Method and device for backfilling and repairing ground pile toe wind erosion sandpit

Abstract

The invention provides a method for backfilling and repairing a wind erosion sand pit around a ground pile toe, which is characterized in that an integrated self-feeding mixer truck combining mixing equipment and a mechanical arm tamping function is adopted, and a soybean urease solution doped with an additive and a salt solution are efficiently and uniformly mixed in a desert site through the device to prepare a cementing fluid. The integrated self-feeding mixer truck can automatically take site in-situ sand in batches to be mixed with cementing liquid to form mortar, the mortar is automatically conveyed to a sand pit around a pile toe through the sand conveying pipe, the mechanical arm, the tamping machine head and other components, the mortar is compacted and flattened to be flush with the surface of a surrounding desert, and then a windproof reinforcing and repairing layer is formed in the sand pit. The backfilled windproof reinforcing and repairing layer can resist shaking of the pile foundation and weaken the wind field of the pile, so that the long-term stability of the pile foundation is improved. In addition, a parameterization control method is introduced, and accurate control over the dosage of the SICP solution under different working conditions on site can be achieved. Compared with a traditional mechanical backfilling and chemical consolidation method, the method has the advantages that the construction effect and efficiency are improved, meanwhile, the method is more environmentally friendly, 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 and a device for backfilling and repairing wind-eroded sand pits around the toes of desert photovoltaic panel piles. Background Art

[0002] As the global demand for clean energy grows, photovoltaic power generation has become an important energy option due to its pollution-free and renewable characteristics. Desert areas have vast land and abundant sunshine, making them ideal places to build photovoltaic power stations. Desert photovoltaic power stations not only effectively utilize land resources and reduce the occupation of agricultural land, but also significantly increase the supply of clean energy. However, in the desert environment, due to the frequent occurrence of extreme windy and sandy weather, the pile foundation of photovoltaic power stations often faces the challenge of wind erosion, which poses a serious threat to the stability of the pile foundation.

[0003] Under high wind speed conditions, the pile foundation of the desert photovoltaic power station will form local turbulence around the pile toe due to the blocking effect of the photovoltaic panel pile foundation, causing the sand in the area to be continuously eroded and transported, gradually forming pits. The existence of these pits will not only aggravate the wind erosion damage in the area around the pile foundation, but also reduce the wind and sand fixation effect, further affecting the long-term stability and safety of the pile foundation. Traditional treatment methods mainly include mechanical backfilling and chemical consolidation, but the sand backfilled by mechanical means is easily eroded again under the action of wind and sand, and chemical consolidation has potential harm to the environment and does not meet the requirements of sustainable development.

[0004] To this end, the present invention proposes an innovative method combining microbial solidification and stirring backfill technology, and backfills and reinforces the wind-eroded sand pit around the pile toe by utilizing soybean urease-induced calcium carbonate precipitation (SICP) technology. This method can not only effectively improve the cohesion and compressive strength of sand and reduce the damage of wind erosion to the pile foundation, but also achieve accurate control of the amount of SICP solution by introducing a parametric control formula, and determine the ratio and usage of the cementing liquid under different construction conditions. Accurate SICP solution control makes the construction process more efficient, reduces material waste, and can flexibly adjust the ratio according to the actual needs of the site, so as to adapt to the changing environmental conditions. Through these technical advantages, this method can form a stable and efficient windproof solidification layer, redistribute the wind field around the pile foundation, significantly reduce the shaking and displacement of the pile foundation, and greatly improve the long-term stability of the pile foundation. At the same time, this method avoids the environmental pollution problems of traditional mechanical backfill and chemical consolidation methods, provides a green, environmentally friendly and lasting solution, and comprehensively improves the operational safety and reliability of desert photovoltaic power stations in extreme environments, which meets the requirements of green and sustainable development. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention aims to solve the following technical problems: to provide a method and implementation steps for backfilling and repairing wind-eroded sand pits around the toes of desert photovoltaic panel piles that can be constructed conveniently and efficiently, so as to enhance the long-term stability of the pile foundation and improve the operating safety and reliability of the desert photovoltaic power station in extreme environments. The technical solutions adopted by the present invention are as follows:

[0006] A method for backfilling and repairing wind-eroded sand pits at the toes of piles, the repair technology combining a microbial sand fixation method (SICP) using soybean urease-induced calcium carbonate precipitation and a stirring backfilling technology:

[0007] The binder liquid of the microbial sand fixation method is formed by mixing 10 components: 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 concentrations of the components of the binder liquid are: 20g / L-100g / L soybean urease solution; 30g / L-80g / L salt solution; 1g / L xanthan gum, 3g / L skimmed milk powder, 1g / L magnesium chloride, 1g / L polylysine, 7# sodium montmorillonite, 8# polyacrylamide, 9# glass fiber, and 10# silica fume. Acid 0.5g / L, sodium montmorillonite 2g / L, polyacrylamide 0.5g / L, glass fiber 2g / L, silica fume 3g / L; the soybean urease solution is directly extracted from soybeans, the soybeans are completely dried and ground into soybean powder, and then 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; the salt solution is formed by mixing calcium chloride and urea with equal concentrations;

[0008] The mixing backfilling technology is realized by an integrated self-loading mixer truck with mixing, mixing and sand conveying and tamping functions. The integrated self-loading mixer truck includes a mixing device, a liquid adding tank, a pumping system, a hydraulic bucket, a mixing tank, a sand conveying pipe, a mechanical arm and a tamping head, and a central control system. The functions of automatically preparing the cementing liquid, preparing the mortar, and conveying and tamping the sand are realized by inputting the required working condition parameters into the central control system.

[0009] The mixing and backfilling process of the integrated self-loading mixer truck is as follows:

[0010] (S1) adding xanthan gum, skimmed milk powder, magnesium chloride, polylysine, sodium montmorillonite, polyacrylamide, glass fiber, and silica fume to the soybean urease solution, and stirring and mixing the mixture to form a composite soybean urease solution;

[0011] (S2) conveying the mixed solution and the salt solution formed in step (S1) into a mixing device and stirring them sufficiently to form a binder, and then conveying the mixed binder to a liquid adding tank for standby use;

[0012] (S3) according to the on-site construction design requirements, the volume of the binder required for the unit volume of sand is determined according to the following formula, and then the total amount of the binder is determined based on the amount of sand used, and input into the central control system;

[0013]

[0014] Where: V SICP V is the volume of cementing fluid required for a unit volume of sand under the target strength and cementing fluid concentration set on site; S is the amount of sand used for filling per unit volume; q u is the target unconfined compressive strength under design requirements; q u0 It is the benchmark strength measured under standard working conditions, which can be obtained through indoor tests under standard conditions (standard urease solution concentration and calcium ion solution concentration, standard reaction time); C standard C is the product of the concentration of standard urease solution and the concentration of calcium chloride solution under standard working conditions; urease is the concentration of soybean urease solution used in the actual field; C Ca is the concentration of calcium chloride solution used in the actual field; α and λ are empirical coefficients for indoor experimental calibration, which can be obtained by fitting multiple sets of indoor test results under conditions of changing concentration, time, etc.; Δt is the reaction time;

[0015] (S4) According to the set parameters, the integrated self-loading mixer truck automatically transports the binder liquid into the mixing tank and mixes it with the in-situ sand to form mortar;

[0016] (S5) The wind-eroded sand pit around the pile toe is backfilled with mortar and flattened by the sand conveying pipe, mechanical arm and tamping head of the integrated self-loading mixer truck, thereby forming a windproof reinforcement repair layer.

[0017] Preferably, the other components of the composite soybean urease solution need to be added in batches into the 1# soybean urease solution and stirred evenly, and the order of adding the other components is: 1) fully dissolving 3# xanthan gum to form a stable thickening matrix to prolong the residence time of the binder on the surface of the sand to promote the precipitation and solidification of calcium carbonate; 2) adding 8# polyacrylamide and 6# polylysine to ensure uniform fusion between polymers and play a synergistic thickening and bonding role to increase the cohesion and friction of the sand; 3) adding 5# magnesium chloride and 7# sodium montmorillonite Stone allows inorganic salts and clay to be fully dispersed in the polymer system, increases the amount and efficiency of calcium carbonate precipitation by providing more nucleation sites, promotes the formation of hard and stable crystals, and improves the strength and durability of the solidified layer; 4) Add 4# skimmed milk powder to provide additional bonding aids, enhance the microbial activity during the calcium carbonate deposition process, and thus promote the precipitation and solidification of calcium carbonate; 5) Add 9# glass fiber and 10# silica fume to enhance the bonding effect and the compressive and shear strength of the reinforcement layer, while preventing cracks from forming in stress concentration areas.

[0018] Preferably, the mixing equipment in the integrated self-loading mixer truck includes an air flow conveying system, a liquid mixing unit, a liquid adding and conveying system and an atomizing spray device.

[0019] Preferably, the side of the bottom plate of the rammer head in the integrated self-loading mixer truck that contacts the pile toe is arc-shaped, and the arc is consistent with the arc of the cylindrical pile toe on site, so that the rammer head can work without dead angles, thereby improving the compaction effect and efficiency.

[0020] Preferably, the liquid mixing unit includes a puree container and a gas outlet, a control valve and a static mixer located at the top of the puree container; one end of the water inlet pipe is connected to the control valve, and the other end is connected to the static mixer. The static mixer is used to achieve preliminary uniform mixing of the two solutions, and the mixed solution enters the puree container through the water inlet pipe for further uniform mixing; the other end of the static mixer is connected to a fluid convergence device through a pipe for efficient guidance and input of liquid.

[0021] Preferably, the air flow conveying system includes an air vent installed on the side wall of the raw pulp container, a regulating valve and an air flow injection device. The air flow injection device is composed of an air compressor, a gas distribution system and a pipeline. When the two air compressors are started at the same time and the regulating valve is opened, bubbles will be generated in the liquid in the raw pulp container. The rising bubbles drive the liquid to flow, thereby achieving complete mixing of the liquid.

[0022] Preferably, the liquid adding and conveying system includes a control valve, a conveying pipeline, a liquid adding pump and a spray device with an atomizing function. The liquid is conveyed to the spray device through the liquid adding pump system, and a flow regulator is installed in front of the spray device to accurately control the injection amount of the liquid.

[0023] A working method of an integrated self-loading mixer truck comprises the following steps:

[0024] Step 1, prepare various components of the composite soybean urease solution of claim 1: 20g / L-100g / L soybean urease solution; 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, 2g / L glass fiber, 3g / L silica fume; then add the corresponding components according to the addition sequence steps of claim 2 and stir them thoroughly; prepare a salt solution with a concentration of 30g / L-80g / L by adding equal concentrations of calcium chloride and urea;

[0025] Step 2, pumping the composite soybean urease solution and salt solution described in step 1 into different water trucks, driving the water trucks to a work platform near the site, and then inputting equal volumes into the mixing device of the integrated self-loading mixer truck, and starting the mixing device to fully stir to form a cementing liquid;

[0026] Step 3, the prepared cementing liquid is then transported into the liquid adding tank for standby use;

[0027] Step 4: using the integrated self-loading mixer truck to take the in-situ sand batch by batch and weigh it, and transmit the weighing data to the control center, and then the integrated self-loading mixer truck adds the in-situ sand to the mixing tank batch by batch, and the time interval between each batch is 2-5 minutes; when 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 the binder to be added under the current sand addition conditions, and controls the liquid adding pump to pump the corresponding weight of the binder into the mixing tank; when the in-situ sand taken in batches reaches the set volume, stop taking the sand, let the mixing tank be in a stirring state, form a mixed mortar, and prevent the mortar from solidifying;

[0028] Step five: operate the integrated self-loading mixer truck to transport mortar to the area around the pile toe pit, operate the robotic arm to adjust the rammer head to the appropriate position and direction, set the ramming frequency and energy on the control panel interface, and compact in layers until the pit surface is filled. Use a scraper to wipe off the excess part to make the pit surface smooth, and wait for the backfill mortar to solidify to form a hard shell layer to resist wind erosion damage.

[0029] The present invention has the following beneficial effects:

[0030] 1. The present invention introduces quantitative parameter control of the mortar backfill process, and accurately determines the amount of cementing liquid per unit volume of sand under the conditions of setting the concentration of each component solution of the cementing liquid and the expected reaction time. Construction personnel can flexibly adjust the amount of cementing liquid according to site requirements: when higher strength is required, the concentration of urease or calcium chloride can be increased accordingly, or the reaction time can be extended, thereby reducing the amount of solution at a higher or equal target strength; when the site needs to shorten the reaction time due to construction period requirements, the concentration of each component and the amount of cementing liquid can also be adjusted; when environmental conditions (such as air temperature, humidity, wind speed) change, the target requirements can also be met by correcting parameters. Unlike traditional simple control based on compaction, the control method of the present invention makes full use of 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 solidification repair layer.

[0031] 2. The present invention innovatively proposes an integrated self-loading mixer truck that integrates mixing, stirring, and sand transport and tamping functions, so that the soybean urease solution and salt solution mixed with additives can be efficiently and evenly mixed in the same device, significantly improving the solidification effect of the binder and sand reaction. Relying on the onboard automation system and central control system of the integrated self-loading mixer truck, the proportioning, stirring and conveying processes are controlled in real time to reduce human operation errors; at the same time, the coordinated work of the self-loading function and the mechanical arm tamping module greatly simplifies the construction organization and material transfer process, avoids the influence of the external environment on the mixing quality, and further ensures the uniformity and overall strength of the backfill layer, thereby achieving efficient repair of the sand pit and strengthening the long-term stability of the pile foundation.

[0032] 3. The binder used in the present invention is composed of soybean urease solution, salt solution and various additives, and is mixed and stirred in a certain order. The addition order of the present invention can effectively avoid cross-interference between the components, fully ensure the dissolution and mixing of the components, achieve good bonding performance and overall strength, and is conducive to the formation of 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 sandy foundation, prevents the pile foundation from sliding and tilting under the action of lateral force, and improves the overall stability of the pile foundation.

[0033] 4. During the reinforcement process of the sandy foundation around the pile foundation, the present invention forms a uniform windproof solidified layer, which effectively reduces the wind speed and turbulence effect around the pile foundation by changing the surface roughness and wind field structure, reduces the direct impact force of wind load on the pile foundation, significantly reduces the shaking and displacement of the pile foundation in extreme wind and sand environment, and enhances the long-term stability and durability of the pile foundation.

[0034] 5. The soybean urease solution of the present invention can be directly extracted from soybeans, and has lower use cost than commercial soybean urease solutions. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a flow chart of the implementation steps of the present invention.

[0036] Figure 2 This is a front view of the integrated self-loading mixer truck of the present invention.

[0037] Figure 3 This is a top view of the integrated self-loading mixer truck of the present invention.

[0038] Figure 4 It is a left side view of the integrated self-loading mixer truck of the present invention.

[0039] Figure 5 This is a front view of the mixing equipment in the integrated self-loading mixer truck of the present invention.

[0040] Figure 6 It is a top view of the mixing device in the integrated self-loading mixer truck of the present invention.

[0041] Figure 7 It is a left side view of the mixing device in the integrated self-loading mixer truck of the present invention.

[0042] Figure 8 It is a schematic diagram of the modification of the tamping head in the integrated self-loading mixer truck of the present invention.

[0043] Fig. 9 These are the compressive strength test results of the solidified sand on the surface of the windproof reinforcement repair layer of Example 1 and Comparative Examples 1 to 3 of the present invention.

[0044] Fig.10 These are the compressive strength test results of the solidified sand on the surface of the windproof reinforcement and repair layer of Examples 1 to 4 of the present invention.

[0045] Fig.11 These are the shear strength test results of the solidified sand on the surface of the windproof reinforcement and repair layer of Examples 1 to 4 of the present invention.

[0046] Fig.12 These are the test results of installing an ultrasonic anemometer at a height of 0.5 m on the pile foundations of Examples 1 to 4 of the present invention.

[0047] Figure 2-4 In: 1. Hydraulic bucket, 2. Mixing tank, 3. Liquid adding tank, 4. Mixing equipment, 5. Sand transport pipe, 6. Mechanical arm, 7. Ramming machine head.

[0048] Figure 5-7In: 8. Raw pulp container, 9. Gas outlet, 10. Liquid inflow control valve of raw pulp container, 11. Section A water pipe, 12. Static mixer, 13. Section B water pipe, 14. Fluid convergence device, 15. Gas regulating valve, 16. Air inlet, 17. Gas pipeline, 18. Air compressor and gas distribution system, 19. Liquid outflow control valve of raw pulp container, 20. Section C water pipe, 21. Liquid adding pump, 22. Flow regulator, 23. Spray device.

[0049] Figure 8 Middle: 24, rammer head bottom plate, 25, pile toe. DETAILED DESCRIPTION

[0050] The present invention is 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 used to limit the present invention.

[0051] Example 1

[0052] In this embodiment, the parameters of formula (1) are first calibrated through indoor tests, and the standard conditions are set as follows: the concentration of soybean urease solution is 20g / L; the concentration of urea is 0.25M; the concentration of calcium chloride is 0.25M; and the standard reaction time (Δt) is 72h. Under the above standard conditions, the benchmark unconfined compressive strength (q u0 ) is 0.6MPa. Through the fitting analysis of multiple sets of indoor test data, two empirical parameters in formula (1) are determined: α≈1.0, λ≈0.02.

[0053] Under the aforementioned standard conditions, by setting the target unconfined compressive strength value (to simulate the working conditions of different requirements on site), the formula proposed in the present invention can be used for calculation:

[0054]

[0055] Where: V SICP V is the volume of cementing fluid required for a unit volume of sand under the target strength and cementing fluid concentration set on site; S is the amount of sand used for filling per unit volume; q u is the target unconfined compressive strength under design requirements; q u0 It is the benchmark strength measured under standard working conditions, which can be obtained through indoor tests under standard conditions (standard urease solution concentration and calcium ion solution concentration, standard reaction time); C standard C is the product of the concentration of standard urease solution and the concentration of calcium chloride solution under standard working conditions; urease is the concentration of soybean urease solution used in the actual field; C Cais the concentration of calcium chloride solution actually used on site; α and λ are empirical coefficients for indoor experimental calibration, which can be obtained by fitting multiple sets of indoor test results under conditions of changing concentration, time, etc.; Δt is the reaction time.

[0056] In this embodiment, the target intensity q u =0.8Mpa, the concentration of soybean urease solution is 30g / L, the concentrations of urea and calcium chloride are both 0.4M, the reaction time is 72h, and the formula is used to calculate the reaction time per 1m 3 The aeolian sand required for filling is about 0.1317m 3 The above process can be input 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 complete the calculation of the process. Figure 2-Figure 4 As shown, the hydraulic bucket 1 of the integrated self-loading mixer truck is used to take the in-situ sand batch by batch and weigh it on site, and the weighing data is transmitted to the control center. The integrated self-loading mixer truck adds the in-situ sand to the mixing tank 2 batch by batch, and the interval between each batch is 2-5 minutes. When each batch of in-situ sand is added, the control center determines the solid-liquid ratio according to the SICP solution dosage control formula determined by the present invention and the input parameters in the control panel, calculates the weight of the binder to be added, and controls the liquid adding pump to pump the corresponding weight of the binder from the liquid adding tank 3 into the mixing tank 2. When the in-situ sand taken reaches the set volume, the sand is stopped, and the mixing tank 2 is kept in a stirring state to form a uniformly mixed mortar, while preventing the mortar from solidifying.

[0057] The formation process of the cementing fluid is as follows:

[0058] The soybean urease solution and salt solution mixed with additives prepared in the laboratory were transported to the desert site by a water truck. The aforementioned composite soybean urease solution and salt solution were injected into the fluid convergence device of the mixing device 4 in the integrated self-loading mixer truck through the water conveyor belt of the water truck in equal volumes. Figure 5-Figure 7 As shown, the mixing device is composed of a liquid mixing unit, an air flow conveying system, a liquid adding conveying system and an atomizing spray device. Specifically, the substructures of the liquid mixing unit include: a raw pulp container 8, a gas outlet 9, a raw pulp container liquid inflow control valve 10, a section A water pipe 11, a static mixer 12, a section B water pipe 13, and a fluid convergence device 14; the substructures of the air flow conveying system include: a gas regulating valve 15, an air inlet 16, a gas pipeline 17, an air compressor and a gas distribution system 18; the substructures of the liquid adding conveying system and the atomizing spray device include: a raw pulp container liquid outflow control valve 19, a section C water pipe 20, a liquid adding pump 21, a flow regulator 22, and a spray device 23.

[0059] The use process of the mixing equipment is as follows: First, the two liquids are injected into the static mixer 12 through the fluid convergence device 14 to achieve preliminary uniform mixing; then, the mixed liquid flows into the stock container 1 through the A section water pipe 11; then, the air compressor and the gas distribution system 18 are started, and the gas enters the stock container 8 through the gas pipeline 17, the air inlet 16, and the regulating valve 15. The bubbles drive the liquid to circulate during the rising process in the stock container 8, so that the liquid is fully mixed and finally prepared into a binder liquid, in which the gas flows out through the gas outlet 9. Open the liquid outflow control valve 19 of the stock container, and transport the binder liquid to the spray device 23 through the C section water pipe 20 and the liquid adding pump 21. The flow rate is controlled by the flow regulator 22 and injected into the water tank and liquid adding tank of the integrated self-loading mixer truck.

[0060] Subsequently, the sediment was divided into three batches and added into the cementing liquid for stirring. The solid-liquid ratio of the first to third batches of sediment and the corresponding cementing liquid was calculated by the proposed formula.

[0061] Then, operate the integrated self-loading mixer truck and deliver mortar to the area around the pile toe pit through the sand delivery pipe 5, operate the mechanical arm 6 to adjust the tamping head 7 to the appropriate position and direction, set the tamping frequency and energy in the control panel, and compact in layers until the pit surface is filled, and use a scraper to wipe off the excess part to make the pit surface smooth, waiting for the backfill mortar to solidify to form a hard shell layer to resist wind erosion damage. Figure 8 As shown, the side where the bottom plate of the rammer head contacts the pile toe is arc-shaped, and the arc is consistent with the arc of the cylindrical pile toe on site, which allows the rammer head to work without dead angles and improves the compaction effect and efficiency.

[0062] Comparative Example 1

[0063] In this comparative example, the target intensity q u Take 0.9Mpa, soybean urease solution concentration of 35g / L, urea and calcium chloride concentration of 0.5M, reaction time is still 72h, the values ​​of various parameters under standard conditions remain unchanged, and the calculated value per 1m 3 Filling sand requires about 0.1011m 3 The SICP binder is thus determined by using this ratio to determine the amount of binder in this comparative example. The rest is consistent with Example 1.

[0064] Comparative Example 2

[0065] In this comparative example, the target intensity q u Take 1.0Mpa, soybean urease solution concentration of 40g / L, urea and calcium chloride concentration of 0.6M, reaction time is still 72h, the values ​​of various parameters under standard conditions remain unchanged, and the calculated value per 1m 3 Filling sand requires about 0.0814m 3The SICP binder is thus determined by using this ratio to determine the amount of binder in this comparative example. The rest is consistent with Example 1.

[0066] Comparative Example 3

[0067] In this comparative example, the target intensity q u Take 1.1Mpa, soybean urease solution concentration of 45g / L, urea and calcium chloride concentration of 0.7M, reaction time of 24 hours, the values ​​of each parameter under standard conditions remain unchanged, and the calculated value per 1m 3 Filling sand requires about 0.1803m 3 The SICP binder is thus determined by using this ratio to determine the amount of binder in this comparative example. The rest is consistent with Example 1.

[0068] The performance of Example 1 and Comparative Examples 1 to 3 are evaluated below.

[0069] Fig. 9 The results of compressive strength test of surface solidified sand after backfilling mortar around the pile toe to form a windproof reinforcement repair layer in Example 1 and Comparative Examples 1 to 3. The sample preparation method is: fill the surface solidified sand of the example and comparative example into a cylindrical mold, dry it after curing for 72 hours, and obtain a cylindrical sample with a diameter of 50mm and a height of 100mm. The unconfined compressive strength test was carried out using a universal testing machine, and the compressive strength of each sample was obtained as shown in the figure. Fig. 9 As shown, the test data are detailed in Table 1. The experimental results show that: in the tests of Example 1 and Comparative Examples 1 to 3, according to the formula (1) proposed in the present invention, the target unconfined compressive strength, the concentrations of soybean urease solution, urea and calcium chloride solution, and the reaction time were independently set, and the corresponding ratio of SICP binder to sand was obtained based on these settings. The final measured unconfined compressive strength of the cured sample is in good agreement with the preset target value. It is explained that the ratio conditions determined by the 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 adopt a formula, the formula control method proposed in this patent makes the SICP reinforcement process more predictable and more accurate, and the reaction time can be flexibly adjusted according to the construction period. It also shows high reliability and rationality in the three groups of comparative tests, proving the applicability and practical value of the formula.

[0070] Table 1 (Unit: MPa)

[0071] Specimen type Example 1 Comparative Example 1 Comparative Example 2 Comparative Example 3 Compressive strength 0.77 0.86 1.03 1.15

[0072] Example 2

[0073] In this comparative example, the mixing equipment of the integrated self-loading mixer of the present invention is not used when preparing the binder liquid. Instead, the soybean urease solution and salt solution mixed with additives are injected into an iron bucket in a common manner, and stirred thoroughly to mix them as much as possible, and then injected into the liquid adding tank. The remaining processing steps are consistent with Example 1.

[0074] Example 3

[0075] In this comparative example, when the integrated self-loading mixer truck takes sand and mixes it with the cementing liquid to form mortar, the batch sand taking and mixing method proposed in the present invention is not adopted, but all the sand of the target volume is taken at one time and poured into the mixing tank, and the cementing liquid is pumped and mixed and stirred with the sand according to the SICP cementing liquid dosage control formula proposed in the present invention. The rest is the same as Example 1.

[0076] Example 4

[0077] In this comparative example, when backfilling and compacting the mortar in layers, the mechanical arm and tamping head of the integrated self-loading mixer truck are not used for compaction, but an ordinary handheld small tamping machine is used, and the rest is consistent with Example 1.

[0078] The performance of Examples 1 to 4 is evaluated below.

[0079] Fig.10 The compressive strength test results of surface solidified sand after backfilling mortar around the pile toes to form a windproof reinforcement repair layer in Examples 1 to 4 are shown in Table 2 for details of the test data. The experimental results show that the compressive strength of the sample made from the surface solidified sand treated with the method of Example 1 is higher than that of Example 2, indicating that the mixing equipment of the integrated self-loading mixer truck in the present invention can prepare a large volume of uniform binder liquid, and can fully mix the binder liquid through the liquid mixing unit and the airflow conveying system, thereby playing an important role in improving the final compressive effect of the solidified sand, and solving the problem of uniform mixing of large volumes of binder liquid in a simpler and lower-cost way; the compressive strength of the sample made from the surface solidified sand treated with the method of Example 1 is higher than that of Example 3, indicating that the "batch mixing" proposed in the present invention Compared with the "one-time sand taking and mixing" method, the "sand taking and mixing" method can avoid the problems of uneven mixing and premature solidification caused by one-time sand taking when the amount of binder liquid is the same, so that the calcium carbonate precipitation is more uniform and the particles are finer, thereby obtaining higher compressive strength and overall stability at the same amount, and achieving better consolidation effect; the compressive strength of the sample made of the surface solidified sand treated by the method of Example 1 is higher than that of Example 4, indicating that the use of the mechanical arm and rammer head of the integrated self-loading mixer truck in the present invention for compaction not only increases the degree of automation, but also can improve the final compressive effect of the solidified sand.

[0080] Table 2 (Unit: MPa)

[0081] Specimen type Example 1 Example 2 Example 3 Example 4 Compressive strength 0.77 0.54 0.62 0.69

[0082] Fig.11 The results of shear strength test of surface solidified sand after backfilling the sand pit around the pile toe to form a windproof reinforcement repair layer in Examples 1 to 4 are shown in the figure. The sample preparation method is as follows: fill the surface solidified sand of the examples and comparative examples into a square mold, dry it after curing for 72 hours, and obtain a cubic sample with a volume of 50mm*50mm*50mm. The shear strength test was carried out using a direct shear apparatus, and the shear strength of each sample was obtained as shown in the figure. Fig.11 As shown, the test data are shown in Table 3. The experimental results show that the shear strength of the sample made of the surface solidified sand treated by the method of Example 1 is higher than that of Example 2, indicating that the mixing device invented in the present invention can prepare a large volume of uniform cementing liquid, and can fully mix the cementing liquid through the liquid mixing unit and the air flow conveying system, thereby playing an important role in improving the final shear resistance of the solidified sand, and solving the problem of uniform mixing of large volumes of cementing liquid in a simpler and lower-cost way; the shear strength of the sample made of the surface solidified sand treated by the method of Example 1 is higher than that of Example 3, indicating that the "batch sand mixing" method proposed by the present invention can achieve better cementing effect under the condition of the same amount of cementing liquid compared with the "one-time sand mixing" method; the shear strength of the sample made of the surface solidified sand treated by the method of Example 1 is higher than that of Example 4, indicating that the use of the mechanical arm and tamping head of the integrated self-loading mixer truck in the present invention for compaction not only increases the degree of automation, but also improves the final shear resistance of the solidified sand.

[0083] Table 3 (Unit: MPa)

[0084] Specimen type Example 1 Example 2 Example 3 Example 4 Shear strength 0.46 0.32 0.38 0.41

[0085] Fig.12 The wind speed results obtained by the ultrasonic anemometer are as follows: Fig.12 The test data are shown in Table 4. 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 foundation not treated by the method, and the wind speed result of Example 1 is the smallest, indicating that the method proposed by the present invention can significantly reduce the wind field of the pile foundation and enhance the long-term stability of the pile foundation.

[0086] Table 4 (Unit: m / s)

[0087] Specimen 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 erosion sand pits at the toes of piles, characterized in that: Combined use of microbial sand fixation method and mixing backfill technology: The microbial sand fixation method comprises a cementing fluid; The mixing and backfilling technology is realized by an integrated self-loading mixer truck, which includes a mixing device, a liquid adding tank, a pumping system, a hydraulic bucket, a mixing tank, a sand conveying pipe, a mechanical 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) adding xanthan gum, skimmed milk powder, magnesium chloride, polylysine, sodium montmorillonite, polyacrylamide, glass fiber, and silica fume to the soybean urease solution, and stirring and mixing the mixture to form a composite soybean urease solution; (S2) conveying the mixed solution and the salt solution formed in step (S1) into a mixing device and stirring them sufficiently to form a binder, and then conveying the mixed binder to a liquid adding tank for standby use; (S3) determining the volume of the binder required per unit volume of sand according to formula (1), and then determining the total amount of the binder based on the amount of sand used, and inputting it into the central control system; Where: V SICP V is the volume of cementing fluid required for a unit volume of sand under the target strength and cementing fluid concentration set on site; S is the amount of sand used for filling per unit volume; q u is the target unconfined compressive strength under design requirements; q u0 It is the benchmark strength measured under standard working conditions, which can be obtained through indoor tests under standard conditions (standard urease solution concentration and calcium ion solution concentration, standard reaction time); C standard C is the product of the concentration of standard urease solution and the concentration of calcium chloride solution under standard working conditions; urease is the concentration of soybean urease solution used in the actual field; C Ca is the concentration of calcium chloride solution actually used on site; α and λ are empirical coefficients for indoor experimental calibration, which can be obtained by fitting multiple sets of indoor test results under conditions of changing concentration, time, etc.; Δt is the reaction time.

2. The method according to claim 1, characterized in that The concentrations of the components of the binder are: soybean urease solution 20g / L-100g / L; salt solution 30g / L-80g / L; xanthan gum 1g / L, skimmed milk powder 3g / L, magnesium chloride 1g / L, polylysine 0.5g / L, sodium montmorillonite 2g / L, polyacrylamide 0.5g / L, glass fiber 2g / L, silica fume 3g / L; the salt solution is formed by mixing equal concentrations of calcium chloride and urea.

3. The method according to claim 1, characterized in that The mixing and backfilling process also includes: (S4) According to the set parameters, the integrated self-loading mixer truck automatically transports the binder liquid into the mixing tank and mixes it with the in-situ sand to form mortar; (S5) The wind-eroded sand pit around the pile toe is backfilled with mortar and flattened by the sand conveying pipe, mechanical arm and tamping head of the integrated self-loading mixer truck, thereby forming a windproof reinforcement repair layer.

4. The method according to claim 1, characterized in that The other components of the composite soybean urease solution are added in batches into the 1# soybean urease solution and stirred evenly. The order of adding the other components is as follows: 1) fully dissolving 3# xanthan gum to form a stable thickening matrix to prolong the residence time of the binder on the surface of the sand particles to promote the precipitation and solidification of calcium carbonate; 2) adding 8# polyacrylamide and 6# polylysine to ensure uniform fusion between polymers and play a synergistic thickening and bonding role to increase the cohesion and friction of the sand; 3) adding 5# magnesium chloride and 7# sodium montmorillonite to allow the inorganic salt and clay to be fully dispersed in the polymer system, and by providing more nucleation sites to increase the precipitation amount and efficiency of calcium carbonate, promote the formation of hard and stable crystals, and improve the strength and durability of the solidified layer; 4) adding 4# skimmed milk powder to provide additional bonding aids to enhance the microbial activity during the calcium carbonate deposition process to promote the precipitation and solidification of calcium carbonate; 5) Add 9# glass fiber and 10# silica fume to enhance the bonding effect and the compressive and shear strengths of the reinforcement layer, while preventing cracks from forming in stress concentration areas.

5. The method according to claim 1, characterized in that The mixing equipment of the integrated self-loading mixer truck comprises an air flow conveying system, a liquid mixing unit, a liquid adding conveying system and an atomizing spraying device.

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

7. The method according to claim 5, characterized in that The liquid mixing unit includes a raw pulp container and a gas outlet, a control valve and a static mixer located on the top of the raw pulp container; one end of the water inlet pipe is connected to the control valve, and the other end is connected to the static mixer. The static mixer is used to achieve preliminary uniform mixing of the two solutions. The mixed solution enters the raw pulp container through the water inlet pipe for further uniform mixing; the other end of the static mixer is connected to a fluid convergence device through a pipe for efficiently guiding and inputting liquid.

8. The method according to claim 5, characterized in that The air flow conveying system includes an air vent installed on the side wall of the raw pulp container, a regulating valve and an air flow injection device. The air flow injection device is composed of an air compressor, a gas distribution system and a pipeline. When the two air compressors are started at the same time and the regulating valve is opened, bubbles will be generated in the liquid in the raw pulp container. The rising bubbles drive the liquid to flow, thereby achieving complete mixing of the liquid.

9. The method according to claim 5, characterized in that The liquid adding and conveying system comprises a control valve, a conveying pipeline, a liquid adding pump and a spray device with an atomizing function. The liquid is conveyed to the spray device through the liquid adding pump system, and a flow regulator is installed in front of the spray device to accurately control the injection amount of the liquid.

10. A working method of an integrated self-loading mixer truck, characterized in that: The following steps are involved: Step 1, preparing the composite soybean urease solution of claim 1, wherein the concentration of each component is the concentration of each component in claim 2; then adding the corresponding components according to the addition sequence steps of claim 4 and stirring them sufficiently; preparing a salt solution with a concentration of 30 g / L-80 g / L by adding equal concentrations of calcium chloride and urea; Step 2, pumping the composite soybean urease solution and salt solution described in step 1 into different water trucks, driving the water trucks to a work platform near the site, and then inputting equal volumes into the mixing device of the integrated self-loading mixer truck, and starting the mixing device to fully stir to form a cementing liquid; Step 3, the prepared cementing liquid is then transported into the liquid adding tank for standby use; Step 4: using the integrated self-loading mixer truck to take the in-situ sand batch by batch and weigh it, and transmitting the weighing data to the control center, and then the integrated self-loading mixer truck adds the in-situ sand to the mixing tank batch by batch, and the time interval between each batch is 2-5 minutes; when each batch of in-situ sand is added, the control center determines the solid-liquid ratio according to formula (1) in claim 1 and the parameters input in the control panel, calculates the volume of the binder to be added under the current sand addition conditions, and controls the liquid adding pump to pump the corresponding weight of the binder into the mixing tank; when the in-situ sand taken in batches reaches the set volume, stop taking the sand, let the mixing tank be in a stirring state, form a mixed mortar, and prevent the mortar from solidifying; Step five: operate the integrated self-loading mixer truck to transport 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, and compact in layers until the pit surface is filled, waiting for the backfill mortar to solidify to form a hard shell layer to resist wind erosion damage.

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