Environment-friendly sand high-efficiency infiltration reduction composite material and application thereof

Abstract

This invention discloses an environmentally friendly, high-efficiency permeability-reducing composite material for sand and its applications. The environmentally friendly, high-efficiency permeability-reducing composite material comprises xanthan gum, nano-silica, and pectinase, used to improve the strength and reduce the permeability of sand. The invention first mixes sand and soil in equal proportions to obtain clayey sand, then incorporates the environmentally friendly, high-efficiency permeability-reducing composite material to obtain remolded sand. Permeability tests, triaxial shear tests, and microscopic tests on the remolded sand show that after incorporating the environmentally friendly, high-efficiency permeability-reducing composite material, gel material is uniformly distributed on the surface and within the pores of the remolded sand, forming a non-penetrating pore structure within it, reducing the permeability of the remolded sand. Furthermore, long-term curing can improve the strength and ductility of the remolded sand. The environmentally friendly, high-efficiency permeability-reducing composite material provided by this invention is environmentally friendly, efficient, low-cost, and applicable to multiple scenarios, with broad application prospects.

Description

Technical Field

[0001] This invention relates to the field of seepage reduction materials technology, and in particular to an environmentally friendly, high-efficiency seepage reduction composite material for sand and soil and its application. Background Technology

[0002] Sand water seepage reduction refers to technical measures that lower the groundwater level or reduce groundwater infiltration in sandy soil layers. These measures are commonly used in construction projects to prevent groundwater from affecting construction. Currently, commonly used seepage reduction technologies include two-component grout sealing, waterproof coatings, and geomembranes.

[0003] For two-component grout sealing technology, the two-component grout typically consists of a main agent (such as cement grout or sodium silicate) and a quick-setting agent (such as water glass or calcium chloride). Both remain liquid before mixing and undergo a chemical reaction (such as gelation, precipitation, or solidification) after mixing, forming a high-strength solidified body in a short time. This method is greatly affected by ambient temperature and humidity, and the effect may be unstable due to too rapid solidification (blocking pipes) or too slow solidification (loss). Furthermore, the investment in materials (such as acrylates and water glass) and specialized equipment is large, making large-scale application economically unfeasible. In addition, some chemical grouts may contain toxic components (such as chromates), polluting groundwater or soil, thus limiting the effectiveness of two-component grout sealing technology. For waterproof coatings, some materials are prone to aging and cracking. For example, polyurethane-based coatings are susceptible to UV aging and require an additional protective layer; asphalt-based coatings soften at high temperatures and crack at low temperatures. Additionally, the joints of waterproof coatings after film formation can become weak points, requiring reinforcement with sealing materials. Geomembrane descaling technology is an engineering method that utilizes the low permeability of polymer materials (such as HDPE, LDPE, PVC, etc.) to construct seepage barriers to reduce the infiltration of water or pollutants. For geomembranes such as HDPE and PVC membranes, large temperature changes can cause the membrane to shrink or expand, potentially cracking the anchoring ends or creating wrinkles that allow water to accumulate. Simultaneously, ultraviolet radiation and chemical corrosion (such as landfill leachate) can reduce the material's lifespan, requiring regular replacement. Furthermore, large-area installation requires heavy machinery, and construction efficiency is low in complex terrain areas (such as slopes and corners).

[0004] In summary, while commonly used sand-based deseepage reduction technologies can achieve some deseepage reduction under specific conditions, they suffer from numerous problems, including environmental pollution, complex construction, high cost, limited application scenarios, and poor seepage prevention effects. Therefore, developing an environmentally friendly, efficient, low-cost, and widely applicable sand-based deseepage reduction material is of paramount importance. Summary of the Invention

[0005] To address the problems existing in current sand and soil de-seepage materials, this invention provides an environmentally friendly, high-efficiency sand and soil de-seepage composite material and its applications.

[0006] In the first aspect, an environmentally friendly, high-efficiency sand-soil permeability-reducing composite material is provided, comprising a main permeability-reducing material and an accelerator. The main permeability-reducing material is xanthan gum and nano-silica, and the accelerator is selected from calcium chloride, lipase, and pectinase. The mass ratio of xanthan gum, nano-silica, and accelerator is 0.5~3:0.2~0.8:1.

[0007] Preferably, the mass ratio of xanthan gum, nano silica, and accelerator is 2:0.6:1.

[0008] Preferably, the particle size of the nano-silica is 15~30nm.

[0009] Preferably, the promoter is pectinase.

[0010] Secondly, the environmentally friendly, high-efficiency sand-soil permeability-reducing composite material is used to reduce the permeability of sand.

[0011] Preferably, the sandy soil is a clayey sandy soil obtained by mixing soil and sand in a mass ratio of 1:1.

[0012] Preferably, the soil particle size is 0.2~1mm, and the sand particle size is 0.2~0.6mm.

[0013] Preferably, the steps for using environmentally friendly, high-efficiency sand-de-permeability composite materials to reduce the permeability of sand include:

[0014] (1) Add xanthan gum, nano silica and accelerator to clay sand in proportion, mix well to obtain a mixture;

[0015] (2) Add distilled water to the above mixture and mix well to obtain remolded sand.

[0016] Preferably, permeability tests, triaxial shear tests, and microscopic tests are conducted on the remolded sand.

[0017] Preferably, the remolded sand has a uniformly distributed gel material on its surface and in the pores, forming a non-penetrating pore structure inside. The permeability coefficient of the remolded sand is reduced by 3 orders of magnitude compared to that of clayey sand. After 3 days of curing, the strength of the remolded sand is 100% higher than that of clayey sand, and after 7 days of curing, the strength of the remolded sand is 120% higher than that of clayey sand.

[0018] The environmentally friendly, high-efficiency seepage-reducing composite material for sand and soil provided by this invention has the following advantages:

[0019] (1) High fluidity: Environmentally friendly sand and soil high-efficiency seepage-reducing composite material can achieve infiltration grouting in clayey sand;

[0020] (2) Good permeability reduction: Compared with clayey sand, the permeability coefficient of remolded sand is reduced by 3 orders of magnitude;

[0021] (3) Rapid response: After adding environmentally friendly sand and soil high-efficiency de-permeability composite material, the permeability coefficient of the remolded sand and soil immediately decreases;

[0022] (4) Strong sustainability: After adding environmentally friendly sand and soil high-efficiency de-seepage composite material, gel material is evenly distributed on the surface and between the pores of the remolded sand and soil and a non-penetrating pore structure is formed inside it. The gel material gradually solidifies over time, and the strength and de-seepage performance of the remolded sand and soil are gradually enhanced.

[0023] (5) Environmental protection: The raw materials of this environmentally friendly sand and soil high-efficiency de-permeability composite material are non-toxic and harmless, and some of them can be used in food, without polluting the environment;

[0024] (6) Low cost: The raw materials of this environmentally friendly sand and soil high-efficiency seepage reduction composite material are inexpensive and readily available, resulting in low cost and strong feasibility;

[0025] (7) Wide range of applications: This environmentally friendly sand and soil high-efficiency seepage reduction composite material can be used in various scenarios such as tunnel seepage control, foundation pit excavation, dam seepage prevention and pollutant migration barrier.

[0026] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the main osmosis-reducing materials (a: xanthan gum; b: nano silica).

[0028] Figure 2 This is a schematic diagram of the promoters (a: calcium chloride; b: lipase; c: pectinase; d: urea).

[0029] Figure 3 This is a flowchart illustrating the application and testing of environmentally friendly, high-efficiency permeability-reducing composite materials for sand and soil.

[0030] Figure 4 Example 2 illustrates the effect of xanthan gum addition on the permeability coefficient of remolded sand.

[0031] Figure 5 Example 3 illustrates the effect of the amount of single nano-silica added on the permeability coefficient of remolded sand.

[0032] Figure 6 Example 4 illustrates the effect of different amounts of xanthan gum added (0.2%) on the permeability coefficient of remolded sand.

[0033] Figure 7 Example 5 illustrates the effect of different amounts of xanthan gum added (0.4%) on the permeability coefficient of remolded sand.

[0034] Figure 8Example 6 illustrates the effect of different xanthan gum addition amounts on the permeability coefficient of remolded sand when the amount of nano-silica added is 0.6%.

[0035] Figure 9 Example 7 illustrates the effect of different xanthan gum addition amounts on the permeability coefficient of remolded sand when the amount of nano-silica added is 0.8%.

[0036] Figure 10 Example 8 shows the effect of different accelerators on the permeability coefficient of remolded sand when the amount of nano-silica added is 0.6% and the amount of xanthan gum added is 2%.

[0037] Figure 11 The results of triaxial shear tests on clay sand from Example 1 and reconstituted sand from Example 8 with added 0.6% nano silica, 2% xanthan gum, and 1% pectinase after 3 days of curing are shown (a: clay sand, b: reconstituted sand).

[0038] Figure 12 The results of triaxial shear tests after 7 days of curing are as follows: clay sand of Example 1 and reconstituted sand of Example 8 with the addition of 0.6% nano silica, 2% xanthan gum and 1% pectinase (a: clay sand, b: reconstituted sand).

[0039] Figure 13 These are SEM images of clayey sand from Example 1 (a: 200x, b: 500x, c: 1000x, d: 2000x).

[0040] Figure 14 This is a SEM image of reconstituted sand with 0.6% nano silica, 2% xanthan gum, and 1% pectinase added in Example 8 (a: 200x magnification, b: 500x magnification, c: 1000x magnification, d: 2000x magnification). Detailed Implementation

[0041] The present invention will be further described below. It should be noted that this embodiment is based on the present technical solution and provides detailed implementation methods and specific operation processes, but the present invention is not limited to this embodiment.

[0042] This study primarily utilizes biopolymer-inorganic nanocomposite materials to reduce osmosis; xanthan gum and nano-silica samples are shown. Figure 1Xanthan gum, sourced from Shandong Fufeng Biotechnology Co., Ltd., is a food-grade biopolymer, appearing as a pale yellow ultrafine powder (D50=45 μm), with an intrinsic viscosity of 8.9 mPa·s (1% aqueous solution, 25℃) and a pH of 6.9±0.3 (10 g / L solution). Before use, it undergoes 200-mesh (74 μm) vibrating sieving and is stored in a dry, light-protected environment. Nano-silica, sourced from Foshan Yuante New Materials Co., Ltd., is selected in this invention as oleophilic-hydrophobic nano-silica with a particle size of 20 nm, appearing as an amorphous white powder. The accelerators are selected from calcium chloride, lipase, pectinase, and urea. Food-grade calcium chloride is used, appearing as a white powder; lipase is a white crystalline powder; pectinase is a light yellow powder; and urea is a white crystal. (See attached image for details.) Figure 2 .

[0043] Example 1

[0044] This embodiment provides a method for preparing clayey sand, the specific process of which includes ( Figure 3 ):

[0045] (1) Mix soil with a particle size of 0.2~1mm and sand with a particle size of 0.2~0.6mm in a mass ratio of 1:1 to obtain a mixture;

[0046] (2) Take 160g of the above mixture, add 60mL of distilled water, mix well, and obtain clay sand.

[0047] Example 2

[0048] This embodiment provides an application of an environmentally friendly, high-efficiency permeability-degrading composite material for sandy soil. The specific process includes:

[0049] (1) Mix soil with a particle size of 0.2~1mm and sand with a particle size of 0.2~0.6mm in a mass ratio of 1:1 to obtain clayey sandy soil;

[0050] (2) Take five portions of clayey sand, each 160g. Add 0.8g, 1.0g, 1.5g, 2.0g, and 2.5g of xanthan gum to the five portions of clayey sand respectively and mix well (accounting for 0.5%, 1.0%, 1.5%, 2.0%, and 2.5% of the mass of clayey sand respectively). Add 60mL of distilled water to each portion and mix well to obtain five portions of remolded sand.

[0051] Example 3

[0052] This embodiment provides an application of an environmentally friendly, high-efficiency permeability-degrading composite material for sandy soil. The specific process includes:

[0053] (1) Mix soil with a particle size of 0.2~1mm and sand with a particle size of 0.2~0.6mm in a mass ratio of 1:1 to obtain clayey sandy soil;

[0054] (2) Take four portions of clayey sand, each 160g, and add 0.32g, 0.64g, 0.96g and 1.28g of nano silica to the four portions of clayey sand respectively and mix well (accounting for 0.2%, 0.4%, 0.6% and 0.8% of the mass of clayey sand respectively). Add 60mL of distilled water to each portion and mix well to obtain four portions of remolded sand.

[0055] Example 4

[0056] This embodiment provides an application of an environmentally friendly, high-efficiency permeability-degrading composite material for sandy soil. The specific process includes:

[0057] (1) Mix soil with a particle size of 0.2~1mm and sand with a particle size of 0.2~0.6mm in a mass ratio of 1:1 to obtain clayey sandy soil;

[0058] (2) Take six portions of clayey sand, each 160g. Add 0.32g of nano-silica (0.2% of the mass of clayey sand) to each of the six portions of clayey sand and mix well. Do not add xanthan gum to one portion. Add 0.8g, 1.0g, 1.5g, 2.0g, and 2.5g of xanthan gum (0.5%, 1.0%, 1.5%, 2.0%, and 2.5% of the mass of clayey sand, respectively) to the other portions and mix well. Add 60mL of distilled water to each portion and mix well to obtain six portions of remolded sand.

[0059] Example 5

[0060] This embodiment provides an application of an environmentally friendly, high-efficiency permeability-degrading composite material for sandy soil. The specific process includes:

[0061] (1) Mix soil with a particle size of 0.2~1mm and sand with a particle size of 0.2~0.6mm in a mass ratio of 1:1 to obtain clayey sandy soil;

[0062] (2) Take six portions of clay sand, each 160g. Add 0.64g of nano silica (0.4% of the mass of clay sand) to each of the six portions of clay sand and mix well. Do not add xanthan gum to one portion. Add 0.8g, 1.0g, 1.5g, 2.0g, and 2.5g of xanthan gum (0.5%, 1.0%, 1.5%, 2.0%, and 2.5% of the mass of clay sand, respectively) to the other five portions and mix well. Add 60mL of distilled water to each portion and mix well to obtain six portions of remolded sand.

[0063] Example 6

[0064] This embodiment provides an application of an environmentally friendly, high-efficiency permeability-degrading composite material for sandy soil. The specific process includes:

[0065] (1) Mix soil with a particle size of 0.2~1mm and sand with a particle size of 0.2~0.6mm in a mass ratio of 1:1 to obtain clayey sandy soil;

[0066] (2) Take six portions of clay sand, each 160g. Add 0.96g of nano silica (0.6% of the mass of clay sand) to each of the six portions of clay sand and mix well. Do not add xanthan gum to one portion. Add 0.8g, 1.0g, 1.5g, 2.0g, and 2.5g of xanthan gum (0.5%, 1.0%, 1.5%, 2.0%, and 2.5% of the mass of clay sand, respectively) to the other five portions and mix well. Add 60mL of distilled water to each portion and mix well to obtain six portions of remolded sand.

[0067] Example 7

[0068] This embodiment provides an application of an environmentally friendly, high-efficiency permeability-degrading composite material for sandy soil. The specific process includes:

[0069] (1) Mix soil with a particle size of 0.2~1mm and sand with a particle size of 0.2~0.6mm in a mass ratio of 1:1 to obtain clayey sandy soil;

[0070] (2) Take six portions of clayey sand, each 160g. Add 1.28g of nano-silica (0.8% of the mass of clayey sand) to each of the six portions of clayey sand and mix well. Do not add xanthan gum to one portion. Add 0.8g, 1.0g, 1.5g, 2.0g, and 2.5g of xanthan gum (0.5%, 1.0%, 1.5%, 2.0%, and 2.5% of the mass of clayey sand, respectively) to the other five portions and mix well. Add 60mL of distilled water to each portion and mix well to obtain five portions of remolded sand.

[0071] Example 8

[0072] This embodiment provides an application of an environmentally friendly, high-efficiency permeability-degrading composite material for sandy soil. The specific process includes the following steps:

[0073] (1) Mix soil with a particle size of 0.2~1mm and sand with a particle size of 0.2~0.6mm in a mass ratio of 1:1 to obtain clayey sandy soil;

[0074] (2) Take five portions of clay sand, each 160g. Add 3.2g xanthan gum (2% of the mass of clay sand) and 0.96g nano silica (0.6% of the mass of clay sand) to each of the five portions of clay sand and mix well. Do not add accelerator to one portion. Add 1.6g calcium chloride (1% of the mass of clay sand), 1.6g lipase, 1.6g pectinase and 1.6g urea to the other five portions respectively and mix well. Add 60mL of distilled water to each portion and mix well to obtain five portions of remolded sand.

[0075] Test methods

[0076] (1) Ring sampler

[0077] Samples of clayey sand and remolded sand from Examples 1-8 were taken using a ring cutter with dimensions of Φ61.8mm × H40mm, respectively, yielding a moisture content of approximately 27wt% and a dry density of 1.8g / cm³. 3 Ring cutter specimens of clayey sand and remolded sand.

[0078] (2) Permeation test

[0079] According to the requirements of GB / T50123-2019 "Standard for Geotechnical Test Methods" 19.3.2, the clayey sand ring sample and the remolded sand ring sample were vacuum-evacuated to fully saturate the samples. After 24 hours, the permeability coefficient of the samples was determined according to the requirements of GB / T50123-2019 "Standard for Geotechnical Test Methods" "16.3 Variable Head Permeability Test".

[0080] (2) Triaxial shear test

[0081] Samples were prepared according to the requirements of GB / T50123-2019 "Standard for Geotechnical Test Methods" 19.3.1, using clayey sand from Example 1 and reconstituted sand from Example 8 with 2% xanthan gum, 0.6% nano silica, and 1% pectinase. The samples were cured under standard conditions (temperature 20±2℃, relative humidity 60~80%). Samples cured for 3 days and 7 days were taken respectively. According to GB / T50123-2019 "Standard for Geotechnical Test Methods" "19.4 Unconsolidated undrained shear test", triaxial shear tests were conducted using the TSZ-3A standard stress path triaxial test system under three confining pressures of 100 kPa, 200 kPa, and 300 kPa.

[0082] (3) Microscopic experiments

[0083] Sample blocks of 1×1×0.5 cm were taken from the reshaped sand ring cutter sample of Example 1 and the clay sand ring cutter sample with 2% xanthan gum, 0.6% nano silica and 1% pectinase added in Example 8, respectively. These samples were dried in an oven at 105℃ for 10 hours, and the surface of the sample blocks was leveled (the specific steps were: 1) First, place the sample block in a beaker container, then place the small beaker in a slightly larger cylinder, use a vacuum pump to evacuate the cylinder to 10 kPa, and maintain this state for 15 minutes; 2) Take 100 ml of epoxy resin and 200 ml of acetone, mix thoroughly, then add 7 ml of curing agent ethylenediamine and 2 ml of plasticizer dibutyl phthalate, and continue to mix thoroughly for 5 minutes; 3) Using a separatory funnel, slowly add the prepared solution to the small beaker, then remove the sample block for curing. After confirming that curing is complete, perform a series of operations such as cutting, grinding, polishing and gold spraying. Then, use Thermo Scientific Apreo... The 2S ultra-high resolution field emission scanning electron microscope was used to perform SEM scanning microscopy experiments on the sample at different magnifications.

[0084] Results Analysis

[0085] (1) Results of the permeation test

[0086] The results of the permeation tests are as follows: Figures 4-10 As shown. Figure 4 The effect of adding xanthan gum alone on the permeability coefficient of remolded sand. Figure 4 It can be seen that the addition of xanthan gum alone can stably reduce the permeability coefficient of the remolded sand sample by one order of magnitude, from 10. -3 cm / s decreased to 10 -4 cm / s. In the initial stage of xanthan gum addition, a small amount of xanthan gum can cause a sharp decrease in the permeability coefficient. This is because the unique molecular structure of xanthan gum forms a viscous network in the soil, effectively filling the pores between soil particles and hindering fluid seepage channels. When the xanthan gum content exceeds 2%, the rate of decrease in permeability coefficient gradually slows down, and even a slight rebound occurs (when xanthan gum content increases from 2% to 2.5%, the permeability coefficient of the remolded sand sample actually increases from 1.63 × 10 cm / s). -4 cm / s increased to 1.91 × 10 -4 The flow rate (cm / s) is likely due to the formation of gel aggregates by excessive xanthan gum in the soil, altering the internal pore structure and creating new seepage channels. Therefore, considering both cost and improvement effect, the optimal addition amount of xanthan gum alone is 2% (percentage of clayey sand by mass).

[0087] Figure 5 The effect of single nano-silica addition amount on the permeability coefficient of remolded sand. Figure 5It can be seen that adding only nano-silica can reduce the permeability coefficient of the remolded sand sample by an order of magnitude, and the permeability coefficient gradually decreases with increasing nano-carbon dioxide content. When the amount of nano-silica added is 0.6%, the rate of decrease in the curve becomes relatively slow, and further increasing the amount of nano-silica added results in a very small decrease in permeability coefficient. Considering all factors, the optimal amount of nano-silica added is 0.6% (percentage of clayey sand mass).

[0088] Figures 6-9 The effects of xanthan gum additions of 0%, 0.5%, 1%, 1.5%, 2%, and 2.5% on the permeability coefficient of remolded sand samples were investigated when the addition amounts of nano-silica were controlled at 0.2%, 0.4%, 0.6%, and 0.8%, respectively. The four figures show that the remolded sand samples exhibited better permeability reduction under the combined effect of xanthan gum and nano-silica. The optimal permeability coefficient of all four groups of remolded sand samples improved from the initial value of 10. -3 The magnitude was reduced to 10 -7 The permeability coefficient decreased by a stable four orders of magnitude. Furthermore, with a fixed amount of nano-silica added, the rate of decrease in permeability coefficient of the sand samples gradually slowed down with increasing xanthan gum addition, stabilizing at a xanthan gum addition of 2%. Comparing the four sets of experiments, the remolded sand sample with 0.6% nano-silica showed the lowest permeability coefficient when the xanthan gum addition was 2%. In conclusion, the combination of 0.6% nano-silica and 2% xanthan gum is the optimal addition amount for remolded sand.

[0089] Figure 10 This study investigated the effects of different accelerators on the permeability coefficient of remolded sand when the addition levels of nano-silica (0.6%) and xanthan gum (2%) were present. The figure shows that, with the main permeability-degrading material at its optimal ratio, the addition of calcium chloride, lipase, and pectinase further reduced the permeability coefficient of the remolded sand from 1.17 × 10⁻⁶. -7 cm / s decreased to 4.97 × 10 -8 cm / s, 6.23×10 -8 cm / s and 2.72×10 -8The permeability coefficient was measured in cm / s, with pectinase showing the best effect as a promoter. This is because pectinase can partially degrade the long-chain polysaccharides of xanthan gum, resulting in shorter and more uniform gel fragments. These fragments can be more evenly distributed in the soil pores, improving filling efficiency and forming a more complete gel system, thus further reducing the permeability coefficient. Adding urea actually increased the permeability coefficient of the remolded sand, possibly because urea is a strong hydrogen bond disruptor, which can combine with the hydroxyl groups on xanthan gum or nano-silica, thereby disrupting the entire gel network system and making the particle aggregates slightly looser. Based on the above discussion, the optimal ratio of environmentally friendly, high-efficiency permeability-reducing material for remolded sand is 0.6% nano-silica, 2% xanthan gum, and 1% pectinase.

[0090] (2) Triaxial shear test results

[0091] The deviatoric stress-axial strain curves of the clayey sand sample (Example 1) and the remolded sand sample (Example 8, with the addition of 2% xanthan gum, 0.6% nano silica, and 1% pectinase) obtained by triaxial shear tests are shown below. Figure 11 , Figure 12 As shown.

[0092] from Figure 11 It can be seen that after 3 days of curing, under confining pressures of 100 kPa, 200 kPa, and 300 kPa, the peak deviatoric stresses of the clayey sand samples were 104.28 kPa, 107.11 kPa, and 113.41 kPa, respectively. The deviatoric stresses decreased rapidly after reaching their peak values, exhibiting characteristics of brittle failure. In contrast, the peak deviatoric stresses of the remolded sand samples under the three confining pressures were 212.71 kPa, 218.78 kPa, and 226.82 kPa, respectively, representing increases of 104%, 104%, and 100% compared to the clayey sand. This indicates that the environmentally friendly, high-efficiency permeability-reducing composite material significantly improves the soil strength of the sand. After reaching their peak values ​​under the three confining pressures, the deviatoric stress in the remolded sand samples decreased at a slower rate, reaching a stable stage at 141.78 kPa, 161.25 kPa, and 168.08 kPa, respectively. This represents a decrease of only 33%, 26%, and 26% compared to the peak deviatoric stress, indicating that the remolded sand retains a certain residual strength after shear failure. Furthermore, the failure strain of the remolded sand samples increased significantly, indicating improved ductility.

[0093] from Figure 12It can be seen that after 7 days of curing, under the confining pressures of 100 kPa, 200 kPa, and 300 kPa, the peak values ​​of the deviatoric stress in the clayey sand samples were 146.71 kPa, 151.19 kPa, and 154.25 kPa, respectively. The deviatoric stress dropped sharply after reaching its peak, indicating that the clayey sand samples still exhibited typical brittle failure characteristics. In contrast, the deviatoric stress in the remolded sand samples reached its maximum value under the three confining pressures, and then entered a stable period at 221.37 kPa, 246.52 kPa, and 262.99 kPa, respectively. Compared to the maximum deviatoric stress, the decrease was only 31%, 25%, and 23%, demonstrating excellent residual strength retention. Comparing the test results after 3 days and 7 days of curing, it was found that the maximum deviatoric stress of the clayey sand sample increased from 113.41 kPa to 154.25 kPa, while the maximum deviatoric stress of the remolded sand sample jumped from 226.82 kPa to 340.06 kPa, an increase of 120% compared to the clayey sand sample, indicating that the strength of the sand samples increased with the extension of curing time. Furthermore, compared with 3 days of curing, the failure strain of the remolded sand sample cured for 7 days was increased, indicating that long-term curing can further improve the ductility of the soil.

[0094] (3) Microscopic test results

[0095] The SEM scanning electron microscopy results of clayey sand and remolded sand are as follows: Figure 13 , Figure 14 As shown.

[0096] from Figure 13 It can be seen that at a magnification of 200x ( Figure 13 a) Clayey sand exhibits significant heterogeneity: the particle size distribution spans a wide range, the particle shape is highly irregular, and the surface edges are prominent. However, the coarse-to-fine gradation is relatively good. This particle size distribution helps to form a pore-filling effect. Combined with the presence of clay particles in the clayey sand, this results in a high particle packing density, forming a relatively dense packing state. The magnification is increased to 500x ( Figure 13 (b) The contact state between particles is clearer: Although the presence of clay promotes interparticle bonding, the forces of these bonds are weak, barely holding the particle surfaces together without forming chemical bonds or cementation. The interparticle bonds lack sufficient strength to form stable multi-particle aggregate structures. This weak bonding makes the soil prone to relative sliding between particles under stress, significantly limiting the improvement of sample strength. Increasing the magnification to 1000x ( Figure 13 c) 2000 times ( Figure 13d) The microstructure of the clayey sand sample can be observed more clearly: although the filling effect caused by the difference in particle size reduces the number of large pores to some extent, the contact mode between particles is still mainly point-to-point and point-to-surface contact, resulting in insufficient effective contact area. This contact mode retains a large number of interconnected small pores, providing channels for fluid seepage. In addition, although clay particles can partially fill the pores, due to their lack of cementing ability, the particles are still in a relatively weak connection state, resulting in a still high permeability coefficient, poor shear strength, and poor structural stability of the sample.

[0097] from Figure 14 It can be seen that at a magnification of 200x ( Figure 14 (a) Reconstituted sand exhibits structural characteristics distinctly different from clayey sand: honeycomb-like gel material is uniformly distributed on the particle surface and between pores of the reconstituted sand. Through the combined effects of filling and cementing, this significantly enhances the originally weak connections between particles. With the gel filling, the particles are more densely packed, their originally sharp edges are altered, their roundness is significantly improved, and large pores are effectively filled and refined, forming a relatively dense microstructure. The magnification is increased to 500x (…). Figure 14 (b) It can be seen that the gelling material promotes the tight cementation of multiple particles to form stable multi-particle aggregates, and the contact mode between particles has undergone a significant change. Unlike the direct point-to-point or point-to-surface contact between particles in clayey sand, the particles in remolded sand form indirect contact through cementing materials such as CSH, achieving a stable connection between particles. This surface-to-surface contact mode significantly increases the effective contact area between particles, making stress transmission more uniform and efficient, and significantly improving the overall strength of the soil. The magnification is increased to 1000x ( Figure 14 c) 2000 times ( Figure 14 d) The microstructure of the sample can be observed more clearly: although the internal structure of the aggregates has been greatly optimized, a small number of pores still exist between the aggregates. However, the filling distribution of the gel material effectively blocks the connectivity between the pores, forming a non-penetrating pore structure, which greatly hinders fluid seepage. In addition, the filling effect of the gel material on the microcracks on the particle surface significantly enhances the integrity of the remolded sand structure. Through the combined effects of filling, cementation, and blocking, the permeability coefficient of the remolded sand shows a significant decrease.

[0098] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. An environmentally friendly, high-efficiency permeability-reducing composite material for sandy soil, characterized in that: It includes a main osmosis-reducing material and an accelerator, wherein the main osmosis-reducing material is xanthan gum and nano-silica, and the accelerator is pectinase; The mass ratio of xanthan gum, nano silica, and pectinase was 2:0.6:

1.

2. The application of the environmentally friendly sand and soil high-efficiency permeability-reducing composite material of claim 1 in reducing the permeability of sand and soil.

3. The application of the environmentally friendly, high-efficiency permeability-reducing composite material for sand and soil according to claim 2, characterized in that: Sandy soil is a clayey sandy soil obtained by mixing soil and sand in a 1:1 mass ratio.

4. The application of the environmentally friendly, high-efficiency permeability-reducing composite material for sand and soil according to claim 3, characterized in that: The particle size of soil is 0.2~1mm, and the particle size of sand is 0.2~0.6mm.

5. The application of the environmentally friendly sand and soil high-efficiency permeability-reducing composite material according to claim 4, characterized in that: Specifically, the following steps are included: (1) Add xanthan gum, nano silica and accelerator to clay sand, mix well to obtain a mixture; (2) Add distilled water to the above mixture and mix well to obtain remolded sand.

6. The application of the environmentally friendly, high-efficiency permeability-reducing composite material for sand and soil according to claim 5, characterized in that: This includes permeability tests, triaxial shear tests, and SEM scanning electron microscopy tests on remolded sand.

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