Construction method of carbon dioxide water-based foam cement soil high-pressure jet grouting pile

Abstract

According to the construction method of the carbon dioxide water-based foam cement soil high-pressure jet grouting pile, on the basis of a traditional triple-pipe high-pressure jet grouting pile construction technology, a triple-pipe high-pressure jet grouting drilling machine and a foaming machine for preparing carbon dioxide water-based foam are used in a combined mode; a foaming machine for preparing the carbon dioxide water-based foam, a cement paste preparation device, a water supply device and an air supply device are connected to a pumping transportation device through parallel pipelines, and the pumping transportation device conveys the carbon dioxide water-based foam, the cement paste, high-pressure water and air to a high-pressure jet grouting drilling machine. According to the method, on-site carbon dioxide curing conditions of the cement-soil jet grouting pile are achieved, carbon dioxide curing accelerates the cement carbonization effect and improves the carbonization degree, the early strength of the cement-soil jet grouting pile is greatly improved, and the curing period is shortened. And meanwhile, bubble holes of the carbon dioxide water-based foam have considerable carbon storage and carbon sequestration capabilities.

Description

Technical Field

[0001] The present invention relates to the field of green and low-carbon construction technology for geotechnical engineering under the national strategy of carbon peak and carbon neutrality, and specifically to a construction method of carbon dioxide water-based foam cement soil high-pressure rotary jet piles. Background Art

[0002] In the process of accelerating urbanization, the construction industry has developed rapidly, which inevitably increased carbon dioxide emissions, leading to a series of problems such as rising sea levels and global warming. On the other hand, a large amount of carbon dioxide gas will be produced in cement production due to fuel combustion and clinker calcination. According to statistics from the Information Research Center of the China Cement Association: Every ton of limestone calcined will produce 0.9 to 1.2 tons of carbon dioxide, and the carbon dioxide emissions in the cement production cycle account for about 25% of the total emissions. Last year, my country's total cement production exceeded 2.3 billion tons. Therefore, in the 21st century, countries began to pay attention to carbon dioxide emission reduction, storage, and dissipation technologies. However, the existing carbon dioxide maintenance cost is high and it is difficult to implement on site. How to efficiently and reasonably use carbonization reactions to achieve carbon neutrality goals is an important issue in geotechnical engineering today.

[0003] High-pressure rotary jet grouting is a process that combines high-pressure water jet cutting technology and chemical grouting technology for building foundation reinforcement. Its principle is to use slurry making, pumping, drilling and other equipment to place the injector with a nozzle installed at the bottom of the grouting pipe at a predetermined depth of the soil layer, and then use high-pressure water flow and compressed air flow to cut the soft soil underground and then inject cement slurry to mix with the cut soil to form a reinforced pile body. The high-pressure rotary jet pile construction process was first used by Japanese experts for foundation reinforcement and waterproof curtain construction, thus forming a new foundation reinforcement technology. The technology was originally developed by the Japanese Chemical Grouting Association in 1968, and it has gradually developed from the single-tube construction method (Chemical Churning Pile) to the double-tube construction method (Jambo Special Pile) to the triple-tube rotary jet grouting method (Column Jet Pile). The crushing energy of the soil by the three construction methods increases successively, and the diameter of the reinforced piles formed also increases accordingly, from 0.6~1.0m to about 1.5m, and the maximum reinforcement depth reaches 30m. The triple-tube rotary jet grouting method is to form a composite high-pressure jet flow by surrounding the compressed air outside the high-pressure water flow to cut and crush the soil, and then inject cement slurry to mix with the chopped soil to form a reinforced pile.

[0004] CN107089838B discloses a sulphoaluminate cement foamed concrete using carbon dioxide as a foaming gas and a preparation method thereof, wherein the foaming gas in the sulphoaluminate cement foamed concrete is carbon dioxide; the foamed concrete is composed of the following components by mass: 150-310 parts of sulphoaluminate cement, 60-120 parts of mineral admixtures, 10-30 parts of carbon dioxide foaming agent, 1-4 parts of foam stabilizer, and 150-250 parts of water. The present invention uses carbon dioxide as the foaming gas of the sulphoaluminate cement foamed concrete, so that the prepared aluminum sulfate cement foamed concrete has better thermal insulation and heat insulation properties, and the fire resistance grade reaches Class A while also being able to improve the strength of the foamed concrete.

[0005] CN115157443A discloses a device suitable for preparing water-based foam and mixing it with cement slurry, comprising a gas cylinder, a flask, a foam chamber and a mixing drum, the gas cylinder is filled with inert gas, the gas outlet of the gas cylinder is connected with the gas inlet pipe and the T-shaped three-way pipe in sequence, the other two ends of the T-shaped three-way pipe are respectively connected with the foaming liquid inlet pipe at the opening of the flask and the open pipe at the lower left end of the foam chamber, the flask is filled with foaming liquid, the foam chamber is provided with multiple layers of porous media with gradually increasing porosity, fillers are provided between adjacent layers of porous media, a discharge pipe is provided at the bottom of the foam chamber, a foam outlet pipe is provided at the middle and upper end of the foam chamber, the foam outlet pipe is connected with the mixing drum, the upper end of the mixing drum is provided with a slurry inlet for inputting cement slurry, and the lower end of the mixing drum is provided with a slurry outlet. The device prepares uniform, fine and stable carbon dioxide water-based foam and foam cement slurry with low foam break rate, large contact area and uniform mixing.

[0006] CN113277787B discloses an optimized preparation method of lightweight CO2 foam cement-based materials based on carbonization, which belongs to the field of geotechnical engineering materials. The preparation process includes: S1: pre-selecting existing commonly used cement-based foaming agents and foam stabilizers. S2: preparing carbon dioxide water-based foam. S3: preparing slurry, mixing carbon dioxide water-based foam with cement slurry to form lightweight CO2 foam cement-based materials, S4: selecting different types and concentrations of foaming machines, types and concentrations of foam stabilizers to prepare slurry, conducting slurry performance tests and optimizing. S5: optimizing the initial water-cement ratio and foam ratio parameters. S6: optimizing the air addition amount (water pump speed) parameter. The present invention can reduce the slurry coagulation time, increase the strength of the stone body, and has the advantages of low specific gravity and low stone body density of lightweight mud. It solves the problems of high on-site construction cost and difficult process implementation of carbon dioxide curing mud in the geotechnical field.

[0007] The above invention only involves the preparation method and indoor mixing device of CO2 foam cement-based materials and concrete, and does not provide the application of CO2 foam in cement soil geotechnical engineering to realize the process of on-site carbon dioxide curing of cement soil. Summary of the invention

[0008] Technical problem: The purpose of the present invention is to provide a construction method of carbon dioxide water-based foam cement soil high-pressure rotary jet piles. Under the background of the dual carbon national strategic goals and the green and low-carbon transformation of civil engineering, in the field of low-carbon foundation reinforcement technology in geotechnical engineering, the main technical problem solved by the present invention is to realize the underground carbon dioxide maintenance environment of cement soil piles with the help of high-pressure rotary jet pile construction method, thereby achieving distributed storage of carbon dioxide combined with underground engineering.

[0009] Technical solution: Based on the traditional triple-tube high-pressure rotary jet pile construction process, the triple-tube high-pressure rotary jet drilling rig is used in conjunction with a foaming machine for preparing carbon dioxide water-based foam. The foaming machine for preparing carbon dioxide water-based foam is connected to a pumping and transporting device together with a cement slurry preparation device, a water supply device, and an air supply device using parallel pipelines. The pumping and transporting device transports carbon dioxide water-based foam, cement slurry, high-pressure water, and air to the high-pressure rotary jet drilling rig. The construction process is: first, high-pressure water is sprayed to cut the soil; then, carbon dioxide water-based foam is sprayed to enter the loose soil formed by high-pressure water cutting; next, cement slurry is sprayed into the loose soil and mixed with carbon dioxide water-based foam, which mainly plays the role of filling and replacing the pores in the loose soil; finally, air is sprayed, and the mud floating on the cement slurry is discharged to the air port and extracted using the air lift principle, and finally a CO2 water-based foam cement soil high-pressure rotary jet pile is formed. The present invention realizes the on-site carbon dioxide curing conditions for cement soil jet grouting piles. Carbon dioxide curing accelerates the carbonization of cement and improves the carbonization degree, greatly improves the early strength of cement soil jet grouting piles and shortens the curing period. At the same time, the bubble pores of carbon dioxide water-based foam have considerable carbon storage and carbon sequestration capabilities.

[0010] The construction method of the carbon dioxide water-based foam cement soil high-pressure rotary jet pile of the present invention is based on a high-pressure rotary jet drilling rig, including a drilling rig walking and positioning device, a rotary drill bit, a nozzle, a carbon dioxide gas cylinder, a foaming machine, a cement slurry preparation device, a pumping and transportation device, and an air and water supply device; wherein the drilling rig walking and positioning device is equipped with a high-pressure rotary jet drilling rig for walking and positioning; the rotary drill bit is installed at the lower end of the drill rod for drilling holes; the nozzle is installed on the drill rod at the rear of the rotary drill bit, and according to the construction procedure requirements, water, CO2 water-based foam, cement slurry, and air are sprayed at different construction periods; a monitoring sensor device is installed inside the nozzle, Monitor the injection pressure of high-pressure water, CO2 water-based foam, cement slurry and air; the carbon dioxide cylinder, foaming machine, cement slurry preparation device and pumping and transporting device are connected in series in sequence, and the gas and water supply devices are connected to the pumping and transporting device in sequence with a conveying pipeline. The carbon dioxide cylinder is used for the supply of carbon dioxide during the preparation of carbon dioxide water-based foam; the foaming machine is used for the preparation of carbon dioxide water-based foam; the cement slurry preparation device is used for the preparation of cement slurry; the gas and water supply device is used for the supply of air and water, and the pumping and transporting device transports carbon dioxide water-based foam, cement slurry, high-pressure water and air to the high-pressure rotary jet drilling rig.

[0011] The construction method comprises the following steps: Step 1: Screening experiment of foaming agent and foam stabilizer: Use a foaming machine to conduct preliminary experiments on commonly used foaming agents and foam stabilizers, and conduct preliminary screening of foaming agents and foam stabilizers based on the stabilization time and foaming height of water-based foams; Step 2: Determination of carbon dioxide gas addition amount: Carry out gas addition amount test test for carbon dioxide water-based foamed cement slurry with optimal preparation parameters to test the flow properties of carbon dioxide water-based foamed cement slurry, and obtain the optimal carbon dioxide gas addition amount of carbon dioxide water-based foamed cement slurry according to the flow properties requirements; Step 3: Preparation of carbon dioxide water-based foam on-site foaming agent: prepare the foaming liquid according to the optimal type of foaming agent and foam stabilizer and the optimized concentration parameters; Step 4: Foaming effect test: Use the foaming multiple and foaming half-life to test the foaming effect; Step 5: Use the drilling rig travel and positioning device installed on the high-pressure jet grouting drilling rig to control the travel and positioning of the drilling rig, and accurately locate the construction position of the high-pressure jet grouting pile; Step 6: Drill to the designed elevation using a rotary drill bit at the predetermined pile position to complete the drilling of the high-pressure jet grouting pile; Step 7: Insert the drill rod into the ground for the second time to the designed elevation of the pile bottom, open the nozzle to spray high-pressure water as the drill bit is lifted, and play the role of cutting deep soil; Step 8: After completing steps 1 to 4, insert the drill rod into the ground for the third time to the designed elevation of the pile bottom, open the nozzle and spray carbon dioxide water-based foam as the drill bit is lifted, so that it enters the loose soil formed by high-pressure water cutting; Step 9: Based on the water-cement ratio and specific gravity required by the project, after preparing the cement slurry, insert the drill rod into the formation for the fourth time to the designed elevation of the pile bottom, open the nozzle and spray the cement slurry into the loose soil during the drilling process, and mix it with the carbon dioxide water-based foam, which mainly plays the role of filling and replacing the pores in the loose soil; Step 10: Insert the drill rod into the ground for the fifth time to the designed elevation of the pile bottom, open the nozzle to spray air as the drill bit is lifted, and use the air lift principle to drain the mud floating on the cement slurry to the air outlet and extract it, finally forming the CO2 water-based foam cement soil high-pressure jet grouting pile; Step 11: Repeat steps 9 to 10, and perform re-spraying according to construction requirements until the construction is completed and stop construction; Step 12: Move the drilling rig and repeat steps 1 to 11 to construct the next pile.

[0012] Among them, the initial screening is: preparing cement slurry according to the specific engineering requirements of the water-cement ratio of cement-soil jet jet piles; mixing carbon dioxide foam and cement slurry according to different foam ratios to make carbon dioxide water-based foam cement slurry; conducting a range analysis of four performance indicators of the carbon dioxide water-based foam cement slurry, including 7-day compressive strength, density, stone rate, and foam stabilization time, and comprehensively considering the range results to select the best type of foaming agent and foam stabilizer, as well as the optimization of concentration and foam ratio parameters.

[0013] The foaming agent is prepared as follows: according to the best foaming agent type and foam stabilizer type and the optimized concentration parameters, the foaming liquid is modulated, the water pump is turned on, the water pump speed is controlled at 70 rpm, the foaming liquid enters the foaming tube from the self-liquid storage tube in the foaming machine, the carbon dioxide gas cylinder switch is turned on, the primary pressure reducing valve connected to the carbon dioxide gas cylinder is adjusted so that the output gas pressure does not exceed 0.5 MPa, the secondary pressure reducing valve in the foaming machine is adjusted to accurately control the foaming gas pressure, and the foaming gas pressure is controlled not to exceed 0.02 MPa, the carbon dioxide flows into the foaming tube through the gas storage tube and mixes with the foaming liquid, the water pump is turned off, the foaming operation is started, the foaming liquid flows from the foaming tube through the throttle into the blowing port, and the obtained carbon dioxide foam flows out through the bubble outlet connected to the bubble outlet tube.

[0014] The foaming effect test is as follows: the foaming multiple is the ratio of the foam volume to the volume of the foaming liquid, which characterizes the foaming ability; the foaming half-life is the time taken for the foam volume to dissipate to half of the original volume, which characterizes the foam stability.

[0015] Beneficial effects: The following beneficial effects can be obtained through the above technical solution: 1. The present invention provides a method for constructing carbon dioxide water-based foamed cement soil high-pressure rotary jet piles. The connection relationship between the CO2 water gas cylinder, the foaming machine and the traditional triple-tube high-pressure rotary jet drilling rig enables the modified cement soil high-pressure rotary jet pile drilling rig to realize the construction of CO2 water-based foamed cement soil high-pressure rotary jet piles.

[0016] 2. The present invention provides a method for constructing carbon dioxide water-based foam cement soil high-pressure rotary jet piles, comprising: foaming agent and foam stabilizer screening experiments, carbon dioxide addition amount determination, CO2 water-based foam on-site foaming machine preparation, foaming effect inspection, high-pressure rotary jet pile construction water spraying, CO2 water-based foam spraying, cement slurry spraying, and air spraying process steps.

[0017] 3. The on-site carbon dioxide curing conditions for cement soil jet grouting piles are realized. Carbon dioxide curing accelerates the carbonization of cement and increases the carbonization degree, greatly improving the early strength of cement soil jet grouting piles and shortening the curing cycle. At the same time, the bubble pores of carbon dioxide water-based foam have considerable carbon storage and carbon sequestration capabilities. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1It is a schematic diagram of the structure and monitoring sensor device of the carbon dioxide water-based foam cement soil high-pressure rotary jet pile machine; The figure includes: drilling rig travel and positioning device 1, rotating drill bit 2, nozzle 3, carbon dioxide cylinder 4, foaming machine 5, cement slurry preparation device 6, pumping and transportation device 7, air and water supply device 8, monitoring sensor device 9, and transportation pipeline 10. DETAILED DESCRIPTION

[0019] The following is combined with Figure 1 The implementation method of the present invention is described in detail: In a high-pressure rotary jet drilling rig for carbon dioxide water-based foam cement soil rotary jet piles of the present invention, the construction method is based on the high-pressure rotary jet drilling rig, including a drilling rig walking and positioning device 1, a rotary drill bit 2, a nozzle 3, a carbon dioxide gas cylinder 4, a foaming machine 5, a cement slurry preparation device 6, a pumping and transportation device 7, and an air and water supply device 8; wherein the drilling rig walking and positioning device 1 is equipped with a high-pressure rotary jet drilling rig for walking and positioning; the rotary drill bit 2 is installed at the lower end of the drill rod for drilling holes; the nozzle 3 is installed on the drill rod at the rear of the rotary drill bit 2, and according to the construction procedure requirements, water, CO2 water-based foam, cement slurry, and air are sprayed at different construction periods; a monitoring device is installed inside the nozzle 3 The sensing device 9 monitors the injection pressure of high-pressure water, CO2 water-based foam, cement slurry and air; the carbon dioxide cylinder 4, the foaming machine 5, the cement slurry preparation device 6 and the pumping and transporting device 7 are connected in series in sequence; the gas and water supply device 8 is connected to the pumping and transporting device 7 via a conveying pipeline 10 and connected in series in sequence; the carbon dioxide cylinder 4 is used for supplying carbon dioxide during the preparation of carbon dioxide water-based foam; the foaming machine 5 is used for the preparation of carbon dioxide water-based foam; the cement slurry preparation device 6 is used for the preparation of cement slurry; the gas and water supply device 8 is used for the supply of air and water, and the pumping and transporting device 7 transports carbon dioxide water-based foam, cement slurry, high-pressure water and air to the high-pressure rotary jet drilling rig.

[0020] The construction method comprises the following steps: Step 1: Foaming agent and foam stabilizer screening experiment: Use a foaming machine to conduct a preliminary experiment on commonly used foaming agents and foam stabilizers, and conduct a preliminary screening of foaming agents and foam stabilizers according to the water-based foam stabilization time and foaming height; prepare cement slurry according to the specific engineering requirements of the water-cement ratio of the rotary jet pile; according to different foam ratios, carbon dioxide foam and cement slurry are made into carbon dioxide water-based foam cement slurry; carry out the range analysis of four performance indicators such as 7-day compressive strength, density, stone rate, and foam stabilization time of carbon dioxide water-based foam cement slurry, comprehensively consider the range results, and select the best type of foaming agent and foam stabilizer, as well as the optimization of concentration and foam ratio parameters; currently, tea saponin foaming agent with a concentration of 4g / L and sodium dodecylbenzene sulfonate foam stabilizer with a concentration of 5g / L can be used. The present invention completes the optimization of foaming agents and foam stabilizers through orthogonal experiments and range analysis, has fewer test groups than comprehensive tests, arranges the influence degree by the range of different performance ranges of mud, and the test results are scientific and accurate, and the optimization process is efficient.

[0021] The foaming liquid ratio was selected as follows: tea saponin as a foaming agent, with a concentration of 4g / L, sodium dodecylbenzene sulfonate as a foam stabilizer, with a concentration of 5g / L. A comprehensive test of different initial water-cement ratios (1:2.2, 1:2.4, 1:2.6, 1:2.8) and foam ratios (3:1, 5:1, 7:1) was designed, and the slurry performance test (specific gravity, fluidity, consistency, water seepage rate, volume shrinkage rate of the stone body, stone body density, 7-day and 28-day uniaxial compressive strength) was carried out on the prepared slurry. The initial water-cement ratio and foam ratio parameters were optimized according to the slurry performance requirements. Through a comprehensive analysis of the effects of different water-cement ratios (foam ratios) under the same foam ratio (foam ratio) on the strength and density of cement slurry, a "good average value" of water-cement ratio (foam ratio) can be obtained, that is, under this water-cement ratio (foam ratio), the density of cement slurry is relatively low and the strength is relatively high. The engineering performance is excellent and the cost can be controlled. The method is to reduce the maximum and minimum values ​​of density and strength to 0% and 100% respectively, draw two broken lines according to the reduction percentages, and the water-cement ratio (foam ratio) corresponding to their intersection is the average value of the initial water-cement ratio (foam ratio).

[0022] Step 2: Determination of carbon dioxide gas addition amount: Carry out gas addition amount test test for the optimal preparation parameter carbon dioxide water-based foam cement slurry, check the flow performance of carbon dioxide water-based foam cement slurry, and obtain the optimal carbon dioxide gas addition amount of carbon dioxide water-based foam cement slurry according to the flow performance requirements. The density of carbon dioxide water-based foam is related to the gas addition amount and the water pump speed. The greater the gas addition amount, the more carbon dioxide gas in the unit volume of foam, the larger the foam diameter, the greater the water pump speed, the more water content in the foaming agent per unit time, and the smaller the foam diameter. The foaming machine in the preparation step S2 of the present invention controls the foam density by adjusting the water pump speed instead of the gas addition parameter. Compared with the gas addition amount, the water pump speed parameter is easier to control and the effect is more obvious.

[0023] Step 3: Preparation of CO2 water-based foam on-site foaming machine: according to the optimal type of foaming agent and foam stabilizer and the optimized concentration parameters, the foaming liquid is prepared, the water pump is turned on, the water pump speed is controlled at 70 rpm, the foaming liquid enters the foaming tube from the self-liquid storage tube in the foaming machine, the carbon dioxide gas cylinder switch is turned on, and the first-level pressure reducing valve connected to the carbon dioxide gas cylinder is adjusted so that the output gas pressure does not exceed 0.5MPa. The second-level pressure reducing valve in the foaming machine is adjusted to accurately control the foaming gas pressure, and the foaming gas pressure is controlled not to exceed 0.02MPa. Carbon dioxide flows into the foaming tube through the gas storage tube and mixes with the foaming liquid. The water pump is turned off, and the foaming operation is started. The foaming liquid flows from the foaming tube through the throttle into the blowing port, and the obtained carbon dioxide foam flows out through the bubble outlet connected to the bubble outlet tube.

[0024] Step 4: Foaming effect test: The foaming multiple and foaming half-life are used to test the foaming effect. The foaming multiple is the ratio of the foam volume to the volume of the foaming liquid, which characterizes the foaming ability; the foaming half-life is the time taken for the foam volume to dissipate to half of the original volume, which characterizes the foam stability. Based on the foam stability and foaming multiple parameters, the commonly used foaming agents and foam stabilizers were effectively screened to reduce the number of test groups for the later foaming agents and foam stabilizers.

[0025] The intersection of the two broken lines corresponds to a foam ratio of about 4.5:1 and a water-cement ratio of 1:2.4. At this time, the strength of the carbon dioxide foam cement slurry stone body is not low and the stone body density can be controlled. When the foam ratio is higher than 4.5:1 and the water-cement ratio is higher than 1:2.4, the stone body strength is low; when the foam ratio is lower than 4.5:1 and the water-cement ratio is lower than 1:2.4, the stone body density is higher. Therefore, a foam ratio of 4.5:1 and a water-cement ratio of 1:2.4 are selected, and the density and strength performance are both good.

[0026] Step 5: Use the drilling rig walking and positioning device 1 installed on the high-pressure rotary jet drilling rig to control the walking and positioning of the drilling rig, and accurately locate the construction position of the high-pressure rotary jet pile; Step 6: Drill to the designed elevation using the rotary penetration drill bit 2 at the predetermined pile position to complete the drilling of the high-pressure jet grouting pile; Step 7: Insert the drill rod into the ground for the second time to the designed elevation of the pile bottom, open the nozzle 3 to spray high-pressure water during the drilling head lifting process, so as to cut the deep soil; Step 8: After completing steps 1 to 4, the drill rod is inserted into the stratum for the third time to the designed elevation of the pile bottom, and the nozzle 3 is turned on to spray carbon dioxide water-based foam as the drill bit is lifted, so that the foam enters the loose soil formed by high-pressure water cutting; Step 9: Based on the prepared cement slurry according to the water-cement ratio and specific gravity required by the project, the drill rod is inserted into the stratum for the fourth time to the designed elevation of the pile bottom, and the nozzle 3 is turned on to spray cement slurry into the loose soil during the drill bit lifting process, and the cement slurry is mixed with the carbon dioxide water-based foam, which mainly plays the role of filling and replacing the pores in the loose soil; the carbon dioxide foam cement mixture prepared by the present invention has a specific gravity lower than 1.68g / cm, and the carbon dioxide water-based foam is mixed with cement slurry with a water-cement ratio of (1:2.4) and a foam ratio of (5:1) to prepare carbon dioxide foam cement slurry.

[0027] Step 10: Insert the drill rod into the stratum for the fifth time to the designed elevation of the pile bottom, open the nozzle 3 to spray air as the drill bit is lifted, and use the air lift principle to discharge the mud floating on the cement slurry to the air port and extract it, finally forming a CO2 water-based foam cement soil high-pressure rotary jet pile.

[0028] Step 11: Repeat steps 9 to 10, and perform re-spraying according to construction requirements until the construction is completed and stop construction; Step 12: Move the drilling rig and repeat steps 1 to 11 to construct the next pile.

Claims

1. A construction method for carbon dioxide water-based foam cement soil high-pressure jet grouting piles, characterized in that The construction method is based on a high-pressure rotary jet drilling rig, comprising a drilling rig travel and positioning device (1), a rotary drill bit (2), a nozzle (3), a carbon dioxide gas cylinder (4), a foaming machine (5), a cement slurry preparation device (6), a pumping and transportation device (7), and an air and water supply device (8); wherein the drilling rig travel and positioning device (1) is equipped with a high-pressure rotary jet drilling rig for travel and positioning; the rotary drill bit (2) is installed at the lower end of a drill rod for drilling holes; the nozzle (3) is installed on the drill rod at the rear of the rotary drill bit (2) and sprays water, CO2 water-based foam, cement slurry, and air at different construction periods according to construction procedure requirements; a monitoring sensor device (9) is installed inside the nozzle (3) to monitor the pressure of high-pressure water, CO2 water-based foam, cement slurry, and air. The injection pressure of O2 water-based foam, cement slurry and air; the carbon dioxide cylinder (4), the foaming machine (5), the cement slurry preparation device (6) and the pumping and transporting device (7) are sequentially connected in series; the air and water supply device (8) is connected to the pumping and transporting device (7) via a conveying pipeline (10) and sequentially connected in series; the carbon dioxide cylinder (4) is used for supplying carbon dioxide during the preparation of carbon dioxide water-based foam; the foaming machine (5) is used for the preparation of carbon dioxide water-based foam; the cement slurry preparation device (6) is used for the preparation of cement slurry; the air and water supply device (8) is used for the supply of air and water, and the pumping and transporting device (7) transports carbon dioxide water-based foam, cement slurry, high-pressure water and air to the high-pressure jet drilling rig.

2. The construction method of carbon dioxide water-based foam cement soil high-pressure jet grouting pile according to claim 1 is characterized in that The construction method comprises the following steps: Step 1: Screening experiment of foaming agent and foam stabilizer: Use a foaming machine to conduct preliminary experiments on commonly used foaming agents and foam stabilizers, and conduct preliminary screening of foaming agents and foam stabilizers based on the stabilization time and foaming height of water-based foams; Step 2: Determination of carbon dioxide gas addition amount: Carry out gas addition amount test test for carbon dioxide water-based foamed cement slurry with optimal preparation parameters to test the flow properties of carbon dioxide water-based foamed cement slurry, and obtain the optimal carbon dioxide gas addition amount of carbon dioxide water-based foamed cement slurry according to the flow properties requirements; Step 3: Preparation of carbon dioxide water-based foam on-site foaming agent: prepare the foaming liquid according to the optimal type of foaming agent and foam stabilizer and the optimized concentration parameters; Step 4: Foaming effect test: Use the foaming multiple and foaming half-life to test the foaming effect; Step 5: Using the drilling rig travel and positioning device (1) installed on the high-pressure jet grouting drilling rig to control the travel and positioning of the drilling rig, and accurately locate the construction position of the high-pressure jet grouting pile; Step 6: Drilling to the designed elevation using the rotary drill bit (2) at the predetermined pile position to complete the drilling of the high-pressure jet grouting pile; Step 7: Insert the drill rod into the ground for the second time to the designed elevation of the pile bottom, and open the nozzle (3) to spray high-pressure water as the drill bit is lifted, so as to cut the deep soil. Step 8: After completing steps 1 to 4, the drill rod is inserted into the ground for the third time to the designed elevation of the pile bottom, and the nozzle (3) is turned on to spray carbon dioxide water-based foam as the drill bit is lifted, so that the foam enters the loose soil formed by high-pressure water cutting; Step 9: After preparing cement slurry according to the water-cement ratio and specific gravity required by the project, the drill rod is inserted into the stratum for the fourth time to the designed elevation of the pile bottom, and the nozzle (3) is turned on to spray cement slurry into the loose soil as the drill bit is lifted. The cement slurry is mixed with carbon dioxide water-based foam to fill and replace the pores in the loose soil. Step 10: The drill rod is inserted into the ground for the fifth time to the designed elevation of the pile bottom, and the nozzle (3) is opened to spray air as the drill bit is lifted. The mud floating on the cement slurry is discharged to the air outlet and extracted by the air lift principle, and finally a CO2 water-based foamed cement soil high-pressure jet grouting pile is formed; Step 11: Repeat steps 9 to 10, and perform re-spraying according to construction requirements until the construction is completed and stop construction; Step 12: Move the drilling rig and repeat steps 1 to 11 to construct the next pile.

3. The construction method of carbon dioxide water-based foam cement soil high-pressure jet grouting pile according to claim 2 is characterized in that The initial screening is as follows: preparing cement slurry according to the specific engineering requirements of the water-cement ratio of cement-soil jet jet piles; preparing carbon dioxide water-based foam cement slurry by mixing carbon dioxide foam with cement slurry according to different foam ratios; carrying out range analysis of four performance indicators of carbon dioxide water-based foam cement slurry, including 7-day compressive strength, density, stone rate, and foam stabilization time, and comprehensively considering the range results to select the best type of foaming agent and foam stabilizer, as well as the optimization of concentration and foam ratio parameters.

4. The construction method of carbon dioxide water-based foam cement soil high-pressure jet grouting pile according to claim 2 is characterized in that The foaming agent is prepared as follows: according to the best foaming agent type and foam stabilizer type and the optimized concentration parameters, the foaming liquid is modulated, the water pump is turned on, the water pump speed is controlled at 70 rpm, the foaming liquid enters the foaming tube from the self-liquid storage tube in the foaming machine, the carbon dioxide gas cylinder switch is turned on, the primary pressure reducing valve connected to the carbon dioxide gas cylinder is adjusted so that the output gas pressure does not exceed 0.5 MPa, the secondary pressure reducing valve in the foaming machine is adjusted to accurately control the foaming gas pressure, and the foaming gas pressure is controlled not to exceed 0.02 MPa, the carbon dioxide flows into the foaming tube through the gas storage tube and mixes with the foaming liquid, the water pump is turned off, the foaming operation is started, the foaming liquid flows from the foaming tube through the throttle into the blowing port, and the obtained carbon dioxide foam flows out through the bubble outlet connected to the bubble outlet tube.

5. The construction method of carbon dioxide water-based foam cement soil high-pressure jet grouting pile according to claim 2 is characterized in that The foaming effect test is as follows: the foaming multiple is the ratio of the foam volume to the volume of the foaming liquid, which characterizes the foaming ability; the foaming half-life is the time taken for the foam volume to dissipate to half of the original volume, which characterizes the foam stability.

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