Carbon dioxide water-based foam cement soil mixing pile construction device and construction method

Abstract

The invention provides a carbon dioxide water-based foam cement soil mixing pile construction device and method in the technical field of building engineering. The carbon dioxide water-based foam cement soil mixing pile construction device comprises a mixing pile drilling machine, a cement paste preparation device, a foam production device and a pumping transportation device. The cement paste preparation device and the foam production device are both connected to the pumping transportation device, and the cement paste and the carbon dioxide water-based foam are conveyed to the stirring pile drilling machine through a conveying pipeline; a vertical stirring shaft and a stirring head vertically mounted at the lower part of the stirring shaft are mounted on the stirring pile drilling machine, and a slurry conveying pipe is arranged in the stirring shaft; the top of the slurry conveying pipe is connected with two conveying pipelines through a change-over valve, and the bottom is connected with a nozzle arranged on the side surface of the bottom of the stirring shaft. By means of the mixing pile construction mode, the underground carbon dioxide curing environment of the cement-soil pile is achieved, and distributed storage of carbon dioxide combined with underground engineering is achieved; the on-site carbon dioxide curing condition of the cement-soil mixing pile is achieved, the cement carbonization effect is accelerated, and the carbonization degree is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of construction engineering, and more specifically, relates to a construction device and a construction method for a carbon dioxide water-based foam cement-soil mixing pile. Background Art

[0002] In the process of accelerating urbanization construction, the construction industry has developed rapidly, inevitably increasing carbon dioxide emissions, leading to a series of problems such as rising sea levels and global warming. On the other hand, in cement production, due to fuel combustion and clinker calcination, a large amount of carbon dioxide gas is generated. According to statistics from the Information Research Center of the China Cement Association: about 0.9 - 1.2 tons of carbon dioxide are generated for every ton of limestone calcined, and the carbon dioxide emissions during the cement production cycle account for about 25% of the total emissions. The total cement production in China last year exceeded 2.3 billion tons. Therefore, in the 21st century, countries have begun to pay attention to carbon dioxide emission reduction, storage, and dissipation technologies. However, the existing carbon dioxide curing cost is relatively high and the on-site implementation is difficult.

[0003] Some preparation methods of CO2 foam cement-based materials and concrete and indoor mixing devices are disclosed in the prior art, but there is no provision for the geotechnical engineering application of CO2 foam in cement soil and the process for realizing on-site curing of cement soil with carbon dioxide. Summary of the Invention

[0004] The object of the present invention is to address the above deficiencies and provide a construction device and a construction method for a carbon dioxide water-based foam cement-soil mixing pile. The mixing pile drilling rig is used in combination with a foaming machine for preparing carbon dioxide water-based foam. The foaming machine and the cement slurry preparation device are connected to the pumping and transportation device through parallel pipelines. The pumping and transportation device transports carbon dioxide water-based foam and cement slurry to the mixing pile drilling rig. By means of the mixing pile construction method, an underground carbon dioxide curing environment for the cement-soil pile is realized, achieving distributed storage of carbon dioxide in combination with underground engineering.

[0005] To achieve the above object, the present invention is realized through the following technical solutions: In a first aspect, the present invention provides a construction device for a carbon dioxide water-based foam cement-soil mixing pile, including a mixing pile drilling rig, a cement slurry preparation device, a foam production device, and a pumping and transportation device; Both the cement slurry preparation device and the foam production device are connected to the pumping and transportation device, and transport cement slurry and carbon dioxide water-based foam to the mixing pile drilling rig through a conveying pipeline; A vertical mixing shaft and a mixing head vertically installed at the lower part of the mixing shaft are installed on the mixing pile drilling rig. A slurry conveying pipe is arranged inside the mixing shaft; the top of the slurry conveying pipe is connected to two conveying pipelines through a conversion valve, and the bottom is connected to a nozzle arranged on the side of the bottom of the mixing shaft.

[0006] Further, the foam production device includes a carbon dioxide gas cylinder and a foaming machine. The carbon dioxide gas cylinder is connected to the foaming machine and is used to supply carbon dioxide to the foaming machine. The foaming machine is connected to a pumping and transportation device and is used to produce carbon dioxide water-based foam.

[0007] Further, the mixing pile drill also includes a hoisting winch and a pile frame. The lifting rope of the hoisting winch bypasses the top of the pile frame and is connected to the mixing shaft. The mixing shaft moves up and down along the chute on the pile frame under the traction of the lifting rope.

[0008] Further, the mixing shaft is fixedly connected to the slider, and the slider is slidably connected to the chute, so that the mixing shaft can move up and down along the chute under the traction of the lifting rope.

[0009] Further, the mixing pile drill also includes a guiding frame. The hoisting winch and the pile frame are respectively installed at both ends of the guiding frame. The pile frame is vertically connected to the guiding frame, and a support rod is also connected between the pile frame and the guiding frame.

[0010] Further, considering that carbon dioxide is likely to form carbonic acid and is corrosive, the inner walls of the foam production device, the pumping and transportation device, the conveying pipeline, the slurry conveying pipe and the nozzle of the present invention are all provided with anti-corrosion coatings.

[0011] In a second aspect, the present invention also provides a construction method for a carbon dioxide water-based foam cement-soil mixing pile. Based on the construction device described in the first aspect, the construction method includes: Screen the types of foaming agents and foam stabilizers through the foam production device, and optimize the concentration parameters and foam-slurry ratio parameters; Measure the carbon dioxide gas injection volume according to the optimized foam-slurry ratio parameters to obtain the optimal carbon dioxide gas injection volume; Prepare carbon dioxide water-based foam on site according to the selected best types of foaming agents and foam stabilizers and the optimized concentration parameters, and conduct a foaming effect test; Determine the installation position of the mixing pile drill according to the construction requirements and install the mixing pile drill; Prepare cement slurry on site according to a preset ratio; Sink and rotate the mixing shaft to cut and loosen the deep soil mass with the mixing head. When the mixing shaft sinks to the designed depth, open the switching valve, connect the conveying pipeline for transporting carbon dioxide water-based foam, turn on the pumping and transportation device, and inject the carbon dioxide water-based foam into the loosened deep soil mass through the nozzle, while spraying and rotating; Connect the conveying pipeline for transporting cement slurry through the switching valve, lift and rotate the mixing shaft at a set lifting speed, and spray cement slurry through the nozzle during the lifting process. The mixing head fully mixes the carbon dioxide water-based foam, the cement slurry and the loosened soil mass; Repeat the sinking and lifting agitation. After reaching the set number of times and time, perform the final agitation and lifting of the mixing shaft. The operation method of the final agitation and lifting is as follows: After the preset agitation time, the cement soil begins to solidify initially. After each re-agitation of one mixing pile height, the mixing head re-agitates the next section of cement soil simultaneously, and so on to complete the operation of the final agitation and lifting stage of the cement soil mixing pile.

[0012] Further, screen the types of foaming agents and foam stabilizers through the foam production device, and optimize the concentration parameters and foam slurry ratio parameters, including: Use a foaming machine to conduct preliminary experiments on common foaming agents and foam stabilizers, and conduct a preliminary screening of foaming agents and foam stabilizers based on the stable time and foaming height of water-based foam. Prepare cement slurry according to the specific engineering requirements of the water-cement ratio of the cement soil mixing pile; according to different foam slurry ratios, make carbon dioxide water-based foam cement slurry from carbon dioxide water-based foam and cement slurry. Carry out range analysis of the performance indicators of carbon dioxide water-based foam cement slurry, and select the best types of foaming agents and foam stabilizers according to the analysis results, and optimize the concentration parameters and foam slurry ratio parameters. The performance indicators include the specific gravity, fluidity, consistency, bleeding rate, volume shrinkage rate of the stone body, density of the stone body, uniaxial compressive strength at 7 days and 28 days, etc. of the slurry.

[0013] Further, prepare carbon dioxide water-based foam on-site according to the selected best types of foaming agents and foam stabilizers and the optimized concentration parameters, and conduct a foaming effect test, including: Prepare the foaming liquid according to the selected best types of foaming agents and foam stabilizers and the optimized concentration parameters. Turn on the water pump of the foaming machine and control the water pump speed to the set rotation speed. The foaming liquid enters the foaming pipe from the self-storage liquid pipe in the foaming machine. Open the switch of the carbon dioxide gas cylinder, adjust the primary pressure reducing valve on the carbon dioxide gas cylinder so that the output air pressure does not exceed 0.5 Mpa; adjust the secondary pressure reducing valve in the foaming machine to precisely control the foaming air pressure, and control the foaming air pressure not to exceed 0.02 Mpa. Carbon dioxide flows into the foaming pipe through the gas storage pipe and mixes with the foaming liquid. Turn off the water pump and start the foaming operation; the foaming liquid flows through the throttler from the foaming pipe into the bubble blowing port, and the prepared carbon dioxide water-based foam flows out through the bubble outlet connected to the foam outlet pipe. Use the foaming multiple and foaming half-life to detect 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 used when the foam volume dissipates to half of the original volume, which characterizes the foam stability.

[0014] Further, determine the installation position of the mixing pile drilling rig according to the construction requirements and install the mixing pile drilling rig, including: Set out the pile positions according to the traverse points and leveling points transferred by the planning survey unit; before setting out the pile positions, review the traverse points and leveling points transferred by the planning survey unit, and use them after confirmation. Measure and set the construction contour line of the soil-cement mixing pile on site. Excavate the construction trench according to the on-site soil-cement mixing pile contour line. Set the positioning control line of the soil-cement mixing pile on the edge of the trench. Set pile position marks at regular intervals on the positioning control line of the soil-cement mixing pile. Install the mixing pile drilling rig according to the pile position marks. The deviation between the mixing pile drilling rig and the pile position shall not be greater than 50 mm. During installation, observe through a theodolite or a plumb bob to ensure that the perpendicularity accuracy of the mixing shaft is not less than 1 / 200.

[0015] Furthermore, the construction method further includes: After completing the mixing construction of one pile position, clean the residual cement slurry in all pipelines and the debris adhering to the mixing head. Repeat the screening of the types of foaming agents and foam stabilizers, the measurement of the carbon dioxide gas addition amount, the on-site preparation of carbon dioxide water-based foam and the inspection of the foaming effect, and then carry out the mixing construction of the next pile position.

[0016] Compared with the prior art, the beneficial effects of the present invention are: The present invention combines the mixing pile drilling rig with the cement slurry preparation device and the foaming machine for preparing carbon dioxide water-based foam, so that the modified soil-cement mixing pile drilling rig can realize the construction and piling of carbon dioxide water-based foam soil-cement piles; by means of the mixing pile construction method, an underground carbon dioxide curing environment for soil-cement piles is realized, achieving distributed storage of carbon dioxide in underground engineering. The construction method of the present invention realizes the on-site carbon dioxide curing conditions for soil-cement mixing piles. Carbon dioxide curing accelerates the carbonation of cement and improves the degree of carbonation, greatly enhancing the early strength of soil-cement mixing piles and shortening the curing period; at the same time, the bubble holes of carbon dioxide water-based foam have considerable carbon storage and carbon sequestration capabilities, realizing underground storage of carbon dioxide. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic structural diagram of a carbon dioxide water-based foam soil-cement mixing pile provided in Embodiment 1 of the present invention; In the figure: 1, guide frame; 2, hoisting winch; 3, pile frame; 4, mixing head; 5, mixing shaft; 6, lifting rope; 7, support rod; 8, cement slurry preparation device; 9, carbon dioxide gas cylinder; 10, foaming machine; 11, nozzle; 12, pumping and transportation device; 13, conveying pipeline; 14, chute; 15, slurry pipe; 16, slider. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0018] The preferred embodiments of the present invention will be described in more detail below in conjunction with the accompanying drawings and specific embodiments.

[0019] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more.

[0020] In the description of the present invention, it should be noted that unless otherwise clearly specified and limited, the terms "installed", "connected", "connected" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific situations.

[0021] Embodiment 1: This embodiment provides a construction device for a carbon dioxide water-based foam cement-soil mixing pile, including a mixing pile drilling rig, a cement slurry preparation device 8, a foam production device, and a pumping and transportation device 12.

[0022] As Figure 1 shown, in this embodiment, the mixing pile drilling rig includes a guiding frame 1, a hoisting winch 2, a pile frame 3, and a mixing shaft 5; the hoisting winch 2 is installed at one end of the guiding frame 1, the pile frame 3 is vertically fixed at the other end of the guiding frame 1, and a support rod 7 is also connected between the pile frame 3 and the guiding frame 1; the lifting rope 6 of the hoisting winch 2 bypasses the top of the pile frame 3 and is connected to the mixing shaft 5. The mixing shaft 5 is fixedly connected with a slider 16, and the slider 16 is slidably connected with a chute 14, so that the mixing shaft 5 moves up and down along the chute 14 on the pile frame 3 under the traction of the lifting rope 6. The mixing shaft 5 is vertically installed, a mixing head 4 is vertically installed at the lower part of the mixing shaft 5, and a nozzle 11 is provided on the bottom side; a slurry conveying pipe 15 is arranged inside the mixing shaft 5, the top of the slurry conveying pipe 15 is connected to two conveying pipes 13 through a conversion valve (not shown in the figure), and the bottom is connected to the nozzle 11.

[0023] In this embodiment, the foam production device includes a carbon dioxide gas cylinder 9 and a foaming machine 10. The carbon dioxide gas cylinder 9 is connected to the foaming machine 10 to supply carbon dioxide to the foaming machine 10. The foaming machine 10 is connected to a pumping and transportation device 12 to produce carbon dioxide-based water foam. After the carbon dioxide-based water foam is produced by the foaming machine 10, it passes through the pumping and transportation device 12 and is connected to a slurry conveying pipe 15 in a stirring shaft 5 through a conveying pipe 13. In this embodiment, the cement slurry preparation device 8 is used for preparing cement slurry. After the cement slurry is produced by the cement slurry preparation device 8, it passes through the pumping and transportation device 12 and is connected to the slurry conveying pipe 15 in the stirring shaft 5 through a conveying pipe 13. The switching valve controls the switching of the two conveying pipes 13 for conveying cement slurry and carbon dioxide-based water foam.

[0024] Considering that carbon dioxide is likely to form carbonic acid and is corrosive, in this embodiment, all the pipes and devices inside the foaming machine 10, the conveying pipe 13, the slurry conveying pipe 15, the pumping and transportation device 12, and the nozzle 11 are subjected to corrosion resistance treatment, such as spraying an anti-corrosion coating.

[0025] Embodiment 2: This embodiment provides a construction method for a carbon dioxide-based water foam cement-soil mixing pile. Based on the carbon dioxide-based water foam cement-soil mixing pile construction device described in Embodiment 1, the construction method specifically includes the following steps: Step 1: Screening experiment of foaming agent and foam stabilizer The foaming machine 10 is used to conduct preliminary experiments on common foaming agents and foam stabilizers. According to the stability time and foaming height of the water-based foam, the initial screening of the foaming agent and foam stabilizer is carried out. According to the specific engineering requirements of the water-cement ratio of the cement-soil mixing pile, cement slurry is prepared. According to different foam-slurry ratios, carbon dioxide-based water foam and cement slurry are made into carbon dioxide-based water foam cement slurry. Conduct a range analysis of four performance indicators of the carbon dioxide-based water foam cement slurry, such as 7-day compressive strength, density, stone formation rate, and foam stability time. Considering the range results comprehensively, the best types of foaming agent and foam stabilizer, as well as the optimization of concentration and foam-slurry ratio parameters, are selected. A tea saponin foaming agent with a concentration of 4 g / L and a sodium dodecyl benzene sulfonate foam stabilizer with a concentration of 5 g / L are used. The present invention completes the optimization of the foaming agent and foam stabilizer through orthogonal experiments and range analysis, has fewer test groups than a more comprehensive test, and the test results are scientific and accurate through the arrangement of the influence degree of the range of different properties of the slurry, and the optimization process is efficient.

[0026] Select the foam solution ratio as follows: tea saponin as the foaming agent with a concentration of 4 g / L, sodium dodecyl benzene sulfonate as the foam stabilizer with a concentration of 5 g / L. Design a comprehensive experiment with different initial water-cement ratios (1:2.2, 1:2.4, 1:2.6, 1:2.8) and slurry-foam ratios (3:1, 5:1, 7:1). Conduct slurry performance tests (7-day compressive strength, density, stone formation rate, foam stability time) on the prepared slurry. Optimize the initial water-cement ratio and slurry-foam ratio parameters according to the slurry performance requirements. Through the comprehensive analysis of the effects of different water-cement ratios (slurry-foam ratios) on the strength and density of cement slurry at the same slurry-foam ratio (water-cement ratio), as shown in Table 1 and Table 2, a "good average value" of the water-cement ratio (slurry-foam ratio) can be obtained. That is, at this water-cement ratio (slurry-foam ratio), the density of the cement slurry is relatively low, the strength is relatively high, the engineering performance is excellent, and the cost can also be controlled. The method is to make the percentage reduction of the maximum and minimum values of density and strength be 0% and 100% respectively. Draw two broken lines according to the percentage reduction, and the water-cement ratio (slurry-foam ratio) corresponding to the intersection point is the good average value of the initial water-cement ratio (slurry-foam ratio).

[0027] Table 1: Effects of Different Water-Cement Ratios on the Density and 7-Day Compressive Strength of Cement Slurry

[0028] Table 2: Effects of Different Slurry-Foam Ratios on the Density and 7-Day Compressive Strength of Cement Slurry

[0029] Step 2: Measurement of Carbon Dioxide Gas Injection Volume Based on the optimal slurry-foam ratio parameter of carbon dioxide water-based foam cement slurry, conduct a gas injection volume test to examine the fluidity performance of the carbon dioxide water-based foam cement slurry. According to the fluidity performance requirements, obtain the optimal carbon dioxide gas injection volume of the carbon dioxide water-based foam cement slurry. The density of the carbon dioxide water-based foam is related to the gas injection volume and the water pump speed. The larger the gas injection volume, the more carbon dioxide gas in the foam per unit volume, and 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. In this embodiment, the foaming machine 10 in this preparation step controls the foam density by adjusting the water pump speed instead of the gas injection volume parameter. Compared with the gas injection volume, the water pump speed parameter is easier to control and the effect is more obvious.

[0030] Step 3: On-Site Preparation of Carbon Dioxide Water-Based Foam According to the selected optimal types of foaming agents and foam stabilizers and the optimized concentration parameters, prepare the foaming liquid. Turn on the water pump and control the water pump speed at 70 revolutions per second. The foaming liquid enters the foaming pipe from the self-storage liquid pipe in the foaming machine 10. Open the switch of the carbon dioxide gas cylinder 9, adjust the primary pressure reducing valve connected to the carbon dioxide gas cylinder 9 so that the output air pressure does not exceed 0.5 MPa, and adjust the secondary pressure reducing valve in the foaming machine 10 to precisely control the foaming air pressure, ensuring that the foaming air pressure does not exceed 0.02 MPa. Carbon dioxide flows into the foaming pipe through the gas storage pipe and mixes with the foaming liquid. Turn off the water pump and start the foaming operation. The foaming liquid flows from the foaming pipe through the throttle into the bubble blowing port, and the prepared carbon dioxide foam flows out through the bubble outlet connected to the bubble outlet pipe.

[0031] Step 4: Foaming effect inspection Use the foaming multiple and the foaming half-life to detect the foaming effect. The foaming multiple is the ratio of the foam volume to the volume of the foaming liquid, representing the foaming ability; the foaming half-life is the time used when the foam volume dissipates to half of the original volume, representing the foam stability. Based on the foam stability and foaming multiple parameters, effective screening of common foaming agents and foam stabilizers was carried out respectively, reducing the number of groups of subsequent foaming agent and foam stabilizer optimization tests.

[0032] In this embodiment, the slurry-to-foam ratio corresponding to the intersection of the two broken lines drawn in Step 1 is approximately 4.5:1, and the water-cement ratio is 1:2.4. At this time, the strength of the carbon dioxide foam cement slurry stone body is not low and the density of the stone body can also be controlled. When the slurry-to-foam ratio is higher than 4.5:1 and the water-cement ratio is higher than 1:2.4, the strength of the stone body is lower; when the slurry-to-foam ratio is lower than 4.5:1 and the water-cement ratio is lower than 1:2.4, the density of the stone body is higher. Therefore, a slurry-to-foam ratio of 4.5:1 and a water-cement ratio of 1:2.4 are selected, and their density and strength properties are both good.

[0033] Step 5: Pile position lofting Carry out pile position lofting according to the traverse points and level points transferred by the planning survey unit; before pile position lofting, review the traverse points and level points transferred by the planning survey unit, and use them after confirmation.

[0034] Step 6: Excavate the trench Set out the construction contour line of the soil-cement mixing pile on site, excavate the construction trench according to the on-site soil-cement mixing pile contour line, set the positioning control line of the soil-cement mixing pile on the edge of the trench, and set pile position marks every 5 meters on the positioning control line of the soil-cement mixing pile to ensure that the lap between piles meets the specifications and design requirements.

[0035] Step 7: Pile driver positioning Install the mixing pile drilling rig according to the pile position marks, and the deviation between the mixing pile drilling rig and the pile position is not greater than 50 mm; the pile driver should be stable and level, and observed with a theodolite or a plumb bob to ensure that the verticality accuracy of the mixing shaft is not lower than 1 / 200.

[0036] Step 8: Prepare the cement slurry For the cement delivered to the site, weigh it to ensure the weight of the cement. When controlling the preparation of the cement slurry, use the weight ratio method. Put the cement into the mixer according to the preset ratio to prepare the cement slurry on-site.

[0037] Step 9: Sink and mix After the cooling water circulation of the mixer is normal, start the motor of the mixing shaft 5 and loosen the hoisting rope 6 of the hoisting winch 2, so that the mixing shaft 5 sinks along the pile frame 3 to cut the soil. The sinking speed can be controlled by the current monitoring meter of the motor, and the working current should not be greater than the rated current. The mixing head 4 cuts and loosens the deep soil mass; When the mixing shaft 5 sinks to the designed depth, open the switching valve, connect the conveying pipeline 13 for transporting the carbon dioxide water-based foam, turn on the pumping and transporting device 12, and inject the carbon dioxide water-based foam into the loosened deep soil mass through the nozzle 11, while spraying and rotating.

[0038] Step 10: Lift and mix Connect the conveying pipeline 13 for transporting the cement slurry through the switching valve, lift and rotate the mixing shaft 5 at the set lifting speed. During the lifting process, spray the cement slurry through the nozzle 11, and the mixing head 4 fully mixes the carbon dioxide water-based foam, the cement slurry and the loosened soil mass; On the basis of preparing the cement slurry according to the water-cement ratio and specific gravity required by the project, spray the cement slurry into the loosened soil mass during the lifting process of the mixing head 4 and mix it with the carbon dioxide water-based foam. Together, they mainly play the role of filling and replacing the pores in the loosened soil mass; the specific gravity of the carbon dioxide foam cement mixture prepared by the present invention is lower than 1.68 g / cm. Mix the carbon dioxide water-based foam with the cement slurry with a water-cement ratio of (1:2.4) and a foam-slurry ratio of (5:1) to make the carbon dioxide water-based foam cement slurry.

[0039] Step 11: Repeat mixing: Repeat the sinking and mixing in Step 9 and the lifting and mixing in Step 10. The number of mixing times should meet the design requirements. When the mixing shaft 5 is lifted to the designed top elevation, the cement slurry in the aggregate hopper should be just emptied. To make the soil, the carbon dioxide water-based foam and the cement slurry evenly mixed, generally multiple mixings are required.

[0040] Step 12: Final mixing and lifting After mixing for 30 minutes, the cement soil begins to solidify preliminarily. After each re-mixing of a mixing pile height, the mixing head 4 re-mixes the next section of the cement soil at the same time, and so on to complete the operation of the final mixing and lifting stage of the cement soil mixing pile.

[0041] Step 13: Cleaning Inject an appropriate amount of hot water into the aggregate hopper, turn on the pumping and transportation device 12, and clean the residual cement slurry in all pipelines until it is basically clean, and also clean the sundries adhering to the mixing head 4.

[0042] Step 14: Shifting Repeat the above steps 1-4, and then carry out the construction of the next pile.

[0043] The embodiments of the present invention have been described above. The above description is exemplary and not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes are obvious to those of ordinary skill in the art without departing from the scope and technical principle of the described embodiments, and these modifications and changes should also be regarded as the protection scope of the present invention.

Claims

1. A carbon dioxide water-based foam cement soil mixing pile construction device, characterized in that: It includes a mixing pile drilling machine, a cement slurry preparation device (8), a foam production device and a pumping and transportation device (12); The cement slurry preparation device (8) and the foam production device are both connected to the pumping and transporting device (12), and transport the cement slurry and the carbon dioxide water-based foam to the mixing pile drilling rig through the transport pipeline (13); The mixing pile drilling rig is provided with a vertical mixing shaft (5) and a mixing head (4) vertically mounted at the bottom of the mixing shaft (5); the mixing shaft (5) has a built-in slurry delivery pipe (15); the top of the slurry delivery pipe (15) is connected to two delivery pipelines (13) via a conversion valve, and the bottom is connected to a nozzle (11) arranged on the side of the bottom of the mixing shaft (5).

2. The carbon dioxide water-based foamed cement soil mixing pile construction device according to claim 1 is characterized in that: The foam production device comprises a carbon dioxide gas cylinder (9) and a foaming machine (10), wherein the carbon dioxide gas cylinder (9) is connected to the foaming machine (10) to supply carbon dioxide to the foaming machine (10), and the foaming machine (10) is connected to a pumping and transporting device (12).

3. The carbon dioxide water-based foamed cement soil mixing pile construction device according to claim 1 is characterized in that: The mixing pile drilling rig also includes a hoisting winch (2) and a pile frame (3). The hoisting rope (6) of the hoisting winch (2) passes over the top of the pile frame (3) and is connected to the mixing shaft (5). The mixing shaft (5) is lifted and moved along the slide groove (14) on the pile frame (3) by the traction of the hoisting rope (6).

4. The carbon dioxide water-based foamed cement soil mixing pile construction device according to claim 3 is characterized in that: The mixing pile drilling rig further comprises a guide frame (1), the hoisting winch (2) and the pile frame (3) are respectively mounted at two ends of the guide frame (1), the pile frame (3) is vertically connected to the guide frame (1), and a support rod (7) is further connected between the pile frame (3) and the guide frame (1).

5. The carbon dioxide water-based foamed cement soil mixing pile according to claim 1, characterized in that: The inner walls of the foam production device, the pumping and transporting device (12), the delivery pipeline (13), the slurry delivery pipe (15) and the nozzle (11) are all provided with an anti-corrosion layer.

6. A construction method for carbon dioxide water-based foamed cement soil mixing piles, based on the construction device according to any one of claims 1 to 5, characterized in that: The construction method comprises: Screen the types of foaming agents and foam stabilizers through the foam production device, and optimize the concentration parameters and foam-to-slurry ratio parameters; The carbon dioxide addition amount is measured according to the optimized foam-slurry ratio parameters to obtain the optimal carbon dioxide addition amount; According to the selected best foaming agent and foam stabilizer types, as well as the optimized concentration parameters, carbon dioxide water-based foam is prepared on-site and the foaming effect is tested; Determine the installation location of the mixing pile drilling rig according to the construction requirements and install the mixing pile drilling rig; Prepare cement slurry on site according to preset proportions; The stirring shaft (5) is sunk and rotated to make the stirring head (4) cut and loosen the deep soil. When the stirring shaft (5) is sunk to the designed depth, the switching valve is opened to connect the delivery pipeline (13) for delivering the carbon dioxide water-based foam, and the pumping and transporting device (12) is opened to inject the carbon dioxide water-based foam into the loosened deep soil through the nozzle (11), while rotating. The conveying pipe (13) for conveying cement slurry is connected through a conversion valve, and the stirring shaft (5) is lifted and rotated according to a set lifting speed. During the lifting process, the cement slurry is sprayed through the nozzle (11), and the stirring head (4) fully mixes the carbon dioxide water-based foam, the cement slurry and the loose soil; The stirring is repeated by sinking and lifting. After reaching the set number of times and time, the stirring shaft (5) is lifted for final stirring.

7. The construction method of carbon dioxide water-based foamed cement soil mixing pile according to claim 6, characterized in that: The method of screening the types of foaming agents and foam stabilizers by using a foam production device and optimizing concentration parameters and foam-to-slurry ratio parameters includes: A foaming machine (10) is used to conduct a preliminary experiment on commonly used foaming agents and foam stabilizers, and preliminary screening of the foaming agents and foam stabilizers is performed based on the stability time and foaming height of the water-based foam; Prepare cement slurry according to the engineering requirements of water-cement ratio of cement soil mixing pile; prepare carbon dioxide water-based foam and cement slurry into carbon dioxide water-based foam cement slurry according to different foam-slurry ratios; Carry out range analysis of the performance indicators of carbon dioxide water-based foam cement slurry, select the best type of foaming agent and foam stabilizer based on the analysis results, and optimize the concentration parameters and foam ratio parameters.

8. The construction method of carbon dioxide water-based foamed cement soil mixing pile according to claim 6, characterized in that: The method of preparing carbon dioxide water-based foam on site and testing the foaming effect according to the selected best foaming agent type and foam stabilizer type and the optimized concentration parameters includes: Modulating the foaming liquid according to the selected best foaming agent and foam stabilizing agent types and the optimized concentration parameters; Turning on the water pump of the foaming machine (10) and controlling the speed of the water pump to a set speed, so that the foaming liquid enters the foaming tube from the self-storage liquid tube in the foaming machine (10); Turn on the switch of the carbon dioxide gas cylinder (9), adjust the primary pressure reducing valve on the carbon dioxide gas cylinder (9) so that the output gas pressure does not exceed 0.5 MPa; adjust the secondary pressure reducing valve in the foaming machine (10) to accurately control the foaming gas pressure, and control the foaming gas pressure to not exceed 0.02 MPa; The carbon dioxide flows into the foaming pipe through the gas storage pipe and mixes with the foaming liquid. The water pump is turned off and the foaming operation is started. The foaming effect is tested by the foaming multiple and the foaming half-life.

9. The construction method of carbon dioxide water-based foamed cement soil mixing pile according to claim 6, characterized in that: The method of determining the installation position of the mixing pile drilling rig according to the construction requirements and installing the mixing pile drilling rig includes: Stake out the pile positions according to the guide points and leveling points handed over by the planning survey unit; The construction contour line of the cement-soil mixing pile is measured and set on site, and the construction trench is excavated according to the contour line of the cement-soil mixing pile on site. The positioning control line of the cement-soil mixing pile is set at the edge of the trench, and the pile position marks are set at set intervals on the positioning control line of the cement-soil mixing pile; Install the mixing pile drill according to the pile position markings. The deviation between the mixing pile drill and the pile position should not exceed 50mm. During installation, observe with a theodolite or plumb bob to ensure that the verticality accuracy of the mixing shaft is not less than 1 / 200.

10. The construction method of carbon dioxide water-based foamed cement soil mixing pile according to claim 6, characterized in that: The construction method also includes: After completing the mixing construction at one pile position, clean the remaining cement slurry in all pipelines and the debris adhering to the mixing head (4); After repeatedly screening the types of foaming agents and foam stabilizers, measuring the amount of carbon dioxide added, preparing carbon dioxide water-based foam on site and testing the foaming effect, the mixing construction of the next pile position can be carried out.

Images