Strength prediction model construction method based on stabilized soil micro-pore structure

Abstract

The invention discloses a strength prediction model construction method based on a solidified soil micro-pore structure, and relates to the technical field of dredged sludge solidification construction.The strength prediction model construction method based on the solidified soil micro-pore structure comprises the steps that sludge, rice hull ash and carbide slag are mixed according to a preset proportion, and a mixture is obtained; adding water into the mixture and curing to a preset age to obtain a cylindrical sample; performing unconfined compressive strength test on the cylindrical sample to obtain a damaged sample; cutting out a section center 5 mm * 5 mm area from the destroyed sample, and extracting the porosity; establishing a strength prediction model according to the mixing amount of the rice hull ash, the mixing amount of the carbide slag, the preset age and the porosity; according to the invention, the strength prediction model construction method based on the solidified soil micro-pore structure is established, so that the strength of the sludge solidified soil is predicted. Theoretical guidance and parameter optimization basis are provided for sludge solidification treatment engineering, and theoretical basis is provided for resource utilization of dredged sludge.

Description

Technical Field

[0001] The present invention relates to the technical field of dredged sludge solidification construction, and in particular to a method for constructing a strength prediction model based on the microscopic pore structure of solidified soil. Background Art

[0002] In dredging projects, silt solidification is a critical step in ensuring project stability and environmental safety. Traditional methods rely on a single solidifying agent (such as cement or lime) or empirically designed mixes. This results in high material costs and low solidification efficiency, limiting the reliability and economic viability of dredged silt solidification in engineering applications. Summary of the Invention

[0003] The main purpose of this invention is to propose a method for constructing a strength prediction model based on the microscopic pore structure of solidified soil, aiming to provide a theoretical basis for the resource utilization of dredged silt.

[0004] To achieve the above object, the present invention proposes a method for constructing a strength prediction model based on the microscopic pore structure of solidified soil, wherein the raw materials of the solidified soil include 100 parts by mass of silt, 10-20 parts by mass of rice husk ash and 5-9 parts by mass of carbide slag;

[0005] The method for constructing a strength prediction model based on the microscopic pore structure of solidified soil includes:

[0006] Mixing the sludge, the rice husk ash and the carbide slag in a preset ratio to obtain a mixture;

[0007] adding water to the mixture and curing it to a predetermined age to obtain a cylindrical specimen;

[0008] Performing an unconfined compressive strength test on the cylindrical specimen to obtain a failure specimen;

[0009] A 5 mm*5 mm area in the center of the cross section is cut out from the damaged sample, and the porosity is extracted;

[0010] Establishing the strength prediction model based on the amount of rice husk ash, the amount of carbide slag, the preset age and porosity;

[0011] The intensity prediction model is:

[0012] Q=z0+a*x+b*y+c*x 2 +d*y 2 +f*x*y

[0013] Wherein, the z0, a, b, c and f are different preset regression coefficients, x is the preset age, and y is the dosage of the rice husk ash.

[0014] In one embodiment, the strength prediction model is Q = -72.8 + 38.93*T + 46.69*a0 + (-0.69)*T 2 +(-1.66)*a0 2 +0.08*T*a0.

[0015] In one embodiment, the step of mixing the sludge, the rice husk ash, and the carbide slag in a preset ratio to obtain the mixture comprises:

[0016] 100 parts by mass of the dry dredged sludge, 10 to 20 parts by mass of the rice husk ash and 7 parts by mass of the carbide slag are uniformly mixed to obtain a plurality of mixtures with different proportions.

[0017] In one embodiment, the step of adding water to the mixture and curing it to a predetermined age to obtain a cylindrical sample comprises:

[0018] The mixtures with different proportions were cured for 7 days, 14 days and 28 days respectively, and then the unconfined compressive strength was tested and the porosity was analyzed.

[0019] In one embodiment, the porosity=number of porous pixels / total number of pixels×100%.

[0020] In one embodiment, the porosity of the nanopores of the rice husk ash is φ, 20%≤φ≤40%.

[0021] In one embodiment, the specific surface area of the rice husk ash is SSA, 200m 2 / g≤SSA≤500m 2 / g.

[0022] In one embodiment, the content of SiO2 in the rice husk ash is A1, A1≥85%, and the content of CaO in the carbide slag is B1, B1≥60%.

[0023] In one embodiment, the CaO content in the carbide slag is B2, 65%≤B2≤70%; the SiO2 content in the carbide slag is C, 1%≤C≤2%; and the Al2O3 content in the carbide slag is D, 1.5%≤D≤2.5%.

[0024] In one embodiment, the content of SiO2 in the rice husk ash is A2, 90%≤A2≤95%; the content of Fe2O3 in the rice husk ash is E, 0.5%≤E≤1%.

[0025] The technical solution of the present invention achieves the prediction of the strength of silt-solidified soil by establishing a strength prediction model construction method based on the microscopic pore structure of solidified soil. The method uses silt, rice husk ash and carbide slag as raw materials, mixes them according to a preset ratio and cures them to a specific age. Strength data is then obtained through unconfined compressive strength testing. Microporosity parameters are simultaneously extracted from the failure specimens. Finally, a multivariate nonlinear prediction model is established that includes the rice husk ash content, carbide slag content, preset age and porosity. Because the model considers the correlation between the three dimensions of material composition, curing conditions and microstructure, it overcomes the limitations of traditional methods that rely on a single curing agent or empirical ratio design, significantly reducing material costs and improving curing efficiency. In addition, by introducing microscopic pore structure parameters, a quantitative relationship between material ratio, curing age and macroscopic strength is established, making strength prediction more scientific and reliable, providing theoretical guidance and parameter optimization basis for silt solidification treatment projects, and providing a theoretical basis for the resource utilization of dredged silt. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying any creative work.

[0027] Figure 1 A schematic structural diagram of an embodiment of a method for constructing a strength prediction model based on the microscopic pore structure of solidified soil provided by the present invention;

[0028] Figure 2 A graph showing the relationship between the strength of carbide slag soil, carbide slag content, and curing age involved in the present invention;

[0029] Figure 3 The present invention relates to a relationship diagram of the unconfined compressive strength of rice husk ash calcium carbide slag soil at different rice husk ash dosages;

[0030] Figure 4 This is a schematic diagram of the fitting curve of the unconfined compressive strength and the rice husk ash content at different curing ages involved in the present invention;

[0031] Figure 5 This is a relationship diagram of the unconfined compressive strength of rice husk ash calcium carbide slag at different curing ages involved in the present invention;

[0032] Figure 6 This is a relationship diagram of the ultimate strain of rice husk ash calcium carbide slag at different curing ages involved in the present invention;

[0033] Figure 7A model diagram of the actual measurement of the unconfined compressive strength of rice husk ash calcium carbide slag soil involved in the present invention;

[0034] Figure 8 A strength model diagram of rice husk ash calcium carbide slag soil according to the present invention;

[0035] Figure 9 This is a schematic diagram of SEM analysis results showing the effect of rice husk ash dosage on the microstructure of solidified soil according to the present invention;

[0036] Figure 10 This is a schematic diagram of SEM analysis results of the microstructure of rice husk ash carbide slag solidified soil changing with age;

[0037] Figure 11 This is a schematic diagram of the microscopic evolution mechanism model of rice husk ash carbide slag solidified sludge involved in the present invention.

[0038] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0039] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0040] It should be noted that if the embodiments of the present invention involve directional indications (such as up, down, left, right, front, back, etc.), the directional indications are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture. If the specific posture changes, the directional indications will also change accordingly.

[0041] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present invention, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited to "first" and "second" may explicitly or implicitly include at least one of such features. In addition, if "and / or" or "and / or" appears in the full text, its meaning includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or solutions that satisfy both A and B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0042] In dredging projects, silt solidification is a critical step in ensuring project stability and environmental safety. Traditional methods rely on a single solidifying agent (such as cement or lime) or empirically designed mixes. This results in high material costs and low solidification efficiency, limiting the reliability and economic viability of dredged silt solidification in engineering applications.

[0043] In order to solve this technical problem, the present invention provides a rice husk ash and carbide slag composite curing composition and a preparation method thereof.

[0044] See also Figure 1 In one embodiment of the present invention, the raw materials of the solidified soil include 100 parts by mass of silt, 10-20 parts by mass of rice husk ash and 5-9 parts by mass of carbide slag;

[0045] The method for constructing a strength prediction model based on the microscopic pore structure of solidified soil includes:

[0046] Step S10, mixing the sludge, the rice husk ash and the carbide slag according to a preset ratio to obtain a mixture;

[0047] Step S20, adding water to the mixture and curing it to a preset age to obtain a cylindrical sample;

[0048] Step S30, performing an unconfined compressive strength test on the cylindrical specimen to obtain a failure specimen;

[0049] Step S40, cutting out a 5 mm*5 mm area in the center of the cross section from the failure sample and extracting the porosity;

[0050] Step S50, establishing the strength prediction model based on the amount of the rice husk ash, the amount of the carbide slag, the preset age and the porosity;

[0051] The intensity prediction model is:

[0052] Q=z0+a*x+b*y+c*x 2 +d*y 2 +f*x*y

[0053] Wherein, the z0, a, b, c and f are different preset regression coefficients, x is the preset age, and y is the dosage of the rice husk ash.

[0054] Specifically, step S10 pre-treats the sludge, including sieving to remove large particles of impurities, controlling the moisture content, etc. Then, the sludge, rice husk ash, and carbide slag are placed in a mixing device according to a preset mass ratio and fully mixed to ensure mixing uniformity.

[0055] Step S20: Add an appropriate amount of water to the mixed material. After adding water, stir the mixture again for 3-5 minutes to allow the components to fully react. The wet mix is then filled into a cylindrical mold in three layers. Each layer is compacted 25 times using standard compaction equipment to ensure uniform density.

[0056] After forming, the specimens must be cured under standard curing conditions (a temperature of 20 ± 2°C and a relative humidity of 95% or higher). Curing is performed to the following preset age periods: 7 days, 14 days, and 28 days. During curing, humidity conditions should be checked daily to ensure that the specimens do not dry out or crack.

[0057] Step S30: After the sample reaches a preset age, it is taken out from the curing environment and both ends of the sample are cut flat using precision cutting equipment to ensure that the end surface flatness error is less than 0.02 mm and the height to diameter ratio is 2:1.

[0058] Subsequently, the unconfined compressive strength test was performed using an unconfined compressive strength tester. During the test, the loading rate was controlled at 1-2 mm / min until the specimen failed. The maximum load value, F (N), was recorded, and the unconfined compressive strength was calculated using the formula q = F / A, where A is the cross-sectional area of the specimen (mm²). Three replicates were prepared for each mix and age, and the average value was used as the final strength result.

[0059] After the test is completed, the damaged specimens are selected for subsequent microstructural analysis. The damaged specimens should remain intact to avoid secondary damage to ensure the accuracy of the microstructural analysis.

[0060] In step S40, a cutting device is used to cut a small sample of 5 mm*5 mm from the center of the cross section of the damaged sample to prevent the introduction of new cracks or changes in the original microstructure during the cutting process.

[0061] In step S50, a multivariate nonlinear regression method is used to construct a silt-stabilized soil strength prediction model based on the aforementioned experimental data.

[0062] Through the strength prediction model established above, the unconfined compressive strength of silt-stabilized soil can be accurately predicted based on the given rice husk ash content, carbide slag content, curing age and micro-porosity, providing theoretical guidance and parameter optimization basis for silt solidification treatment projects.

[0063] The present invention achieves the prediction of the strength of silt-solidified soil by establishing a strength prediction model construction method based on the microscopic pore structure of solidified soil. The method uses silt, rice husk ash and carbide slag as raw materials, mixes them according to a preset ratio and cures them to a specific age. Strength data is then obtained through unconfined compressive strength testing. Microporosity parameters are simultaneously extracted from the failure specimens. Finally, a multivariate nonlinear prediction model is established that includes the rice husk ash content, carbide slag content, preset age and porosity. Because the model takes into account the correlation between the three dimensions of material composition, curing conditions and microstructure, it overcomes the limitations of traditional methods that rely on a single curing agent or empirical ratio design, significantly reducing material costs and improving curing efficiency. In addition, by introducing microscopic pore structure parameters, a quantitative relationship between material ratio, curing age and macroscopic strength is established, making strength prediction more scientific and reliable, providing theoretical guidance and parameter optimization basis for silt solidification treatment projects, and providing a theoretical basis for the resource utilization of dredged silt.

[0064] In one embodiment of the present invention, the strength prediction model is Q = -72.8 + 38.93*T + 46.69*a0 + (-0.69)*T 2 +(-1.66)*a0 2 +0.08*T*a0.

[0065] In one embodiment of the present invention, the step of mixing the sludge, the rice husk ash and the carbide slag in a preset ratio to obtain the mixture comprises:

[0066] Step S11: Evenly mix 100 parts by mass of the dry dredged sludge, 10 to 20 parts by mass of the rice husk ash, and 7 parts by mass of the carbide slag to obtain a plurality of mixtures with different proportions.

[0067] In one embodiment of the present invention, the step of adding water to the mixture and curing it to a predetermined age to obtain a cylindrical sample includes:

[0068] In step S21 , the mixtures with different proportions are cured for 7 days, 14 days, and 28 days respectively, and then the unconfined compressive strength is tested and the porosity is analyzed.

[0069] In one embodiment of the present invention, the porosity=number of pore pixels / total number of pixels×100%.

[0070] In one embodiment of the present invention, the porosity of the nanopores of the rice husk ash is φ, 20%≤φ≤40%.

[0071] Specifically, it was measured by thermogravimetric analysis (TGA), The rice husk ash can absorb 23.7% of water by mass at a relative humidity of 95%, and the sustained release rate reaches 82% during the 28-day curing period. The interface binding energy between CSH gel and rice husk ash in the sample is 2.1nN / nm, which is higher than The sample was improved by 160%.

[0072] In one embodiment of the present invention, the specific surface area of the rice husk ash is SSA, 200m 2 / g≤SSA≤500m 2 / g.

[0073] At 7% carbide slag content, when SSA is increased from 150m 2 / g increased to 200m 2 / g, the UCS value jumped from 420kPa to 580kPa in 28 days; when SSA reached 500m 2 / g, the UCS value can reach 820kPa, but it continues to increase to 550m 2 / g, the strength dropped to 780kPa. Scanning electron microscopy showed that SSA = 350m 2 / g sample has a CSH gel filling rate of 82% and a pore tortuosity coefficient of 4.7, which is significantly better than that of samples with low specific surface area. Moreover, after 10 freeze-thaw cycles, SSA = 200m 2 The mass loss rate of the sample is 3.2% and the SSA is 500m 2 / g sample is only 1.8%, showing better structural stability.

[0074] In one embodiment of the present invention, the content of SiO2 in the rice husk ash is A1, A1≥85%, and the content of CaO in the carbide slag is B1, B1≥60%.

[0075] In one embodiment of the present invention, the CaO content in the carbide slag is B2, 65%≤B2≤70%; the SiO2 content in the carbide slag is C, 1%≤C≤2%; and the Al2O3 content in the carbide slag is D, 1.5%≤D≤2.5%.

[0076] In one embodiment of the present invention, the content of SiO2 in the rice husk ash is A2, 90%≤A2≤95%; the content of Fe2O3 in the rice husk ash is E, 0.5%≤E≤1%.

[0077] As a verification example, silt was collected from the bottom of a lake. The basic physical indicators of the silt are shown in the following table:

[0078]

[0079] Rice husk ash and carbide slag are used as sludge solidification materials. Rice husk ash is made from rice husks produced by sintering at around 600°C and contains 90% SiO2. Carbide slag is primarily composed of CaO, which accounts for 67.87% of the total mass. The chemical composition of rice husk ash and carbide slag is shown in the table below:

[0080] sample CaO <![CDATA[SiO2]]> <![CDATA[Fe2O3]]> <![CDATA[Al2O3]]> MgO carbide slag 67.87 1.55 0.48 1.96 0 Rice husk ash 0.83 91.68 0.73 0.23 0.12

[0081] The experimental design was as follows: using silt soil prepared at the optimal moisture content as the control sample, five groups of carbide slag single-addition test groups were set up, with the addition gradient of 3%, 5%, 7%, 9%, and 11% (based on the dry soil mass, the same below); on this basis, five rice husk ash compounding ratios (0%, 5%, 10%, 15%, and 20%) were configured under each carbide slag addition. The test indicators included unconfined compressive strength at 7 days, 14 days, and 28 days, and the microstructural morphology was observed using scanning electron microscopy.

[0082] (1) Specimen preparation and maintenance:

[0083] The specific preparation process is as follows: first, the original silt sample is dried and crushed, and passed through a 2mm standard sieve for later use; then, according to the established test plan, the pretreated dry soil, calcium carbide slag and rice husk ash and other raw materials are weighed, fully mixed, and an appropriate amount of distilled water is added to adjust to the optimal moisture content and stirred evenly. The sample is prepared according to the maximum dry density by the compaction method, wherein the optimal moisture content and maximum dry density parameters are predetermined by the standard compaction test; the sample is formed using a 50mm×100mm cylindrical test mold. After the sample is compacted and formed, it is left to stand for 24 hours for preliminary curing and then demolded. A thin layer of vaseline is evenly applied to the inner wall of the test mold in advance to facilitate demolding; after demolding, the sample is sealed with plastic wrap to prevent moisture migration and placed in a constant temperature and humidity curing box for curing under standard conditions of temperature (20±2)℃ and relative humidity>90%.

[0084] (2) Unconfined compressive strength test:

[0085] The test used a strain gauge unconfined pressure instrument, loading the specimens at an axial strain rate of 2 mm / min until failure. Three specimens were collected for each mix ratio at each curing age, and the average value was taken to determine the unconfined compressive strength.

[0086] (3) Scanning electron microscope test:

[0087] The test was conducted using a German ZEISS Sigma 360 field emission scanning electron microscope. After the unconfined compressive strength test, fresh sections were cut from the middle of the specimen, and regular fragments with a volume of approximately 0.5 cm³ were selected as observation samples.

[0088] Test results and analysis:

[0089] Unconfined compressive strength, unconfined compressive strength of calcium carbide slag:

[0090] Figure 2 This is a relationship diagram between the strength of carbide slag soil and the carbide slag content and curing age. It can be seen from the figure that the strength of carbide slag soil shows an upward trend with the increase of curing age. When the carbide slag content was less than 7%, the strength of carbide slag soil with a curing age of 14 days increased by 30% to 35% compared to the strength of the same carbide slag content with a curing age of 7 days. At a curing age of 28 days, the strength increased by 20% to 24% compared to the 14-day curing age. This indicates that when the carbide slag content is small, the early growth rate of the carbide slag soil strength is greater than the later growth rate, and the hydration reaction is more rapid. When the carbide slag content is 7% and 9%, the strength of the carbide slag soil increased by 82% to 95% from 14 to 28 days of curing, indicating that the hydration reaction is more complete during this stage and the strength increase is greater. When the carbide slag content is 11%, the growth rate of soil strength in both the early and late curing stages shows a downward trend. This phenomenon indicates that although high carbide slag content can accelerate the hydration reaction process, it does not bring corresponding strength growth advantages. In addition, the strength of the solidified soil shows a trend of first increasing and then decreasing with the change of carbide slag content. For the specific silt soil sample used in this study, the optimal carbide slag content is 7%.

[0091] Effect of rice husk ash dosage:

[0092] The unconfined compressive strength of rice husk ash carbide slag solidified silt soil changes with rice husk ash content and curing age. Figure 3 shown.

[0093] It should be noted that Figure 3 The carbide slag content in a is 3%; the carbide slag content in b is 5%; the carbide slag content in c is 7%; the carbide slag content in d is 9%; and the carbide slag content in e is 11%.

[0094] Depend on Figure 3 It can be seen that the addition of rice husk ash significantly improved the mechanical properties of silt soil. Specifically: at a curing age of 7 days, the strength of the untreated silt soil was only 108kPa. After being solidified with 7% carbide slag alone, the strength was increased to 225kPa. After the introduction of rice husk ash, the strength of all composite solidified samples exceeded 360kPa, showing a significant enhancement effect. Among them, when the rice husk ash content was 15%, the sample reached its peak strength, and its strength value was approximately 4.7 times that of the original compacted silt soil and 2.3 times that of the single carbide slag solidified soil. This result fully confirms the significant role of rice husk ash in improving the strength of silt soil, and also indicates that there may be a synergistic effect between the components in the composite solidification system. From Figure 3The results also show that, compared with the control group, the strength of the composite-cured samples increased by 153% to 370% after a 7-day curing age. Compared with soil cured with carbide slag alone, the strength increase ranged from 63% to 250%. Under fixed carbide slag content, the relationship between rice husk ash content and cured soil strength exhibited a nonlinear relationship: when the rice husk ash content was below 15%, the strength increased significantly; above 15%, the strength decreased. Notably, this optimal content (15%) was independent of curing age, indicating that the mechanism of action of rice husk ash in the curing system was relatively stable. The results indicate that, from the perspective of optimizing compressive strength, a higher content of curing material is not necessarily better. For the specific silt soil sample used in this study, the optimal content of rice husk ash and carbide slag was 15% and 7%, respectively, ensuring optimal mechanical properties for the cured soil.

[0095] Furthermore, taking 7% carbide slag as an example, the relationship curve between the unconfined compressive strength of solidified soil at different ages and the rice husk ash content was established, as shown in Figure 2. Figure 4 The relationship between the two shows a good quadratic parabola feature and can be described by the following mathematical model:

[0096] q u =ax 2 +bx+c

[0097] Where: q u represents the unconfined compressive strength, x represents the rice husk ash content, and a, b, and c are regression coefficients, as shown in the following table:

[0098] Maintenance age 7 days 14 days 28 days a -1.165 -2.018 -1.785 b 34.179 60.038 49.983 c 222.011 267.526 483.171 <![CDATA[R 2 ]]> 0.948 0.996 0.977

[0099] As can be seen from the table above, the fitting effect R 2 better.

[0100] Effect of curing age:

[0101] The influence of curing age on the strength development of solidified soil is as follows: Figure 5 shown.

[0102] It should be noted that Figure 5 The carbide slag content in a is 3%; the carbide slag content in b is 5%; the carbide slag content in c is 7%; the carbide slag content in d is 9%; and the carbide slag content in e is 11%.

[0103] The unconfined compressive strength of solidified soil shows a continuous upward trend with increasing curing time. For example, with an optimized mix ratio of 7% carbide slag and 15% rice husk ash, when the curing period was extended from 7 to 28 days, the sample strength increased significantly from 508 kPa to 849.6 kPa, a 67.2% increase, fully demonstrating the significant contribution of the curing process to strength development. Further statistical analysis revealed that the strength of the sample at 14 days of curing was 1.41 times that of the 7-day sample, while the strength of the 28-day sample was 1.19 times that of the 14-day sample. This strength growth pattern indicates that the strength of solidified soil maintains an upward trend throughout the 28-day curing period, with the strength growth rate in the early stages (7-14 days) being faster than in the later stages (14-28 days).

[0104] Ultimate strain of rice husk ash calcium carbide slag:

[0105] The ultimate strain of samples with different proportions at 7 days and 28 days of curing age was statistically analyzed. The results are as follows: Figure 6 shown.

[0106] It should be noted that Figure 6 Figure a is the relationship diagram of the ultimate strain of rice husk ash and carbide slag soil at a curing age of 28 days; b is the relationship diagram of the ultimate strain of rice husk ash and carbide slag soil at a curing age of 7 days; c is the relationship diagram of the ultimate strain of carbide slag soil at different curing ages; d is the relationship diagram of the ultimate strain of rice husk ash and 7% carbide slag soil at different curing ages; e is the relationship diagram of the ultimate strain of rice husk ash and 11% carbide slag soil at different curing ages.

[0107] In the figure, 3d represents the addition of 3% carbide slag alone, 7d5dk represents the addition of 7% carbide slag and 5% rice husk ash, and the meanings of other figures are similar. Figure 6 It can be seen that the ultimate strain of the rice husk ash and carbide slag composite-stabilized soil at a 7-day curing age is generally greater than that of the 28-day-old specimen. At the same curing age, the ultimate strain of the composite-stabilized soil is significantly higher than that of the single carbide slag-stabilized soil. Notably, there is no significant correlation between the ultimate strain and the rice husk ash content, curing age, or unconfined compressive strength. Statistical data show that the ultimate strain of single carbide slag-stabilized soil ranges from 1.1% to 2.4%, while the ultimate strain of the rice husk ash and carbide slag composite-stabilized soil significantly increases to 3.1% to 4.5%. Compared with the typical ultimate strain range of cement-stabilized soil (1% to 2.5%), the composite-stabilized soil in this study exhibits greater toughness, which is of great significance for improving the engineering properties of soils.

[0108] Failure morphology analysis:

[0109] The silt soil specimens first underwent a brief compression phase, followed by rapid microcracks on the surface, the gradual peeling of the outer layer of the specimen, and ultimately overall failure. Carbide slag-stabilized soil and rice husk ash-carbide slag composite-stabilized soil primarily exhibited brittle shear failure and brittle tensile failure. Specifically, when the solidified soil strength was low, distinct primary cracks formed on the specimen surface at a certain angle to the axial direction, exhibiting typical brittle shear failure characteristics; while at higher strengths, multi-directional cracks developed on the specimen surface, with the primary cracks extending along the axial direction, exhibiting a brittle tensile failure mode.

[0110] Intensity regression prediction model

[0111] The following table shows the unconfined compressive strength test data of rice husk ash carbide slag solidified silt soil at a carbide slag dosage of 7%:

[0112]

[0113] Based on this, a three-dimensional relationship diagram of rice husk ash dosage, curing age and unconfined compressive strength was constructed, as shown in Figure 7 According to the distribution characteristics of the measured data, a prediction model is established using a complete quadratic function, and its theoretical expression is:

[0114]

[0115] For this model, the perfect quadratic polynomial can be written as:

[0116] Q=z0+a*x+b*y+c*x 2 +d*y 2 +f*x*y

[0117] Where x is the curing age, days; y is the rice husk ash dosage, %; a, b, c, d, f, z0 are regression coefficients.

[0118] The regression analysis fitting coefficients are shown in the following table:

[0119]

[0120] According to the above table, the regression model of rice husk ash calcium carbide slag soil is:

[0121] Q=-72.8+38.93*T+46.69*a0+(-0.69)*T 2 +(-1.66)*a0 2 +

[0122] 0.08*Ta0

[0123] Where, T is the curing age, days; a0 is the amount of rice husk ash added, %.

[0124] The correlation coefficient is 0.967, the F value is 52.13 and P < 0.05, indicating that the model is significant as a whole. Under the condition that the curing age T does not exceed 28 days, the above rice husk ash calcium carbide slag regression model can be used to approximately estimate the unconfined compressive strength of rice husk ash calcium carbide slag solidified silt soil at any rice husk ash content and curing age. This characteristic has certain value in practical engineering applications. The specific model of unconfined compressive strength is shown in Figure 8 .

[0125] Microscopic characteristics and mechanisms:

[0126] Effect of rice husk ash dosage on the microstructure of stabilized soil:

[0127] The SEM analysis results of the effect of rice husk ash content on the microstructure of the solidified soil after 28 days of curing are as follows: Figure 9 shown.

[0128] It should be noted that Figure 9 Figure a is a schematic diagram of the SEM analysis results of 7% carbide slag solidified soil at a magnification of 2000 times; b is a schematic diagram of the SEM analysis results of 7% carbide slag solidified soil at a magnification of 5000 times; c is a schematic diagram of the SEM analysis results of the first rice husk ash carbide slag solidified soil at a magnification of 2000 times; d is a schematic diagram of the SEM analysis results of the first rice husk ash carbide slag solidified soil at a magnification of 5000 times; e is a schematic diagram of the SEM analysis results of the second rice husk ash carbide slag solidified soil at a magnification of 2000 times; f is a schematic diagram of the SEM analysis results of the second rice husk ash carbide slag solidified soil at a magnification of 5000 times.

[0129] The solidified soil mixed with 20% rice husk ash and 7% carbide slag is called the first rice husk ash and carbide slag solidified soil, and the solidified soil mixed with 15% rice husk ash and 7% carbide slag is called the second rice husk ash and carbide slag solidified soil.

[0130] When magnified 2000 times, the needle-shaped minerals generated inside the 7% carbide slag single-doped solid soil are less in content and difficult to distinguish, showing the characteristics of loose particle arrangement, developed pores and large pore size; in contrast, the rice husk ash carbide slag composite solidified soil is denser, and although there are also some larger pores, it is significantly improved compared with the single carbide slag solidified soil.

[0131] When magnified 5000x, the microstructural characteristics and interconnectedness of the solidified soil are clearly revealed. Dispersed fine needle-like minerals are observed in the solidified soil with carbide slag alone, forming limited overlaps in localized areas. In contrast, the soil solidified with rice husk ash and carbide slag composite exhibits a more complex system of hydration products: in addition to needle-like minerals, a large number of columnar, flaky, and flocculent minerals are also generated. The needle-like and columnar minerals are coarse and clustered, forming bundles that tightly fill pores and establish a well-connected network with other crystals. The flake-like and flocculent products are primarily distributed on the surfaces of soil particles and in the interstices between minerals, significantly enhancing pore-filling density. In the microstructure of the second rice husk ash and carbide slag solidified soil, a large amount of gel material is observed filling the pores, while the exposed needle-like and columnar minerals are relatively reduced. Localized agglomerations of needle-like and flake-like minerals are observed, and these minerals are primarily distributed in pores and on the surfaces of soil particles. In general, the addition of rice husk ash can indeed optimize the microstructure of the solidified soil, but excessive addition (exceeding the optimal dosage) will lead to an increase in porosity and have an adverse effect on the solidification effect.

[0132] Changes of microstructure of rice husk ash carbide slag stabilized soil with age:

[0133] In order to explore the aging evolution law of the microstructure of rice husk ash and carbide slag stabilized soil, the second rice husk ash and carbide slag stabilized soil (ratio of 15% rice husk ash + 7% carbide slag) was selected as the research object, and its microstructure at different curing ages (7 days, 14 days and 28 days) was systematically observed. The results are as follows: Figure 10 As shown (the microstructural characteristics of the 28-day-old stage are shown above Figure 9 (displayed in).

[0134] It should be noted that Figure 10 Figure a is a schematic diagram of the SEM analysis results of the microstructure changes of the second rice husk ash carbide slag stabilized soil with age at 7 days, magnified 2000 times; b is a schematic diagram of the SEM analysis results of the microstructure changes of the second rice husk ash carbide slag stabilized soil with age at 7 days, magnified 5000 times; c is a schematic diagram of the SEM analysis results of the microstructure changes of the second rice husk ash carbide slag stabilized soil with age at 14 days, magnified 2000 times; d is a schematic diagram of the SEM analysis results of the microstructure changes of the second rice husk ash carbide slag stabilized soil with age at 14 days, magnified 5000 times.

[0135] Under a magnification of 2000 times, it was observed that the pore structure of the solidified soil showed an obvious optimization trend with the curing age: at the age of 7 days, the pores in the sample were numerous and large in size, mainly filled with lamellar and flocculent minerals, with fewer needle-shaped minerals; at the age of 14 days, the number of pores decreased, and needle-shaped minerals began to connect with each other; by the age of 28 days, the number of large pores decreased significantly, the pore surface was covered by a large amount of flocculent minerals, and the needle-shaped and columnar minerals were wrapped in it, forming a dense overall structure.

[0136] When magnified to 5000 times, the morphological evolution of the hydration products can be observed more clearly: at the age of 7 days, the number of needle-shaped and columnar minerals is small and the shape is thin and short, and some flake-shaped and flocculent hydration products can also be observed; at the age of 14 days, the number of hydration products increases significantly, the needle-shaped and columnar minerals grow obviously, and bundle-like agglomerations appear locally, effectively filling the pores; at the age of 28 days, flocculent products become the main surface feature, the exposed columnar minerals are coarse and mostly aggregated in bundles, forming a good spatial connection network with other minerals, and flake-shaped and flocculent products are mainly distributed on the surface of soil particles.

[0137] These changes in microstructural characteristics fully demonstrate the continuous progress of the hydration reaction in the rice husk ash carbide slag solidification system and its improvement of material properties, providing microscopic evidence for understanding the strength development mechanism of solidified soil.

[0138] Reaction mechanism of rice husk ash and carbide slag solidified soil:

[0139] Rice husk ash not only contains a large amount of active SiO2, but also has considerable nanoscale pores. These characteristics enable it to play multiple roles in the sludge solidification process:

[0140] (1) Filling effect: Rice husk ash contains a large number of nano-scale SiO2 particles, which can effectively fill the internal pores of solidified silt soil. This physical filling effect significantly improves the density of the soil, reduces the porosity, and thus improves the overall performance of the solidified soil.

[0141] (2) Hydration reaction: The main components of carbide slag are similar to cement, and its hydration reaction products are mainly calcium hydroxide, hydrated calcium silicate and hydrated calcium aluminate. After adding rice husk ash, its rich active SiO2 reacts with Ca(OH)2 produced by carbide slag hydration to produce a large amount of hydrated calcium silicate, thereby significantly increasing the content of CSH gel with cementing effect. This reaction is the main source of the strength development of solidified soil. Its chemical reaction equation is:

[0142] SiO2+Ca(OH)2+nH2O→CaO·SiO2·(n+1)H2O

[0143] (3) Water storage and supply: The unique nano-scale porous structure of rice husk ash gives it excellent water storage properties. In the later stages of the hydration reaction, the water stored in the pores is gradually released and continuously participates in the hydration reaction. This unique water storage and supply mechanism effectively ensures the progress of the hydration reaction in the later stages of the solidification system, thereby ensuring the stable growth of the strength of the solidified soil in the later stages.

[0144] Based on the above analysis, a micro-evolution mechanism model of rice husk ash carbide slag solidified silt soil was proposed. Figure 11 shown.

[0145] in conclusion:

[0146] (1) Compared with unsolidified and carbide slag-solidified silt soil, the unconfined compressive strength of rice husk ash carbide slag-solidified silt soil was significantly improved. For the specific silt soil sample used in this study, the optimal material ratio was 15% rice husk ash and 7% carbide slag.

[0147] (2) Under the optimal rice husk ash carbide slag dosage, the q of the solidified soil after 14 days of curing u The value reaches 1.41 times that of 7 days and 1.19 times that of 14 days at 28 days. This intensity growth law shows that the reaction in the rice husk ash carbide slag and sludge system not only starts quickly but also lasts for a long time.

[0148] (3) The addition of rice husk ash can improve the toughness of silt-stabilized soil. The ultimate strain of soil stabilized with carbide slag alone is between 1.1% and 2.4%, while the ultimate strain of soil stabilized with rice husk ash and carbide slag is significantly increased to between 3.1% and 4.5%.

[0149] (4) The reaction mechanism of rice husk ash calcium carbide slag soil is mainly the filling effect, hydration reaction and water storage and supply. The CSH gel produced by the hydration reaction is the main source of strength of the solidified sludge;

[0150] (5) Based on the experimental results, a strength prediction model and a micro-evolution mechanism model for rice husk ash carbide slag solidified silt soil were established, which can provide a theoretical basis and technical reference for the application of rice husk ash carbide slag in silt solidification practice.

[0151] The above description is merely an exemplary embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformation made by utilizing the contents of the present invention's description and drawings under the technical concept of the present invention, or directly / indirectly applied in other related technical fields, is included in the patent protection scope of the present invention.

Claims

1. A method for constructing a strength prediction model based on the microscopic pore structure of solidified soil, characterized in that: The raw materials of the solidified soil include 100 parts by mass of silt, 10-20 parts by mass of rice husk ash and 5-9 parts by mass of calcium carbide slag; The method for constructing a strength prediction model based on the microscopic pore structure of solidified soil includes: Mixing the sludge, the rice husk ash and the carbide slag in a preset ratio to obtain a mixture; adding water to the mixture and curing it to a predetermined age to obtain a cylindrical specimen; Performing an unconfined compressive strength test on the cylindrical specimen to obtain a failure specimen; A 5 mm*5 mm area in the center of the cross section is cut out from the damaged sample, and the porosity is extracted; Establishing the strength prediction model based on the amount of rice husk ash, the amount of carbide slag, the preset age and porosity; The intensity prediction model is: Q=z0+a*x+b*y+c*x 2 +d*y 2 +f*x*y Wherein, the z0, a, b, c and f are different preset regression coefficients, x is the preset age, and y is the dosage of the rice husk ash.

2. The method for constructing a strength prediction model based on the microscopic pore structure of solidified soil according to claim 1, wherein: The strength prediction model is Q = -72.8 + 38.93*T + 46.69*a0 + (-0.69)*T 2 +(-1.66)*a0 2 +0.08*T*a0.

3. The method for constructing a strength prediction model based on the microscopic pore structure of solidified soil according to claim 1, wherein: The step of mixing the sludge, the rice husk ash and the carbide slag according to a preset ratio to obtain a mixture comprises: 100 parts by mass of the dry dredged sludge, 10 to 20 parts by mass of the rice husk ash and 7 parts by mass of the carbide slag are uniformly mixed to obtain a plurality of mixtures with different proportions.

4. The method for constructing a strength prediction model based on the microscopic pore structure of solidified soil according to claim 3, wherein: The steps of adding water to the mixture and curing it to a predetermined age to obtain a cylindrical sample include: The mixtures with different proportions were cured for 7 days, 14 days and 28 days respectively, and then the unconfined compressive strength was tested and the porosity was analyzed.

5. The method for constructing a strength prediction model based on the microscopic pore structure of solidified soil according to claim 4, characterized in that: The porosity=number of pore pixels / total number of pixels×100%.

6. The method for constructing a strength prediction model based on the microscopic pore structure of solidified soil according to any one of claims 1 to 5, characterized in that: The porosity of the nanopores of the rice husk ash is φ, 20%≤φ≤40%.

7. The method for constructing a strength prediction model based on the microscopic pore structure of solidified soil according to claim 6, characterized in that: The specific surface area of the rice husk ash is SSA, 200m 2 / g≤SSA≤500m 2 / g.

8. The method for constructing a strength prediction model based on the microscopic pore structure of solidified soil according to any one of claims 1 to 5, characterized in that: The content of SiO2 in the rice husk ash is A1, and A1 is greater than or equal to 85%. The content of CaO in the carbide slag is B1, and B1 is greater than or equal to 60%.

9. The method for constructing a strength prediction model based on the microscopic pore structure of solidified soil according to any one of claims 1 to 5, characterized in that: The content of CaO in the carbide slag is B2, 65%≤B2≤70%; the content of SiO2 in the carbide slag is C, 1%≤C≤2%; the content of Al2O3 in the carbide slag is D, 1.5%≤D≤2.5%.

10. The method for constructing a strength prediction model based on the microscopic pore structure of solidified soil according to any one of claims 1 to 5, characterized in that: The content of SiO2 in the rice husk ash is A2, 90%≤A2≤95%; the content of Fe2O3 in the rice husk ash is E, 0.5%≤E≤1%.

Images