Residue soil improvement method in earth pressure balance shield construction

Abstract

The invention provides a muck improvement method in earth pressure balance shield construction. Comprising the following steps: S1, obtaining cutting process parameters based on an actual process of cutting a reinforced concrete pile by a shield tunneling machine; s2, based on the environment temperature condition generated by shield cutting of the concrete pile in the cutting process parameters, an experiment is conducted under the environment temperature condition generated by simulating shield cutting of the concrete pile, performance parameters of a modifier are determined, and the modifier comprises foam and bentonite; s3, performing a foam performance test to determine foam performance parameters; s4, bentonite performance testing is carried out to determine bentonite performance parameters; s5, measuring the flow plasticity of the improved soil by using a slump test; s6, determining the residue carrying property of the improved soil; and S7, the optimal muck improvement scheme for improving the working efficiency of cutting the reinforced concrete piles by the shield tunneling machine is obtained. The durability and adaptability of the muck improvement effect are enhanced, tool abrasion is reduced, and the cutting efficiency of the shield tunneling machine is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of tunnel engineering, and in particular, to a method for improving muck in earth pressure balance shield construction. Background Art

[0002] The earth pressure balance shield technology, with its high safety, minimal disturbance to the formation, and high degree of mechanization, has increasingly become the dominant method for urban tunnel construction. The core of this technology lies in improving the muck excavated by the cutterhead to reach a plastic flow state, thereby constructing an effective pressure balance inside the soil chamber and ensuring the continuous and smooth advancement of the shield machine. In areas where urban buildings and structures are dense, obstacles such as reinforced concrete pile foundations are often encountered in the shield tunneling path. Given that conventional shield machines usually do not have the ability to directly cut piles, traditional practices often involve pre-treatment measures such as demolishing existing buildings (structures), pulling out piles on the ground, excavating vertical shafts, and removing pile foundations. However, compared with these traditional methods, the direct cutting of piles by the shield machine exhibits multiple advantages such as less interference to the surrounding environment, high cost-effectiveness, and short construction period, with significant social and economic benefits.

[0003] The cutting of reinforced concrete piles is different from that of ordinary rock and soil masses. The challenge lies in how to ensure the safety of the shield machine and the existing pile body during tunneling, reduce the wear of the shield machine, and improve construction efficiency. Current research mostly focuses on ensuring the safety and stability of the shield machine when cutting reinforced concrete piles through mechanical modification measures such as optimizing the cutterhead and tool design. From the perspective of muck improvement to enhance the working efficiency of the shield machine in cutting reinforced concrete piles, relevant technical solutions are still rare.

[0004] The existing technology has the following deficiencies in the muck improvement of the shield machine cutting reinforced concrete piles: (1) Lack of pertinence in the muck improvement plan: The current methods for muck improvement in shield construction are mostly aimed at ordinary rock and soil masses, and there is a lack of specially designed muck improvement plans for cutting special materials such as reinforced concrete piles. This results in insignificant improvement effects when cutting reinforced concrete piles, and cannot effectively reduce tool wear and improve cutting efficiency. (2) The influence of construction temperature on the improved soil is significant: The shield machine generates a certain amount of heat during construction, and these heats may have an adverse impact on the mechanical properties of the improved soil. Especially when cutting reinforced concrete piles, due to the slow tunneling speed, the heat accumulation is more significant, and the existing technology fails to effectively solve this problem, resulting in a reduction in the improvement effect. (3) Difficulty in discharging reinforced concrete residues: The residues generated from cutting reinforced concrete piles are large in volume and high in density, and are prone to accumulate in the soil chamber, affecting the normal advancement of the shield machine. The existing technology lacks effective means to ensure the effective discharge of these residues, thereby avoiding blockages and stagnations during construction. Summary of the Invention

[0005] According to the above-mentioned technical problem that the mechanical properties of the existing improved soil are affected by the construction temperature of the shield machine, a method for improving the muck in earth pressure balance shield construction is provided to improve the work efficiency, safety and stability of the shield machine when cutting reinforced concrete piles.

[0006] The technical means adopted in the present invention are as follows:

[0007] A method for improving the muck in earth pressure balance shield construction includes the following steps:

[0008] S1. Based on the actual process of the shield machine cutting reinforced concrete piles, obtain the cutting process parameters;

[0009] S2. Based on the ambient temperature conditions generated by the shield cutting concrete piles in the cutting process parameters, conduct experiments under the ambient temperature conditions simulated by the shield cutting concrete piles and determine the performance parameters of the modifier. The modifier includes foam and bentonite;

[0010] S3. Conduct foam performance tests to determine the foam performance parameters;

[0011] S4. Conduct bentonite performance tests to determine the bentonite performance parameters;

[0012] S5. Use the slump test to measure the fluidity and plasticity of the improved soil to determine the first injection range;

[0013] S6. Measure the slag-carrying capacity of the improved soil to determine the second injection range;

[0014] S7. Take the intersection of the first injection range and the second injection range to obtain the optimal injection ratio. The scheme that meets the S3 foam performance parameters, S4 bentonite performance parameters and the optimal injection ratio is the optimal muck improvement scheme for improving the work efficiency of the shield machine when cutting reinforced concrete piles.

[0015] Furthermore, S1 specifically includes the following steps:

[0016] S11. Statistically record the propulsion speed v of the shield machine when cutting concrete piles and the tunneling length L of the shield machine, and calculate the average propulsion time t of each ring of segments of the shield machine, t = L / v;

[0017] S12. Collect the improved soil at the slag discharge port of the screw conveyor of the shield machine and measure the temperature to obtain the temperature T of the improved soil during the shield cutting process;

[0018] S13. Wash and screen the improved soil discharged from the screw conveyor to obtain the shape and size of the reinforced concrete residues.

[0019] Furthermore, S3 specifically includes the following steps:

[0020] S31. Prepare foaming agent solutions with different concentrations, foam them using the air flow method, and transfer the generated foam to an incubator with an operation hole for testing the foam performance parameters; the foam performance parameter tests include the foam expansion ratio test and the half-life test.

[0021] S32. By comparing the foam expansion ratios and half-lives of foaming agent solutions with different concentrations, select a high-performance foam that can resist the influence of the shield cutting temperature; the high-performance foam is a foam with a foam expansion ratio between 5 and 30 times and a half-life greater than 5 minutes.

[0022] Further, the foam expansion ratio test in S31 specifically includes the following steps:

[0023] Place the measuring cup on the electronic balance and zero it.

[0024] Fill the measuring cup with the generated foam and weigh it to obtain the mass of the foam.

[0025] Neglect the mass of the gas in the foam, and since the density of the foaming agent solution is approximately 1.0 g / ml, obtain the volume of the foaming agent solution.

[0026] Calculate the foam expansion ratio of the foam according to the following formula:

[0027]

[0028] In the formula: FER is the foam expansion ratio of the foam; V F is the volume of the foam under the foaming pressure; V L is the volume of the foaming agent solution.

[0029] The half-life test in S31 specifically includes the following steps:

[0030] Place the funnel on the electronic balance and zero it.

[0031] Inject the generated foam into the funnel, place it on the electronic balance, and read the mass of the foam.

[0032] Place the funnel on the tripod, and then place the measuring cup on the electronic balance under the tripod, align the funnel with the center of the measuring cup, and record the time it takes for the mass of the foam-dissipated liquid in the measuring cup to reach half of the initial foam mass, which is the half-life of the foam.

[0033] Further, S4 specifically includes the following steps:

[0034] S41. Prepare bentonite slurries with different mass concentrations. After mixing bentonite particles with water, use a stirrer to stir and hydrate in a beaker. During the hydration process, seal the beaker with plastic wrap, and transfer the hydrated bentonite slurry to an incubator with an operation hole for testing the bentonite performance parameters; the bentonite performance parameter tests include the funnel viscosity test and the colloid ratio test.

[0035] S42. By comparing the funnel viscosity and colloid ratio of bentonite slurries with different mass concentrations, a high-performance bentonite that can resist the influence of the shield cutting temperature is selected. The high-performance bentonite is bentonite with a funnel viscosity greater than 40 s and a colloid ratio greater than 95%.

[0036] Further, the funnel viscosity test in S41 specifically includes the following steps:

[0037] Use a Marsh funnel viscometer for testing, and evaluate the viscosity of the slurry by recording the outflow time of the slurry in the funnel;

[0038] The colloid ratio test in S41 specifically includes the following steps:

[0039] Pour the slurry into a test tube. After the slurry stands still, calculate the ratio of the sediment layer of the slurry to the total liquid in the test tube, which is the colloid ratio.

[0040] Further, S5 specifically includes the following steps:

[0041] S51. Select a slump cone for the test;

[0042] S52. Mix the foam, bentonite slurry and soil sample, and stir well;

[0043] The dosages of the bentonite slurry and foam in S53 are controlled by the injection ratios SIR and FIR. The formulas for SIR and FIR are as follows:

[0044]

[0045] In the formula: Volume slurry is the volume of the bentonite slurry, Volume foam is the volume of the foam, Volume soil is the volume of the soil sample to be improved;

[0046] S54. Load the improved soil after mixing in S53 into the slump cone in three layers, and each layer needs to be vibrated. After the surface of the soil sample is flush with the top surface of the cylinder, slowly lift the slump cone, and measure the slump after standing still;

[0047] S55. Continuously test the slump of the improved soil in an incubator. The test is carried out at a frequency of recording once every fixed time, and the total test duration is the average propulsion time t of each ring of segments;

[0048] S56. By plotting the curves of the slump changing with time under different conditions of SIR and FIR, select the range of the injection ratios of the foam and bentonite that can keep the improved soil continuously in good fluidity and plasticity;

[0049] The slump of the improved soil increases with the increase of SIR and FIR. When the slump value is in the range of 150 - 250 nn, the corresponding SIR and FIR ranges in this range are the preferred foam and bentonite injection ratio ranges, that is, the first injection range.

[0050] Furthermore, S6 is implemented through a chute experimental device. The chute experimental device includes a chute, which is an isosceles trapezoidal plate that converges from bottom to top. There is a side plate on each of the left and right sides of the chute. The bottom of the chute is rotatably connected to a support base. A gate is provided on the chute, and a collection box is provided at the bottom of the chute.

[0051] Furthermore, S6 specifically includes the following steps:

[0052] S61. Mix the foam, bentonite slurry and soil sample, and stir well. The injection ratio of the bentonite slurry and foam is the preferred foam and bentonite injection ratio range of S56, and the shape and size of the soil sample are the shape and size obtained in S13;

[0053] S62. Add reinforced concrete residue to the improved soil after mixing in S61 and stir well. The proportion formula of the reinforced concrete residue is as follows:

[0054]

[0055] In the formula: mass residue is the mass of the reinforced concrete residue, mass soil is the mass of the improved soil;

[0056] S63. Pour the mixture of S62 into the sample tank of the chute test device, then tilt the chute to a certain slope with the horizontal plane, and remove the gate;

[0057] S64. When the mixture stops flowing along the chute, separate the sliding material in the collection box into improved soil and reinforced concrete residue, and weigh the improved soil and reinforced concrete residue respectively. Calculate the proportion PR1 of the reinforced concrete residue in the first sliding material according to the proportion formula of the reinforced concrete residue;

[0058] S65. Gradually increase the inclination angle of the chute, and at the end of each step, separate and weigh the sliding material in the collection box, and calculate the proportions PR2, PR3, and PR4 of the reinforced concrete residue in the second to fourth sliding materials;

[0059] S66. Define the slag-carrying coefficient C as shown in the following formula. The closer the C value is to 0, the better the slag-carrying property of the improved soil. The closer the C value is to 1, the worse the slag-carrying property of the improved soil;

[0060]

[0061] S67. By plotting the variation curves of the slag-carrying coefficient C under different SIR and FIR conditions, the range of foam and bentonite injection ratios that can make the improved soil have good slag-carrying performance is optimized;

[0062] When the slag-carrying coefficient C is less than 0.5, the corresponding SIR and FIR ranges of this range are the optimized foam and bentonite injection ratio ranges, that is, the second injection range.

[0063] Compared with the prior art, the present invention has the following advantages:

[0064] From the perspective of muck improvement, the present invention proposes a muck improvement method for enhancing the working efficiency of a shield machine in cutting reinforced concrete piles. By obtaining key parameters through on-site investigations, high-performance foam and bentonite are optimized, and a special chute test device is designed to evaluate the slag-carrying capacity of the improved soil. At the same time, the slump test is used to ensure the fluidity and plasticity of the improved soil. This method enhances the durability and adaptability of the muck improvement effect, reduces tool wear, improves the cutting efficiency of the shield machine, ensures the smooth progress of the construction process, and has significant social and economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0066] Figure 1 It is a flowchart of the method of the present invention.

[0067] Figure 2 It is a schematic diagram of the thermostatic chamber of the present invention.

[0068] Figure 3 It is a device diagram for the foam expansion ratio test and the half-life test of the present invention.

[0069] Figure 4 It is a device diagram for the funnel viscosity test and the colloid ratio test of the present invention.

[0070] Figure 5 It is a device diagram for the slump test of the present invention.

[0071] Figure 6 It is a device diagram for the chute test of the present invention.

[0072] Figure 7 It is a front view of the chute test device of the present invention.

[0073] Figure 8 It is a side view of the chute test device of the present invention.

[0074] In the figure: 1, support base; 2, chute; 3, collection box; 4, gate; 5, sample slot. Specific implementation manners

[0075] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments may be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0076] For the purpose of making the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in combination with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part rather than all of the embodiments of the present invention. The description of at least one exemplary embodiment below is actually only illustrative and in no way restricts the present invention and its application or use. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0077] It should be noted that the terms used herein are only for describing specific implementation manners and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or their combinations.

[0078] Unless otherwise specifically stated, the relative arrangements of the components and steps, numerical expressions and values set forth in these embodiments do not limit the scope of the present invention. At the same time, it should be clear that, for the convenience of description, the dimensions of the various parts shown in the drawings are not drawn in actual proportional relationship. Technologies, methods and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, the technologies, methods and devices should be regarded as part of the authorization specification. In all the examples shown and discussed herein, any specific values should be construed as merely exemplary and not as a limitation. Therefore, other examples of the exemplary embodiments may have different values. It should be noted that: like reference numerals and letters denote like items in the following drawings, and thus, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0079] As Figure 1 shown, the present invention provides a method for improving muck in earth pressure balance shield tunneling, including the following steps:

[0080] S1. Based on the actual process of the shield machine cutting reinforced concrete piles, obtain the cutting process parameters;

[0081] Investigate the construction site of the shield machine cutting reinforced concrete piles. It mainly includes:

[0082] S11. Statistically record the propulsion speed v of the shield machine cutting concrete piles and the tunneling length L of the shield machine, and calculate the average propulsion time t of each segment of the shield machine's lining, where t = L / v;

[0083] S12. When the cutter is cutting reinforced concrete, high temperatures will be generated. Collect the improved soil at the slag discharge port of the screw conveyor and measure its temperature to obtain the temperature T of the improved soil during the shield cutting process.

[0084] At this time, the improved soil is discharged from the shield construction site, and the performance parameters and injection ratio of the selected soil conditioner have no basis, which is not suitable for the shield cutting working conditions.

[0085] S13. Wash and screen the improved soil discharged from the screw conveyor to obtain the shape and size of the reinforced concrete residues.

[0086] S2. To simulate the environmental temperature conditions generated by the shield cutting concrete piles and determine the performance parameters of the soil conditioner accordingly, the test is carried out in a constant temperature oven with an operation hole. The constant temperature oven is set to be consistent with the actual environmental temperature T formed by the shield cutting reinforced concrete piles, so as to test the performance of the soil conditioner under this condition. Foam and bentonite are used as the soil conditioner for the muck. During the shield tunneling process, the soil conditioner is injected into the muck through the nozzle of the shield cutter head and fully mixed. The mixture formed by the soil conditioner + muck is the improved soil.

[0087] The improved soil described in S3 - S7 is prepared in the form of indoor tests. Compared with the on-site working conditions, the selection of the soil conditioner and its injection ratio in the improved soil prepared by indoor tests is more reasonable and more beneficial to the shield cutting working conditions.

[0088] S3. Conduct foam performance tests to determine the foam performance parameters;

[0089] Determine the foam performance parameters. Conduct the foam performance test in a constant temperature oven with an operation hole. The specific process of foam performance determination is as follows:

[0090] S31. Prepare foam agent solutions with different concentrations, use the air flow method for foaming, set the foaming pressure to 0.3 MPa, and transfer the generated foam to a constant temperature oven with an operation hole for performance testing. The foam performance parameters include foam expansion ratio testing and half-life testing.

[0091] S32. By comparing the foaming ratios and half-lives of foaming agent solutions with different concentrations, a high-performance foam that can withstand the influence of the shield cutting temperature is selected. The high-performance foam has a foaming ratio ranging from 5 to 30 times and a half-life greater than 5 minutes.

[0092] Testing method for foaming ratio: First, place a measuring cup with a volume of 2000 ml on an electronic balance and zero it. Then, fill the measuring cup with the emitted foam and weigh it to obtain the mass of the foam. Ignoring the mass of the gas in the foam, since the density of the foaming agent solution is approximately 1.0 g / ml, the volume of the foaming agent solution is obtained, and the foaming ratio of the foam is calculated according to formula (1).

[0093]

[0094] In the formula: FER is the foaming ratio of the foam; VF is the volume of the foam under foaming pressure, ml; VL is the volume of the foaming agent solution, ml.

[0095] Testing method for half-life: First, place a funnel with a volume of 500 ml on an electronic balance and zero it. Then, pour the emitted foam into the 500-ml funnel and place it on the electronic balance to read the mass of the foam. Place the funnel on a tripod, and then place a measuring cup on the electronic balance under the tripod so that the funnel is aligned with the center of the measuring cup. Record the time it takes for the mass of the foam-dissipating liquid in the measuring cup to reach half of the initial foam mass, which is the half-life of the foam. Each group of tests is carried out with three parallel tests and the average value is taken.

[0096] S4. Conduct bentonite performance tests to determine bentonite performance parameters;

[0097] The performance test of bentonite is carried out in a constant-temperature oven with an operation hole. The specific process of determining the bentonite performance is as follows:

[0098] S41. Prepare bentonite slurries with different mass concentrations. After mixing bentonite particles with water, use a stirrer to stir at a speed of 600 rpm for 30 min and hydrate in a beaker for 24 h. During the hydration process, seal the beaker with plastic wrap to prevent external impurities from entering during the 24-h standing period. Transfer the hydrated bentonite slurry to a constant-temperature oven with an operation hole for performance testing. Bentonite performance parameters include funnel viscosity testing and colloid ratio testing.

[0099] S42. By comparing the funnel viscosities and colloid ratios of bentonite slurries with different mass concentrations, a high-performance bentonite that can withstand the influence of the shield cutting temperature is selected. The high-performance bentonite has a funnel viscosity greater than 40 s and a colloid ratio greater than 95%.

[0100] Funnel viscosity test method: Use a 1006 Soxhlet funnel viscometer (at 20°C, the water outflow time is 15±0.5s) to test, and evaluate the viscosity of the mud by recording the outflow time of 500ml of mud in the funnel.

[0101] Colloid rate test method: Pour the mud into a 100ml test tube. After the mud is left to stand for 24 hours, the ratio of the mud sediment layer to the total liquid in the test tube (100ml) is the colloid rate.

[0102] S5. Determine the flow plasticity of the improved soil using the slump test;

[0103] Good flow plasticity is essential to maintain the dynamic balance of soil bin pressure and reduce the wear of cutter disc and cutter. Slump test is a fast and low-cost method that can provide good flow plasticity judgment indicators in the laboratory and construction site. The slump test of improved soil is carried out in a thermostatic box with an operating hole. The specific process is as follows:

[0104] S51. Select a standard slump cone with a bottom diameter of 200mm, a top diameter of 100mm and a height of 300mm for testing.

[0105] S52. Mix the foam, bentonite slurry and soil sample and stir thoroughly for 2 minutes.

[0106] The dosage of S53, bentonite slurry and foam is controlled by injection ratio SIR and FIR. The definitions of SIR and FIR are shown in formulas (2) and (3).

[0107]

[0108] Where: Volume slurry (m 3 ) is the volume of bentonite slurry, Volume foam (m 3 ) is the volume of the foam, Volume soil (m 3 ) is the volume of soil sample that needs to be improved.

[0109] S54. Load the fully mixed improved soil into the slump cone in three layers. Each layer needs to be vibrated 25 times. When the surface of the soil sample is flush with the top surface of the cone, slowly lift the slump cone and measure the slump after it is still for 1 minute.

[0110] S55. To test whether the flow plasticity of the improved soil can be maintained for a long time when the shield machine is excavating at a slow pushing speed and a medium speed, the slump of the improved soil is continuously tested in a constant temperature box. The test is recorded every 5 minutes, and the total test time is the average pushing time t of each ring of segments.

[0111] S56. By plotting the variation curves of slump with time under different SIR and FIR conditions, it is found that the slump of the improved soil increases with the increase of SIR and FIR. When the slump value is in the range of 150 - 250 mm, the corresponding SIR and FIR ranges of this range are the preferred foam and bentonite injection ratio ranges, that is, the first injection range.

[0112] S6. Measure the slag - carrying capacity of the improved soil;

[0113] During the process of the shield cutting the reinforced concrete pile, reinforced concrete residues with a relatively high density will be generated. These residues are likely to deposit at the bottom of the soil bin, making it difficult to be discharged through the screw conveyor. Therefore, the improved soil needs to have good slag - carrying performance to ensure that it can move synchronously with the reinforced concrete residues during transportation. For this requirement, a special chute test device is designed to evaluate the slag - carrying capacity of the improved soil. The chute test device mainly consists of a chute, a support base, a collection box and a gate. The main structure of the chute is a trapezoidal steel plate with a top edge of 400 mm, a bottom edge of 800 mm and a height of 1500 mm. Side plates with a height of 100 mm are arranged on the left and right sides of the trapezoidal steel plate. The bottom edge of the trapezoidal steel plate is connected to the support base through a hinge device, so as to realize the function of the chute rotating around the bottom edge. A removable gate is provided 500 mm from the top edge of the trapezoidal steel plate. During the test, the improved soil is placed in the sample tank surrounded by the gate and the side plates. In addition, a collection box is configured at the bottom of the chute to collect the sliding improved soil.

[0114] To ensure the effective discharge of the reinforced concrete residues, the chute test of the improved soil is carried out in a constant - temperature box with an operation hole. The specific process is as follows: 1) Mix the foam, bentonite slurry and soil sample, and stir well for 2 min. The injection ratios SIR and FIR of the bentonite slurry and foam refer to the results of the slump test. 2) Add a certain amount of reinforced concrete residues to the well - mixed improved soil and stir well for 1 min. The shape and size of the reinforced concrete residues are the shape and size obtained in S13. The proportion of the reinforced concrete residues (PR0) is defined as shown in formula (4).

[0115]

[0116] where: mass residue is the mass of the reinforced concrete residues, mass soilTo improve the quality of the improved soil. 3) Pour the mixture into the sample tank of the chute test device, then tilt the chute to a slope of 20° with the horizontal plane and remove the gate. 4) When the mixture stops flowing along the chute, separate the fallen materials in the collection box into improved soil and reinforced concrete residues, weigh these two parts respectively, and calculate the proportion PR1 of the reinforced concrete residues in the first fallen materials according to formula (4). 5) Gradually tilt the chute by an amplitude of 5° to 35°, at the end of each step, separate and weigh the fallen materials in the collection box, and calculate the proportions PR2, PR3, and PR4 of the reinforced concrete residues in the 2nd to 4th fallen materials. 6) Define the slag-carrying coefficient C as shown in formula (5). The closer the C value is to 0, the better the slag-carrying property of the improved soil. On the contrary, the closer the C value is to 1, the worse the slag-carrying property of the improved soil. 7) By plotting the change curves of the slag-carrying coefficient C under different SIR and FIR conditions, optimize the foam and bentonite injection ratio ranges that can make the improved soil have good slag-carrying property. When the slag-carrying coefficient C is less than 0.5, the SIR and FIR ranges corresponding to this range are the optimized foam and bentonite injection ratio ranges, that is, the second injection range.

[0117]

[0118] S7. Take the intersection of the first injection range and the second injection range to obtain the optimal injection ratio. The solution that meets the foam performance parameters S3, the bentonite performance parameters S4, and the optimal injection ratio is the optimal muck improvement solution for improving the working efficiency of the shield machine in cutting reinforced concrete piles.

[0119] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for improving muck in earth pressure balance shield construction, characterized in that It includes the following steps: S1. Based on the actual process of the shield machine cutting reinforced concrete piles, obtain the cutting process parameters; S2. Based on the environmental temperature conditions generated by the shield cutting concrete piles in the cutting process parameters, conduct experiments under the simulated environmental temperature conditions generated by the shield cutting concrete piles and determine the performance parameters of the modifier. The modifier includes foam and bentonite; S3. Conduct foam performance tests to determine foam performance parameters; S4. Conduct bentonite performance tests to determine bentonite performance parameters; S5. Use the slump test to measure the fluidity and plasticity of the improved soil to determine the first injection range; S6. Measure the slag-carrying capacity of the improved soil to determine the second injection range; S7. Take the intersection of the first injection range and the second injection range to obtain the optimal injection ratio. The scheme that meets the S3 foam performance parameters, S4 bentonite performance parameters and the optimal injection ratio is the optimal muck improvement scheme for improving the working efficiency of the shield machine cutting reinforced concrete piles.

2. The soil improvement method in the earth pressure balance shield construction according to claim 1, characterized in that S1 specifically includes the following steps: S11. Statistically analyze the propulsion speed v of the shield machine cutting concrete piles and the tunneling length L of the shield machine, and calculate the average propulsion time t of each ring of segment of the shield machine. t = L / v; S12. Collect the improved soil at the slag discharge port of the screw conveyor of the shield machine and measure the temperature to obtain the temperature T of the improved soil during the shield cutting process; S13. Wash and screen the improved soil discharged from the screw conveyor to obtain the shape and size of the reinforced concrete residue.

3. The muck improvement method in earth pressure balance shield construction according to claim 1, characterized in that, S3 specifically includes the following steps: S31. Prepare foam agent solutions with different concentrations, use the air flow method to generate foam, and transfer the generated foam to a constant temperature box with an operation hole for foam performance parameter tests; the foam performance parameter tests include foam expansion ratio tests and half-life tests; S32. By comparing the foam expansion ratios and half-lives of foam agent solutions with different concentrations, select high-performance foams that can resist the influence of shield cutting temperature; the high-performance foams are foams with a foam expansion ratio between 5 and 30 times and a half-life greater than 5 minutes.

4. The method for improving muck in earth pressure balance shield construction according to claim 3, characterized in that The foam expansion ratio test in S31 specifically includes the following steps: Place the measuring cup on the electronic balance and zero it; Fill the measuring cup with the generated foam and weigh it to obtain the mass of the foam; Neglecting the mass of the gas in the foam, and the density of the foam agent solution is about 1.0 g / ml, obtain the volume of the foam agent solution; Calculate the foam expansion ratio of the foam according to the following formula: Where: FER is the foaming ratio of the foam; V F is the volume of the foam under the foaming pressure; V L is the volume of the foaming agent solution; The half-life test in S31 specifically includes the following steps: Place the funnel on the electronic balance and zero it; Inject the generated foam into the funnel, place it on the electronic balance, and read the mass of the foam; Place the funnel on the tripod, and then place the measuring cup on the electronic balance under the tripod, align the funnel with the center of the measuring cup, and record the time it takes for the mass of the foam-dissipated liquid in the measuring cup to reach half of the initial foam mass, which is the half-life of the foam.

5. The method for improving muck in earth pressure balance shield construction according to claim 1, wherein S4 specifically includes the following steps: S41. Prepare bentonite slurries of different mass concentrations, mix bentonite particles with water, stir them with a stirrer, and hydrate them in a beaker. During the hydration process, seal the beaker with a plastic wrap, and transfer the hydrated bentonite slurry to a thermostatic box with an operating hole to perform a bentonite performance parameter test; the bentonite performance parameter test includes a funnel viscosity test and a colloid rate test; S42. By comparing the funnel viscosity and colloid rate of bentonite slurries of different mass concentrations, high-performance bentonite that can withstand the influence of shield cutting temperature is selected; the high-performance bentonite is bentonite with a funnel viscosity greater than 40s and a colloid rate greater than 95%.

6. The method for improving muck in earth pressure balance shield construction according to claim 5, characterized in that, The funnel viscosity test in S41 specifically includes the following steps: The test was conducted using a Soxhlet funnel viscometer, and the viscosity of the mud was evaluated by recording the time it took for the mud to flow out of the funnel; The colloid rate test in S41 specifically includes the following steps: Pour the mud into a test tube. After the mud is allowed to stand, calculate the ratio of the mud sediment layer to the total liquid in the test tube, which is the colloid rate.

7. The method for improving muck in earth pressure balance shield construction according to claim 1, characterized in that, S5 specifically includes the following steps: S51. Select a slump cone for testing; S52, mixing the foam, bentonite slurry and soil sample, and stirring them thoroughly; The dosage of S53 bentonite slurry and foam is controlled by injection ratio SIR and FIR. The formulas of SIR and FIR are as follows: Where: Volume slurry is the volume of bentonite mud, Volume foam is the volume of foam, Volume soil is the volume of the soil sample to be improved; S54, put the improved soil mixed with S53 into the slump cone in three layers, vibrate each layer, and slowly lift the slump cone after the surface of the soil sample is flush with the top surface of the cylinder, and measure the slump after it stops; S55, continuously testing the slump of the improved soil in a constant temperature box, with the test being recorded once at a fixed time interval, and the total test duration being the average advancement time t of each ring of segments; S56. By drawing the curve of slump change over time under different SIR and FIR conditions, the range of foam and bentonite injection ratio that can enable the improved soil to maintain good fluidity and plasticity is optimized; The slump of improved soil will increase with the increase of SIR and FIR. When the slump value is in the range of 150-250nn, the SIR and FIR range corresponding to this range is the preferred foam and bentonite injection ratio range, that is, the first injection range.

8. The method for improving muck in earth pressure balance shield construction according to claim 1, characterized in that S6 is implemented through a slide experimental device, which includes a slide. The slide is an isosceles trapezoidal plate that converges from bottom to top. A side plate is provided on each of the left and right sides of the slide. The bottom of the slide is rotatably connected to a support base. A gate is provided on the slide, and a collection box is provided at the bottom of the slide.

9. The method for improving muck in earth pressure balance shield construction according to claim 8, characterized in that S6 specifically includes the following steps: S61, mixing the foam, bentonite slurry and soil sample, and stirring them thoroughly, the injection ratio of the bentonite slurry and foam is within the preferred foam and bentonite injection ratio range of S56, and the shape and size of the soil sample are the shape and size obtained in S13; S62. Add the steel-reinforced concrete residue to the improved soil after mixing in S61 and stir thoroughly. The proportion of the steel-reinforced concrete residue is as follows: where: mass residue is the mass of the reinforced concrete residue, and mass soil is the mass of the improved soil; S63, pour the mixture of S62 into the sample trough of the chute test device, then tilt the chute to a certain slope with the horizontal plane, and remove the gate; S64. When the mixture stops flowing along the chute, separate the fallen materials in the collection box into improved soil and reinforced concrete residues, weigh the improved soil and the reinforced concrete residues respectively, and calculate the proportion PR1 of the reinforced concrete residues in the first fallen materials according to the proportion formula of the reinforced concrete residues. S65. Gradually increase the inclination angle of the chute, and at the end of each step, separate and weigh the fallen materials in the collection box, and calculate the proportions PR2, PR3, and PR4 of the reinforced concrete residues in the second to fourth fallen materials. S66. Define the formula for the slag-carrying coefficient C as shown below. The closer the C value is to 0, the better the slag-carrying property of the improved soil; the closer the C value is to 1, the worse the slag-carrying property of the improved soil. S67. By plotting the change curves of the slag-carrying coefficient C under different SIR and FIR conditions, optimize the range of foam and bentonite injection ratios that can make the improved soil have good slag-carrying properties. When the slag-carrying coefficient C is less than 0.5, the corresponding SIR and FIR ranges of this range are the optimized foam and bentonite injection ratios, that is, the second injection range.

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