Method for in-situ repair of ground pile toe wind erosion sandpit

Abstract

The invention provides a technology and implementation steps for in-situ remediation of a ground pile toe wind erosion sandpit, firstly, a soybean urease solution containing an additive and a salt solution are uniformly mixed in a desert site by using a mixing device to obtain a cementing solution, and then a plurality of annular baffles are arranged below the surface of the wind erosion sandpit near the ground pile toe of a desert photovoltaic panel in the radial direction; the sand surface of the sand pit is divided into n equal parts, then cementing fluid is sprayed according to a spraying mode for preventing seepage failure of the cementing fluid, the n equal parts are sprayed at intervals in batches, and finally a soybean urease cementing reinforcement repair layer is formed on the surface of the wind erosion sand pit near a pile toe in situ. The windproof reinforcing and repairing layer can resist shaking of the pile foundation and weaken the wind field around the pile, so that the long-term stability of the pile foundation is improved. Compared with an existing common mechanical backfilling and chemical consolidation method, the method for repairing the wind erosion sand pits around the ground pile toe of the desert photovoltaic panel is more effective, construction is convenient and efficient, no pollution is caused to the environment, and the requirement for green and sustainable development is met.

Description

Technical Field

[0001] The invention relates to the field of desert windbreak and sand control, and in particular to a method for in-situ repairing of wind-eroded sand pits at the toes of piles. Background Art

[0002] With the global climate change and the intensification of human activities, desertification and sandstorms are becoming increasingly serious, especially in arid and semi-arid areas, where wind erosion causes a large amount of sand and dust particles to be carried, causing environmental degradation and damage to the ecosystem. At the same time, desert areas have become ideal locations for photovoltaic power generation projects due to their vast land resources and strong solar radiation. However, large-scale photovoltaic panel construction faces a series of challenges such as sand and dust accumulation, equipment loss and increased maintenance costs. To this end, seeking more efficient and environmentally friendly sand fixation technologies can not only prevent the expansion of desertification, but also provide guarantees for the stable operation of photovoltaic power generation projects.

[0003] Since the installation of photovoltaic panel piles changes the wind field in the photovoltaic area, wind accumulation points are formed at the photovoltaic panel piles, and wind accumulation occurs at the toes of the photovoltaic panel piles, thus forming wind erosion pits near the toes. The gradual enlargement of wind erosion pits can easily lead to the instability and tilt of photovoltaic panel piles, thus causing the collapse of photovoltaic panels.

[0004] In addition, in recent years, environmentally friendly bioreinforcement technologies such as 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 presence of a certain slope at the toe of the ground pile, when the spraying reinforcement technology is used to directly treat and repair the wind erosion sand pit at the toe of the ground pile, the repair liquid flows and gathers at the bottom of the sand pit, making it difficult to reinforce the entire sand pit, and the reinforcement effect is poor. On the other hand, due to the small space at the toe of the ground pile, traditional wind-proof and sand-fixing measures such as afforestation are difficult to implement, and chemical sand-fixing agents are difficult to spray on a large area. At the same time, there are also problems such as long construction period and large ecological impact. In addition, the presence of the toe of the ground pile has an impact on the wind field in the area, making it difficult for traditional spraying methods to achieve the expected reinforcement effect. At the same time, the reinforcement effect of the existing urease solution cannot resist the impact of the special shape of the wind erosion sand pit around the ground pile. Therefore, it is urgent to develop new technical solutions to solve the harm caused by the further increase of wind erosion sand pits around the ground pile. Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention aims to solve the following technical problems: to provide a method for repairing wind-eroded sand pits around the toes of desert photovoltaic panel piles by directly spraying a repair solution in situ, so as to enhance the long-term stability of the pile foundation and improve the operating safety and reliability of desert photovoltaic power stations in extreme environments.

[0007] The present invention provides a method for in-situ repairing wind-eroded sand pits at the toes of photovoltaic panel piles in the desert, which combines a microbial sand fixation method (SICP) of soybean urease-induced calcium carbonate precipitation with a spraying method for preventing the seepage failure of a cementing solution used for sand fixation, and comprises the following implementation steps:

[0008] S1) preparing a cementing fluid for sand fixation;

[0009] S2) inserting a plurality of annular baffles of different diameters into the wind-eroded sand pit where the toes of the desert photovoltaic panel piles are located, the annular baffles surround the desert photovoltaic panel piles, and the plurality of annular baffles together divide the surface of the sand pit into n areas, each area is annular, and the first to nth areas are sequentially arranged from the center of the sand pit to the periphery of the sand pit, and the meaning of equal division is that the distance between each baffle is equal, and n is a positive integer;

[0010] S3) spraying the cementing liquid on the surface of the wind erosion sand pit according to a spraying method for preventing the cementing liquid from failing due to seepage, wherein the spraying method performs the following steps:

[0011] S3.1) Spray the first batch of areas from the center of the bunker to the periphery of the bunker, and the first batch of areas are not adjacent to each other;

[0012] S3.2) setting an interval time, after which the second batch of areas are sprayed in a direction from the center of the sand pit to the periphery of the sand pit, the second batch of areas do not overlap with the first batch of areas, and the second batch of areas are not adjacent to each other;

[0013] S3.3) All batches of areas are sprayed according to the spraying method of S3.2, so that the 1st to nth areas have been sprayed; finally, a repair layer with a slope 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 is the 1st to 2m-1th areas, that is, odd-numbered areas; the second batch is the 2nd to 2mth areas, that is, even-numbered areas, m is a positive integer, 2m≤n.

[0015] Preferably, the area to be sprayed is divided into three batches, the first batch of areas is the 1st to 3hth areas, the second batch of areas is the 2nd to 3h+1th areas, the third batch of areas is the 3rd to 3h+2th areas, h is a positive integer, 3h+2≤n.

[0016] Preferably, each annular baffle is composed of 2 to 3 petals, the baffle itself is 5 mm thick, and is arranged around the desert photovoltaic panel piles with a pre-buried 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 binder and the sand in the baffle, and prevent the binder from gathering at the bottom of the sand pit.

[0017] Preferably, the interval duration is 10 hours.

[0018] Preferably, the binder is composed of 1# soybean urease solution, 2# salt solution, 3# xanthan gum, 4# skimmed milk powder, 5# magnesium chloride, 6# polylysine, 7# sodium montmorillonite, 8# polyacrylamide, 9# glass fiber, and 10# silica ash, and the preparation steps include: mixing 3# xanthan gum, 4# skimmed milk powder, 5# magnesium chloride, 6# polylysine, 7# sodium montmorillonite, 8# polyacrylamide, 9# glass fiber and 10# silica ash as additives, and adding them into 1# soybean urease solution; and fully mixing the soybean urease solution mixed with additives and 2# salt solution composed of calcium chloride and urea to form a binder.

[0019] Preferably, the concentration of the binder is: 1# soybean urease solution 5 mol / L, 2# salt solution 1-3 g / L, 3# xanthan gum 0.8-1.2 g / L, 4# skimmed milk powder 2.7-3.2 g / L, 5# magnesium chloride 0.8-1.2 g / L, 6# polylysine 0.2-0.7 g / L, 7# sodium montmorillonite 1.7-2.1 g / L, 8# polyacrylamide 0.2-0.7 g / L, 9# glass fiber 1.8-2.3 g / L, 10# silica ash 2.7-3.3 g / L.

[0020] Preferably, the concentration of the binder is: 3# xanthan gum 1g / L, 4# skimmed milk powder 3g / L, 5# magnesium chloride 1g / L, 6# polylysine 0.5g / L, 7# sodium montmorillonite 2g / L, 8# polyacrylamide 0.5g / L, 9# glass fiber 2g / L, 10# silica ash 3g / L.

[0021] In addition, the soybean urease solution is different from the commercial soybean urease solution. The soybean is directly taken from soybeans. The soybeans are completely dried and ground into soybean powder, which is fully stirred and mixed with deionized water at a specific solid-liquid ratio of 1:50-1:10, and the bean dregs are filtered out. The upper solution is centrifuged to obtain a soybean urease solution with a concentration of 20g / L-100g / L, thereby reducing the cost of use.

[0022] The salt solution is a solution formed by fully mixing urea and calcium chloride solutions of equal concentrations. The role of urea is to release free carbonate ions into the solution after being catalyzed and hydrolyzed by soybean urease, and the role of calcium chloride is to provide calcium ions to combine with carbonate ions to form calcium carbonate precipitation, thereby cementing and reinforcing 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; skimmed milk powder can provide additional growth factors, enhance the microbial activity in the calcium carbonate deposition process, thereby promoting the precipitation and solidification of calcium carbonate; magnesium chloride and polylysine can change the crystal morphology of calcium carbonate, promote 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, increase the precipitation amount and efficiency of calcium carbonate; polyacrylamide has good bonding properties, can form a network structure in the sand, effectively combine sand particles, and increase the cohesion and friction of the sand; glass fiber can enhance the compressive strength and shear strength of the windproof reinforcement layer, and prevent cracks from forming in stress concentration areas; silica fume can produce stronger chemical bonds with soybean urease-induced calcium carbonate precipitation, thereby enhancing the bonding effect.

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

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

[0025] (1) An annular baffle was set around the piles, and the formula of the cementing fluid was improved. The microbial sand fixation method of soybean urease-induced calcium carbonate precipitation and the spraying method to prevent the failure of cementing fluid seepage were combined to effectively repair the wind-eroded sand pits around the pile toes of the desert photovoltaic panel piles. By directly forming a dense calcium carbonate solidification layer in situ on the surface of the wind-eroded sand pits in the pile foundation, the compressive strength and shear strength of the wind-eroded sand pits were significantly improved, and the risk of re-erosion of the sand pits was reduced. There was no need to backfill the sand pits in advance or fill the sand pits, 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-eroded sand pits around the toes of photovoltaic panel piles, the annular baffles can form a uniform slope wind-proof solidification system with the calcium carbonate solidification layer, changing the surface roughness of the sand pits and the wind field around the piles, effectively reducing the wind speed and turbulence effect around the piles, reducing the direct impact of wind loads on the pile foundation, and significantly reducing the shaking and displacement of the pile foundation in extreme wind and sand environments, thereby enhancing the long-term stability and durability of the pile foundation.

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

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

[0029] (5) The present invention sets a baffle and a cementing liquid to reinforce the sand, forming an overall reinforcement system, which improves the compressive strength and bearing capacity of the sand foundation around the pile, enhances the friction between the pile foundation and the sand foundation, resists wind erosion, and changes the wind field of the desert photovoltaic panel pile, thereby enhancing the long-term stability of the pile foundation. The in-situ repair maintains the shape of the sand pit depression, that is, the slope of the sand pit is maintained in place, and there is no need to pre-treat the sand pit in advance. In addition, the sloped repair system can also reduce the wind speed of the sand pit around the pile toe and reduce secondary wind erosion. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 Flow chart of the implementation steps of this technology.

[0031] Figure 2 Schematic diagram of the annular baffle (101) in the present technology.

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

[0033] Figure 4 The surface penetration strengths were measured on site after the sand pits around the pile toes were backfilled with mortar to form a windproof reinforcement repair layer in Examples 1 to 6 and Comparative Examples 1 to 14.

[0034] Figure 5 These are the results of Examples 1 to 6 and Comparative Examples 1 to 14 where an ultrasonic anemometer was installed at a height of 0.5 m on the pile foundation to measure the wind field at the same time after the sand pit around the pile toe was backfilled with mortar to form a windproof reinforcement repair layer.

[0035] In the figure: 101 is an annular baffle; 102 is a wind-eroded sand pit around the toe of the photovoltaic panel pile; 103 is the photovoltaic panel pile. DETAILED DESCRIPTION

[0036] The present invention will be described in detail below according to the accompanying drawings and preferred embodiments, and the purpose and effect of the present invention will become more clear. The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0037] The present invention combines a microbial sand fixation method (SICP) of soybean urease-induced calcium carbonate precipitation and a spraying method for preventing cementing liquid seepage failure. The cementing liquid forms calcium carbonate precipitation after being solidified on the surface of the sand pit. The calcium carbonate precipitate is deposited between the sand grains, fills the gaps and bonds the sand grains, forming a dense slope surface solidification layer, increasing the density of the sand while also improving its compressive strength and bearing capacity. At the same time, the wind-eroded sand around the annular baffle can be bonded to the annular baffle to form a wind-proof solidification system after being solidified by the cementing liquid; the formed calcium carbonate precipitate can also play a "bridging" role between the sand grains, enhancing the adhesion between the particles, thereby significantly improving the shear strength and wind erosion resistance of the wind-eroded sand pit surface; in addition, the calcium carbonate precipitate will also form a rough, adhesive surface on the particle surface, increasing the contact area and friction between the pile foundation and the surrounding sandy foundation; the wind-proof solidification system finally formed can also effectively reduce the wind speed and turbulence effect around the pile foundation, and reduce the direct impact of wind load on the pile foundation. Therefore, through the present invention, the long-term stability of the pile foundation can be significantly improved while repairing the sand pit.

[0038] Example 1

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

[0040] The urea and calcium chloride solutions are fully mixed to form a salt solution, 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 mixed with additives prepared in the laboratory were transported to the desert site.

[0042] A fully mixed and uniform cementing solution is prepared on site by uniformly mixing equal volumes of soybean urease solution and salt solution to prepare a final cementing solution;

[0043] A wind-eroded sand pit where the toe of the desert photovoltaic panel pile is located is selected, and the wind-eroded sand pit contains a pile. In a naturally formed wind-eroded sand pit, the pile is usually located at the center of the wind-eroded sand pit. Three annular baffles 101 are set radially in the sand pit to divide the sand surface of the sand pit into 4 equal parts, each of which is annular, and the annular baffle 101 is buried at a depth of 100 mm;

[0044] Spray the binder along the direction from the center of the sand pit to the periphery of the sand pit and perpendicular to the surface of the sand pit. The first batch sprays the 1st and 3rd areas. After an interval of 10 hours, start spraying the second batch, which sprays the 2nd and 4th areas.

[0045] Comparative Example 1

[0046] In this comparative example, no additives were added to the soybean urease solution, and other aspects were exactly the same as those of Example 1.

[0047] Comparative Example 2

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

[0049] Comparative Example 3

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

[0051] Comparative Example 4

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

[0053] Comparative Example 5

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

[0055] Comparative Example 6

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

[0057] Comparative Example 7

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

[0059] Comparative Example 8

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

[0061] Comparative Example 9

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

[0063] Comparative Example 10

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

[0065] Comparative Example 11

[0066] The additives in the soybean urease solution of this comparative example are: 1g / L xanthan gum, 3g / L skimmed milk powder, 1g / L magnesium chloride, 0.5g / L polylysine, 2g / L sodium montmorillonite, and 2g / L glass fiber as additives. Other aspects are exactly the same as Example 1.

[0067] Comparative Example 12

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

[0069] Comparative Example 13

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

[0071] Comparative Example 14

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

[0073] Example 2

[0074] In this embodiment, when spraying the cementing liquid, a pile sand pit with a similar area and depth as in the first embodiment is selected, and the annular baffle 101 is not provided. When spraying, the cementing liquid is sprayed perpendicularly to the surface of the sand pit from the inside to the outside along the radial direction of the pile, and the intermittent spraying method is not adopted. The cementing liquid of this embodiment is the same as that of the first embodiment.

[0075] Example 3

[0076] When spraying the binder liquid in this embodiment, two annular baffles 101 are radially arranged below the surface of the wind-eroded sand pit near the toe of the desert photovoltaic panel piles to divide the sand surface of the sand pit into three equal parts; then the binder liquid is sprayed perpendicularly to the surface of the sand pit three times along the radial direction of the pile from the inside to the outside, and the interval between each spraying cycle is 10 hours. Other aspects are exactly the same as Example 1.

[0077] Example 4

[0078] In this embodiment, when spraying the binder, four annular baffles 101 are radially arranged below the surface of the wind-eroded sand pit near the toe of the desert photovoltaic panel pile, dividing the sand surface of the sand pit into five equal parts; the binder is sprayed along the direction from the center of the sand pit to the periphery of the sand pit and perpendicular to the surface of the sand pit, the first batch sprays the first, third, and fifth areas, and the second batch starts spraying after an interval of 10 hours, and the second batch sprays the second and fourth areas. The spraying method and other features not mentioned are the same as those in Example 1.

[0079] Example 5

[0080] Find out the best way to set the baffle

[0081] Change the setting mode of the baffle, use a straight baffle to insert the sand along the radius direction of the sand pit, select two ground pile sand pits C and D with similar area and depth as Example 1, divide the ground pile sand pit C into 4 equal sectors, and divide the ground pile sand pit D into 6 equal sectors, numbered 1 to n in sequence. Refer to the spraying method of Example 1, that is, each batch of the first batch of areas is sprayed along the direction from the center of the sand pit to the periphery of the sand pit, and the first batch of areas are not adjacent to each other, and the interval is more than 10 hours, and then the second batch of areas is sprayed along the direction from the center of the sand pit to the periphery of the sand pit, and the second batch of areas does not overlap with the first batch of areas, and the second batch of areas are not adjacent to each other; spray all batches of areas so that all areas have been sprayed. In this experiment, for the ground pile sand pit C, the first batch of areas are the 1st and 3rd areas, and the second batch of areas are the 2nd and 4th areas. There is an interval of 10 hours after the spraying is completed. For the ground pile bunker D, the first batch of areas are the 1st, 3rd and 5th areas, and the second batch of areas are the 2nd, 4th and 6th areas.

[0082] Example 6

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

[0084] Example 7

[0085] Performance evaluation was performed on Examples 1 to 6 and Comparative Examples 1 to 14.

[0086] like Figure 4 Shown is the surface penetration strength measured on-site after the sand pits around the pile toes were backfilled with mortar to form a windproof reinforcement repair layer in Examples 1 to 6 and Comparative Examples 1 to 14. The test method is: first, place the handheld penetrometer vertically on the surface of the solidified layer and ensure that the zero point calibration of the instrument is correct. Then push the cone head of the penetrometer to slowly penetrate the surface of the solidified layer to apply the penetration force and record the penetration depth. The force value measured at the standard depth (20mm) is then used as the surface penetration strength. Repeat the measurement 3 to 5 times at different locations and take the average value of the final result. The surface penetration strength is calculated according to the following formula:

[0087]

[0088] Where: q c is the surface penetration strength, MPa; F is the penetration force, N; A is the cone head area, mm 2 .

[0089] like Figure 5As shown, after the sand pit around the pile toe is backfilled with mortar to form a windproof reinforcement repair layer in Examples 1 to 6 and Comparative Examples 1 to 14, an ultrasonic anemometer is installed on the pile foundation at a height of 0.5m to measure the wind field at the same time. The pile foundations in Examples 1 to 6 and Comparative Examples 1 to 14 are in the same area, and an ultrasonic anemometer is installed at the same height position of a pile foundation not treated by this method in the same area, and the wind speed results are obtained by the ultrasonic anemometer.

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

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

[0092]

[0093]

[0094] From the comparison between Comparative Examples 1-14 and Example 1, it can be seen that the surface penetration strength of the samples made of 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 to 11. It shows that adding xanthan gum, skimmed milk powder, magnesium chloride, polylysine, sodium montmorillonite and polyacrylamide to the soybean urease solution has the effect of enhancing the curing effect and improving the bearing capacity of the sandy foundation, and compared with using only one or only some of the additives, the combined use of the additives in the above formula has a better synergistic effect.

[0095] According to the penetration strengths measured in Examples 1-4, the surface penetration strength of the sample made of the surface solidified sand treated by the method of Example 4 is higher than that of Examples 1 and 3, and the sand pit A of Example 2 is the lowest. This indicates that the baffle and spraying method provided by the present invention effectively reduce the flow of the cementing liquid on the surface and shallow layer of the sand pit, form a reliable reinforcement layer, and improve the surface penetration strength of the reinforcement layer.

[0096] According to the wind speeds measured in Examples 1-4, the wind speed result of Example 4 is the smallest, which is smaller than that of Examples 1 and 3, and the wind speed result of the bunker A in Example 2 is the largest. This indicates that the method proposed in the present invention can significantly reduce the wind field of the pile foundation and enhance the long-term stability of the pile foundation.

[0097] It can be seen from the penetration strength test results of Example 2 and Example 1 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 second and subsequent batches can prevent the newly sprayed cementing liquid from being absorbed by the nearby soil because the interior of the nearby soil has been reinforced with the cementing liquid during spraying, thereby helping the cementing liquid to consolidate the area to be sprayed.

[0098] According to the comparison results of Example 1 and Implementation 5, it can be seen that the reinforcement effect ultimately brought by the annular partition area is better than that of the fan-shaped partition. The reason may be that the structural integrity of the annular partition is enhanced, the annular partition is more continuous in the overall structure, and the length and width of the coverage area are larger. Compared with the fan-shaped partition, the annular partition reduces the weakened area in shape and further improves the overall stability.

[0099] According to the comparison results of Example 6 and Example 1, the extension of the spraying interval time does not significantly reduce the spraying effect, so there is greater buffering and operability when arranging the spraying time.

[0100] The above specific implementation modes are used to explain the present invention rather than to limit the present invention. Any modification and change made to the present invention within the spirit of the present invention and the protection 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 toes of piles, characterized in that: The microbial sand fixation method (SICP) of soybean urease-induced calcium carbonate precipitation and the spraying method for preventing the seepage failure of the cementing solution used for sand fixation are combined, and the implementation steps are as follows: S1) preparing a cementing fluid for sand fixation; S2) inserting a plurality of annular baffles (101) of different diameters into the wind-eroded sand pit where the toes of the desert photovoltaic panel piles are located, the annular baffles surround the desert photovoltaic panel piles, and the plurality of annular baffles together divide the surface of the sand pit into n areas, each area is annular, and the first to nth areas are sequentially arranged from the center of the sand pit to the periphery of the sand pit, and the meaning of equal division is that the distance between each baffle is equal, and n is a positive integer; S3) spraying the cementing liquid on the surface of the wind erosion sand pit according to a spraying method for preventing the cementing liquid from failing due to seepage, wherein the spraying method performs the following steps: S3.1) Spray the first batch of areas from the center of the bunker to the periphery of the bunker, and the first batch of areas are not adjacent to each other; S3.2) setting an interval time, after which the second batch of areas are sprayed in a direction from the center of the sand pit to the periphery of the sand pit, the second batch of areas do not overlap with the first batch of areas, and the second batch of areas are not adjacent to each other; S3.3) Spray all batches of areas according to the spraying method of S3.2, so that the 1st to nth areas have been sprayed; finally, a repair layer with a slope 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 is the 1st to 2m-1th areas, that is, the odd-numbered areas; the second batch is the 2nd to 2mth areas, that is, the even-numbered areas, where m is a positive integer, 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 is from the 1st to 3hth areas, the second batch is from the 2nd to 3h+1th areas, and the third batch is from the 3rd to 3h+2th areas. h is a positive integer, 3h+2≤n.

4. The method according to claim 1, characterized in that Each annular baffle (101) is composed of 2 to 3 petals, the baffle itself is 5 mm thick, and is arranged around the desert photovoltaic panel piles, with a pre-buried depth of 50 to 150 mm, and is used to separate the surface of the wind-eroded sand pit, increase the contact time between the cementing liquid and the sand in the baffle, and prevent the cementing liquid from gathering at the bottom of the sand pit.

5. The method according to claim 1, characterized in that The binder liquid is composed of 1# soybean urease solution, 2# salt solution, 3# xanthan gum, 4# skimmed milk powder, 5# magnesium chloride, 6# polylysine, 7# sodium montmorillonite, 8# polyacrylamide, 9# glass fiber, and 10# silica fume; The preparation steps include: mixing 3# xanthan gum, 4# skimmed milk powder, 5# magnesium chloride, 6# polylysine, 7# sodium montmorillonite, 8# polyacrylamide, 9# glass fiber and 10# silica fume as additives, and adding them into 1# soybean urease solution; fully mixing the soybean urease solution mixed with additives and 2# salt solution composed of calcium chloride and urea to form a binder.

6. The method according to claim 5, characterized in that The concentration of the binder is: 1# soybean urease solution 5 mol / L, 2# salt solution 1-3 g / L, 3# xanthan gum 0.8-1.2 g / L, 4# skimmed milk powder 2.7-3.2 g / L, 5# magnesium chloride 0.8-1.2 g / L, 6# polylysine 0.2-0.7 g / L, 7# sodium montmorillonite 1.7-2.1 g / L, 8# polyacrylamide 0.2-0.7 g / L, 9# glass fiber 1.8-2.3 g / L, 10# silica ash 2.7-3.3 g / L.

7. The method according to claim 6, characterized in that The concentration of the binder is: 3# xanthan gum 1g / L, 4# skimmed milk powder 3g / L, 5# magnesium chloride 1g / L, 6# polylysine 0.5g / L, 7# sodium montmorillonite 2g / L, 8# polyacrylamide 0.5g / L, 9# glass fiber 2g / L, 10# silica fume 3g / L. The method according to claim 1 , wherein the interval is 10 hours.

9. Use of the method for in-situ repairing of wind-eroded sand pits at the toes of piles according to any one of claims 1 to 8 in repairing wind-eroded sand pits at piles.

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