Aeolian sand filler layered compaction construction method

Abstract

The invention provides an aeolian sand filler layered compaction construction method which comprises the following steps: base treatment and primary compaction: digging out a soil layer and vegetation with a preset depth in a dike base range to obtain a foundation pit, backfilling the foundation pit to a preset height by using aeolian sand, and carrying out primary compaction; paving the improved filler, namely paving the improved filler on the base platform to form a main body filling layer with a flat surface; the grid water storage comprises the steps that improved filler is piled and filled on the main body filling layer to construct a plurality of sand ridges to form grids, and water is injected into each grid; the three-stage rolling compaction comprises the following steps: sequentially carrying out pressure stabilization, vibration compaction and final compaction on the main body filling layer after the grid water storage to form a compact embankment layer; and compaction degree detection comprises the steps of carrying out compaction degree detection on the dense embankment layer, supplementing pressure when the compaction degree is unqualified, entering the next layer of improved filler paving until the compaction degree is qualified, and trimming a slope and paving a protective layer after paving to a designed elevation. After the scheme is implemented, an embankment body project is reliable in quality and stable in performance.

Description

Technical Field

[0001] This invention belongs to the field of geotechnical engineering technology, and specifically relates to a method for layered compaction of aeolian sand filler. Background Technology

[0002] Aeolian sand is widely distributed in the arid and semi-arid regions of Northwest my country. Its uniform particle size, lack of stickiness, and low moisture content make it difficult to directly compact in traditional embankment construction projects. Currently, embankment construction in these areas still generally relies on transporting clay or gravel from elsewhere as fill material, which not only incurs high transportation costs and long construction periods but also causes significant damage to the ecological environment of the soil extraction areas.

[0003] While existing technologies have explored ways to improve or compact aeolian sand, they often have significant limitations. For example, direct compaction results in loose interlayers, making the sand susceptible to erosion by wind and rain. Simply adding a modifier alone fails to create effective synergy with the overall compaction process, preventing the improvement from being fully translated into the overall strength of the fill. Conventional water spraying methods struggle to precisely control the uniform distribution and penetration depth of moisture in loose sand layers, often resulting in surface water accumulation and crusting while the lower layers remain dry, severely impacting compaction uniformity. Furthermore, rolling compaction relies heavily on experience, lacking clear parameter guidance tailored to the dynamic response characteristics of aeolian sand, making it prone to under-compaction or over-compaction leading to loosening and failing to guarantee consistently high compaction standards. Summary of the Invention

[0004] The purpose of the embodiments in this specification is to provide a method for layered compaction of aeolian sand filler.

[0005] To solve the above-mentioned technical problems, the embodiments of this application are implemented in the following way: base treatment and preliminary compaction → improved filler laying → grid water storage → three-stage rolling compaction → compaction degree detection.

[0006] This application provides a method for layered compaction of aeolian sand fill material, the method comprising:

[0007] The foundation treatment and preliminary compaction include: removing the soil layer and vegetation at a predetermined depth within the embankment foundation area to obtain the foundation pit, backfilling the foundation pit with aeolian sand to a predetermined height, and preliminary compaction to form a foundation platform with a compaction degree ≥90%.

[0008] The improved fill material paving includes: spreading the improved fill material formed by mixing aeolian sand and a modifier on the base platform, with the loose thickness controlled at 45-50cm, and forming a main fill layer of about 30cm thickness after compaction.

[0009] The grid water storage method includes: piling modified fill material on the main filling layer to construct several sand embankments to form a grid, injecting water into each grid, controlling the moisture content of the modified fill material in the grid within the range of 10% ± 2%, and then letting it stand for 2-3 hours to allow the water to penetrate evenly.

[0010] The three-stage compaction process includes: sequentially stabilizing, vibratory compaction, and final compaction of the main fill layer after grid water storage to form a dense embankment layer. The vibratory compaction is carried out by using a vibratory roller with a vibration frequency of 30-40Hz and an amplitude of 0.4-0.8mm for 4-6 passes.

[0011] Compaction testing includes: testing the compaction of the dense embankment layer; if the compaction is not up to standard, additional compaction is carried out until the compaction is up to standard before proceeding to the next layer of improved fill material; after paving to the design elevation, the slope is trimmed and a protective layer is laid.

[0012] In one embodiment, the modifier is silt or clay;

[0013] The improved filler material is aeolian sand mixed with silt or clay at a volume ratio of 10%-20%.

[0014] In one embodiment, the modifier is a gel material;

[0015] The improved filler is aeolian sand mixed with gel material at a mass ratio of 2%-4%.

[0016] In one embodiment, the gelling material is cement or lime.

[0017] In one embodiment, in the grid water storage, after water is injected, the water penetration depth needs to be checked by digging a pit. If the lower layer is dry, water is added again until the bottom of the main filling layer reaches a state of slight water seepage, and the water injection is completed.

[0018] In one embodiment, the main fill layer after grid water storage is subjected to sequential pressure stabilization, vibration pressure, and final pressure, including:

[0019] Stabilize the compaction: Turn off the vibration function of the vibratory roller, perform static compaction 1-2 times to initially stabilize the layer;

[0020] Vibratory compaction: Turn on the vibration function of the vibratory roller and compact it at a uniform speed for 4-6 passes under the set vibration parameters to achieve main body compaction;

[0021] Final compaction: Turn off the vibration function of the vibratory roller again and perform static compaction 1-2 times.

[0022] In one embodiment, during vibratory compaction, the vibration parameters of the vibratory roller are: a vibration frequency of 30-40Hz, an amplitude of 0.4-0.8mm, a travel speed of 2-4km / h, and the overlap width of adjacent compaction zones is not less than 1 / 3 of the rolling width, and the overlap length between two compaction zones is not less than 20 meters.

[0023] In one embodiment, the compaction degree of the dense embankment layer is tested using a ring cutter method or a nuclear density meter.

[0024] In one embodiment, the compaction degree of the dense embankment layer is tested every 1000m. 2 At least two points should be randomly inspected, with an area of ​​less than 1000 square meters. 2 There should be no fewer than 2 points on each floor.

[0025] As can be seen from the technical solutions provided in the embodiments of this specification above, this solution significantly optimizes the particle size distribution and cementing properties of aeolian sand by incorporating clay or cementing materials, completely solving the inherent defect of aeolian sand being difficult to compact due to its lack of cohesion. This method effectively avoids the necessity of long-distance transportation of clay or stone, not only significantly reducing the cost of engineering materials but also significantly reducing the environmental damage caused by the extraction and borrowing of soil, demonstrating outstanding economic and environmental benefits. This technology not only eliminates the hidden dangers of mobile sand sources that originally harmed the environment but also successfully transforms them into embankment engineering entities that benefit the local area, fully embodying the advanced concept of resource recycling. This has important demonstrative significance for areas facing severe desertification and can powerfully drive the implementation of more sand-based desertification control projects in the region. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments or prior art of this specification, the drawings used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this specification. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 A schematic diagram of the construction method for the layered compaction of aeolian sand filler provided in this application. Detailed Implementation

[0028] To enable those skilled in the art to better understand the technical solutions in this specification, the technical solutions in the embodiments of this specification will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this specification, and not all embodiments. Based on the embodiments in this specification, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of this specification.

[0029] In the following description, specific details such as particular system architectures and techniques are set forth for illustrative purposes and not for limitation, in order to provide a thorough understanding of the embodiments of this application. However, those skilled in the art will understand that this application may also be implemented in other embodiments without these specific details. In other instances, detailed descriptions of well-known systems, apparatuses, circuits, and methods have been omitted so as not to obscure the description of this application with unnecessary detail.

[0030] Various modifications and variations can be made to the specific embodiments described in this application without departing from the scope or spirit of this application, as will be apparent to those skilled in the art. Other embodiments derived from this application will be obvious to those skilled in the art. This application specification and embodiments are merely exemplary.

[0031] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0032] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0033] Reference Figure 1 The diagram illustrates a flow chart of the layered compaction construction method for aeolian sand filler provided in this application. The layered compaction construction method for aeolian sand filler provided in this application is applicable to desert and semi-desert regions.

[0034] like Figure 1 As shown, the layered compaction construction method for aeolian sand filler may include:

[0035] Step 1, Foundation Treatment and Preliminary Compaction, includes: removing the soil layer and vegetation at a predetermined depth within the embankment foundation area to obtain the foundation pit, backfilling the foundation pit with aeolian sand to the predetermined height, and preliminarily compacting it to form a foundation platform with a compaction degree ≥90%.

[0036] Specifically, the preset depth and preset height can be set according to actual needs, for example, preset depth ≥ 0.3 meters and preset height ≥ 0.6 meters.

[0037] The excavated soil and vegetation include organic soil rich in plant roots and humus, uncompacted and loose silty sand, collapsible soil, etc.

[0038] The aeolian sand used for backfilling foundation pits can be either raw sand readily available in desert areas or improved sand that has been modified from the raw sand.

[0039] Preliminary compaction of the aeolian sand backfilled in the foundation pit can be achieved using a vibratory roller for static compaction. Depending on the actual situation, static compaction can be performed 1-2 times to ensure the formation of a foundation platform with a compaction degree ≥90%.

[0040] Step 2, Improved filler laying, includes: spreading the improved filler formed by mixing aeolian sand and amendment on the base platform, with the loose thickness controlled at 45-50cm, and forming a main filler layer of about 30cm thickness after compaction.

[0041] In one embodiment, the modifier is silt or clay; the modified filler is aeolian sand mixed into silt or clay at a volume ratio of 10%-20%.

[0042] In one embodiment, the modifier is a gelling material; the modifier filler is aeolian sand added to the gelling material at a mass ratio of 2%-4%. The gelling material is cement or lime.

[0043] When making modified filler, after the aeolian sand is mixed with the modifier, it can be mixed ≥3 times with a road mixer until it is evenly mixed.

[0044] To improve the filler material, the optimal dosage of cohesive soil, fly ash, or cement is determined based on compaction tests to improve the particle size distribution and cementing performance of aeolian sand.

[0045] Specifically, dump trucks are used to transport the prepared modified fill material to the base platform treated in step one. Then, the dump trucks unload the material evenly across the entire width of the embankment, perpendicular to the embankment line. This avoids the fill material from accumulating in one place, reducing subsequent paving work and ensuring the initial uniformity of the fill material distribution. Next, bulldozers or graders are used to spread and initially level the unloaded material pile according to the designed loose-lay thickness. The loose-lay thickness should be controlled at 45-50cm, resulting in approximately 30cm after compaction. When paving to the slopes on both sides of the embankment, an additional 0.5 meters is added to the outer side. This ensures that the fill material in the slope area retains sufficient density and the designed slope after compaction, preventing "slope deficiencies" or loose edges, and guaranteeing the overall stability and compaction quality of the slope. Finally, a grader is used again to finely level and shape the paved surface, forming a smooth, uniformly thick main fill layer.

[0046] Step 3, grid water storage, includes: piling modified filler material on the main filling layer to construct several sand ridges to form a grid, injecting water into each sand ridge, and controlling the moisture content of the modified filler material in the grid within the range of 8%-12%, and then letting it stand for 2-3 hours to allow the water to penetrate evenly.

[0047] After water injection, the depth of water penetration needs to be checked by digging a pit. If the lower layer is dry, water should be added until the bottom of the main filling layer reaches a state of slight water seepage, thus completing the water injection.

[0048] Specifically, on the main fill layer laid in step two, sand embankments are constructed manually or using small machinery, using modified filler material. The height of the sand embankments can be set according to actual needs, for example, 15 centimeters high. Several sand embankments are interconnected to form closed grids. By constructing sand embankments, the entire main fill layer is divided into multiple smaller, independent water storage units, preventing injected water from overflowing and ensuring that water is confined within the grid and seeps vertically downwards.

[0049] Then, water is injected into each grid cell using a water pipe until the upper layer is fully saturated and the lower layer is partially saturated. This results in a thin layer of water visible on the surface, but water has penetrated into the middle layer, while the bottom layer remains moist but not fully saturated. Injecting water makes it easier to compact the material during subsequent rolling.

[0050] After stopping water injection, allow the water to stand within the grid for 2-3 hours. This allows sufficient and even downward penetration time, ensuring a uniform moisture content across the entire loose-laid thickness. This prevents a muddy surface and a dry lower layer.

[0051] In addition, after allowing the water to seep in, test pits should be randomly dug in several grids to observe the actual depth of water penetration. If the lower layer (especially near the bottom) of the improved filler is still dry, water should be added immediately until the water penetrates to the bottom of the main filler layer and reaches a state of micro-permeability.

[0052] After confirming that the moisture has penetrated evenly, use a grader to lightly scrape the surface. Scrape away the grid and excess water on the surface, as well as the very thin layer that may have become too soft due to water saturation, to create a smooth, evenly moist working surface.

[0053] After water is stored in the grid, the average moisture content of the entire main filling layer is kept within the optimal range of 10% ± 2%.

[0054] By meticulously implementing gridding, segmented permeability, and process inspection of the main fill layer, the previously uncontrollable moisture content variable has been transformed into a core parameter that can be precisely managed and evenly distributed. This is a crucial prerequisite for ensuring successful subsequent compaction and achieving high compaction.

[0055] Step four, three-stage compaction, includes: sequentially stabilizing, vibrating, and final compacting the main fill layer after grid water storage to form a dense embankment layer. The vibrating compaction is carried out by using a vibratory roller with a vibration frequency of 30-40Hz and an amplitude of 0.4-0.8mm for 4-6 passes.

[0056] Through three-stage compaction, loose modified fill material with optimized moisture content can be transformed into a high-strength, high-density embankment.

[0057] The main fill layer after grid water storage undergoes sequential pressure stabilization, vibration pressure, and final pressure testing, including:

[0058] Stabilization: Turn off the vibration function of the vibratory roller and perform static compaction 1-2 times to initially stabilize the layer. Stabilization is used to initially compress the loose fill layer to form a stable working surface with a certain initial bearing capacity, preventing pushing and wavy deformation during subsequent vibratory compaction. In addition, it can also seal surface pores, reducing the upward movement of fine particles and energy loss during vibratory compaction.

[0059] Vibratory compaction: Activate the vibration function of the vibratory roller and compact it at a uniform speed for 4-6 passes under the set vibration parameters to achieve the desired compaction. The vibration parameters are: vibration frequency of 30-40Hz, amplitude of 0.4-0.8mm, and travel speed of 2-4km / h. The overlap width between adjacent compaction zones should be no less than 1 / 3 of the rolling width, and the overlap length between consecutive compaction zones should be no less than 20 meters. The overlap width of adjacent compaction zones (no less than 1 / 3 of the rolling width) ensures that the entire working surface is compacted without any gaps in the transverse direction. The overlap length of consecutive compaction zones (no less than 20 meters) eliminates compaction blind spots at the joints of sections, ensuring uniform longitudinal compaction. In this stage, high-frequency vibration causes the sand particles to move, overcoming inter-particle friction and rearranging them to their densest state, thus achieving the designed compaction degree.

[0060] Final compaction: Turn off the vibratory roller's vibration function again and perform static compaction 1-2 times. On the already compacted surface, continue static compaction 1-2 times to eliminate the vibratory roller marks left during the vibration compaction stage, resulting in a smooth and aesthetically pleasing surface. Additionally, it can further close any tiny cracks that may have been caused by vibration, forming a smooth, dense sealing layer and enhancing the embankment's resistance to wind and water erosion.

[0061] Step 5, compaction test, including: testing the compaction of the dense embankment layer. If the compaction is not up to standard, additional compaction is carried out until the compaction is up to standard before proceeding to the next layer of improved fill material. After the embankment is laid to the design elevation, the slope is trimmed and a protective layer is laid.

[0062] Among them, the compaction degree of dense embankment layers is tested using the ring cutter method or nuclear density meter.

[0063] Among them, when conducting compaction tests on the dense embankment layer, every 1000m 2 At least two points should be randomly inspected, with an area of ​​less than 1000 square meters. 2 There should be no fewer than 2 points on each floor.

[0064] Specifically, on the compacted embankment layer in step four, based on every 1000m... 2 At least two points should be randomly inspected, with an area of ​​less than 1000 square meters. 2Following the principle of having no fewer than two testing points per layer, the specific locations for this inspection are determined using a grid method or a random point distribution method, and marked with markers (such as flags or spray paint). This ensures that the distribution of testing points scientifically and comprehensively represents the compaction quality of the entire work surface.

[0065] When using the ring cutter method for testing: at the marked point, a ring cutter of known volume is vertically driven into the compacted layer, the undisturbed soil sample is taken out, weighed, dried, and its dry density is calculated.

[0066] When using a nuclear density meter for testing: at the marked point, place the radioactive source probe of the nuclear density meter close to or insert it into the surface of the packing material, and operate according to the prescribed procedure. The instrument will directly and quickly display the wet density and moisture content of that point, and then calculate the dry density.

[0067] The measured dry density is compared with the maximum dry density of the modified filler to obtain the compaction degree. The qualified compaction degree threshold can be set according to actual needs, such as 95%, that is, the calculated compaction degree is ≥95%, which is qualified. Record the data of all test points.

[0068] If all test points pass, the compaction process for this layer is complete. After cleaning the site, the next layer can be started in a new cycle.

[0069] If any test point fails to meet the requirements, expand the testing area around that point to investigate the cause (such as uneven moisture content, insufficient compaction passes, excessively thick paving layers, etc.). Based on the cause, develop and implement a targeted compaction plan until all test points meet the requirements.

[0070] Once all fill layers are completed and the embankment reaches the design elevation, the overall slope is trimmed (including removing the 0.5m portion of the excess fill), and a protective layer (such as a concrete grid, grass slope protection, or gravel facing) is laid according to the design. This forms the final stable embankment.

[0071] The layered compaction method for aeolian sand filler provided in this application solves the problems of aeolian sand being difficult to compact, having poor stability, high cost of transporting filler material from other areas, and causing ecological damage, thereby achieving sand control and sustainable development.

[0072] The layered compaction method for aeolian sand filler provided in this application improves the aeolian sand by incorporating clay or cementing materials, significantly optimizing its particle size distribution and cementing properties, and completely solving the inherent defect of aeolian sand being difficult to compact due to its lack of cohesion. This method effectively avoids the necessity of long-distance transportation of clay or stone, not only significantly reducing engineering material costs but also significantly reducing the environmental damage caused by excavating and borrowing soil, demonstrating outstanding economic and environmental benefits. This technology not only eliminates the potential threat of mobile sand sources that would otherwise harm the environment but also successfully transforms them into a beneficial embankment engineering entity, fully embodying the advanced concept of resource recycling. This has important demonstrative significance for areas facing severe desertification and can powerfully drive the implementation of more sand-based desertification control projects in the region.

[0073] The layered compaction method for aeolian sand filler provided in this application was applied to the dike of the Babusha Water Source Project in Gansu Province. Actual test results show that the maximum dry density of the improved filler increased to 1.85 g / cm³. 3 Approximately 1.72 g / cm³ before improvement 3 The optimal moisture content was increased from 4% to 9%, significantly improving compaction characteristics. After completion, the compaction degree of the embankment reached over 96% (standard compaction), with some sections even exceeding 98%, far exceeding the specifications. Comparing the indicators before and after the improvement, the unconfined compressive strength of the aeolian sand fill increased by 20%–30% at 7 days, and the apparent deformation modulus increased by approximately 25%, indicating a significant improvement in the overall strength and stability of the embankment. Comparative tests in the field test section also verified this: before the improvement, the in-situ sand could only achieve about 90% compaction under the same rolling conditions, while after the improvement, it easily exceeded 95%, fully demonstrating the effectiveness of the invention. The embankment was monitored and inspected after construction. Settlement observation data showed that the embankment settlement rate was relatively fast during construction, stabilizing after 3 months, with the total settlement less than the design allowable value of 0.1m, indicating good structural stability. Several strong winds have not damaged the constructed embankment. In summary, the embankment project achieved reliable quality and stable performance after the implementation of this invention.

[0074] It should be noted that the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0075] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on describing the differences from other embodiments. In particular, the system embodiments are basically similar to the method embodiments, so the description is relatively simple; relevant parts can be referred to the descriptions in the method embodiments.

Claims

1. A method for layered compaction of aeolian sand filler, characterized in that, The method includes: The foundation treatment and preliminary compaction include: removing the soil layer and vegetation at a predetermined depth within the embankment foundation area to obtain the foundation pit, backfilling the foundation pit with aeolian sand to a predetermined height, and preliminary compaction to form a foundation platform with a compaction degree ≥90%. The improved fill material paving includes: spreading the improved fill material formed by mixing aeolian sand and a modifier on the base platform, with the loose thickness controlled at 45-50cm, and forming a main fill layer of about 30cm thickness after compaction. The grid water storage method includes: piling the modified filler on the main filling layer to construct several sand embankments to form a grid, injecting water into each grid, and controlling the moisture content of the modified filler in the grid within the range of 10% ± 2%, and then letting it stand for 2-3 hours to allow the water to penetrate evenly. The three-stage compaction process includes: sequentially stabilizing, vibratory compaction, and final compaction of the main fill layer after grid water storage to form a dense embankment layer. The vibratory compaction is carried out by using a vibratory roller with a vibration frequency of 30-40Hz and an amplitude of 0.4-0.8mm for 4-6 passes. The compaction test includes: testing the compaction of the dense embankment layer; if the compaction is not up to standard, additional compaction is carried out until the compaction is up to standard before proceeding to the next layer of improved fill material; after the layer is laid to the design elevation, the slope is trimmed and a protective layer is laid.

2. The method for layered compaction of aeolian sand filler according to claim 1, characterized in that, The amendment is silt or clay; The improved filler is aeolian sand mixed with silt or clay at a volume ratio of 10%-20%.

3. The method for layered compaction of aeolian sand filler according to claim 1, characterized in that, The modifier is a gel material; The improved filler is aeolian sand mixed into the gel material at a mass ratio of 2%-4%.

4. The method for layered compaction of aeolian sand filler according to claim 3, characterized in that, The gel material is cement or lime.

5. The method for layered compaction of aeolian sand filler according to claim 1, characterized in that, In the grid water storage, after water is injected, the water penetration depth needs to be checked by digging a pit. If the lower layer is dry, water is added again until the bottom of the main filling layer reaches a slightly permeable state, and the water injection is completed.

6. The method for layered compaction of aeolian sand filler according to claim 1, characterized in that, The process of sequentially stabilizing, vibrating, and finalizing the main fill layer after grid water storage includes: Stabilize the compaction: Turn off the vibration function of the vibratory roller, perform static compaction 1-2 times to initially stabilize the layer; Vibratory compaction: Turn on the vibration function of the vibratory roller and compact it at a uniform speed for 4-6 passes under the set vibration parameters to achieve main body compaction; Final compaction: Turn off the vibration function of the vibratory roller again and perform static compaction 1-2 times.

7. The method for layered compaction of aeolian sand filler according to claim 6, characterized in that, In the vibratory compaction process, the vibration parameters of the vibratory roller are: vibration frequency of 30-40Hz, amplitude of 0.4-0.8mm, travel speed of the vibratory roller of 2-4km / h, and the overlap width of adjacent compaction zones is not less than 1 / 3 of the rolling width, and the overlap length of two consecutive compaction zones is not less than 20 meters.

8. The method for layered compaction of aeolian sand filler according to claim 1, characterized in that, The compaction degree of the dense embankment layer is tested using the ring cutter method or a nuclear density meter.

9. The method for layered compaction of aeolian sand filler according to claim 1, characterized in that, When performing compaction testing on the dense embankment layer, every 1000m... 2 At least two points should be randomly inspected, with an area of ​​less than 1000 square meters. 2 There should be no fewer than 2 points on each floor.

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