roads in the Gobi region using Gobi soil on-site.

[0389] This verification example is an independent repeat verification based on Example 1, with each group of specimens being re-prepared and tested;

[0390] The Gobi soil used was from the same source as in Examples 1 to 5;

[0391] After the soil sample was air-dried naturally until the mass change between two consecutive weighings did not exceed 0.5%, plant roots, stones, and non-soil debris were removed.

[0392] The Gobi soil is crushed to a size that can pass through a 20mm square hole sieve, and then screened using a 5mm square hole sieve.

[0393] The material passing through a 5mm square hole sieve is used as fine particles of Gobi soil, while the particles retained in the 5mm square hole sieve and able to pass through a 20mm square hole sieve are used as skeleton particles.

[0394] With the total dry weight of Gobi soil fine particles and skeleton particles as 100 parts, each group used 28 parts of Gobi soil fine particles and 72 parts of skeleton particles.

[0395] The total amount of hydrated powder is 8 parts, including 3 parts quicklime, 2 parts calcium aluminate, and 3 parts slag powder;

[0396] The total water addition was 10 parts, the thickness of the consolidation layer was 100mm, the total number of compaction passes was 5, and the sealing curing conditions were 20℃±2℃ covered and sealed.

[0397] The only difference between the groups is the process route. This verification example will not break down each process step, but will instead compare the complete process route with the two conventional routes as a whole.

[0398] The complete process assembly was carried out according to the complete process conditions described in Example 1;

[0399] Specifically, spray 3 parts of water into the fine particles of Gobi soil, stir for 5 minutes during the water spraying process, let stand for 15 minutes after stopping the water spraying, and then sieve again using a 5mm square hole sieve.

[0400] After dry mixing of quicklime, calcium aluminate and slag powder for 3 minutes, add it to the fine particles of Gobi soil after double sieving, and stir for 4 minutes to allow the hydrated powder to adhere to the surface of the fine particles of Gobi soil. No water is added during the powder adsorption stage.

[0401] Mix the fine particles of Gobi soil with attached hydration powder with the skeleton particles, lay the mixture, and level it.

[0402] After leveling, the layer to be consolidated is directly subjected to two rounds of initial compaction without water replenishment.

[0403] After the initial pressure is completed, spray in 7 parts of the second stage of water, let it stand for 20 minutes, and then pressurize 3 times.

[0404] No more hydration powder is added after the re-pressing is completed;

[0405] Before covering and sealing, the surface of the layer to be consolidated is not rinsed. Instead, a polyethylene film is applied to the surface of the layer to be consolidated for covering and sealing curing.

[0406] Control group A adopted a one-time wet-mix compaction process, which is as follows: Gobi soil fine particles, skeleton particles, quicklime, calcium aluminate, slag powder and all water are added at one time and mixed for 5 minutes. After mixing, it is laid as a 100mm thick layer to be consolidated. It is compacted 5 times continuously using the same small vibratory compactor as the complete process group, and then covered and sealed for curing under the same conditions.

[0407] Control group B adopted a process of first laying and then spraying and compacting slurry. Specifically, the fine particles and skeleton particles of Gobi soil were mixed and laid as a 100mm thick layer to be consolidated. Then, 3 parts of quicklime, 2 parts of calcium aluminate, 3 parts of slag powder and 10 parts of water were mixed and stirred for 3 minutes to make a hydrated powder slurry.

[0408] The grout is injected into the pores of the layer to be consolidated by uniform surface spraying. During spraying, the grout moves back and forth along the surface of the layer to be consolidated to avoid concentrated injection.

[0409] It should be noted that the grout is sprayed onto the surface of the layer to be consolidated in two stages. After each spraying, the next spraying is carried out only after there is no obvious liquid accumulation on the surface.

[0410] After the grout is poured in, it is left to stand for 20 minutes, and then compacted 5 times continuously using a small vibratory compactor identical to the complete process group, and covered and sealed for curing under the same conditions.

[0411] The concentration ratio of hydration products in the particle contact zone was determined as follows: After 7 days of curing, 3 profile samples were cut from each group;

[0412] Three locations where the skeleton particles abut each other and the surrounding pores were selected as the particle contact area for each profile sample.

[0413] Cross-sectional photographs were taken under the same lighting conditions, at the same magnification, and at the same shooting distance.

[0414] The hydration product area is marked by the continuous, cemented, light-colored area within the interparticle pores. The reflective area of ​​the skeleton particles, the cutting dust area, and the isolated powder spots are not included in the hydration product area.

[0415] Calculated as 100% of the area of ​​hydration products in the particle contact zone / the total area of ​​hydration products in the cross-section, and the average value is taken;

[0416] In the unconfined compressive strength test, three cylindrical specimens with a diameter of 50 mm and a height of 50 mm were prepared for each group, and the test results were taken as the average value of the three specimens.

[0417] The strength retention rate after immersion in water for 48 hours is the ratio of the unconfined compressive strength after immersion in water to the unconfined compressive strength without immersion in water at the same age.

[0418] In the wet-dry cycle test, each cycle includes immersion in water for 12 hours and placement in an indoor environment of 20℃±2℃ and relative humidity of 50%±10% for 12 hours. A total of 5 cycles are performed. After the cycle, the mass of the specimen is weighed and the mass loss rate is calculated.

[0419] The maximum thickness of the identifiable slurry zone on the surface is determined by cross-sectional observation, recording the maximum depth of the surface mud-like or fine powder-rich area extending inward from the surface.

[0420] The test results are shown in Table 6;

[0421] Table 6: Comprehensive Comparison Results of Complete Process and Conventional Wet Mixing and Grouting Processes

[0422] Parameter name Complete process group Control group A: One-time wet mixing and compaction Control group B: Laying the grout first, then spraying and compacting it. Dosage of fine particles of Gobi soil (per part) 28 28 28 Dosage of skeleton particles / part 72 72 72 quicklime / part 3 3 3 calcium aluminate / part 2 2 2 Slag powder / part 3 3 3 Total water added / serving 10 10 10 Total number of compaction passes / passes 5 5 5 Concentration of hydration products in the particle contact zone / % 65.8 35.6 40.9 7d unconfined compressive strength / MPa 2.19 1.66 1.72 28-day unconfined compressive strength / MPa 3.47 2.53 2.66 Strength retention rate after immersion in water for 48 hours / % 86.5 66.9 70.8 Mass loss rate after 5 wet-dry cycles / % 2.8 6.7 5.9 Maximum thickness of the identifiable slurry zone on the surface / mm 0.7 3.8 3.1

[0423] As shown in Table 6, when the amounts of fine particles, skeleton particles, hydrated powder, total water content, laying thickness, total number of compaction passes, and closed curing conditions of Gobi soil are all the same, the concentration ratio of hydrated products in the particle contact zone of the complete process group is 65.8%, which is higher than 35.6% of control group A and 40.9% of control group B.

[0424] The results indicate that, in the complete process group, the hydration reaction products are formed more in the contact area of ​​the skeleton particles and in the pores around them, rather than being mainly distributed in the non-particle contact area or the surface area.

[0425] Control group A adopted a one-time wet mixing and compaction process. The hydrated powder came into contact with all the water during the mixing stage. Some of the hydrated powder was wetted and aggregated or reacted early before the fine particles of Gobi soil entered the contact area of ​​the skeleton particles.

[0426] The concentration of hydration products in the particle contact zone of this group was 35.6%, and the maximum thickness of the identifiable pulping zone on the surface was 3.8 mm.

[0427] Control group B adopted a process of first laying and then spraying and compacting slurry. The hydrated powder entered the pores of the layer to be consolidated in the form of slurry. The slurry easily migrated along larger pores or surface channels. The concentration ratio of hydrated products in the particle contact area was 40.9%, which was higher than that of control group A, but still lower than that of the complete process group.

[0428] In the complete process, the fine particles of Gobi soil are first pre-wetted with water and screened again, and then contacted with the hydrated powder after being mixed in a dry state.

[0429] No water is added during the powdering stage, so that the hydrated powder mainly enters the subsequent mixing and initial compaction process along with the fine particles of Gobi soil.

[0430] The initial pressure without water replenishment allows the fine Gobi soil particles carrying hydration powder to enter the contact position of the skeleton particles and the surrounding pores. The second stage of water is added after the initial pressure and after a period of rest, the pressure is repressurized to enable the hydration powder, water and fine Gobi soil particles to react near the particle contact area.

[0431] No more hydration powder is added after repressing, no rinsing is done before covering and sealing, and the covering layer is in contact with the surface of the layer to be consolidated, which helps to maintain the particle arrangement and water content after repressing.

[0432] In terms of mechanical and water resistance properties, the 28-day unconfined compressive strength of the complete process group was 3.47 MPa, which was higher than that of control group A (2.53 MPa) and control group B (2.66 MPa).

[0433] After immersion in water for 48 hours, the strength retention rate was 86.5%, which was higher than that of control group A (66.9%) and control group B (70.8%).

[0434] After 5 cycles of wet and dry drying, the mass loss rate was 2.8%, which was lower than 6.7% in control group A and 5.9% in control group B.

[0435] Under the same conditions of hydration powder dosage, total water addition and total number of compaction passes, the complete process group still achieved a high concentration ratio of hydration products in the particle contact zone, 28-day unconfined compressive strength and strength retention rate after 48 hours of immersion in water. This indicates that the process sequence between pre-wetting and screening, dry powder adsorption, initial compaction without water replenishment, second stage water stop and re-compacting, and covering and sealing curing has an impact on the consolidation effect.

[0436] The comprehensive verification results correspond to the verification results of each individual step in Examples 1 to 5, indicating that the pre-wetting and re-screening, dry powder adsorption, initial pressing without water replenishment, second-stage water-stopping re-pressing, and covering and sealing curing in the complete process route jointly affect the formation and consolidation stability of hydration products in the particle contact zone.

Claims

1. A method for enhancing the hydration and consolidation of fine particles of Gobi soil, characterized by, include: S1. Soil separation: The Gobi soil is crushed and screened to separate fine particles and skeleton particles. S2. Pre-wetting fine particles: Spray the first stage of water into the Gobi soil fine particles, while simultaneously turning the Gobi soil fine particles. After stopping the water spraying, the fine particles of Gobi soil are left to stand. The fine particles of Gobi soil that have stood are then screened again. During the screening, the aggregates that do not pass through the sieve holes are loosened and screened again. S3, Adhesive hydration powder: Hydrated lime, calcium aluminate and slag powder are mixed to form hydration powder; Add the hydrated powder to the fine Gobi soil particles that have passed through the sieve, and turn the fine Gobi soil particles and the hydrated powder over without adding water, so that the hydrated powder adheres to the surface of the fine Gobi soil particles. S4. Mixed laying: The fine particles of Gobi soil obtained in S3 are mixed with the skeleton particles obtained in S1 to obtain the soil material to be consolidated, and the soil material to be consolidated is laid into the layer to be consolidated. S5. Initial compaction without water replenishment: Initial compaction is performed on the layer to be consolidated. During the initial compaction, no water is added to the layer to be consolidated, nor is any water-containing slurry added. S6. Contact area water replenishment and repressurization: The second stage of water is sprayed into the layer to be consolidated after the initial pressurization. After the second stage of water is sprayed in, the layer to be consolidated is stopped, and then the layer to be consolidated is repressurized. S7. Sealing and curing: After the re-pressurization is completed, the layer to be consolidated is covered and sealed for curing. The surface of the layer to be consolidated is not rinsed before covering and sealing. During the covering and sealing process, the covering layer is in contact with the surface of the layer to be consolidated.

2. The method for strengthening Gobi soil through fine-particle hydration consolidation as described in claim 1, characterized in that: In S1, the fine particles of Gobi soil are the undersize material collected separately after screening; The skeleton particles are the sieve material collected separately after screening; The secondary screening in S2 uses a sieve with the same mesh size as that used in S1 to separate fine particles of Gobi soil.

3. The method for strengthening Gobi soil through fine-particle hydration consolidation as described in claim 1, characterized in that: In S2, the first stage of water is added before the fine particles and skeleton particles of Gobi soil are mixed; The amount of water added in the first stage is less than the amount of water added in the second stage; After the first water is sprayed in, the fine particles of Gobi soil are left to stand before being sieved again.

4. The method for strengthening Gobi soil through fine-particle hydration consolidation as described in claim 1, characterized in that: In S2, agglomerates that did not pass through the sieve holes during the second screening are loosened and then screened again. Aggregates that fail to pass through the sieve openings after a second sieve will not proceed to S3.

5. The method for strengthening fine-particle Gobi soil through hydration consolidation as described in claim 1, characterized in that: In S3, quicklime, calcium aluminate and slag powder are dry-mixed before the addition of fine Gobi soil particles; After the hydrated powder is added to the fine particles of Gobi soil, no additional water is added to the mixture.

6. The method for strengthening Gobi soil through fine-particle hydration consolidation as described in claim 1, characterized in that: In S3, the fine particles of Gobi soil after hydration powder adheres are sieved before entering S4, and the residue on the sieve surface is returned to S3 for re-tumbling. Fine particles of Gobi soil passing through the sieve are mixed with the skeleton particles.

7. The method for strengthening Gobi soil through fine-particle hydration consolidation as described in claim 1, characterized in that: In S4, leveling is carried out after the consolidated soil material is laid. The leveled layer to be consolidated proceeds directly to S5; After leveling and before initial compaction, do not spray the second stage of water into the layer to be consolidated.

8. The method for strengthening Gobi soil through fine-particle hydration consolidation as described in claim 1, characterized in that: In S6, the second stage of water is added after the initial pressure is completed; After the second stage of water injection, wait for the solidified layer to stop before repressurizing; No more hydration powder is added to the layer to be consolidated after the re-pressing is completed.

9. The method for strengthening Gobi soil through fine-particle hydration consolidation as described in claim 1, characterized in that: In S7, closed maintenance is carried out using a covering method; The surface of the layer to be consolidated should not be rinsed before the cover is sealed. After the cover is sealed, the cover layer comes into contact with the surface of the layer to be consolidated.

10. The method for strengthening Gobi soil through fine-particle hydration consolidation as described in claim 1, characterized in that: After the S7 sealing and curing is completed, a cross-sectional sample of the unconsolidated layer is taken. The contact area is defined as the point where adjacent skeletal particles abut against each other and the surrounding pores. The interparticle pore area in the profile sample, excluding the particle contact area, is taken as the non-particle contact area. The location where the skeleton particles abut each other and the surrounding pores in the profile sample are selected as the observation location. Record the proportion of fine particles retained in the Gobi soil within the observation location, and the proportion of the area of ​​hydrated powder reaction products in the non-particle contact zone to the total area of ​​the profile reaction products. When the proportion of fine particles retained in the Gobi soil at the observation location is lower than the fine particle retention judgment value, when re-executing the Gobi soil fine particle hydration consolidation enhancement method, extend the time for loosening the agglomerates before the S2 re-screening, or increase the number of compaction passes of the initial compaction described in S5, and correspondingly reduce the number of compaction passes of the re-compaction in S6 when increasing the number of initial compaction passes, so as to keep the total number of compaction passes unchanged. When the proportion of the area of ​​hydrated powder reaction products in the non-particle contact zone to the total area of ​​reaction products in the profile is higher than the reaction product distribution judgment value, when re-implementing the Gobi soil fine particle hydration consolidation enhancement method, the time for turning over the Gobi soil fine particles and hydrated powder in S3 should be increased, or the dwell time after the second stage of water injection in S6 should be extended.

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