A method and apparatus for backfilling and repairing toe erosion gullies of ground piles

Abstract

The application provides a method for backfilling and repairing wind-eroded sand pits around pile toes of foundation piles, characterized in that an integrated self-feeding mixer truck combining a mixing device and a mechanical arm with a tamping function is used to prepare a cementing solution by efficiently and uniformly mixing a soybean urease solution and a salt solution into which additives are added on a desert site. The integrated self-feeding mixer truck can automatically take batches of in-situ sand and cementing solution to form sand slurry, and automatically deliver the sand slurry to the sand pit around the pile toe through a sand conveying pipe, a mechanical arm, a tamping head and other components to compact the sand slurry, flatten it to be flush with the surrounding desert surface, and then form a wind-resistant reinforcing repair layer in the sand pit. The wind-resistant reinforcing repair layer after backfilling can resist the shaking of the pile foundation and weaken the wind field of the pile to increase the long-term stability of the pile foundation. In addition, the application introduces a set of parameterized control method to realize precise control of the amount of SICP solution under different working conditions on site. Compared with the traditional mechanical backfilling and chemical consolidation method, the application has better environmental friendliness while improving the construction effect and efficiency, 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 and apparatus for backfilling and repairing wind-eroded sand pits around the toe of photovoltaic panel foundation piles in the desert. Background Technology

[0002] With the growing global demand for clean energy, photovoltaic (PV) power generation has become an important energy option due to its pollution-free and renewable characteristics. Desert regions, with their vast land and abundant sunshine, are ideal locations for building PV power plants. Desert PV power plants not only effectively utilize land resources and reduce the occupation of agricultural land, but also significantly increase the supply of clean energy, contributing to the achievement of carbon neutrality goals. However, in desert environments, the frequent occurrence of extreme sandstorms poses a challenge to the pile foundations of PV power plants, as they are often subjected to wind erosion, seriously threatening their stability.

[0003] Under high wind speeds, the pile foundations of desert photovoltaic power stations experience localized turbulence around the pile toes due to the obstruction of the photovoltaic panel piles. This erosion and transport of sand in the area gradually forms pits. These pits not only exacerbate wind erosion around the pile foundation but also reduce windbreak and sand-fixing effectiveness, further impacting the long-term stability and safety of the pile foundation. Traditional treatment methods include mechanical backfilling and chemical consolidation. However, mechanically backfilled sand is easily eroded again by wind and sand, while chemical consolidation poses potential environmental hazards and does not meet the requirements of sustainable development.

[0004] To address this, this invention proposes an innovative method combining microbial solidification and mixing backfilling technologies. By utilizing soybean urease-induced calcium carbonate precipitation (SICP) technology, wind-eroded sand pits around the pile toe are backfilled and reinforced. This method not only effectively improves the cohesion and compressive strength of the sand, reducing wind erosion damage to the pile foundation, but also achieves precise control of the SICP solution dosage through the introduction of parametric control formulas, determining the ratio and usage of the binder under different construction conditions. Precise SICP solution control makes the construction process more efficient, reduces material waste, and allows for flexible adjustment of the ratio according to actual site needs, thus adapting to changing environmental conditions. Through these technological advantages, this method can form a stable and efficient windproof solidification layer, redistributing the wind field around the pile foundation, significantly reducing pile sway and displacement, and greatly improving the long-term stability of the pile foundation. Simultaneously, this method avoids the environmental pollution problems of traditional mechanical backfilling and chemical consolidation methods, providing a green, environmentally friendly, and durable solution, comprehensively improving the operational safety and reliability of desert photovoltaic power stations in extreme environments, and meeting the requirements of green and sustainable development. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention aims to solve the following technical problems: providing a convenient and efficient method and implementation steps for backfilling and repairing wind-eroded sand pits around the toes of desert photovoltaic panel foundation piles, 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. The technical solution adopted by this invention is as follows:

[0006] A method for backfilling and repairing wind-eroded sand pits at the toes of ground piles, wherein the repair technology combines a microbial sand fixation method (SICP) induced by soybean urease to precipitate calcium carbonate with a mixing backfilling technique:

[0007] The cementing solution of the microbial sand-fixing method is composed of 10 components: soybean urease solution, salt solution, xanthan gum, skim milk powder, magnesium chloride, polylysine, sodium montmorillonite, polyacrylamide, glass fiber, and silica fume. The concentrations of each component in the cementing solution are as follows: soybean urease solution 20g / L-100g / L, salt solution 30g / L-80g / L, 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.

[0008] The soybean urease solution described in this application is obtained by direct extraction from soybeans. After the soybeans are completely dried, they are ground into soybean powder, which is then thoroughly mixed with deionized water at a specific solid-liquid ratio of 1:50 to 1:10. The soybean residue is then filtered out, and the upper layer solution is centrifuged to obtain a soybean urease solution with a concentration of 20 g / L to 100 g / L. The salt solution is formed by mixing calcium chloride and urea of ​​equal concentration.

[0009] The mixing and backfilling technology is achieved by an integrated self-loading mixer truck that integrates mixing, stirring and sand conveying and compaction functions. The integrated self-loading mixer truck includes mixing equipment, liquid tank, hydraulic bucket, mixing tank, sand conveying pipe, robotic arm and tamping head, and central control system. After inputting the required working parameters into the central control system, the functions of automatically preparing cementing liquid, preparing mortar and conveying and compacting sand are realized.

[0010] The mixing and backfilling process of the integrated self-loading mixer truck is as follows:

[0011] (S1) Add xanthan gum, skim milk powder, magnesium chloride, polylysine, sodium montmorillonite, polyacrylamide, glass fiber, and silica fume to the soybean urease solution, and stir and mix thoroughly to form a composite soybean urease solution.

[0012] (S2) By feeding the compound soybean urease solution and salt solution formed in step (S1) into the mixing equipment and stirring thoroughly, a gelling liquid is formed. Then, the mixed gelling liquid is transported to the liquid addition tank for later use.

[0013] (S3) Based on the on-site construction design requirements, determine the volume of cementing liquid required per unit volume of sand according to the following formula, then determine the total amount of cementing liquid based on the amount of sand used, and input it into the central control system.

[0014]

[0015] In the formula: V SICP To determine the volume of cementing solution required per unit volume of sand at the target strength and cementing solution concentration; V S q represents the amount of sand used per unit volume of fill. u The target unconfined compressive strength under design requirements; q u0 The reference strength, determined under standard operating conditions, is obtained through indoor testing under standard conditions, which include: standard urease solution concentration, calcium ion solution concentration, and standard reaction time; C standard C is the product of the standard urease solution concentration and the calcium chloride solution concentration under standard operating conditions. urease C represents the concentration of soybean urease solution used in the actual field. Ca The concentration of calcium chloride solution used in the actual field is denoted as α; α and λ are empirical coefficients calibrated in the laboratory experiments, obtained by fitting multiple sets of laboratory experiment results under varying concentration and time conditions; Δt is the reaction time.

[0016] (S4) According to the set parameters, the integrated self-loading mixer truck automatically transports the cementing liquid to the mixing tank and mixes it with the in-situ sand to form mortar;

[0017] (S5) The sand conveying pipe, mechanical arm and tamping head of the integrated self-loading mixer truck are used to backfill the wind erosion sand pit around the pile toe with mortar and flatten it, thereby forming a windproof and reinforced repair layer.

[0018] Preferably, the other components of the composite soybean urease solution are added to the soybean urease solution in batches and stirred evenly. The order of addition of the other components is as follows: 1) Fully dissolve xanthan gum to form a stable thickening matrix, which prolongs the residence time of the cementitious liquid on the surface of the sand particles, thereby promoting the precipitation and solidification of calcium carbonate; 2) Add polyacrylamide and polylysine to ensure uniform fusion between polymers and play a synergistic thickening and bonding role, increasing the cohesion and friction of the sand; 3) Add magnesium chloride and sodium montmorillonite to allow inorganic salts and clay to be fully dispersed in the polymer system, thereby increasing the precipitation amount and efficiency of calcium carbonate by providing more nucleation sites, promoting the formation of hard and stable crystals, and improving the strength and durability of the solidified layer; 4) Add skim milk powder to provide additional bonding aids, enhance the microbial activity during the calcium carbonate deposition process, thereby promoting the precipitation and solidification of calcium carbonate; 5) Add glass fiber and silica fume to enhance the cementing effect and the compressive strength and shear strength of the reinforced layer, while preventing the formation of cracks in stress concentration areas.

[0019] Preferably, the mixing equipment in the integrated self-loading mixer truck includes an air conveying system, a liquid mixing unit, a liquid addition and conveying system, and an atomizing spray device.

[0020] Preferably, the side of the tamping head bottom plate of the integrated self-loading mixer truck that contacts the pile toe is arc-shaped, and the arc shape is consistent with the curvature of the cylindrical pile toe on site, so that the tamping head can work without dead angles, improving the compaction effect and efficiency.

[0021] Preferably, the liquid mixing unit includes a raw slurry container, a gas outlet located at the top of the raw slurry container, a raw slurry container liquid inflow control valve, and a static mixer; one end of the A-section water pipe is connected to the raw slurry container liquid inflow control valve, and the other end is connected to the static mixer, which achieves preliminary uniform mixing of the two solutions. The mixed solution enters the raw slurry container for further uniform mixing after passing through the raw slurry container liquid inflow control valve via the A-section water pipe; the other end of the static mixer is connected to a fluid gathering device via the B-section water pipe for efficient guidance and input of the liquid.

[0022] Preferably, the pneumatic conveying system includes a vent, a gas regulating valve, and a pneumatic jetting device installed on the side wall of the raw slurry container. The pneumatic jetting device consists of an air compressor, a gas distribution system, and pipelines. When two air compressors start simultaneously and open the gas regulating valve, bubbles are generated in the liquid in the raw slurry container. The rising bubbles drive the liquid to flow, thereby achieving complete mixing of the liquid.

[0023] Preferably, the liquid delivery system includes a liquid outflow control valve for the raw slurry container, a C-section water pipe, a liquid delivery pump, and a spray device with atomization function. The liquid is delivered to the spray device through the liquid delivery pump system, and a flow regulator is installed in front of the spray device to precisely control the amount of liquid sprayed.

[0024] A method for operating an integrated self-loading mixer truck includes the following steps:

[0025] Step 1: Prepare the various components of the compound soybean urease solution: soybean urease solution 20g / L-100g / L, 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; then add the corresponding components and stir thoroughly; prepare a salt solution with a concentration of 30g / L-80g / L using calcium chloride and urea of ​​equal concentration;

[0026] In this process, other components of the composite soybean urease solution are added to the soybean urease solution in batches and stirred evenly. The order of addition of the other components is as follows: 1) Fully dissolve xanthan gum to form a stable thickening matrix, which prolongs the residence time of the cementitious solution on the surface of sand particles, thereby promoting the precipitation and solidification of calcium carbonate; 2) Add polyacrylamide and polylysine to ensure uniform fusion between polymers and play a synergistic thickening and bonding role, increasing the cohesion and friction of sand; 3) Add magnesium chloride and sodium montmorillonite to allow inorganic salts and clay to be fully dispersed in the polymer system, thereby increasing the precipitation amount and efficiency of calcium carbonate by providing more nucleation sites, promoting the formation of hard and stable crystals, and improving the strength and durability of the solidified layer; 4) Add skim milk powder to provide additional bonding aids, enhance the microbial activity during the calcium carbonate deposition process, thereby promoting the precipitation and solidification of calcium carbonate; 5) Add glass fiber and silica fume to enhance the cementing effect and the compressive strength and shear strength of the reinforced layer, while preventing the formation of cracks in stress concentration areas.

[0027] Step 2: Pump the compound soybean urease solution and salt solution described in Step 1 into different water trucks, which then drive to the work platform near the site. The solutions are then fed into the mixing equipment of the integrated self-loading mixer truck in equal volumes, and the mixing equipment is started to fully stir and form a gelled liquid.

[0028] Step 3: Immediately transfer the prepared cementing solution into the liquid addition tank for later use;

[0029] Step 4: Use the integrated self-loading mixer truck to take in-situ sand batch by batch on-site and weigh it. Transmit the weighing data to the control center. Then, the integrated self-loading mixer truck adds in-situ sand to the mixing tank batch by batch, with an interval of 2-5 minutes between each batch. At the same time as each batch of in-situ sand is added, the control center determines the solid-liquid ratio according to formula (1) and the parameters input in the control panel, calculates the volume of cementing liquid to be added under the current sand addition conditions, and controls the liquid addition pump to pump the corresponding weight of cementing liquid into the mixing tank. When the in-situ sand taken in batches reaches the set volume, stop taking sand and keep the mixing tank in a stirring state to form a uniformly mixed slurry, while avoiding the slurry from solidifying.

[0030] Step 5: Operate the integrated self-loading mixer truck to deliver mortar to the area around the pile toe pit. Operate the robotic arm to adjust the tamping head to the appropriate position and direction. Set the tamping frequency and energy on the control panel interface. Compact the mortar in layers until the surface of the pit is filled. Use a scraper to remove the excess mortar to make the surface of the pit flat. Wait for the backfilled mortar to solidify and form a hard shell layer to resist wind erosion.

[0031] The present invention has the following beneficial effects:

[0032] 1. This invention introduces a quantitative parameter control method for the mortar backfilling process, precisely determining the amount of mortar used per unit volume of sand under the conditions of setting the concentration of each component solution of the binder and the expected reaction time. Construction personnel can flexibly adjust the amount of binder used according to site requirements: when higher strength is needed, the concentration of urease or calcium chloride can be increased accordingly, or the reaction time can be extended, thereby reducing the amount of solution used at a higher or equivalent target strength; when the reaction time needs to be shortened due to project time constraints, the concentration of each component and the amount of binder used can also be adjusted; when environmental conditions (such as temperature, humidity, and wind speed) change, the parameters can also be modified to meet the target requirements. Unlike traditional simple control based on compaction degree, the control method of this invention fully utilizes the microbial and chemical reaction characteristics of SICP, making the performance of the backfill layer more predictable and controllable, thereby significantly improving the long-term stability and reliability of the windproof and cured repair layer.

[0033] 2. This invention innovatively proposes an integrated self-loading mixer truck that combines mixing, stirring, and sand conveying and compaction functions. This allows for efficient and thorough mixing of soybean urease solution and salt solution with additives within the same device, significantly improving the solidification effect of the cementitious liquid and sand reaction. The integrated self-loading mixer truck's onboard automation system and central control system provide real-time regulation of the mixing ratio, stirring, and conveying process, reducing human error. Simultaneously, the collaborative work of the self-loading function and the robotic arm compaction module greatly simplifies construction organization and material transfer processes, avoiding the influence of the external environment on the mixing quality, further ensuring the uniformity and overall strength of the backfill layer, thereby achieving efficient repair of sand pits and strengthening the long-term stability of the pile foundation.

[0034] 3. The cementing solution used in this invention is composed of soybean urease solution, salt solution and various additives, which are mixed and stirred in a certain order. The order of addition in this invention can effectively avoid cross-interference between the components, fully ensure the dissolution and mixing of each component, achieve good cementing performance and overall strength, and facilitate the formation of a windproof reinforcement and repair layer with higher adhesion and higher strength. At the same time, it also enhances the friction between the pile foundation and the surrounding sandy foundation, prevents the pile foundation from sliding and tilting under lateral force, and improves the overall stability of the pile foundation.

[0035] 4. During the reinforcement process of sandy foundations around the pile foundation, the present invention forms a uniform windproof and solidified layer. By changing the surface roughness and wind field structure, it effectively reduces the wind speed and turbulence effect around the pile foundation, reduces the direct impact of wind load on the pile foundation, significantly reduces the swaying and displacement of the pile foundation in extreme wind and sand environments, and enhances the long-term stability and durability of the pile foundation.

[0036] 5. The soybean urease solution of the present invention can be directly extracted from soybeans, and its usage cost is lower than that of commercially available soybean urease solutions. Attached Figure Description

[0037] Figure 1 This is a flowchart illustrating the implementation steps of the present invention.

[0038] Figure 2 This is a front view of the integrated self-loading mixer truck of the present invention.

[0039] Figure 3 This is a top view of the integrated self-loading mixer truck of the present invention.

[0040] Figure 4 This is a left-side view of the integrated self-loading mixer truck of the present invention.

[0041] Figure 5 This is a front view of the mixing equipment in the integrated self-loading mixer truck of the present invention.

[0042] Figure 6 This is a top view of the mixing equipment in the integrated self-loading mixer truck of the present invention.

[0043] Figure 7 This is a left-side view of the mixing equipment in the integrated self-feeding mixer truck of the present invention.

[0044] Figure 8 This is a schematic diagram of the modification of the tamping head in the integrated self-feeding mixer truck of the present invention.

[0045] Figure 9 These are the compressive strength test results of the surface solidified sand of the windproof reinforcement and repair layer in Embodiment 1 and Comparative Examples 1 to 3 of the present invention.

[0046] Figure 10 These are the compressive strength test results of the surface solidified sand of the windproof reinforcement and repair layer in Examples 1 to 4 of the present invention.

[0047] Figure 11 These are the shear strength test results of the surface solidified sand of the windproof reinforcement and repair layer in Examples 1 to 4 of the present invention.

[0048] Figure 12 These are the test results of an ultrasonic anemometer installed at a height of 0.5m on the pile foundations of Embodiments 1 to 4 of the present invention.

[0049] Figure 2-4 The components include: 1. Hydraulic bucket, 2. Mixing tank, 3. Liquid filling tank, 4. Mixing equipment, 5. Sand conveying pipe, 6. Robotic arm, and 7. Rammer head.

[0050] Figure 5-7 In the middle section: 8. Raw material container, 9. Gas outlet, 10. Raw material container liquid inflow control valve, 11. Section A water pipe, 12. Static mixer, 13. Section B water pipe, 14. Fluid gathering device, 15. Gas regulating valve, 16. Air inlet, 17. Gas pipeline, 18. Air compressor and gas distribution system, 19. Raw material container liquid outflow control valve, 20. Section C water pipe, 21. Liquid addition pump, 22. Flow regulator, 23. Spray device.

[0051] Figure 8 24. Rammer head base plate; 25. Pile toe. Detailed Implementation

[0052] 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.

[0053] Example 1

[0054] In this embodiment, the parameters of formula (1) were first calibrated through indoor experiments. The standard conditions were set as follows: soybean urease solution concentration of 20 g / L; urea concentration of 0.25 M; calcium chloride concentration of 0.25 M; and standard reaction time (Δt) of 72 h. Under the above standard conditions, the reference unconfined compressive strength (q) under the reference working condition was determined. u0 The pressure is 0.6 MPa. Through fitting analysis of multiple sets of indoor test data, two empirical parameters in formula (1) were determined: α≈1.0, λ≈0.02.

[0055] Under the aforementioned standard conditions, by setting the target unconfined compressive strength value (to simulate different on-site working conditions), the formula proposed in this invention can be used for calculation:

[0056]

[0057] In the formula: V SICP To determine the volume of cementing solution required per unit volume of sand at the target strength and cementing solution concentration; V S q represents the amount of sand used per unit volume of fill. u The target unconfined compressive strength under design requirements; q u0 The reference strength, determined under standard operating conditions, can be obtained through laboratory testing under standard conditions (standard urease solution concentration, calcium ion solution concentration, and standard reaction time); C standard C is the product of the standard urease solution concentration and the calcium chloride solution concentration under standard operating conditions. urease C represents the concentration of soybean urease solution used in the actual field. Ca α represents the concentration of calcium chloride solution used in the actual field; α and λ are empirical coefficients calibrated in the laboratory experiment, which can be obtained by fitting multiple sets of laboratory test results under different conditions such as concentration and time; Δt is the reaction time.

[0058] In this embodiment, the target intensity q u =0.8 MPa, soybean urease solution concentration is 30 g / L, urea and calcium chloride concentrations are both 0.4 M, reaction time is 72 h, substitute into the formula to calculate per 1 m 3 The fill requires approximately 0.1317 m³ of aeolian sand. 3 The amount of SICP binder used. The above process can be completed by inputting q into the control panel of the integrated self-loading mixer truck of the invention. u q u0 C urease The integrated self-loading mixer truck will automatically calculate parameters such as these to complete the process. Figures 2-4 As shown, the integrated self-loading mixer truck uses its hydraulic bucket 1 to collect and weigh in-situ sand batch by batch. The weighing data is transmitted to the control center. The integrated self-loading mixer truck then adds in-situ sand batch by batch into the mixing tank 2, with an interval of 2-5 minutes between each batch. Simultaneously with each batch of sand added, the control center determines the solid-liquid ratio according to the SICP solution dosage control formula determined in this invention and the parameters input into the control panel, calculates the weight of the cementing liquid to be added, and controls the pump to pump the corresponding weight of cementing liquid from the filling tank 3 into the mixing tank 2. Once the collected in-situ sand reaches the set volume, sand collection stops, allowing the mixing tank 2 to remain in a mixing state, forming a uniformly mixed slurry while preventing the slurry from solidifying.

[0059] The formation process of the cementing liquid is as follows:

[0060] A soybean urease solution and salt solution, prepared in the laboratory and incorporating additives, are transported to the desert site by water truck. The aforementioned compound soybean urease solution and salt solution are then injected in equal volume via the water truck's conveyor belt into the fluid collection device of mixing equipment 4 in the integrated self-loading mixer truck. For example... Figures 5-7 As shown, the mixing equipment consists of a liquid mixing unit, an airflow conveying system, a liquid addition and delivery system, and an atomizing spray device. Specifically, the liquid mixing unit has the following substructures: raw slurry container 8, gas outlet 9, raw slurry container liquid inflow control valve 10, section A water pipe 11, static mixer 12, section B water pipe 13, and fluid gathering device 14; the airflow conveying system has the following substructures: gas regulating valve 15, air inlet 16, gas pipeline 17, air compressor and gas distribution system 18; the liquid addition and delivery system and the atomizing spray device have the following substructures: raw slurry container liquid outflow control valve 19, section C water pipe 20, liquid addition pump 21, flow regulator 22, and spray device 23.

[0061] The operating procedure of the mixing equipment is as follows: First, the two liquids are injected into the static mixer 12 through the fluid gathering device 14 to achieve preliminary uniform mixing; then, the mixed liquid flows into the raw slurry container 1 through the A-section water pipe 11; next, the air compressor and gas distribution system 18 are started, and the gas enters the raw slurry container 8 through the gas pipe 17, air inlet 16, and gas regulating valve 15. As the bubbles rise in the raw slurry container 8, they drive the liquid to circulate, making the liquid fully mixed, and finally preparing a cemented liquid, in which the gas flows out through the gas outlet 9. The liquid outflow control valve 19 of the raw slurry container is opened, and the cemented liquid is transported to the spray device 23 through the C-section water pipe 20 and the liquid addition pump 21. The flow rate is controlled by the flow regulator 22 and injected into the water tank and liquid addition tank of the integrated self-loading mixer truck.

[0062] Subsequently, the silt was divided into three batches and added to the cementing solution for stirring. The solid-liquid ratio of the first to third batches of silt and the corresponding cementing solution was calculated using the proposed formula.

[0063] Subsequently, the integrated self-loading mixer truck is operated to transport mortar to the area around the pile toe pit via sand conveying pipe 5. The robotic arm 6 is operated to adjust the tamping head 7 to a suitable position and direction. The tamping frequency and energy are set in the control panel, and the mortar is compacted in layers until the pit surface is filled. The excess is then removed with a scraper to make the pit surface smooth, and the backfilled mortar is allowed to solidify and form a hard shell layer to resist wind erosion. For example, Figure 8 As shown, the side of the tamping head bottom plate that contacts the pile toe is arc-shaped, and the arc shape is consistent with the arc of the cylindrical pile toe on site, which allows the tamping head to work without dead angles, improving the compaction effect and efficiency.

[0064] Comparative Example 1

[0065] In this comparative example, the target intensity q uUsing a pressure of 0.9 MPa, a soybean urease solution concentration of 35 g / L, and urea and calcium chloride concentrations of 0.5 M, with the reaction time remaining at 72 h, and all parameters unchanged under standard conditions, the values ​​per 1 m were calculated according to the formula. 3 Approximately 0.1011 m³ of fill sand is required. 3 The SICP binder was used, therefore this ratio was adopted to determine the amount of binder used in this comparative example. The rest is the same as in Example 1.

[0066] Comparative Example 2

[0067] In this comparative example, the target intensity q u Using a standard reaction conditions of 1.0 MPa, a soybean urease solution concentration of 40 g / L, and urea and calcium chloride concentrations of 0.6 M, with a reaction time of 72 h, and all parameters remaining constant, the values ​​per 1 m were calculated according to the formula. 3 Approximately 0.0814 m³ of fill sand is required. 3 The SICP binder was used, therefore this ratio was adopted to determine the amount of binder used in this comparative example. The rest is the same as in Example 1.

[0068] Comparative Example 3

[0069] In this comparative example, the target intensity q u Using a standard condition, the following parameters were calculated: 1.1 MPa, soybean urease solution concentration of 45 g / L, urea and calcium chloride concentrations of 0.7 M, reaction time of 24 hours, and all parameters remaining constant. The result was calculated per 1 m... 3 Approximately 0.1803 m³ of fill sand is required. 3 The SICP binder was used, therefore this ratio was adopted to determine the amount of binder used in this comparative example. The rest is the same as in Example 1.

[0070] The performance of Example 1 and Comparative Examples 1-3 will be evaluated below.

[0071] Figure 9 The results of compressive strength tests were conducted on surface-cured sand samples taken after backfilling the sand pits around the pile toes in Examples 1 and Comparative Examples 1-3 to form a windproof reinforcement repair layer. The sample preparation method was as follows: the surface-cured sand from the examples and comparative examples was filled into a cylindrical mold, cured for 72 hours, and then dried to obtain cylindrical samples with a diameter of 50 mm and a height of 100 mm. Unconfined compressive strength tests were performed using a universal testing machine, and the compressive strength of each sample was obtained as follows: Figure 9As shown, the experimental data are detailed in Table 1. The experimental results show that in the tests of Example 1 and Comparative Examples 1-3, the target unconfined compressive strength, the concentrations of soybean urease solution, urea and calcium chloride solution, and the reaction time were independently set according to the formula (1) proposed by this invention. Based on these settings, the corresponding ratio of SICP cementitious liquid to sand was obtained, and the final measured unconfined compressive strength of the cured sample was in good agreement with the preset target value. This indicates that the ratio conditions determined by this formula can achieve the expected strength target under different working conditions (including urease solution concentration and Ca ion concentration, required reaction time, etc.). Compared with the traditional empirical adjustment method that does not use the formula, the formulaic control method proposed by this patent makes the SICP reinforcement process more predictable and more accurate, and allows for flexible adjustment of the reaction time according to the construction period. It also demonstrates high reliability and rationality in the three sets of comparative experiments, proving the applicability and practical value of the formula.

[0072] Table 1 (Unit: MPa)

[0073] Sample type Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 compressive strength 0.77 0.86 1.03 1.15

[0074] Example 2

[0075] In this comparative example, the integrated self-feeding mixer of the present invention is not used when preparing the cementitious liquid. Instead, a conventional method is used, in which the soybean urease solution and salt solution with additives are injected into an iron drum and stirred thoroughly to mix them as much as possible. Then the mixture is injected into the liquid addition tank. The remaining processing steps are the same as in Example 1.

[0076] Example 3

[0077] In this comparative example, when sand is taken from the integrated self-loading mixer truck and mixed with cementing liquid to form mortar, the batch sand taking and mixing method proposed in this invention is not used. Instead, all the sand of the target volume is taken at once and poured into the mixing tank. The proportion of cementing liquid dosage is determined according to the SICP cementing liquid dosage control formula proposed in this invention, and the cementing liquid is pumped to mix with it. The rest is the same as in Example 1.

[0078] Example 4

[0079] In this comparative example, when backfilling and compacting mortar in layers, the robotic arm and rammer head of the integrated self-loading mixer truck are not used for compaction; instead, a regular handheld small rammer is used. Otherwise, it is the same as in Example 1.

[0080] The performance of Examples 1 to 4 will be evaluated below.

[0081] Figure 10Table 2 shows the results of compressive strength tests on surface-cured sand after backfilling the sand pit around the pile toe to form a windproof reinforcement repair layer, as described in Examples 1-4. The experimental data are detailed in Table 2. The results show that the compressive strength of the samples made from the surface-cured sand treated in Example 1 is higher than that in Example 2. This indicates that the integrated self-loading mixer truck of this invention can prepare a large volume of uniform cementitious liquid, and can fully mix the cementitious liquid through the liquid mixing unit and airflow conveying system, thus playing an important role in improving the final compressive strength of the cured sand. It solves the problem of uniform mixing of large volume cementitious liquid in a simple and low-cost way. Furthermore, the compressive strength of the samples made from the surface-cured sand treated in Example 1 is higher than that in Example 3, indicating that the "batch" method proposed in this invention... Compared to the "one-time sand mixing" method, the "sand taking and mixing" method can avoid problems such as uneven mixing and premature solidification caused by one-time sand taking under the same amount of cementing liquid. This makes the calcium carbonate precipitation more uniform and the particles finer, thereby obtaining higher compressive strength and overall stability under the same amount, and achieving better consolidation effect. The compressive strength of the sample made from the surface-cured sand treated by the method in Example 1 is higher than that in Example 4, indicating that the mechanical arm and tamping head of the integrated self-feeding mixer truck in this invention not only increases the degree of automation, but also improves the compressive strength of the final cured sand.

[0082] Table 2 (Unit: MPa)

[0083] Sample type Example 1 Example 2 Example 3 Example 4 compressive strength 0.77 0.54 0.62 0.69

[0084] Figure 11 The results of shear strength tests were conducted on surface-cured sand samples taken after backfilling the sand pits around the pile toes in Examples 1-4 to form a windproof reinforcement repair layer. The sample preparation method was as follows: surface-cured sand from the examples and comparative examples was filled into a square mold, cured for 72 hours, and then dried to obtain cubic samples with a volume of 50mm*50mm*50mm. Shear strength tests were performed using a direct shear apparatus, and the shear strength of each sample was obtained as follows: Figure 11As shown in Table 3, the experimental data are detailed below. The experimental results show that the shear strength of the sample made from the surface-cured sand treated by the method in Example 1 is higher than that in Example 2. This indicates that the mixing equipment invented in this invention can prepare a large volume of uniform cementitious liquid, and can fully mix the cementitious liquid through the liquid mixing unit and the airflow conveying system, thus playing an important role in improving the final shear strength of the cured sand. It solves the problem of uniform mixing of large volume cementitious liquid in a simpler and lower-cost way. The shear strength of the sample made from the surface-cured sand treated by the method in Example 1 is higher than that in Example 3, indicating that the "batch sand mixing" method proposed in this invention can achieve a better cementing effect with the same amount of cementitious liquid compared to the "one-time sand mixing" method. The shear strength of the sample made from the surface-cured sand treated by the method in Example 1 is higher than that in Example 4, indicating that using the robotic arm and tamping head of the integrated self-feeding mixer truck in this invention not only increases the degree of automation but also improves the final shear strength of the cured sand.

[0085] Table 3 (Unit: MPa)

[0086] Sample type Example 1 Example 2 Example 3 Example 4 shear strength 0.46 0.32 0.38 0.41

[0087] Figure 12 The results of wind field measurements at the same time were obtained by installing an ultrasonic anemometer at a height of 0.5m on the pile foundations after backfilling the sand pits around the pile toes to form a windproof reinforcement and repair layer, as described in Examples 1-4 (the pile foundations of Examples 1-4 were in the same area, and the ultrasonic anemometer was installed at the same height on a selected pile foundation in the same area that had not been treated by this method). The wind speed results obtained by the ultrasonic anemometer are as follows: Figure 12 As shown in Table 4, the experimental data are detailed. The experimental results show that the wind speed results of Examples 1 to 4 are all lower than the wind speed results of the pile foundations that have not been treated by this method, and the wind speed result of Example 1 is the lowest. This indicates that the method proposed in this invention can significantly reduce the wind field of the pile foundation and enhance the long-term stability of the pile foundation.

[0088] Table 4 (Unit: m / s)

[0089] Sample type Example 1 Example 2 Example 3 Example 4 Untreated pile foundation wind speed 2.35 3.37 2.91 2.66 4.56

Claims

1. A method for backfilling and repairing wind-eroded sand pits at the toe of ground piles, characterized in that, Combined use of microbial sand fixation methods and mixing backfill technology: The microbial sand-fixing method includes a cementing solution; The mixing and backfilling technology is implemented by an integrated self-loading mixer truck, which includes mixing equipment, a liquid addition tank, a hydraulic bucket, a mixing tank, a sand conveying pipe, a robotic arm and a tamping head, and a central control system. The mixing and backfilling process of the integrated self-loading mixer truck is as follows: S1. Add xanthan gum, skim milk powder, magnesium chloride, polylysine, sodium montmorillonite, polyacrylamide, glass fiber, and silica fume to the soybean urease solution, and stir and mix thoroughly to form a compound soybean urease solution. S2. By feeding the compound soybean urease solution and salt solution formed in step S1 into the mixing equipment and stirring thoroughly, a cementitious liquid is formed. The mixed cementitious liquid is then transported to the addition tank for later use. The salt solution is formed by mixing calcium chloride and urea of ​​equal concentration. The concentrations of each component in the cementing solution are as follows: soybean urease solution 20g / L-100g / L, salt solution 30g / L-80g / L, 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. S3. Determine the volume of cementing liquid required per unit volume of sand according to formula (1), then determine the total amount of cementing liquid based on the amount of sand used, and input it into the central control system. In the formula: V SICP To determine the volume of cementing solution required per unit volume of sand at the target strength and cementing solution concentration; V S q represents the amount of sand used per unit volume of fill. u The target unconfined compressive strength under design requirements; q u0 The reference strength is determined under standard operating conditions and obtained through indoor testing under standard conditions, namely, the standard urease solution concentration, the calcium ion solution concentration, and the standard reaction time; C standard C is the product of the standard urease solution concentration and the calcium chloride solution concentration under standard operating conditions. urease C represents the concentration of soybean urease solution used in the actual field. Ca The concentration of calcium chloride solution used in the actual field is denoted as α; α and λ are empirical coefficients calibrated in the laboratory experiments, obtained by fitting multiple sets of laboratory experiment results under varying concentration and time conditions; Δt is the reaction time. S4. According to the set parameters, the integrated self-loading mixer truck automatically transports the cementing liquid to the mixing tank and mixes it with the in-situ sand to form mortar. S5. The sand conveying pipe, robotic arm and tamping head of the integrated self-loading mixer truck are used to backfill the wind erosion sand pits around the pile toe with mortar and flatten it, thereby forming a windproof reinforcement and repair layer.

2. The method according to claim 1, characterized in that, In the soybean urease solution, the other components of the compound soybean urease solution are added in batches and stirred evenly. The order of addition of the other components is as follows: 1) Fully dissolve xanthan gum to form a stable thickening matrix, which prolongs the residence time of the cementitious liquid on the surface of sand particles, thereby promoting the precipitation and solidification of calcium carbonate; 2) Add polyacrylamide and polylysine to ensure uniform fusion between polymers and play a synergistic thickening and bonding role, increasing the cohesion and friction of sand; 3) Add magnesium chloride and sodium montmorillonite to allow inorganic salts and clay to be fully dispersed in the polymer system, thereby increasing the precipitation amount and efficiency of calcium carbonate by providing more nucleation sites, promoting the formation of hard and stable crystals, and improving the strength and durability of the solidified layer. 4) Add skim milk powder to provide additional binding aids, enhance microbial activity during the calcium carbonate deposition process, thereby promoting the precipitation and solidification of calcium carbonate; 5) Adding glass fiber and silica fume enhances the bonding effect and the compressive and shear strength of the reinforcement layer, while preventing cracks from forming in stress concentration areas.

3. The method according to claim 1, characterized in that, The integrated self-loading mixer truck's mixing equipment includes an airflow conveying system, a liquid mixing unit, a liquid addition and conveying system, and an atomizing spray device; The liquid mixing unit includes a raw slurry container, a gas outlet located at the top of the raw slurry container, a liquid inflow control valve for the raw slurry container, and a static mixer. One end of section A water pipe is connected to the liquid inflow control valve for the raw slurry container, and the other end is connected to the static mixer. The static mixer achieves preliminary uniform mixing of the two solutions. The mixed solution enters the raw slurry container for further uniform mixing after passing through section A water pipe and the liquid inflow control valve. The other end of the static mixer is connected to a fluid gathering device through section B water pipe for efficient guidance and input of the liquid. The pneumatic conveying system includes a vent, a gas regulating valve, and a pneumatic jetting device installed on the side wall of the raw slurry container. The pneumatic jetting device consists of an air compressor, a gas distribution system, and pipelines. When two air compressors start simultaneously and open the gas regulating valve, bubbles are generated in the liquid in the raw slurry container. The rising bubbles drive the liquid to flow, thereby achieving complete mixing of the liquid. The liquid delivery system includes a liquid outflow control valve for the raw slurry container, a C-section water pipe, a liquid delivery pump, and a spray device with atomization function. The liquid is delivered to the spray device through the liquid delivery pump, and a flow regulator is installed in front of the spray device to precisely control the amount of liquid sprayed.

4. The method according to claim 1, characterized in that, The bottom plate of the tamping head of the integrated self-loading mixer truck has an arc shape on the side that contacts the pile toe, and the arc shape is consistent with the arc of the cylindrical pile toe on site, so that the tamping head can work without dead angles, improving the compaction effect and efficiency.

5. A working method for an integrated self-loading mixer truck, characterized in that, Includes the following steps: Step 1: Add xanthan gum, skim milk powder, magnesium chloride, polylysine, sodium montmorillonite, polyacrylamide, glass fiber, and silica fume to the soybean urease solution, and stir and mix thoroughly to form a compound soybean urease solution; a salt solution is formed by mixing calcium chloride and urea of ​​equal concentration. In this process, other components of the composite soybean urease solution are added to the soybean urease solution in batches and stirred evenly. The order of addition of the other components is as follows: 1) Fully dissolve xanthan gum to form a stable thickening matrix, which prolongs the residence time of the cementitious solution on the surface of sand particles, thereby promoting the precipitation and solidification of calcium carbonate; 2) Add polyacrylamide and polylysine to ensure uniform fusion between polymers and play a synergistic thickening and bonding role, increasing the cohesion and friction of sand; 3) Add magnesium chloride and sodium montmorillonite to allow inorganic salts and clay to be fully dispersed in the polymer system, thereby increasing the precipitation amount and efficiency of calcium carbonate by providing more nucleation sites, promoting the formation of hard and stable crystals, and improving the strength and durability of the solidified layer; 4) Add skim milk powder to provide additional bonding aids, enhance the microbial activity during the calcium carbonate deposition process, thereby promoting the precipitation and solidification of calcium carbonate; 5) Add glass fiber and silica fume to enhance the cementing effect and the compressive strength and shear strength of the reinforced layer, while preventing the formation of cracks in stress concentration areas. Step two: The compound soybean urease solution and salt solution described in step one are pumped to different water trucks, which then travel to a work platform near the site. The solutions are then fed into the mixing equipment of the integrated self-loading mixer truck in equal volumes, and the mixing equipment is activated to thoroughly stir and form a cementitious liquid. The concentrations of each component in the cementitious liquid are as follows: soybean urease solution 20g / L-100g / L, salt solution 30g / L-80g / L, 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. Step 3: Immediately transfer the prepared cementing solution into the liquid addition tank for later use; Step 4: Use the integrated self-loading mixer truck to take in-situ sand batch by batch on-site and weigh it. Transmit the weighing data to the control center. Then, the integrated self-loading mixer truck adds in-situ sand to the mixing tank batch by batch, with an interval of 2-5 minutes between each batch. At the same time as each batch of in-situ sand is added, the control center determines the solid-liquid ratio according to formula (1) and the parameters input in the control panel, calculates the volume of cementing liquid to be added under the current sand addition conditions, and controls the liquid addition pump to pump the corresponding weight of cementing liquid into the mixing tank. When the in-situ sand taken in batches reaches the set volume, stop taking sand and keep the mixing tank in a stirring state to form a uniformly mixed slurry, while avoiding the slurry from solidifying. In the formula: V SICP To determine the volume of cementing solution required per unit volume of sand at the target strength and cementing solution concentration; V S q represents the amount of sand used per unit volume of fill. u The target unconfined compressive strength under design requirements; q u0 The reference strength is determined under standard operating conditions and obtained through indoor testing under standard conditions, namely, the standard urease solution concentration, the calcium ion solution concentration, and the standard reaction time; C standard C is the product of the standard urease solution concentration and the calcium chloride solution concentration under standard operating conditions. urease C represents the concentration of soybean urease solution used in the actual field. Ca The concentration of calcium chloride solution used in the actual field is denoted as α; α and λ are empirical coefficients calibrated in the laboratory experiments, obtained by fitting multiple sets of laboratory experiment results under varying concentration and time conditions; Δt is the reaction time. Step 5: Operate the integrated self-loading mixer truck to deliver mortar to the area around the pile toe pit. Operate the robotic arm to adjust the tamping head to the appropriate position and direction. Set the tamping frequency and energy on the control panel interface. Compact the mortar in layers until the surface of the pit is filled. Wait for the backfilled mortar to solidify and form a hard shell layer to resist wind erosion.

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