Method for improving dispersive soil by using calcium carbide dust and glass powder

Abstract

The invention discloses a method for improving dispersive soil by using calcium carbide dust and glass powder. The method comprises the following steps: 1, obtaining and treating original dispersive soil; designing modifier components by taking calcium carbide dust and glass powder as components; 2, measuring physical property indexes of the undisturbed dispersive soil; 3, comprehensively identifying the dispersibility of the original-state dispersive soil through a pinhole test, a fragment test and a mud ball test; 4, adding the modifier into the to-be-treated dispersive soil, and solidifying and improving to obtain improved soil; and 5, backfilling the improved soil. The calcium carbide dust and the glass powder are used as modifiers to effectively fill pores in the dispersive soil, so that the compactness and the stability of the soil are remarkably improved, the distance and the gap between soil particles are reduced, and the adjacent soil particles are bonded to form a communication structure through hydration gelatinization and geological polymerization, so that the water stability of a soil sample is enhanced, and the soil quality is improved. The soil pH balance is maintained, the cost of the modifier is reduced, the pollution discharge is reduced, and the method is suitable for the field of soil improvement.

Description

Technical Field

[0001] The invention belongs to the technical field of dispersive soil improvement, and in particular relates to a method for improving dispersive soil by utilizing calcium carbonate and glass powder. Background Art

[0002] Dispersive soil refers to a type of clay soil in which the mutual repulsion between ions in low-salinity water (or pure water) exceeds the mutual attraction, resulting in the dispersion of soil particles. Dispersive soil will show special properties and instability under certain conditions. When the water content of dispersed soil is high or it is soaked in water, it is easy to cause crack erosion, seepage damage and dispersed pipe bursts in reservoirs, channels and other engineering structures that are directly or indirectly in contact with dispersed soil, thus causing serious engineering accidents.

[0003] There are methods for improving and reinforcing dispersed soils at home and abroad. For example, Wang Xi found in the experimental research on improving dispersed soils with microbial induced calcium carbonate precipitation technology (MICP) that adding lime to dispersed soils can improve dispersed soils. Studies have shown that lime can improve dispersed soils; or the mixing of cement and zeolite can improve the dispersion and swelling properties of four different plastic clays, and can significantly increase the strength of the clay (JIANG NJ, DU YJ, LIU SY, et al. Multi-scale laboratory evaluation of the physical, mechanical, and microstructural properties of soft highway subgrade soil stabilized with calcium carbide residue).

[0004] However, the above method has the following disadvantages: most of the research on the modification of dispersed soil focuses on the method of adding traditional admixtures such as lime and cement. However, in large-scale projects, if a large amount of cement and lime are discharged into the environment without proper treatment, it may have a negative impact on the surrounding soil and water bodies. For example, lime produces a large amount of dust pollution during the dissolution process. At the same time, once lime water overflows into the surrounding waters, it will pollute the water source and change the soil properties near the basin, which is not conducive to the growth of crops and vegetation. Summary of the invention

[0005] The technical problem to be solved by the present invention is to provide a method for improving dispersed soil by using calcium carbonate and glass powder in view of the shortcomings of the above-mentioned prior art. The method uses calcium carbonate and glass powder as improvers to improve dispersed soil, which can effectively fill the internal pores of dispersed soil, significantly improve the density and stability of soil, change the roughness of soil particles, reduce the distance and gap between soil particles, and bond adjacent soil particles to form a connected structure through hydration gelation and geological polymerization, thereby enhancing the water stability of soil samples, reducing the dispersibility of soil samples, and effectively maintaining the pH balance of soil, reducing the cost of improvers and reducing pollution, thereby solving the problem that the existing improvement methods are not effective and pollute the environment.

[0006] The technical solution provided by the present invention is: a method for improving dispersible soil by using calcium carbonate and glass powder, characterized in that the method comprises the following steps:

[0007] Step 1: obtaining original dispersed soil at the sampling site, and then crushing, grinding, air-drying and sieving the original dispersed soil in sequence, and taking the sieve-down as dispersed soil to be treated; at the same time, designing improver components with calcium carbonate and glass powder as ingredients according to different proportions;

[0008] Step 2: According to GB / T 50123-2019 "Standard for Geotechnical Test Methods", the physical properties of the original dispersed soil in step 1 are determined by compaction test, limit moisture content test, and particle analysis test, including moisture content, density, particle size distribution, plastic limit, and liquid limit;

[0009] Step 3: According to T / CECS1337-2023 "Standard for Test Methods of Unsaturated Soils" and ASTM D4647 and ASTMD6572, the dispersibility of the original dispersible soil in step 1 is comprehensively identified through pinhole test, fragment test and mud ball test;

[0010] Step 4: According to the physical property index of the original dispersible soil measured in step 2 and the dispersibility result identified in step 3, the improver prepared in step 1 is added to the dispersible soil to be treated and water is added for solidification and improvement, and improved soil is obtained after curing, and then the dispersibility of the improved soil is identified according to the method in step 3 to obtain the best improver ratio;

[0011] Step 5: Fill the improved soil obtained after solidification and improvement with the best modifier ratio in step 4 back into the foundation of the sampling address in step 1, and compact it to its original state with a sheep horn roller.

[0012] The above-mentioned method of improving dispersed soil by using calcium carbonate and glass powder is characterized in that in step 1, the original dispersed soil is crushed with a small wooden hammer, and after natural air drying, it is sieved through 0.5 mm and 2 mm holes for later use.

[0013] The above-mentioned method of improving dispersible soil by using calcium carbonate and glass powder is characterized in that the percentage of each component of the improver added to the dispersible soil to be treated in step 4 is: calcium carbonate 0.5% to 6.5%, glass powder no more than 16%, and the amount of water added is the optimal moisture content of the original dispersible soil after adding the improver. Usually, the optimal moisture content of the original dispersible soil after adding the improver is 12% to 16%.

[0014] The above-mentioned method of improving dispersible soil by using calcium carbonate and glass powder is characterized in that the original dispersible soil in step 1 is high Na + The content of dispersed soil, the percentage of each component of the modifier added to the dispersed soil to be treated in step 4 is: 4.5% to 6.5% of calcium carbonate, 4% to 8% of glass powder, and the amount of water added is the optimal moisture content of the original dispersed soil after adding the modifier.

[0015] The above-mentioned method of improving dispersed soil using calcium carbonate and glass powder is characterized in that the original dispersed soil described in step one is dispersed soil with a higher pH value, and the percentage of each component of the improver added to the dispersed soil to be treated in step four is: calcium carbonate 0.5% to 2.5%, glass powder 4% to 16%, and the amount of water added is the optimal moisture content of the original dispersed soil after adding the improver.

[0016] The above-mentioned method of improving dispersed soil using calcium carbonate and glass powder is characterized in that the original dispersed soil described in step one is dispersed soil with a higher montmorillonite content, and the percentage of each component of the improver added to the dispersed soil to be treated in step four is: calcium carbonate 1% to 4%, glass powder 4% to 8%, and the amount of water added is the optimal moisture content of the original dispersed soil after adding the improver.

[0017] The main components of the calcium carbonate in the improver of the present invention include calcium oxide CaO, magnesium oxide MgO and aluminum oxide Al2O3, and the main component of the glass powder is SiO2 silicon dioxide. The improver composed of calcium carbonate and glass powder is called a calcium-based composite material, and its improvement mechanism for dispersed soil is as follows:

[0018] (1) In the early stage, the calcium-based composite material quickly fills the pores inside the dispersed soil, especially the large pores with good connectivity are divided into multiple small pores, which significantly enhances the filling effect, not only reducing the total volume of soil pores, but also significantly improving the density and stability of the soil. By effectively filling the pores, the roughness of the soil particles is changed, thereby improving the mechanical properties of the soil.

[0019] (2) Soil dispersion is affected by many factors, among which Na + Content is one of the key factors. Studies have shown that Na + The water ionosphere is relatively thick and contains Na +The double layer thickness of soil particles is significantly greater than that of other common cations (such as Ca 2+ Mg 2+ and Al 3+ ) double layer thickness, so when Na adsorbed on the surface of soil particles + As the electric double layer increases, the water film around it also becomes thicker; when soil particles come into contact with water, the thickness of the surface double layer increases dramatically.

[0020] The present invention releases a large amount of soluble Ca into the soil pore solution by adding calcium-based composite materials. 2+ Mg 2+ and Al 3+ According to the cation exchange theory, Na adsorbed on the surface of soil particles + can be replaced by these soluble cations. According to the charge balance theory, the Na + A large amount of soluble Ca 2+ Mg 2+ and Al 3+ After replacement, the thickness of the double electric layer will decrease rapidly, resulting in a significant decrease in the thickness of the water film around the soil particles, thereby reducing the distance and gap between the soil particles, achieving the effect of improving dispersed soil, such as Figure 1 shown.

[0021] Due to the adsorption of Na + The higher the content, the greater the distance between soil particles, the smaller the attraction, and the less likely it is to bind the soil particles together, resulting in a dispersed effect. During the curing process of the improver of the present invention, as the curing time increases, the amount of calcium silicate hydrate (CSH) and geopolymer (CASH) gel generated gradually increases, and the corresponding chemical reaction is shown below: [ :

[0022] Ca 2+ +SiO2+OH - +(n-1)H2O→CaO·SiO2·nH2O

[0023] (Al,Si) s Complex + H2O + CaOH → Ca z [-(SiO2) y -AlO2-] n mH2O

[0024] These cementing substances gradually bond adjacent soil particles together to form a connected structure, cut off the seepage channels of free soil particles, and restrict the free movement of soil particles. In addition, the products of the ion exchange reaction work synergistically with the hydrates and geopolymer products to enhance the water stability of the soil sample and reduce the dispersibility of the soil sample. Therefore, the modifier of the present invention greatly improves the soil structural strength and inhibits the dispersion of dispersed soil. The modification process and mechanism are as follows: Figure 2 shown.

[0025] In addition, common dispersed soils include exchangeable Na + For dispersed soil with more exchangeable sodium ions, you can choose to use a higher calcium carbonate content and less glass powder (calcium carbonate 4.5% to 6.5%, glass powder 4% to 8%), because more sodium ions require more Ca 2 + Mg 2+ and Al 3+ The purpose of the exchange is to increase the activity of SiO2 in the soil, and the glass powder can play the role and effect of a catalyst. Moreover, calcium carbonate is cheaper than glass powder, and has better solidification and improvement effects, and is more economical. For dispersed soils with higher pH values, use lower calcium carbonate with more glass powder (calculated lime 0.5% to 2.5%, glass powder 4% to 16%), because calcium carbonate itself is alkaline, and silicon dioxide is an acidic oxide, so use less calcium carbonate with more glass powder to maintain the soil pH balance while ensuring the solidification and improvement effect. For dispersed soils with higher montmorillonite, take the value between the two (calculated lime 1% to 4%, glass powder 4% to 8%) to maintain the soil pH balance while ensuring the solidification and improvement effect.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] 1. The present invention adopts calcium carbonate and glass powder as modifiers to improve dispersed soil, which can effectively fill the internal pores of dispersed soil, significantly improve the density and stability of soil, change the roughness of soil particles, and reduce the distance and gap between soil particles through the ion exchange effect in the modifier. In addition, hydration, gelation and geological polymerization occur during the curing process, which bond adjacent soil particles to form a connected structure, restrict the free movement of soil particles, enhance the water stability of soil samples, and reduce the dispersibility of soil samples, thereby achieving the improvement effect.

[0028] 2. The calcium carbonate and glass powder used in the present invention are more environmentally friendly and avoid the large amount of pollutant emissions generated during the production of other improvers such as cement and lime, including carbon dioxide, sulfur compounds and nitrogen oxides. In addition, the glass powder is a powder material processed from waste glass and has good environmental performance.

[0029] 3. Excessive use of traditional curing agents can easily lead to soil compaction, calcification, increased alkalinity, and reduced soil ventilation, which is not conducive to vegetation survival and subsequent engineering construction. The improver of the present invention effectively maintains the balance of soil pH by adjusting the composition, and significantly improves the condition of soil embrittlement.

[0030] 4. The improver components of the present invention include calcium carbonate and glass powder, which are industrial wastes left over from industrial construction. They have a low recycling rate and are mostly disposed of in landfills. Using them as soil improvers can effectively save and recycle resources and actively promote the realization of sustainable development goals.

[0031] 5. The improved dispersed soil obtained by the present invention has significantly improved soil strength. The compression resistance, compression resistance or permeability tests all show that the modifier of the present invention has a good effect on improving soil strength.

[0032] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a schematic diagram of the ion exchange process of the improver of the present invention acting on dispersed soil.

[0034] Figure 2 This is a mechanism diagram of the modification process of the modifier of the present invention on dispersed soil.

[0035] Figure 3 The present invention is a process flow chart for improving dispersible soil by using calcium carbonate and glass powder.

[0036] Figure 4 This is the sampling address of the original dispersed soil in Example 1 of the present invention.

[0037] Figure 5 This is a physical picture of the calcium carbonate used in Example 1 of the present invention.

[0038] Figure 6 This is a physical picture of the glass powder used in Example 1 of the present invention.

[0039] Figure 7 This is a particle size distribution curve of the original dispersed soil of Example 1 of the present invention.

[0040] Figure 8 This is the pinhole test device used in Example 1 of the present invention.

[0041] Fig. 9 This is the fragment test device used in Example 1 of the present invention.

[0042] Fig.10 This is the mud ball test device used in Example 1 of the present invention.

[0043] Fig.11 This is a graph showing the pinhole test results of some samples obtained after the original dispersed soil was solidified and improved by a series of improvers in Example 1 of the present invention.

[0044] Fig.12 This is a graph showing the test results of some sample fragments obtained after the original dispersed soil was solidified and improved by a series of improvers in Example 1 of the present invention.

[0045] Fig.13 This is a graph showing the results of a mud ball test on some samples obtained after the original dispersed soil was solidified and improved by a series of improvers in Example 1 of the present invention.

[0046] Fig.14 This is a diagram showing the comprehensive judgment results of the dispersibility test after a series of improvers were used to solidify and improve the original dispersible soil in the embodiments of the present invention.

[0047] Fig.15 This is a graph showing the strength results of soil samples after a series of improvers were used to solidify and improve the original dispersed soil in an embodiment of the present invention.

[0048] Fig.16 This is a compression characteristic diagram of soil samples after a series of improvers were used to solidify and improve the original dispersed soil in the embodiment of the present invention.

[0049] Fig.17 This is a graph of the permeability coefficient of soil samples after a series of improvers are used to solidify and improve the improved soil in an embodiment of the present invention. Fig.18 This is a schematic diagram of the position of the improved soil backfilled into the dam in Example 1 of the present invention. DETAILED DESCRIPTION

[0050] Example 1

[0051] like Figure 3 As shown, the method of improving dispersible soil by using calcium carbonate and glass powder in this embodiment comprises the following steps:

[0052] Step 1: Figure 4 The sampling address shown obtains high Na + The original dispersed soil contains Na +The mass proportion is as high as 1.02%. Then the original dispersed soil is crushed and ground with a small wooden hammer, naturally air-dried and passed through 0.5mm and 2mm hole sieves in turn, and the sieve-down is taken as the dispersed soil to be treated; the moisture content of the original dispersed soil is measured to be 13.5% by the drying method; at the same time, Figure 5 The calcium carbonate and Figure 6 The glass powder shown is a modifier component designed according to different proportions;

[0053] Step 2: According to GB / T 50123-2019 "Standard for Geotechnical Test Methods", the physical properties of the original dispersed soil in step 1 are determined by compaction test, limit moisture content test, and particle analysis test, including moisture content, density, particle size distribution, plastic limit, and liquid limit;

[0054] Compaction test: The optimal moisture content and maximum dry density of the original dispersed soil (the test object is the original dispersed soil under the sieve of 2mm hole sieve) were measured using SJL-1 standard portable compactor. The compaction power per unit volume was 592.2kJ / m 3 The results show that the optimal moisture content of the original dispersed soil is 14.2%, and the maximum dry density is 1.71 g˙cm -3 ;

[0055] Limit moisture content test: The limit moisture content of the original dispersed soil (the test object is the original dispersed soil under the 0.5mm hole sieve) is measured by using the liquid-plastic limit combined determination method and a digital soil liquid-plastic limit combined determination instrument. Three samples are taken for determination and the average value is taken. The results show that the liquid limit (wl) of the original dispersed soil is 26.4%, the plastic limit (wp) is 15%, and the plasticity index (lp) is 11.4.

[0056] Particle analysis test: Use a laser particle size analyzer to measure the particle size composition and corresponding content of the original dispersed soil (the measurement object is the original dispersed soil that passes through a 0.5mm hole sieve). The results are as follows: Figure 7 As shown, from Figure 7 It can be seen that the mass content of clay particles in the original dispersed soil is 6.47%, the mass content of silt particles is 65.72%, and the mass content of sand particles is 27.81%;

[0057] Step 3: According to T / CECS1337-2023 "Standard for Test Methods of Unsaturated Soils" and ASTM D4647 and ASTMD6572, the dispersibility of the original dispersible soil in step 1 is comprehensively identified through pinhole test, fragment test and mud ball test;

[0058] Pinhole test: Use Figure 8The pinhole test device shown in the figure adds water to the original dispersed soil sample (the treatment object is the original dispersed soil under the sieve of 2mm hole sieve) to make it close to the optimal moisture content (±2%). The amount of water added is calculated by formula (1);

[0059]

[0060] In formula (1): m w —Amount of water added, g;

[0061] m—soil sample mass, g;

[0062] w0—moisture content of soil sample, %;

[0063] w—optimal moisture content, %;

[0064] The soil sample after adding water was tightly wrapped with plastic film and placed in a container for 24 hours. Then the soil sample after 24 hours was weighed and compacted in multiple times. The layers were roughened and each layer was compacted with a hammer to more than 95% of the maximum dry density. The total height of the soil sample after compaction was 38.1 mm.

[0065] Push the small cone into the center of the compacted soil sample into the water, take a 1mm diameter hard steel wire through the small cone and penetrate the entire soil sample, rotate the hard steel wire to make the soil sample pinhole clean and unobstructed, and wax the surface of the soil sample into the water, and do not allow wax oil to flow into the pinhole to block the aperture;

[0066] Assemble the pinhole test device, connect the water inlet to the rubber tube, and adjust the water head height to let the soil sample flow through under different water heads (50mm, 180mm, 380mm and 1020mm) in turn, and observe and record the water flow rate per minute, the color of the water in the measuring cylinder, and the changes in the pinhole of the soil sample;

[0067] After the test, disassemble the pinhole test device, take out the soil sample from the cylinder of the pinhole test device, cut the soil sample to check the pinhole size, and use a ruler to measure the hole size. According to the pinhole test judgment standard in Table 1, judge the dispersibility of the original dispersible soil;

[0068] Table 1

[0069]

[0070] Block test: The original dispersed soil sample (the treatment object is the original dispersed soil that has been naturally air-dried and not sieved) is put into the mold to prepare the molded soil block, and a 1cm piece of 3 The soil blocks were used as samples. Fig. 9The fragment test device shown in the figure is used to conduct the fragment test; the sample is carefully picked up with tweezers and placed in a beaker containing 250 mL of deionized water, the disintegration rate and crushing phenomenon of the debris in the sample are observed, and the dispersion and disintegration of the sample and the data at 2 min, 1 h, and 6 h are recorded. The test results are generally based on the 1 h result. If the dispersibility level of the soil block changes significantly after 6 h, the 6 h result is used as the judgment result; according to the ASTM D6572 standard and the "Dispersibility Soil Research", the dispersibility soil judgment standard shown in Table 2 is determined, and the dispersibility of the original dispersible soil is judged;

[0071] Table 2

[0072]

[0073]

[0074] Mud ball test: Based on the ASTM D6572 standard and the fragment test in the "Dispersible Soil Research", it is improved using Fig.10 The mud ball test device shown in the figure is used to add deionized water to the original dispersed soil sample (the treatment object is the undersize of the original dispersed soil after passing through a 2mm hole sieve) to keep its water content near the liquid limit to obtain a sample. The sample is rolled into a mud ball with a diameter of about 15mm and a smooth surface. Then, the mud ball is carefully placed in the center of a beaker containing 200mL of deionized water with tweezers. The dispersion of the mud ball in the water and the turbidity of the water in the beaker are observed. The disintegration of the mud ball in the water at 5min, 10min, 30min, 1h, 3h, and 6h is recorded, and the image is retained to record the test data. The criteria for distinguishing dispersed soil corresponding to the fragment test are shown in Table 3.

[0075] Table 3

[0076]

[0077]

[0078] Through the pinhole test, fragment test and mud ball test, it is comprehensively judged that the original dispersed soil in step 1 is a typical dispersed soil;

[0079] Step 4: According to the physical property index of the original dispersible soil measured in step 2 and the dispersibility result identified in step 3, the modifiers of different proportions prepared in step 1 are respectively added to the dispersible soil to be treated (the treatment object is the undersize of the original dispersible soil through a 2mm hole sieve) and fully mixed, and water is added to mix manually until uniform, tightly wrapped with plastic film, stored in a sealed bag, and placed in a moisturizing cylinder at room temperature for curing to the corresponding age, and the curing time is 1d, 7d, and 14d, respectively, to obtain improved soil; then, the dispersibility of the improved soil is identified according to the method in step 3, i.e., the pinhole test, the mud ball test, and the fragment test, and the improvement effect of different proportions of calcium carbonate and glass powder on the original dispersible soil is obtained and compared, and the best modifier ratio is obtained;

[0080] In this embodiment, CxPy is used to represent that the modifier components including calcium carbonate with a mass fraction of x% and glass powder with a mass fraction of y% are added to the dispersed soil to be treated, and the values ​​of x% are 0%, 0.5%, 2.5%, 4.5%, and 6.5%, respectively, and the values ​​of y% are 0%, 4%, 8%, 12%, and 16%, respectively. The moisture content (%) and the optimal moisture content (%) of the dispersed soil to be treated after adding each group of modifier components are determined by the drying method and the compaction test in step 2, respectively, and then the amount of water added (%) corresponding to each group of modifier components is calculated according to formula (1) in step 3;

[0081] The different components of a series of improvers in this embodiment, the amount of water added and the sample numbers of the improved soil after corresponding solidification and improvement are shown in Table 4 below:

[0082] Table 4

[0083]

[0084]

[0085] According to the components of the improver in Table 4, the improver is prepared to solidify and improve the dispersed soil to be treated. The improved soil prepared after solidification and improvement is made into a sample with a compaction degree of 95% for the pinhole test and the mud ball test in step 3. After the pinhole test, the moisture content is kept at the liquid limit and the mud ball with a diameter of 15 mm is made into a sample for the mud ball test. The sample for the fragment test is the same as the sample for the pinhole test, and the result with the strongest dispersion among the pinhole test, mud ball test and fragment test is used as the comprehensive judgment standard;

[0086] Dispersibility test of original dispersible soil after solidification and improvement

[0087] (1) Pinhole test results: Based on the pinhole test results of the sample Fig.11It can be seen that when the modifier component is C0P0, that is, the amount of calcium carbonate and glass powder is 0, the sample is placed under a water head of 50 mm and continuously flows through the pinhole test device for 5 minutes, and the final flow rate reaches 1.1 mL / s. After the test, it is observed that the water in the measuring cylinder is turbid. The sample is taken out and cut, and the results show that the pore size of the sample exceeds 2 times the diameter of the steel needle. According to the dispersion criterion of the pinhole test, the sample is classified as dispersed soil, which confirms that the original dispersed soil used in this embodiment belongs to dispersed soil;

[0088] When the content of calcium carbonate and glass powder in the modifier components was 0.5% and 4% to 16% respectively, the sample was placed under a water head of 50 mm and flowed through the pinhole test device for 10 minutes. The final flow rate reached 1.4 mL / s. After the end, it was observed that the water in the measuring cylinder was turbid. The sample was taken out and cut. The results showed that the pore diameter of the sample exceeded 1.5 times the diameter of the steel needle. According to the dispersion criterion of the pinhole test, the sample was classified as dispersed soil.

[0089] When the content of calcium carbonate and glass powder in the modifier components was 2.5% and 4% to 16% respectively, the sample was placed under a water head of 180 mm and 380 mm and continuously flowed through the pinhole test device for 5 minutes. The final flow rate was in the range of 1.2 mL / s to 1.5 mL / s. After the test, it was observed that the water in the measuring cylinder was slightly turbid. The sample was taken out and cut. The results showed that the pore diameter of the sample exceeded 1.5 times the diameter of the steel needle. According to the dispersion criterion of the pinhole test, the sample was classified as transitional soil.

[0090] When the content of calcium carbonate and glass powder in the modifier components is 4.5% to 6.5% and 4% to 16% respectively, the sample is placed under a water head of 1020 mm and continuously flows through the pinhole test device for 5 minutes. The final flow rate is in the range of 1.7 mL / s to 1.9 mL / s. After the test, it is observed that the water in the measuring cylinder is clear. The sample is taken out and cut. The results show that the sample pore diameter is equal to the diameter of the steel needle. According to the dispersion criterion of the pinhole test, the soil sample is classified as non-dispersible soil.

[0091] (2) Piece test results: Based on the piece test results of the sample Fig.12 It can be seen that when the modifier component is C0P0, that is, the amount of calcium carbonate and glass powder is 0, the sample disintegrates instantly, the sample particles disperse rapidly, and a large amount of thick suspended matter is produced at the bottom of the cup, forming a "cloudy" turbidity phenomenon. According to the dispersibility discrimination standard of the fragment test, the sample is classified as dispersible soil, which confirms that the original dispersible soil used in this embodiment belongs to dispersible soil;

[0092] When the content of calcium carbonate and glass powder in the modifier components is 0.5% and 4% to 16% respectively, the sample disintegrates, and the "cloudy" state produced by the clay suspension can be clearly seen near or around the surface of the sample. According to the dispersibility judgment standard of the fragment test, the sample is classified as dispersible soil;

[0093] When the content of calcium carbonate and glass powder in the modifier components is 2.5% and 4% to 16% respectively, there is a slight visible suspension of colloid particles near or around the surface of the sample, and the water is slightly turbid. According to the dispersion judgment standard of the fragment test, the sample is classified as transitional soil.

[0094] When the content of calcium carbonate and glass powder in the modifier components is 4.5% to 6.5% and 4% to 16% respectively, the sample does not disintegrate after contact with water or there is no turbidity after disintegration, and the water is clear and transparent. According to the dispersibility judgment standard of the fragment test, the sample is classified as non-dispersible soil;

[0095] (3) Mud ball test results: Based on the mud ball test results of the sample Fig.13 It can be seen that when the modifier component is C0P0, that is, the amount of calcium carbonate and glass powder is 0, the mud ball disintegrates quickly, the soil-water boundary is completely blurred, and a large amount of thick suspended matter is produced at the bottom of the cup, forming a "cloudy" turbidity phenomenon. According to the dispersion judgment standard of the mud ball test, the sample is classified as dispersed soil;

[0096] When the content of calcium carbonate and glass powder in the modifier components is 0.5% and 4% to 16% respectively, the soil-water boundary is blurred, and the cloudiness produced by the clay suspension can be clearly seen near or around the surface of the mud ball. According to the dispersion judgment standard of the mud ball test, the sample is classified as dispersed soil.

[0097] When the content of calcium carbonate and glass powder in the modifier was 2.5% and 4% respectively, there was turbid water produced by the suspension of colloid particles visible to the naked eye near or around the surface of the mud ball, and the soil-water boundary was slightly blurred. According to the dispersion judgment standard of the mud ball test, the soil sample was classified as transitional soil.

[0098] When the dosage of calcium carbonate and glass powder in the modifier components is 2.5% to 6.5% and 8% to 16% respectively, there is no turbidity after the mud ball disintegrates in contact with water, and the soil-water boundary is clear. According to the dispersion judgment standard of the mud ball test, the soil sample is classified as non-dispersible soil.

[0099] Fig.14 Figure 1 is a comprehensive evaluation result of the dispersion test of a series of modifiers on the improved soil after solidification in this embodiment. Figure (a), Figure (b) and Figure (c) represent different curing ages of 1d, 7d and 14d, respectively. Fig.14It can be seen that at each curing age, with the increase of the calcium-based composite material content, the dispersibility of the soil sample shows a trend of "dispersibility-transitional-non-dispersibility", which indicates that the calcium-based composite material, i.e., the modifier, significantly inhibits the dispersibility of the soil sample, and when the calcium lime content in the modifier exceeds 4.5% and the glass powder content exceeds 4%, the curing effect is better; Comprehensively judged, for high Na + The best amendment ratio for original dispersible soil is C6.5P8.

[0100] Mechanical properties test of original dispersed soil after solidification and improvement

[0101] The main goal of improving natural soil is to improve its load-bearing capacity, including the load-bearing capacity of buildings, foundations and hydraulic structures, and to enhance its resistance to overload, climate change and natural disasters such as earthquakes and landslides. The unconfined compressive strength test, compression test and permeability test were used to test the strength of the soil samples after the original dispersed soil was solidified and improved by a series of improvers in the embodiments of the present invention. The results are as follows: Fig.15 As shown. Fig.15 It can be seen that improving the compaction degree is beneficial to the interaction between the calcium-based composite curing agent and soil particles, promoting the reaction, thereby further improving the strength. This shows that the dispersed soil improved by the modifier of the present invention has good load resistance for buildings, foundations and hydraulic structures, and enhances its resistance to overload, climate change and natural disasters such as earthquakes and landslides.

[0102] The compressibility of soil refers to the property of soil to reduce its volume under the action of external forces. Fig.16 The compression characteristics of soil samples after a series of modifiers were used to improve the original dispersed soil in the embodiment of the present invention are shown in FIG. Fig.16 It can be seen that under the same compaction degree and curing age, with the increase of calcium carbonate and glass powder content, the compression coefficient generally shows a downward trend, indicating that the addition of calcium carbonate and glass powder in the modifier can effectively improve the compression performance of the soil and make its deformation under load smaller.

[0103] The pores between soil solid particles are interconnected, and water flows through these pores driven by pressure difference or energy difference. This process is called seepage. The characteristic that measures the seepage capacity of soil is called permeability, which is usually characterized by the permeability coefficient. Fig.17 The permeability coefficient diagram of the soil sample after a series of modifiers were used to solidify and improve the original dispersed soil in the embodiment of the present invention. Fig.17It can be seen that the modifier has a good effect in improving the soil permeability characteristics. At a higher calcium carbonate content, the permeability coefficient of the solidified soil is significantly reduced, and with the increase of calcium carbonate and glass powder content, the permeability coefficient generally shows a decreasing trend. Therefore, the permeability performance of the soil can be optimized by reasonably adjusting the content of the modifier.

[0104] Step 5: Fill the improved soil obtained after solidification and improvement with the best ratio of improver in step 4 back into the foundation of the sampling address in step 1, and compact it to the original state with a sheep horn roller. Fig.18 described.

[0105] In order to ensure that the solidification of dispersed soil can achieve the best effect, the backfill depth should be 0.5m each time the improved soil is backfilled, and the solidification time of each layer of soil is 7 to 28 days. When the soil strength is stable, another layer of soil is applied on it, and this is repeated until the backfill reaches the designed depth.

[0106] Example 2

[0107] The difference between this embodiment and embodiment 1 is that the original dispersible soil obtained in step 1 is an original dispersible soil of high pH type, with a pH as high as 9.2; the values ​​of x% in the modifier component CxPy in step 4 are 0.5%, 1.5%, 2.5%, and 4.5%, respectively, and the values ​​of y% are 4%, 8%, 12%, and 16%, respectively;

[0108] Dispersibility test of original dispersible soil after solidification and improvement

[0109] (1) Pinhole test results: From the pinhole test results of the samples obtained after the original dispersible soil was solidified and improved by a series of improvers in this embodiment, it can be seen that when the improver component is C0.5P4, that is, the calcium carbonate and glass powder are added in an amount of 0.5% and 4% respectively, the sample is placed under a head of 50 mm and continuously flows through the pinhole test device for 10 minutes. The final flow rate reaches 1.4 mL / s. After the end, it is observed that the water in the measuring cylinder is turbid. The sample is taken out and cut. The results show that the pore diameter of the sample exceeds 1.5 times the diameter of the steel needle. According to the dispersion judgment standard of the pinhole test, the sample is classified as dispersible soil;

[0110] When the content of calcium carbonate and glass powder in the modifier components is 1.5% to 2.5% and 8% to 16% respectively, the sample is placed under a water head of 1020 mm and continuously flows through the pinhole test device for 5 minutes. The final flow rate is in the range of 1.6 mL / s to 1.8 mL / s. After the test, it is observed that the water in the measuring cylinder is clear. The sample is taken out and cut. The results show that the sample pore diameter is equal to the diameter of the steel needle. According to the dispersion criterion of the pinhole test, the soil sample is classified as non-dispersible soil.

[0111] When the total content of calcium carbonate and glass powder in the modifier is more than 4.5%, calcium carbonate content should not exceed 2.5% because calcium carbonate itself is alkaline. Although increasing its content will further weaken the dispersibility, it will have an impact on the soil.

[0112] (2) Piece fragment test results: From the piece fragment test results of the samples obtained after the original dispersible soil was solidified and improved by a series of improvers in this embodiment, it can be seen that when the calcium carbonate and glass powder in the improver components are added in an amount of 0.5% and 4% to 8% respectively, the sample disintegrates, and the "cloudy" state produced by the clay particle suspension can be clearly seen near or around the surface of the sample. According to the dispersibility judgment standard of the piece fragment test, the sample is classified as dispersible soil;

[0113] When the content of calcium carbonate and glass powder in the modifier components is 1.5% to 2.5% and 4% to 8% respectively, there is a slight visible suspension of colloid particles near or around the surface of the sample, and the water is slightly turbid. According to the dispersion judgment standard of the fragment test, the sample is classified as transitional soil.

[0114] When the content of calcium carbonate and glass powder in the modifier components is 2.5% and 8% to 16% respectively, the sample does not disintegrate after contact with water or there is no turbidity after disintegration, and the water is clear and transparent. According to the dispersion judgment standard of the fragment test, the sample is classified as non-dispersible soil.

[0115] With the pinhole test, when the calcium carbonate content in the improver component is too high ≥4.5%, the soil will become too alkaline, pH ≥8.7, so the calcium carbonate content should be reduced and the glass powder content should be increased.

[0116] In this embodiment, according to the most unfavorable principle, the result with the strongest dispersion in the pinhole test, mud ball test and fragment test is used as the comprehensive judgment standard. It is found that the pinhole test and mud ball test can determine that the original dispersed soil after solidification and improvement in this embodiment has gone beyond the category of dispersed soil, so the mud ball test is no longer carried out.

[0117] In summary, based on the pinhole and fragment test results, it can be determined that the optimal amendment ratio for dispersed soil with high pH is C2.5P16.

[0118] Example 3

[0119] The difference between this embodiment and embodiment 1 is that: in step 1, the original dispersible soil with a high montmorillonite content is obtained, and the montmorillonite content is 8.5%; in step 4, the values ​​of x% in the modifier component CxPy are 0.5%, 1.5%, 2.5%, and 4.5%, respectively, and the values ​​of y% are 4%, 8%, 12%, and 16%, respectively;

[0120] Dispersibility test of original dispersible soil after solidification and improvement

[0121] (1) Pinhole test results: From the pinhole test results of the samples obtained after the original dispersible soil was solidified and improved by a series of improvers in this embodiment, it can be seen that when the improver components, namely, calcium carbonate and glass powder, are added in an amount of 0.5% to 1.5% and 4 to 16% respectively, the sample is placed under a head of 50 mm and continuously flows through the pinhole test device for 10 minutes, and the final flow rate reaches 1.4 mL / s. After the end, it is observed that the water in the measuring cylinder is turbid. The sample is taken out and cut, and the results show that the pore diameter of the sample exceeds 1.5 times the diameter of the steel needle. According to the dispersion judgment standard of the pinhole test, the sample is classified as dispersible soil;

[0122] When the content of calcium carbonate and glass powder in the modifier components is 2.5% to 4.5% and 4% to 16% respectively, the sample is placed under a water head of 1020mm and flows through the pinhole test device for 5 minutes. The final flow rate is in the range of 1.6mL / s to 1.8mL / s. After the test, it is observed that the water in the measuring cylinder is clear. The sample is taken out and cut. The results show that the sample pore size is equal to the diameter of the steel needle. According to the dispersion judgment standard of the pinhole test, the soil sample is classified as non-dispersible soil. However, when the calcium carbonate content is 4.5%, the pH value of the improved soil is 8.8-9.1 as measured by a pH meter, which will damage the original soil, so the content of calcium carbonate is reduced;

[0123] (2) Piece fragment test results: From the piece fragment test results of the samples obtained after the original dispersible soil was solidified and improved by a series of improvers in this embodiment, it can be seen that when the calcium carbonate and glass powder in the improver components are added in an amount of 0.5% and 4% to 8% respectively, the sample disintegrates, and the "cloudy" state produced by the clay particle suspension can be clearly seen near or around the surface of the sample. According to the dispersibility judgment standard of the piece fragment test, the sample is classified as dispersible soil;

[0124] When the content of calcium carbonate and glass powder in the modifier components is 1.5% and 4% to 8% respectively, there is a slight visible suspension of colloid particles near or around the surface of the sample, and the water is slightly turbid. According to the dispersion judgment standard of the fragment test, the sample is classified as transitional soil.

[0125] When the content of calcium carbonate and glass powder in the modifier components is 2.5% to 4.5% and 8% to 16% respectively, the sample does not disintegrate after contact with water or there is no turbidity after disintegration, and the water body is clear and transparent. According to the dispersibility judgment standard of the fragment test, the sample is classified as non-dispersible soil. However, the pH value of the improved soil within this range is 8.8-9.5 as measured by the pH meter, which will damage the original soil, so the content of calcium carbonate should be reduced as much as possible.

[0126] In this embodiment, according to the most unfavorable principle, the result with the strongest dispersion in the pinhole test, mud ball test and fragment test is used as the comprehensive judgment standard. It is found that the pinhole test and mud ball test can determine that the original dispersed soil after solidification and improvement in this embodiment has gone beyond the category of dispersed soil, so the mud ball test is no longer carried out.

[0127] In summary, based on the results of pinhole and fragment tests, it can be determined that the optimal amendment ratio for original dispersible soil with a high montmorillonite content is C2.5P8.

[0128] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for improving dispersible soil using calcium carbonate and glass powder, characterized in that: The method comprises the following steps: Step 1: obtaining original dispersed soil at the sampling site, and then crushing, grinding, air-drying and sieving the original dispersed soil in sequence, and taking the sieve-down as dispersed soil to be treated; at the same time, designing improver components with calcium carbonate and glass powder as ingredients according to different proportions; Step 2: According to GB / T 50123-2019 "Standard for Geotechnical Test Methods", the physical properties of the original dispersed soil in step 1 are determined by compaction test, limit moisture content test, and particle analysis test, including moisture content, density, particle size distribution, plastic limit, and liquid limit; Step 3: According to T / CECS1337-2023 "Standard for Test Methods of Unsaturated Soils" and ASTM D4647 and ASTMD6572, the dispersibility of the original dispersible soil in step 1 is comprehensively identified through pinhole test, fragment test and mud ball test; Step 4: According to the physical property index of the original dispersible soil measured in step 2 and the dispersibility result identified in step 3, the improver prepared in step 1 is added to the dispersible soil to be treated and water is added for solidification and improvement, and improved soil is obtained after curing, and then the dispersibility of the improved soil is identified according to the method in step 3 to obtain the best improver ratio; Step 5: Fill the improved soil obtained after solidification and improvement with the best modifier ratio in step 4 back into the foundation of the sampling address in step 1, and compact it to its original state with a sheep horn roller.

2. The method for improving dispersible soil by using calcium carbonate and glass powder according to claim 1, characterized in that: In step 1, the original dispersed soil is crushed with a small wooden hammer, and after natural air drying, it is sieved through 0.5 mm and 2 mm holes for later use.

3. The method for improving dispersible soil by using calcium carbonate and glass powder according to claim 1, characterized in that: The percentage of each component of the modifier added to the dispersed soil to be treated in step 4 is: 0.5% to 6.5% of calcium carbonate, no more than 16% of glass powder, and the amount of water added is the optimal moisture content of the original dispersed soil after adding the modifier.

4. The method for improving dispersible soil by using calcium carbonate and glass powder according to claim 3, characterized in that: The original dispersible soil in step 1 is high Na + The content of dispersed soil, the percentage of each component of the modifier added to the dispersed soil to be treated in step 4 is: 4.5% to 6.5% of calcium carbonate, 4% to 8% of glass powder, and the amount of water added is the optimal moisture content of the original dispersed soil after adding the modifier.

5. The method for improving dispersible soil by using calcium carbonate and glass powder according to claim 3, characterized in that: The original dispersed soil described in step one is a dispersed soil with a higher pH value. The percentage of each component of the modifier added to the dispersed soil to be treated in step four is: 0.5% to 2.5% of calcium carbonate, 4% to 16% of glass powder, and the amount of water added is the optimal moisture content of the original dispersed soil after adding the modifier.

6. The method for improving dispersible soil by using calcium carbonate and glass powder according to claim 3, characterized in that: The original dispersible soil described in step one is a dispersible soil with a high montmorillonite content. The percentage of each component of the modifier added to the dispersible soil to be treated in step four is: 1% to 4% of calcium carbonate, 4% to 8% of glass powder, and the amount of water added is the optimal moisture content of the original dispersible soil after adding the modifier.

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