A method of repairing in situ a pile toe wind erosion gully of a ground pile

Abstract

The application provides a technology and implementation steps for repairing a wind-erosion sand pit around a pile toe of a ground pile in situ. A mixed device is used to uniformly mix a soybean urease solution containing an additive and a salt solution on a desert site to obtain a cementing solution. A plurality of annular baffles are arranged radially below the surface of a wind-erosion sand pit near a pile toe of a desert photovoltaic panel ground pile, the sand pit sand surface is divided into n equal parts, then the cementing solution is sprayed according to a spraying mode for preventing seepage failure of the cementing solution, the n equal parts are sprayed in batches, and finally a soybean urease cementing and reinforcing repair layer is formed in situ on the surface of the wind-erosion sand pit near the pile toe. The wind-preventing reinforcing repair layer can resist the shaking of the pile foundation and weaken the wind field around the pile, so as to increase the long-term stability of the pile foundation. Compared with the commonly used mechanical backfilling and chemical cementing methods, the wind-erosion sand pit repair method provided by the application is more effective, convenient and efficient, and has no pollution to the environment, and meets the requirements of green and sustainable development.

Description

Technical Field

[0001] This invention relates to the field of desert windbreak and sand control, specifically to a method for in-situ repair of wind-eroded sand pits at the toes of ground piles. Background Technology

[0002] With the intensification of global climate change and human activities, desertification and dust storms are becoming increasingly serious problems, especially in arid and semi-arid regions. Wind erosion carries large amounts of dust particles, causing environmental degradation and ecosystem damage. Meanwhile, desert regions, due to their vast land resources and intense solar radiation, have become ideal locations for photovoltaic power generation projects. However, large-scale photovoltaic panel construction faces a series of challenges, including dust accumulation, equipment wear and tear, and increased maintenance costs. Therefore, seeking more efficient and environmentally friendly sand-fixing technologies can not only prevent the expansion of desertification but also ensure the stable operation of photovoltaic power generation projects.

[0003] Because the installation of photovoltaic (PV) panel ground piles alters the wind field within the PV area, wind stagnation points are formed at the ground pile locations. This stagnation accumulates at the pile toes, creating wind-eroded sand pits near the pile toes. The gradual enlargement of these sand pits can lead to instability and tilting of the PV panel ground piles, ultimately causing the PV panels to collapse.

[0004] In addition, in recent years, environmentally friendly bio-stabilization technologies based on soybean urease-induced calcium carbonate solidification have achieved certain results in desert windbreak and sand fixation.

[0005] However, on the one hand, due to the slope of the wind-eroded sand pits at the toes of ground piles, the spraying reinforcement technology, when directly treating and repairing these pits, causes the repair fluid to accumulate at the bottom of the pit, making it difficult to achieve a comprehensive reinforcement effect. On the other hand, the limited space at the toes of ground piles makes traditional windbreak and sand-fixing measures such as afforestation difficult to implement, and chemical sand-fixing agents are difficult to spray over large areas, while also presenting problems such as long construction periods and significant ecological impacts. Furthermore, the presence of the ground pile toes affects the wind field in the area, making it difficult for traditional spraying methods to achieve the desired reinforcement effect. Additionally, the reinforcement effect of existing urease solutions cannot withstand the influence of the unique shape of the wind-eroded sand pits around the ground piles. Therefore, there is an urgent need to develop new technical solutions to address the hazards caused by the further enlargement of wind-eroded sand pits around ground piles. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention aims to solve the following technical problems: providing a method for spraying a repair solution directly in situ to repair wind-eroded sand pits around the pile toes of desert photovoltaic panel foundations, thereby enhancing the long-term stability of the pile foundation and improving the operational safety and reliability of desert photovoltaic power stations in extreme environments.

[0007] This invention provides a method for in-situ repair of wind-eroded sand pits at the toes of photovoltaic panel foundation piles in deserts. It combines a microbial sand-fixing method using soybean urease-induced calcium carbonate precipitation with a spraying method to prevent seepage failure of the cementing solution used for sand fixation. The method includes the following implementation steps:

[0008] S1) Prepare a cementing solution for sand fixation;

[0009] S2) Insert multiple annular baffles of different diameters into the wind-eroded sand pit where the ground pile of the desert photovoltaic panel is located. The annular baffles surround the ground pile of the desert photovoltaic panel. The multiple annular baffles together divide the surface of the sand pit into n equal parts. Each part is ring-shaped. From the center of the sand pit to the outer perimeter of the sand pit, they are the 1st to the nth equal parts. The meaning of equal parts is that the distance between each baffle is equal. n is a positive integer.

[0010] S3) Spray cementing solution onto the surface of the wind-eroded sand pit according to the spraying method for preventing cementing solution seepage failure, wherein the spraying method is performed in the following steps:

[0011] S3.1) Spray the first batch of areas in a direction from the center of the sandpit outwards, with each area in the first batch being non-adjacent to the others;

[0012] S3.2) Set an interval time. After the interval time, spray the second batch of areas in the direction from the center of the sand pit to the outer edge of the sand pit. The second batch of areas does not overlap with the first batch of areas, and the areas in the second batch are not adjacent to each other.

[0013] S3.3) Spray all batches of areas according to the spraying method in S3.2, so that the first to nth equal parts of the area have been sprayed; finally, a sloped repair layer is formed in situ on the surface of the wind-eroded sand pit.

[0014] Preferably, the area to be sprayed is divided into two batches. The first batch consists of the 1st, 3rd, 5th, ... to the 2m-1th area, i.e., the odd-numbered areas; the second batch consists of the 2nd, 4th, 6th, ... to the 2mth area, i.e., the even-numbered areas, where m is a positive integer and 2m≤n.

[0015] Preferably, the area to be sprayed is divided into three batches. The first batch consists of areas numbered 3, 6, ... to 3h, the second batch consists of areas numbered 1, 4, ... to 3h+1, and the third batch consists of areas numbered 2, 5, ... to 3h+2, where h is a positive integer and 3h+2 ≤ n.

[0016] Preferably, each annular baffle is composed of 2 to 3 segments spliced ​​together, with a thickness of 5 mm. It is set around the ground piles of the desert photovoltaic panel and has a pre-embedded depth of 50 to 150 mm. It is used to separate the surface of the wind-eroded sand pit, increase the contact time between the cementing liquid and the sand inside the baffle, and prevent the cementing liquid from accumulating at the bottom of the sand pit.

[0017] Preferably, the interval is 10 hours.

[0018] Preferably, the cementing solution is composed of soybean urease solution, salt solution, xanthan gum, skim milk powder, magnesium chloride, polylysine, sodium montmorillonite, polyacrylamide, glass fiber, and silica fume. The preparation steps include: mixing xanthan gum, skim milk powder, magnesium chloride, polylysine, sodium montmorillonite, polyacrylamide, glass fiber, and silica fume as additives and incorporating them into the soybean urease solution; and thoroughly mixing the soybean urease solution with additives and the salt solution composed of calcium chloride and urea to form the cementing solution.

[0019] Preferably, the concentration of the cementing solution is as follows: soybean urease solution 5 mol / L, salt solution 1-3 g / L, xanthan gum 0.8-1.2 g / L, skim milk powder 2.7-3.2 g / L, magnesium chloride 0.8-1.2 g / L, polylysine 0.2-0.7 g / L, sodium montmorillonite 1.7-2.1 g / L, polyacrylamide 0.2-0.7 g / L, glass fiber 1.8-2.3 g / L, and silica fume 2.7-3.3 g / L.

[0020] Preferably, the concentration of the cementing solution is: xanthan gum 1g / L, skim milk powder 3g / L, magnesium chloride 1g / L, polylysine 0.5g / L, sodium montmorillonite 2g / L, polyacrylamide 0.5g / L, glass fiber 2g / L, and silica fume 3g / L.

[0021] Furthermore, the soybean urease solution described above differs from commercially available soybean urease solutions. It is derived directly from soybeans, which are completely dried, ground into soybean powder, and then thoroughly mixed with deionized water at a specific solid-liquid ratio of 1:50 to 1:10. After filtering out the soybean residue, the upper layer of solution is centrifuged to obtain a soybean urease solution with a concentration of 20g / L to 100g / L, thus reducing the cost of use.

[0022] The salt solution is formed by thoroughly mixing urea and calcium chloride solutions of equal concentration. The role of urea is to release free carbonate ions into the solution after being hydrolyzed by soybean urease, while the role of calcium chloride is to provide calcium ions that combine with carbonate ions to form calcium carbonate precipitate, thereby cementing and reinforcing the sand particles. Xanthan gum, as a thickener and stabilizer, can prolong the residence time of the solution on the surface of sand particles, thereby promoting the precipitation and solidification of calcium carbonate; skim milk powder can provide additional growth factors, enhancing the microbial activity during the calcium carbonate deposition process, thus promoting the precipitation and solidification of calcium carbonate; magnesium chloride and polylysine can change the crystal morphology of calcium carbonate, promoting the formation of harder and more stable crystal forms, thereby improving the strength and durability of the solidified layer; sodium montmorillonite, as a nucleating agent, can provide more nucleation sites, increasing the amount and efficiency of calcium carbonate precipitation; polyacrylamide has good bonding properties, can form a network structure in sand, effectively bind sand particles, and increase the cohesion and friction of sand; glass fiber can enhance the compressive strength and shear strength of the windproof reinforcement layer, preventing cracks from forming in stress concentration areas; silica fume can form stronger chemical bonds with soybean urease-induced calcium carbonate precipitation, enhancing the bonding effect.

[0023] The present invention also provides the application of the above-mentioned method for in-situ repair of wind erosion sand pits at the toe of ground piles in the repair of wind erosion sand pits of ground piles.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) A ring-shaped baffle was installed around the pile, and the formula of the cementing solution was improved. The microbial sand fixation method of inducing calcium carbonate precipitation by soybean urease and the spraying method to prevent seepage failure of the cementing solution were combined to effectively repair the wind erosion sand pits around the pile toes of the desert photovoltaic panel piles. By directly forming a dense calcium carbonate solidification layer on the surface of the wind erosion sand pits in situ, the compressive strength and shear strength of the wind erosion sand pits were significantly improved, the risk of re-erosion of the sand pits was reduced, and the sand pits did not need to be backfilled or filled in in advance, which reduced the construction difficulty and improved the construction efficiency. It has the advantages of good effect, environmental protection and long-term stability.

[0026] (2) During the repair process of wind erosion sand pits around the toe of photovoltaic panel piles, the ring baffle can form a uniform slope windproof and solidification system with the calcium carbonate solidification layer, which changes the surface roughness of the sand pit and the wind field around the pile, effectively reduces the wind speed and turbulence effect around the pile, reduces the direct impact force of wind load on the pile foundation, significantly reduces the swaying and displacement of the pile foundation in extreme wind and sand environment, and enhances the long-term stability and durability of the pile foundation.

[0027] (3) The improved cementitious liquid formula of the present invention has a better soil reinforcement effect. The combination of soybean urease solution and specific additives forms a windproof reinforcement and repair layer with higher adhesion and higher strength. At the same time, it enhances the friction between the pile foundation and the surrounding sand, prevents the pile foundation from sliding and tilting under the action of lateral force, and improves the overall stability of the pile foundation.

[0028] (4) The circular segmented and step-by-step spraying reinforcement method proposed in this invention significantly improves the wind erosion resistance of the sand pit after reinforcement.

[0029] (5) The combined effect of the baffle and the cementing liquid in this invention forms an integrated reinforcement system, which improves the compressive strength and bearing capacity of the sandy foundation around the piles, enhances the friction between the piles and the sandy foundation, resists wind erosion, and changes the wind field of the desert photovoltaic piles, thereby enhancing the long-term stability of the pile foundation. In-situ repair maintains the shape of the sand pit depression, that is, it maintains the original slope of the sand pit, eliminating the need for pre-treatment of the sand pit. Furthermore, the sloping repair system can also reduce the wind speed in the sand pit around the pile toe, reducing secondary wind erosion. Attached Figure Description

[0030] Figure 1 This is a flowchart illustrating the implementation steps of this technology.

[0031] Figure 2 This is a schematic diagram of the annular baffle (101) in this technology.

[0032] Figure 3 This is a schematic diagram of the embedding of the annular baffle (101) in this technology.

[0033] Figure 4 The surface penetration strength was measured on-site after backfilling sand pits around pile toes to form a windproof reinforcement and repair layer, as described in Examples 1-6 and Comparative Examples 1-14.

[0034] Figure 5 The results of wind field measurements were taken at the same time by installing an ultrasonic anemometer at a height of 0.5m on the pile foundation after backfilling the sand pit around the pile toe with mortar to form a windproof reinforcement and repair layer in Examples 1-6 and Comparative Examples 1-14.

[0035] In the diagram: 101 is a ring-shaped baffle; 102 is a wind-eroded sand pit around the toe of the photovoltaic panel ground pile; 103 is the photovoltaic panel ground pile. Detailed Implementation

[0036] The present invention will be described in detail below with reference to the accompanying drawings and preferred embodiments. The objectives and effects of the present invention will become clearer as a result. The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only for explaining the present invention and are not intended to limit the present invention.

[0037] This invention combines a microbial sand fixation method (SICP) induced by soybean urease to precipitate calcium carbonate with a spraying method to prevent seepage failure of the cementing solution. After the cementing solution solidifies on the surface of the sand pit, calcium carbonate precipitate forms. The calcium carbonate precipitate deposits between sand grains, filling voids and binding the sand grains to form a dense, solidified slope layer. This increases the density of the sand and improves its compressive strength and bearing capacity. Simultaneously, the wind-eroded sand around the annular baffle, after being solidified by the cementing solution, can bond with the annular baffle to form a windproof solidification system. The formed calcium carbonate precipitate also acts as a "bridging" agent between sand grains, enhancing the adhesion between particles, thereby significantly improving the shear strength and wind erosion resistance of the wind-eroded sand pit surface. Furthermore, the calcium carbonate precipitate forms a rough, adhesive surface on the particles, increasing the contact area and friction between the pile foundation and the surrounding sandy foundation. The resulting windproof solidification system effectively reduces wind speed and turbulence around the pile foundation, reducing the direct impact of wind loads on the pile foundation. Therefore, this invention can significantly improve the long-term stability of pile foundations while repairing sand pits.

[0038] Example 1

[0039] In the laboratory, soybeans were completely dried and ground into soybean powder. This powder was then thoroughly mixed with deionized water at a specific solid-liquid ratio, and the soybean residue was filtered out. The supernatant solution was centrifuged to obtain a soybean urease solution. Additives were then added to the soybean urease solution. The additive components and concentrations were: 1 g / L xanthan gum, 3 g / L skim milk powder, 1 g / L magnesium chloride, 0.5 g / L polylysine, 2 g / L sodium montmorillonite, 0.5 g / L polyacrylamide, 2 g / L glass fiber, and 3 g / L silica fume.

[0040] A salt solution is formed by thoroughly mixing urea and calcium chloride solutions, wherein the concentration of the urea solution is 0.5 mol / L and the concentration of the calcium chloride solution is 0.5 mol / L.

[0041] The soybean urease solution and salt solution, prepared in the laboratory and mixed with additives, were transported to the desert site.

[0042] Prepare a thoroughly mixed cementitious solution on-site by uniformly mixing equal volumes of soybean urease solution and salt solution to form the final cementitious solution.

[0043] One wind-eroded sand pit was selected, containing one ground pile. In naturally formed wind-eroded sand pits, the ground pile is usually located at the center. Three annular baffles 101 were installed radially in the sand pit, dividing the sand surface into four equal parts, each of which is annular. The annular baffles 101 were buried at a depth of 100mm.

[0044] Spray the cementing liquid along the direction from the center of the sandpit outwards and perpendicular to the surface of the sandpit. Spray the first batch on areas 1 and 3, with an interval of 10 hours, and then start spraying the second batch on areas 2 and 4.

[0045] Comparative Example 1

[0046] This comparative example is identical to Example 1 in all aspects except that no additives are added to the soybean urease solution.

[0047] Comparative Example 2

[0048] In this comparative example, the additives in the soybean urease solution were: 3 g / L skim milk powder, 1 g / L magnesium chloride, 0.5 g / L polylysine, 2 g / L sodium montmorillonite, 0.5 g / L polyacrylamide, 2 g / L glass fiber, and 3 g / L silica fume. All other aspects were exactly the same as in Example 1.

[0049] Comparative Example 3

[0050] In this comparative example, the additives in the soybean urease solution were: 1 g / L xanthan gum, 1 g / L magnesium chloride, 0.5 g / L polylysine, 2 g / L sodium montmorillonite, 0.5 g / L polyacrylamide, 2 g / L glass fiber, and 3 g / L silica fume. All other aspects were exactly the same as in Example 1.

[0051] Comparative Example 4

[0052] In this comparative example, the additives in the soybean urease solution were: 1 g / L xanthan gum, 3 g / L skim milk powder, 0.5 g / L polylysine, 2 g / L sodium montmorillonite, 0.5 g / L polyacrylamide, 2 g / L glass fiber, and 3 g / L silica fume. All other aspects were exactly the same as in Example 1.

[0053] Comparative Example 5

[0054] In this comparative example, the additives in the soybean urease solution were: 1 g / L xanthan gum, 3 g / L skim milk powder, 1 g / L magnesium chloride, 2 g / L sodium montmorillonite, 0.5 g / L polyacrylamide, 2 g / L glass fiber, and 3 g / L silica fume. All other aspects were exactly the same as in Example 1.

[0055] Comparative Example 6

[0056] In this comparative example, the additives in the soybean urease solution were: 1 g / L xanthan gum, 3 g / L skim milk powder, 1 g / L magnesium chloride, 0.5 g / L polylysine, 0.5 g / L polyacrylamide, 2 g / L glass fiber, and 3 g / L silica fume. All other aspects were exactly the same as in Example 1.

[0057] Comparative Example 7

[0058] In this comparative example, the additives in the soybean urease solution were: 1 g / L xanthan gum, 3 g / L skim milk powder, 1 g / L magnesium chloride, 0.5 g / L polylysine, 2 g / L sodium montmorillonite, 2 g / L glass fiber, and 3 g / L silica fume. All other aspects were exactly the same as in Example 1.

[0059] Comparative Example 8

[0060] In this comparative example, the additives in the soybean urease solution were: 1 g / L xanthan gum, 3 g / L skim milk powder, 1 g / L magnesium chloride, 0.5 g / L polylysine, 2 g / L sodium montmorillonite, 0.5 g / L polyacrylamide, and 3 g / L silica fume. All other aspects were exactly the same as in Example 1.

[0061] Comparative Example 9

[0062] In this comparative example, the additives in the soybean urease solution were: 1 g / L xanthan gum, 3 g / L skim milk powder, 1 g / L magnesium chloride, 0.5 g / L polylysine, 2 g / L sodium montmorillonite, 0.5 g / L polyacrylamide, and 2 g / L glass fiber as additives. All other aspects were exactly the same as in Example 1.

[0063] Comparative Example 10

[0064] In this comparative example, the additives in the soybean urease solution were: 1 g / L xanthan gum, 1 g / L magnesium chloride, 0.5 g / L polylysine, 2 g / L sodium montmorillonite, 0.5 g / L polyacrylamide, and 2 g / L glass fiber as additives. All other aspects were exactly the same as in Example 1.

[0065] Comparative Example 11

[0066] In this comparative example, the additives in the soybean urease solution were: 1 g / L xanthan gum, 3 g / L skim milk powder, 1 g / L magnesium chloride, 0.5 g / L polylysine, 2 g / L sodium montmorillonite, and 2 g / L glass fiber as additives. All other aspects were exactly the same as in Example 1.

[0067] Comparative Example 12

[0068] In this comparative example, the additives in the soybean urease solution were: 1 g / L xanthan gum, 1 g / L magnesium chloride, 0.5 g / L polylysine, 2 g / L sodium montmorillonite, and 2 g / L glass fiber as additives. All other aspects were exactly the same as in Example 1.

[0069] Comparative Example 13

[0070] The additives in this comparative example of soybean urease solution were: 1 g / L xanthan gum, 3 g / L skim milk powder, and 1 g / L magnesium chloride. All other aspects were exactly the same as in Example 1.

[0071] Comparative Example 14

[0072] The additives in this comparative example of soybean urease solution were: 1 g / L xanthan gum, 3 g / L skim milk powder, 1 g / L magnesium chloride, 0.5 g / L polylysine, and 2 g / L sodium montmorillonite. All other aspects were exactly the same as in Example 1.

[0073] Example 2

[0074] In this embodiment, when spraying the binder, a sand pit with a similar area and depth to that in Embodiment 1 is selected. No annular baffle 101 is installed. The binder is sprayed radially from the inside out, perpendicular to the surface of the sand pit, without intermittent spraying. The binder in this embodiment is the same as that in Embodiment 1.

[0075] Example 3

[0076] In this embodiment, when spraying the cementing liquid, two annular baffles 101 are set radially below the surface of the wind-eroded sand pit near the toe of the desert photovoltaic panel ground pile to divide the sand surface of the sand pit into three equal parts; then, the cementing liquid is sprayed three times perpendicular to the surface of the sand pit along the radial direction of the ground pile from the inside out, with each spraying cycle being 10 hours apart, and other aspects are exactly the same as in Embodiment 1.

[0077] Example 4

[0078] In this embodiment, when spraying the cementing liquid, four annular baffles 101 are radially installed below the surface of the wind-eroded sand pit near the toe of the desert photovoltaic panel pile, dividing the sand surface of the pit into five equal parts. The cementing liquid is sprayed in a direction perpendicular to the surface of the sand pit, from the center of the sand pit outwards. The first batch sprays areas 1, 3, and 5, with an interval of 10 hours. The second batch sprays areas 2 and 4. The spraying method and other features not mentioned are the same as in Embodiment 1.

[0079] Example 5

[0080] Exploring the optimal setting of the baffle

[0081] The baffle setup was changed, using a straight baffle inserted into the sand along the radius of the sandpit. Two sandpits, C and D, with similar area and depth to those in Example 1, were selected. Sandpit C was divided into four equal sectors, and sandpit D was divided into six equal sectors, numbered sequentially from 1 to n. Following the spraying method of Example 1, each batch sprayed the first batch of areas from the center of the sandpit outwards, ensuring that the sectors in the first batch were not adjacent to each other. After an interval of at least 10 hours, the second batch of areas was sprayed from the center outwards, ensuring that the second batch did not overlap with the first batch and that the sectors in the second batch were not adjacent to each other. This process was repeated until all batches of areas were sprayed, ensuring that all sectors were covered. In this experiment, for sandpit C, the first batch consisted of sectors 1 and 3, and the second batch consisted of sectors 2 and 4. A 10-hour interval was maintained between each spraying. For the ground pile sand pit D, the first batch of areas are areas 1, 3, and 5, and the second batch of areas are areas 2, 4, and 6.

[0082] Example 6

[0083] In this embodiment, the spraying interval between each batch of cementitious liquid is 1 day, and all other aspects are exactly the same as in Embodiment 1.

[0084] Example 7

[0085] Performance evaluations were conducted for Examples 1-6 and Comparative Examples 1-14.

[0086] like Figure 4 The figures show the surface penetration strength measured on-site after backfilling sand pits around pile toes to form a windproof reinforcement repair layer, as shown in Examples 1-6 and Comparative Examples 1-14. The test method was as follows: First, the handheld penetrator was placed vertically on the surface of the cured layer, ensuring the instrument's zero point was correctly calibrated. Then, the penetrator's cone was slowly pushed into the surface of the cured layer to apply penetration force, and the penetration depth was recorded. The force value measured at the standard depth (20mm) was then taken as the surface penetration strength. Measurements were repeated 3-5 times at different locations, and the final result was the average. The surface penetration strength was calculated using the following formula:

[0087]

[0088] In the formula: q c is the surface penetration strength, MPa; F is the penetration force, N; A is the cone area, mm² 2 .

[0089] like Figure 5The figures show the wind field measurements taken at the same time using an ultrasonic anemometer installed at a height of 0.5m on the pile foundations after backfilling the sand pits around the pile toes in Examples 1-6 and Comparative Examples 1-14 to form a windproof reinforcement and repair layer. The pile foundations in Examples 1-6 and Comparative Examples 1-14 are located in the same area, and an ultrasonic anemometer was installed at the same height on a selected pile foundation in the same area that was not treated by this method. The wind speed results were obtained from the ultrasonic anemometer.

[0090] The experimental results are summarized in Table 1.

[0091] Table 1. Experimental results of different embodiments and comparative examples.

[0092]

[0093] A comparison of Comparative Examples 1-14 and Example 1 shows that the surface penetration strength of the samples prepared from the surface-cured sand treated by the method of Example 1 is the highest, and the surface penetration strength of Comparative Examples 12-14 is relatively higher than that of Comparative Examples 1-11. This indicates that the addition of xanthan gum, skim milk powder, magnesium chloride, polylysine, sodium montmorillonite, and polyacrylamide to the soybean urease solution enhances the curing effect and improves the bearing capacity of the sandy foundation. Furthermore, compared to using one or only a few additives alone, the combined use of the additives in the above formulation has a better synergistic effect.

[0094] Based on the penetration strength measured in Examples 1-4, the surface penetration strength of the sample made from surface-cured sand treated by the method in Example 4 was higher than that in Examples 1 and 3, while the sand pit A in Example 2 was the lowest. This indicates that the baffle and spraying method provided by the present invention effectively reduced the flow of cementitious liquid on the surface and shallow layer of the sand pit, forming a reliable reinforcement layer and improving the surface penetration strength of the reinforcement layer.

[0095] Based on the wind speeds measured in Examples 1-4, Example 4 showed the lowest wind speed, lower than Examples 1 and 3, while Example 2 showed the highest wind speed in sandpit A. This indicates that the method proposed in this invention can significantly reduce the wind field on the pile foundation and enhance its long-term stability.

[0096] According to the penetration strength test results of Example 2 and Example 1, it can be seen that the penetration strength is significantly lower than that of Example 1, which verifies the advantage of the intermittent spraying method of the present invention. When the intermittent spraying method is adopted, the soil inside the second and subsequent batches is reinforced by the cementing liquid, which can prevent the newly sprayed cementing liquid from being absorbed by the surrounding soil, thereby helping the cementing liquid to consolidate the area to be sprayed.

[0097] The comparison results of Example 1 and Example 5 show that the reinforcement effect brought by the annular partition is better than that of the fan-shaped partition. The reason may be that the annular partition enhances the structural integrity, is more continuous in the overall structure, and has a larger length and width of coverage. Compared with the fan-shaped partition, the annular partition reduces the weakened area in shape and further improves the overall stability.

[0098] Based on the comparison results of Example 6 and Example 1, extending the spraying interval does not significantly reduce the spraying effect, thus providing greater buffering and operability when scheduling spraying times.

[0099] The above specific embodiments are used to explain and illustrate the present invention, but not to limit the present invention. Any modifications and changes made to the present invention within the spirit and scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A method for in-situ repair of wind-eroded sand pits at the toe of ground piles, characterized in that, The method of microbial sand fixation using soybean urease-induced calcium carbonate precipitation and the spraying method for preventing seepage failure of the cementing solution used in sand fixation are combined, including the following implementation steps: S1) Prepare a cementing solution for sand fixation; the cementing solution is composed of soybean urease solution, salt solution, xanthan gum, skim milk powder, magnesium chloride, polylysine, sodium montmorillonite, polyacrylamide, glass fiber, and silica fume. The preparation steps include: mixing xanthan gum, skim milk powder, magnesium chloride, polylysine, sodium montmorillonite, polyacrylamide, glass fiber and silica fume as additives, and incorporating them into a soybean urease solution; A cementitious solution is formed by thoroughly mixing a soybean urease solution with additives and a salt solution composed of calcium chloride and urea. S2) Insert multiple annular baffles (101) of different diameters into the wind-eroded sand pit where the ground pile toe of the desert photovoltaic panel is located. The annular baffles surround the ground pile of the desert photovoltaic panel. The multiple annular baffles together divide the surface of the sand pit into n equal parts. Each part is in the shape of a ring. From the center of the sand pit to the outer perimeter of the sand pit, they are the first to the nth part. The meaning of equal parts is that the distance between each baffle is equal, and n is a positive integer. S3) Spray cementing solution onto the surface of the wind-eroded sand pit according to the spraying method for preventing cementing solution seepage failure, wherein the spraying method is performed in the following steps: S3.1) Spray the first batch of areas in a direction from the center of the sandpit outwards, with each area in the first batch being non-adjacent to the others; S3.2) Set an interval time. After the interval time, spray the second batch of areas in the direction from the center of the sand pit to the outer edge of the sand pit. The second batch of areas does not overlap with the first batch of areas, and the areas in the second batch are not adjacent to each other. S3.3) Spray all batches of areas according to the spraying method in S3.2, so that all areas from the first to the nth batch have been sprayed; finally, a sloped repair layer is formed in situ on the surface of the wind-eroded sand pit.

2. The method according to claim 1, characterized in that, The area to be sprayed is divided into two batches. The first batch consists of the 1st, 3rd, 5th, ... to the 2m-1th area, i.e., the odd-numbered areas; the second batch consists of the 2nd, 4th, 6th, ... to the 2mth area, i.e., the even-numbered areas, where m is a positive integer and 2m≤n.

3. The method according to claim 1, characterized in that, The area to be sprayed is divided into three batches. The first batch consists of areas numbered 3, 6, ... to 3h. The second batch consists of areas numbered 1, 4, ... to 3h+1. The third batch consists of areas numbered 2, 5, ... to 3h+2. h is a positive integer and 3h+2 ≤ n.

4. The method according to claim 1, characterized in that, Each annular baffle (101) is made up of 2 to 3 pieces. The baffle itself is 5mm thick and is set around the ground pile of the desert photovoltaic panel. The pre-embedded depth is 50 to 150mm. It is used to separate the surface of the wind-eroded sand pit, increase the contact time between the cementing liquid and the sand inside the baffle, and prevent the cementing liquid from accumulating at the bottom of the sand pit.

5. The method according to claim 1, characterized in that, The concentrations of the cementing solution are as follows: soybean urease solution 5 mol / L, salt solution 1–3 g / L, xanthan gum 0.8–1.2 g / L, skim milk powder 2.7–3.2 g / L, magnesium chloride 0.8–1.2 g / L, polylysine 0.2–0.7 g / L, sodium montmorillonite 1.7–2.1 g / L, polyacrylamide 0.2–0.7 g / L, glass fiber 1.8–2.3 g / L, and silica fume 2.7–3.3 g / L.

6. The method according to claim 5, characterized in that, The concentrations of the cementing solution are: xanthan gum 1 g / L, skim milk powder 3 g / L, magnesium chloride 1 g / L, polylysine 0.5 g / L, sodium montmorillonite 2 g / L, polyacrylamide 0.5 g / L, glass fiber 2 g / L, and silica fume 3 g / L.

7. The method according to claim 1, wherein the interval is 10 hours.

8. The application of the method for in-situ repair of wind-eroded sand pits at the toe of ground piles as described in any one of claims 1-7 in the repair of wind-eroded sand pits at ground piles.

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