Treatment method for solidifying karst cave filling body by microorganisms in construction process of pipe pile while drilling in karst area

Abstract

The invention discloses a treatment method for solidifying a karst cave filling body through microorganisms in the construction process of a pipe-following pile while drilling in a karst area. The treatment method mainly comprises a grouting hole, a grouting device, a grouting pipe, a high-pressure spray head and a tool pipe-following drilling machine while drilling, wherein the tool is matched with construction. According to the scheme, a reinforcing layer is formed on the inner wall of the karst cave through a method for solidifying karst cave cracks through microbial induction, and the karst cave is reinforced through pretreatment. The reinforcing layer formed through microorganism induction has good watertightness, it can be guaranteed that when cement paste is poured in the treatment process, the whole karst cave is fully filled with the cement paste, rubbles and clay components, and after the karst cave is pretreated and reinforced, the reinforcing layer penetrates through the karst cave to enable the pile bottom to reach the lower solid soil layer so that the bearing capacity of the pile bottom of the pipe pile while drilling can be guaranteed; and smooth proceeding of the construction process of the pipe pile while drilling is ensured, and a good reinforcing effect is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of treating karst caves in drilling and pipe piles, and in particular to a method for treating a microbial solidified karst cave filling body during the drilling and pipe pile construction process in a karst area. Background Art

[0002] Karst caves refer to unfavorable geological phenomena such as soil caves, karst (karst caves, karst grooves, karst troughs), etc., which appear due to the complex geological conditions in karst areas. There may even be underground river channels due to the abundance of groundwater. Grouting on the pile side is required during the construction of pipe-sinking piles while drilling. The appearance of karst caves will cause grout leakage on the pile side and reduce frictional resistance, which will have a great impact on the cost and construction period of the project. Therefore, the treatment technology of karst cave pile foundations in karst areas is particularly important in the overall construction process. The existing technology for the treatment of karst caves in karst areas generally adopts the filling method of plain soil, gray soil, gravel, crushed stone, and concrete materials. However, the self-stability of plain soil and gray soil is poor, which can easily cause secondary collapse, resulting in negative friction in the pile foundation, seriously affecting the bearing capacity of the pile foundation; the concrete manufacturing process has the problems of high energy consumption, high emissions, and high pollution. For caves with loose fillings, it is difficult for concrete to enter the cave fillings, so the surface reinforcement effect is good, and the internal reinforcement effect is average; gravel, crushed stone and other materials are easy to obtain and have good filling effects, but there is a problem of secondary collapse caused by the erosion of fine particles or soil layers due to improper selection of gravel diameter and grading. Therefore, finding an effective filling construction method that can both ensure the stability of the backfill material structure and prevent water seepage and erosion has become a common concern in the field of foundation treatment.

[0003] Microbial induced calcium carbonate precipitation (MICP) is an emerging method for foundation improvement. The essence of MICP is to use a certain type of bacteria in nature, whose metabolism can produce urease that decomposes urea. The carbonate ions produced after the decomposition of urea combine with free metal cations in nature to form gelled crystals. The application of MICP technology has low requirements for production energy consumption and production costs, and can also reduce greenhouse gas emissions. MICP technology can improve the geological properties of soil, so it can be used as an alternative geological reinforcement technology. However, the relevant MICP technology has not yet been applied to solidify caves in karst areas.

[0004] Drilling pipe pile (DPC pile) is a new type of non-squeezing pipe pile foundation. When encountering unfavorable geological conditions such as caves during construction in karst areas, it is easy to cause leakage of pile side, seriously affecting the grouting effect of pile side, and finally affecting the performance of pile side friction resistance. Therefore, the treatment technology of drilling pipe pile in karst areas when facing caves is particularly important in the overall construction process. The success of MICP technology depends on the presence of microbial liquid and nutrient solution in the pores of the formation. The microbial liquid and nutrient solution can be smoothly injected into the soil voids through the grouting method. Grouting construction is carried out at any time, and the microbial liquid and nutrient solution are cemented in the soil voids in the cracks of the cave, producing a large amount of calcium carbonate precipitation, making the cave gradually airtight, ensuring that the cave meets the grouting requirements and then grouting cement slurry to fill the cave cavity. After meeting the construction requirements, the relevant construction operations of drilling pipe pile are continued.

[0005] For caves with relatively poor fluidity, microbial bacterial fluid and nutrient solution are more susceptible to cementation reactions, which change the pore structure inside the soil and the interaction mode between particles, and then change some mechanical properties of the soil, cementing fine particles into aggregates, and the aggregates fill the gaps of coarse particles. This phenomenon optimizes the load transfer path between particles, thereby reducing the overall strain and increasing the stiffness of the soil around the cave.

[0006] Compared with the prior art, the present invention effectively solves the construction problems of sinking, tilting, and pile bottom bearing capacity failing to meet the design requirements during the construction of the pile with drilling and pipe piles in the karst caves, and can effectively achieve the effect of reinforcing the karst cave soil and ensure the bearing capacity requirements of the pile bottom of the pile with drilling and pipe piles. At the same time, the construction technology can specifically reinforce the bearing layer of the pile bottom of the pile with drilling and pipe piles in the karst caves, shorten the construction period, and reduce the amount of cement used. Summary of the invention

[0007] The purpose of the invention is to solve the construction problem of existing drilling and pipe piles in karst cave areas, and propose a treatment method for microbial solidification of karst caves in karst areas.

[0008] A method for treating microbial solidified caves in karst areas based on drilling and pipe piles. The main purpose is to provide a method for drilling and pipe piles in karst areas, which pre-treats and reinforces the caves and then penetrates the caves so that the pile bottom reaches the lower solid soil layer to ensure the bearing capacity requirements of the pile bottom, thereby overcoming the shortcomings of the existing technology.

[0009] To achieve the above object, the present invention adopts the following technical solutions:

[0010] The present invention discloses a method for treating a karst area microbial solidification cave based on pile-while-drilling, comprising a grouting hole 1 arranged at the top of the cave, a grouting device 2 arranged next to the grouting hole, a grouting pipe 3 connected to the grouting device, and a high-pressure nozzle 4 arranged on the grouting pipe 3. When treating the cave, the grouting pipe 3 is passed through the grouting hole 1 directly to the middle of the cave, and then the grouting device 2 is turned on, and the bacterial liquid and nutrient solution are sprayed into the cave according to the volume of bacterial liquid and nutrient solution required for the expected MICP grouting reinforcement, and the reinforcement is repeated to ensure that the cracks in the cave are filled with the bacterial liquid and nutrient solution. Under the action of the nutrient solution, the pasteurian spore Sarcina will gradually generate calcium carbonate precipitation.

[0011] As microorganisms induce the precipitation of calcium carbonate in the cracks around the cave, the cave gradually becomes airtight, and the cave chamber will gradually become a closed space with only the grouting pipe 3 opening, which deteriorates the fluidity of the liquid. After the microorganisms induce the calcium carbonate precipitation to solidify the cave, the cave is further treated by pouring cement slurry. The cement slurry reaches the bottom of the cave through the grouting hole 1. While injecting the cement slurry, a certain amount of 1:1 stone and clay are put into the hole to make it denser. This operation is repeated, and the cement slurry and the mixture of stone and clay are poured many times until the cave is filled.

[0012] After the filling of cement slurry and stone and clay mixture, the construction of drilling and pipe piles is carried out. The specific construction steps are as follows: P1: Start the drilling rig and align the pile controller with the pile position, then adjust the pile clamping platform of the pile controller to be horizontal and the drilling rig column to be vertical; P2: The prefabricated pipe pile is hoisted into the pile clamp of the pile controller, the reaming drill bit is installed and connected with the spiral drill rod assembly, and the reaming wings of the reaming drill bit are in the retracted state. The vibrator clamps the prefabricated pipe pile, and the extension of the adjustment cylinder is adjusted to make the reaming drill bit pass through the lower end surface of the prefabricated pipe pile; P3: The power head rotates forward, and the reaming wings of the reaming drill head open under the friction of the soil, and the reaming drilling begins. The clamp of the pile control device is released, and the prefabricated pipe pile is followed by the pile. After a section of the prefabricated pipe pile is piled, a new section of drill rod and prefabricated pipe pile are hoisted according to the method in step P2, and the new drill rod is connected to the existing drill rod, and the new prefabricated pipe pile is connected to the previous prefabricated pipe pile. After the installation is completed, the construction continues; P4: After the pile is driven to the predetermined depth, stop drilling, reverse the power head, retract the reaming wings of the reaming drill, lift the drill rod out of the prefabricated pipe pile, start the vibrator to vibrate the prefabricated pipe pile, so that the pile end of the prefabricated pipe pile fits tightly with the rock and soil layer at the bottom of the hole; P5: Grouting is performed on the pile side and pile bottom to form a pile.

[0013] The microbial culture medium is Bacillus pasteurianus, and 1L of bacterial expansion culture medium is composed of 20g yeast extract, 10g ammonium sulfate, 2g sodium hydroxide and water and other raw materials. The microorganism is inoculated and cultured for 24 hours to form a microbial culture medium; 1L of nutrient solution is composed of 55g calcium chloride, 30g urea, 3g nutrient broth, 10g ammonium chloride, 2.12g sodium bicarbonate and water and other raw materials.

[0014] A treatment method for microbial solidification of caves in karst areas based on drilling and pipe piles, comprising the following steps: first, the number and size of caves in the drilling and pipe pile construction area under the karst area are ascertained; according to the exploration data, a grouting hole 1 is opened at the top of the cave, the grouting hole 1 is connected to the cave to be reinforced, and then the microbial liquid and nutrient solution required for MICP reinforcement are calculated and configured, and a liquid and nutrient solution grouting device 2 is arranged next to the grouting hole 1, and the grouting pipe 3 is connected to the grouting device. A high-pressure nozzle 4 is provided on the grouting pipe 3. The high-pressure nozzle 4 is located in the middle of the cave during construction, which is convenient for spraying the microbial liquid and nutrient solution, and the microbial liquid is evenly sprayed on the inner wall of the cave. After 4 hours, a predetermined volume of nutrient solution is sprayed on the inner wall of the cave, and it is left to stand for 6 hours. Repeat the operation of spraying the microbial liquid and nutrient solution to ensure that calcium carbonate is precipitated in the pores of the cave wall around the cave and fills the pores;

[0016] Replace the slurry in the grouting pipe 3 with cement slurry, continue to pour cement slurry and simultaneously put a certain amount of slab stone and clay in a ratio of 1:1 into the hole, then use a small stroke to impact the poured mixture to make it denser, repeat this operation, pour cement slurry and slab stone and clay mixture multiple times until the cave is full;

[0017] During the construction of pipe piles while drilling, the pipe drilling rig is started to align the pile controller with the pile position, and the pile clamping platform of the pile controller is adjusted to be horizontal, and the drilling rig column is adjusted to be vertical. The prefabricated pipe piles are constructed in the karst area according to the above specific operations. After the piles are driven to the predetermined depth, grouting is performed on the pile sides and pile bottom to form the piles.

[0026] The advantages and effects of the present invention are as follows:

[0027] 1. There is no targeted solution to the problem of drilling and pipe piles during construction in karst areas. The method of solidifying the cracks in the cave by microbial induction can form a reinforcement layer on the inner wall of the cave. Its good impermeability can ensure that when cement slurry is poured during the treatment process, the cement slurry, stone flakes and clay components fully fill the entire cave, which has a good reinforcement effect.

[0028] 2. After the cave is reinforced and filled with MICP, the construction process of drilling and pile pile can be carried out smoothly, making it easy for drilling and pile pile to reach the solid soil layer below and improve the bearing capacity of the pile foundation.

[0029] 3. The drilling of grouting holes and pipe piles can be carried out simultaneously. When the grouting holes complete the entire MICP reinforcement process, the drilling of pipe piles can be carried out directly, which shortens the construction period, saves material loss and reduces construction costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 It is a front view of a treatment method for microbial solidification of caves in karst areas based on drilling and pipe piles.

[0032] Figure 2 This is a schematic diagram of cave reinforcement.

[0033] Figure 3 This is a schematic diagram of prefabricated pipe piles during drilling and pipe pile construction.

[0034] Figure 4 This is a schematic diagram of pile construction using drilling and pipe piles in karst areas. Specific implementation method:

[0036] The specific embodiments of the present invention are further described in detail below with reference to the accompanying drawings.

[0037] A treatment method for microbial solidification caves in karst areas based on drilling and pipe piles mainly includes grouting holes, grouting devices, grouting pipes, high-pressure nozzles, and tools used in conjunction with the construction mainly include drilling and pipe drilling rigs.

[0038] Step 1: Position the drill rig above the proven cave, drill vertically with the drill rod, and after reaching the predetermined depth of the cave, drill the rod into the hole, rotate it and take it out, connect the grouting device with the grouting pipe and high-pressure nozzle and set it next to the borehole, extend the grouting pipe into the cave, and the grouting work is ready.

[0039] Step 2: Spray the prepared microbial solution into the cave through a grouting device. The volume of the solution is calculated based on the discovered pores of the cave.

[0040] Step 3: After the microbial liquid is sprayed, wait for 4 hours, replace the liquid in the grouting device with nutrient solution, and inject the nutrient solution into the cave. The volume of the nutrient solution is proportional to the volume of the microbial liquid.

[0041] Step 4: Let it stand for 6 hours, and repeatedly change the volume of the microbial solution in the grouting device, repeating this process.

[0042] Step 5: After the MICP grouting reinforcement of the cave is completed, the liquid in the grouting device is replaced with cement slurry, the cement slurry is poured into the cave, and a certain amount of stone and clay in a ratio of 1:1 is added into the hole to make the cave denser. This operation is repeated, and cement slurry and stone and clay mixture are poured multiple times until the cave is full.

[0043] Step 6: Pull out the grouting pipe and carry out the construction of the pipe pile while drilling. Start the pipe pile while drilling rig, align the pile controller with the pile position, adjust the pile clamp platform of the pile controller to horizontal, and adjust the drilling rig column to vertical.

[0044] Step 7: Lift the prefabricated pipe pile into the pile clamp of the pile controller, and make the reaming drill bit pass through the lower end surface of the prefabricated pipe pile.

[0045] Step 8: Start drilling and loosen the pile control clamp, and the prefabricated pipe pile will follow. After a section of prefabricated pipe pile is put into place, install a new section of drill rod and prefabricated pipe pile according to the method in step P2, and continue construction after installation.

[0046] Step 9: After the pile is driven to the predetermined depth, stop drilling, pull the drill rod out of the prefabricated pipe pile, start the vibrator to vibrate the prefabricated pipe pile, so that the end of the prefabricated pipe pile fits tightly with the rock and soil layer at the bottom of the hole.

[0047] Step 10: After the pile is driven to the predetermined depth, grouting is performed on the pile side and bottom to form the pile.

[0048] The above embodiment is only a specific implementation of the present invention and is not intended to be a limitation of the present invention. Any simple improvements and replacements made thereto are within the protection scope of the present invention.

Claims

1. A treatment method for microbial solidification of karst caves in karst areas based on drilling and pipe piles, comprising a grouting hole 1 arranged at the top of the cave, a grouting device 2 arranged next to the grouting hole, a grouting pipe 3 connected to the grouting device, and a high-pressure nozzle 4 arranged on the grouting pipe 3. When treating the cave, the grouting pipe 3 is passed through the grouting hole 1 directly to the middle of the cave, and then the grouting device 2 is turned on, and the bacterial liquid and nutrient solution are sprayed into the cave according to the volume of bacterial liquid and nutrient solution required for MICP grouting reinforcement. The reinforcement is repeated to ensure that the cracks in the cave are filled with bacterial liquid and nutrient solution. Under the action of the nutrient solution, the pasteurian spore Sarcina will gradually generate calcium carbonate precipitation.

2. The method for treating karst caves by microbial solidification based on pile-while-drilling according to claim 1 is characterized by: As microorganisms induce the precipitation of calcium carbonate in the cracks around the cave, the cave gradually becomes airtight, and the cave chamber will gradually become a closed space with only the grouting pipe 3 opening, which deteriorates the fluidity of the liquid. After the microorganisms induce the calcium carbonate precipitation to solidify the cave, the cave is further treated by pouring cement slurry. The cement slurry reaches the bottom of the cave through the grouting hole 1. While injecting the cement slurry, a certain amount of 1:1 stone and clay are put into the hole to make it denser. This operation is repeated, and the cement slurry and the mixture of stone and clay are poured many times until the cave is filled.

3. The method for treating karst caves by microbial solidification based on pile-while-drilling according to claim 2 is characterized by: After the filling of cement slurry and stone and clay mixture, the construction of drilling and pipe piles is carried out. The specific construction steps are as follows: P1: Start the drilling rig and align the pile controller with the pile position, then adjust the pile clamping platform of the pile controller to be horizontal and the drilling rig column to be vertical; P2: The prefabricated pipe pile is hoisted into the pile clamp of the pile controller, the reaming drill bit is installed and connected with the spiral drill rod assembly, and the reaming wings of the reaming drill bit are in the retracted state. The vibrator clamps the prefabricated pipe pile, and the extension of the adjustment cylinder is adjusted to make the reaming drill bit pass through the lower end surface of the prefabricated pipe pile; P3: The power head rotates forward, and the reaming wings of the reaming drill head open under the friction of the soil, and the reaming drilling begins. The clamp of the pile control device is released, and the prefabricated pipe pile is followed by the pile. After a section of the prefabricated pipe pile is piled, a new section of drill rod and prefabricated pipe pile are hoisted according to the method in step P2, and the new drill rod is connected to the existing drill rod, and the new prefabricated pipe pile is connected to the previous prefabricated pipe pile. After the installation is completed, the construction continues; P4: After the pile is driven to the predetermined depth, stop drilling, reverse the power head, retract the reaming wings of the reaming drill, lift the drill rod out of the prefabricated pipe pile, start the vibrator to vibrate the prefabricated pipe pile, so that the pile end of the prefabricated pipe pile fits tightly with the rock and soil layer at the bottom of the hole; P5: Grouting is performed on the pile side and pile bottom to form a pile.

4. The method for treating karst caves by microbial solidification based on pile-while-drilling according to claim 3 is characterized by: The microbial culture medium is Bacillus pasteurianus, and 1L of bacterial expansion culture medium is composed of 20g yeast extract, 10g ammonium sulfate, 2g sodium hydroxide and water and other raw materials. The microorganism is inoculated and cultured for 24 hours to form a microbial culture medium; 1L of nutrient solution is composed of 55g calcium chloride, 30g urea, 3g nutrient broth, 10g ammonium chloride, 2.12g sodium bicarbonate and water and other raw materials.

5. The method for treating karst caves by microbial solidification based on pile-while-drilling according to claim 4 is characterized by: The following steps are involved: First, the number and size of caves in the construction area of ​​the pile while drilling under the karst area are ascertained; according to the exploration data, a grouting hole 1 is opened at the top of the cave, and the grouting hole 1 is connected to the cave to be reinforced. Then, the microbial liquid and nutrient solution required for MICP reinforcement are calculated and configured, and a liquid and nutrient solution grouting device 2 is arranged next to the grouting hole 1, and the grouting pipe 3 is connected to the grouting device. A high-pressure nozzle 4 is provided on the grouting pipe 3. The high-pressure nozzle 4 is located in the middle of the cave during construction, which is convenient for spraying microbial liquid and nutrient solution. The microbial liquid is evenly sprayed on the inner wall of the cave. After 4 hours, a predetermined volume of nutrient solution is sprayed on the inner wall of the cave and left to stand for 6 hours. Repeat the operation of spraying microbial liquid and nutrient solution to ensure that calcium carbonate is precipitated in the pores of the cave wall around the cave and fills the pores.

6. The method for treating karst caves by microbial solidification based on pile-while-drilling according to claim 5 is characterized by: Replace the slurry in the grouting pipe 3 with cement slurry, continue to inject cement slurry and at the same time put a certain amount of stone and clay in a ratio of 1:1 into the hole, then use a small stroke to impact the injected mixture to make it denser, repeat this operation, and inject cement slurry and stone and clay mixture multiple times until the cave is full.

7. Construction of pipe piles while drilling, start the pipe pile drilling rig, align the pile controller with the pile position, adjust the pile clamping platform of the pile controller to be horizontal, adjust the drilling rig column to be vertical, and construct the prefabricated pipe piles in the karst area according to the above specific operations. After the piles are inserted to the predetermined depth, grouting is performed on the pile sides and pile bottom to form the piles.

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