A diaphragm wall trench hole mud protection wall stability analysis method
By simulating mud wall protection using a CFD-DEM model, the shortcomings of existing mud wall stability analysis technologies are addressed, enabling accurate simulation of mud wall protection and improving construction safety and project quality.
Patent Information
- Application Number
- CN202311544555.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-11-20
- Publication Date
- 2026-08-25
- Estimated Expiration
- 2043-11-20
AI Technical Summary
Existing technologies fail to accurately consider the permeability characteristics and mud cake formation of slurry when analyzing the stability of diaphragm wall construction, resulting in flawed research results and affecting construction safety.
The discrete element method and computational fluid dynamics method are coupled. The CFD-DEM model is used to simulate mud wall protection, and the mechanical characteristics of mud skin are described by the strain softening model to conduct stability analysis of mud wall protection.
It achieves accurate simulation of mud wall protection, improves construction safety and project quality, and reduces construction costs.
Smart Images
Figure CN117634271B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of underground continuous wall engineering technology, and particularly relates to a method for analyzing the stability of mud slurry wall protection in anti-seepage wall trenches. Background Technology
[0002] With the increasing demand for energy security and the continuous advancement of dam construction technology, more and more structures are being built under complex geological conditions. Consequently, the depth of diaphragm walls is constantly increasing, sometimes reaching hundreds of meters. During excavation, accidents such as instability and collapse frequently occur, making construction extremely difficult. Mud wall support is often used during trenching to maintain the stability of the working face.
[0003] The analysis of the stability of mud wall is generally conducted using the limit equilibrium method under plane strain conditions. This can be extended to three-dimensional studies by further considering end effects and soil arching. However, the limit equilibrium method, due to its inherent limitations, may not yield a rigorous solution. Current analytical techniques often neglect the permeability characteristics of the mud and the formation of mud cake by adding mud pressure. The presence of mud has a significant impact on trenching results, leading to certain deficiencies in the research findings. Summary of the Invention
[0004] To address the aforementioned technical problems, this invention proposes a method for analyzing the stability of mud slurry wall protection in anti-seepage wall trenches, thereby solving the problem that existing technologies cannot accurately analyze the stability of mud slurry wall protection.
[0005] To achieve the above objectives, the present invention provides a method for analyzing the stability of mud slurry wall protection in anti-seepage wall trenches, comprising the following steps:
[0006] Collect information on strata soil samples and mud wall protection materials, and construct a discrete element model based on the strata soil sample information;
[0007] The discrete element model is run under gravity conditions, and a formation model is obtained when it reaches a stable state.
[0008] The geological model is subjected to trenching and a guide wall is generated to obtain a construction environment model;
[0009] The mud structure model is obtained by coupling the mud wall protection material information based on the CFD-DEM model.
[0010] The mud structure model is imported into the construction environment model to obtain the mud wall protection model. Stability calculation is performed based on the mud wall protection model to obtain the stability of the mud wall protection.
[0011] Optionally, the method for constructing the discrete element model includes:
[0012] Based on existing literature, the particle size distribution of the soil samples was determined. The particle size amplification method was used to preprocess the particle data. Based on the preprocessed particle data, a soil sample model was constructed.
[0013] A wall is built around the soil sample model as a fixed boundary, and the top wall is deleted as a free boundary. Based on the layered filling method, soil sample particles with fixed gradation are randomly generated in the boundary area to obtain a discrete element model.
[0014] Optionally, the criteria for determining whether a stable state has been reached include:
[0015] Under gravity conditions, when the ratio of the forces acting on each soil particle in the relative directions reaches 1e... -5 When the time is right, the discrete element model reaches a stable state.
[0016] Optionally, the method for performing trenching and generating guide walls includes:
[0017] Based on the target depth, soil particles are removed from the center of the stratum model to obtain a trench, and a concrete guide wall is generated on top of the trench.
[0018] Optionally, when constructing a discrete element model using soil sample particles, a parallel cementation model can be used to simulate the cementation effect of silt and clay particles.
[0019] Optionally, when simulating fluid dynamics during the import of the mud structure model into the construction environment model, particle blockage behavior can be simulated using the DiFelice resistance model.
[0020] Optionally, the simulated fluid dynamics includes fluid phase simulation and particle phase simulation;
[0021] The fluid phase was simulated using the Navier-Stokes equations and conventional continuous medium methods; the mass conservation equations and momentum conservation equations in the Navier-Stokes equations were solved using the finite volume method.
[0022] Particle phase simulation is based on Newton's laws of motion implemented using DEM.
[0023] Optionally, after importing the mud structure model into the construction environment model, a mud skin structure is generated. The softening problem of the mud skin structure is treated as a two-dimensional problem, and then a three-dimensional constitutive model of the contact is simulated through shear law to obtain the mud wall protection model.
[0024] Compared with the prior art, the present invention has the following advantages and technical effects:
[0025] This invention discloses a method for analyzing the stability of mud slurry wall protection in anti-seepage wall trenches. By coupling discrete element method and computational fluid dynamics method, a strain softening model is used to describe the mechanical characteristics of mud skin. Based on the shear test of mud skin, the material parameters of the strain softening model are obtained to achieve accurate simulation of construction conditions and determine the stability of mud slurry wall protection. Attached Figure Description
[0026] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings:
[0027] Figure 1 This is a flowchart of the mud wall stability analysis method according to an embodiment of the present invention;
[0028] Figure 2 This is a flowchart illustrating the CFD-DEM coupling process in an embodiment of the present invention. Detailed Implementation
[0029] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. This application will now be described in detail with reference to the accompanying drawings and embodiments.
[0030] It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.
[0031] like Figure 1 As shown, this invention proposes a method for analyzing the stability of mud slurry wall protection in anti-seepage wall trenches, comprising the following steps:
[0032] Step 1: Establish a discrete element model based on the obtained stratigraphic data.
[0033] Based on existing literature, soil samples were simulated to determine particle size distribution. Data preprocessing was performed using the particle size amplification method, and the gravity was set to 10g to shorten the simulation time. Walls were built around the model as boundaries, and the top wall was removed as a free boundary. The velocity of all four walls was set to 0. The soil was affected by the trench construction within approximately twice the trench area; therefore, a model within approximately twice this range was established, and the wall damping coefficient was set to 1 to eliminate the influence of boundary conditions.
[0034] In discrete element method, a unified DEM model with reasonable stress distribution is always important. Therefore, the layered filling method is used to sample the soil layers and randomly generate particles with fixed gradation within the boundary area.
[0035] Step 2: Servo-based generation of a stable geological model
[0036] It operates under gravity until the ratio of the forces acting on each particle in the relative directions reaches 1e. -5 If the soil sample particles have reached a stable state, then the required soil layer height is retained to generate a three-layer stratum model.
[0037] Step 3: Excavate a trench to create a guide wall.
[0038] Delete a trench at the target depth of the particulate layer in the center of the model. Generate a concrete guide wall with a depth of 2m and a height of 10cm above the soil layer at the top of the trench to maintain the stability of the top soil.
[0039] Step 4: Import the mud model
[0040] Under gravity-free conditions, a brick-filling method was used in the trench to generate uniformly distributed mud particles by creating a "generalized wall," with the particle radius set to 0.09. The thickness of the mud cake was approximately 10–60 mm, therefore the CFD mesh was set slightly beyond the mud penetration range. The mud generation height was set by default to 0.95 times the trench height, and particles slightly above the mud surface were included to simulate the pressure during mud injection.
[0041] Step 5: Calculation and data processing of mud wall stability.
[0042] The calculation requirement is set to a ratio of 1e between the forces acting in opposite directions. -5 Once the system reaches a stable state, the displacement and stress on both sides of the trench are extracted. The stability is described using a safety factor, and the stability analysis is performed using the strength reduction method.
[0043] Furthermore, in the discrete element particle governing equations, a parallel cementation model is used to simulate the cementation of silt and clay particles. The parallel bonds provide the mechanical behavior of the finite-sized binder material deposited between the two contact blocks.
[0044] In computational fluid dynamics, the DiFelice drag model is used to simulate particle clogging behavior. For example... Figure 2 As shown, the fluid phase of the CFD-DEM coupling process is described using the Navier-Stokes equations and conventional continuum methods, with the mass and momentum conservation equations solved using the finite volume method. The particle phase is governed by Newton's laws of motion using the DEM. The liquid-particle interaction force is calculated using the CFD-DEM coupling method. The CFD-DEM encoding exchanges particle-fluid interaction information and updates the data accordingly at certain time step intervals.
[0045] In the governing equations of the mud crust structure, since the shear curve of the mud crust undergoes a strain softening process, meaning the peak value increases with increasing normal stress, if the model is considered a two-dimensional problem where deformations in the three directions do not affect each other, the three-dimensional constitutive model of the contact can be simulated using shear laws. In the τ-σn space, the constitutive relation can be described by the following equation:
[0046]
[0047] Where A is the coefficient reflecting the tangential strain increment dγ caused by the shear stress increment dτ; B is the coefficient reflecting the volumetric strain increment dεv caused by the shear stress increment dτ; C is the coefficient reflecting the tangential strain dγ caused by the normal pressure dσn, and since normal stress is generally considered not to produce tangential deformation, C = 0; D is the coefficient reflecting the volumetric strain increment dεv caused by the normal pressure dσn. The three parameters A, B, and D in the above equation can be described by four material parameters λ, κ, μ, and M. Where λ and κ are the slopes of the loading curve and the rebound-reloading curve in the isotropic consolidation test, respectively. μ is the friction coefficient, and M and M are the stress ratios under critical conditions, determined by the following formula:
[0048]
[0049] in It is the friction angle.
[0050] The experiment used a large direct shear apparatus to conduct direct shear tests under axial pressures of 200 kPa, 500 kPa, 1200 kPa, and 2000 kPa. The height of the entire soil mass was 100 mm, and the inner diameter was 300 mm. During the test, the upper chamber remained stationary, while the stacked rings of the lower chamber created the shear. The experiment used sodium bentonite mixed with additives such as soda ash, CMC, and barite, diluted with 1:5 fresh water. The viscosity at the Marsh funnel was above 50 s. This mixture was then mixed with coarse-grained soil to form a mud cake.
[0051] To ensure the shear plane occurs near the mud cake, the mud cake thickness is controlled to 20 mm. Sodium-based bentonite is used, and the mud cake density is 1.06 g / cm³. 3 The upper layer of coarse-grained soil has a maximum particle size of 20 mm and a density of 1.90 g / cm³. 3 The shear rate is 0.3 mm / min. Specific parameters can be determined through compression and shear tests on the mud cake, as shown in Table 1.
[0052] Table 1
[0053]
[0054] The parameters of the mud particles were calibrated using an orthogonal experimental method. The experimental factors selected were normal stiffness (kn), shear stiffness (ks), elastic modulus (emodulo), cohesion (c), and tensile strength (σ). The interfacial shear strength index was calculated based on the peak shear stress and the Mohr-Coulomb criterion. The peak strength (Sp) and interfacial friction angle (φi) were used as experimental indicators. Sensitivity analysis was performed on the results. With the goal of obtaining the simulation value closest to the laboratory experiment, the optimal scheme was selected, and multiple rounds of orthogonal experiments were conducted to obtain parameters close to those of the laboratory experiment. Detailed results are shown in Table 2.
[0055] Table 2
[0056]
[0057] To simulate the formation of the mud infiltration zone and generate a mud cake that maintains the stability of the trench walls, a mud infiltration test apparatus was used to conduct a comparative study on the characteristics of mud deposition and clogging, and to determine the parameters of the mud particles. A 1.2m experimental apparatus was set up, and a soil sample with a porosity of 0.36 was generated at the bottom. To form a suitable mud cake, the mud particle radius D15 / d85 was set to 3, and a small amount of mud infiltrated into the trench walls, forming a filter cake.
[0058] The above experiments show that the calculation results of this embodiment are consistent with the actual project, verifying the accuracy of the results. Furthermore, by changing the working conditions, suitable construction schemes such as trench width, mud specifications, and liquid level depth can be calculated, which is conducive to improving construction quality, reducing construction costs, and improving project safety.
[0059] The above are merely preferred embodiments of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.
Claims
1. A method for analyzing the stability of mud slurry wall protection in anti-seepage wall trenches, characterized in that, Includes the following steps: Collect information on strata soil samples and mud wall protection materials, and construct a discrete element model based on the strata soil sample information; The discrete element model is run under gravity conditions, and a formation model is obtained when it reaches a stable state. The geological model is subjected to trenching and a guide wall is generated to obtain a construction environment model; The mud structure model is obtained by coupling the mud wall protection material information based on the CFD-DEM model. The mud structure model is imported into the construction environment model to obtain the mud wall protection model. Stability calculation is performed based on the mud wall protection model to obtain the stability of the mud wall protection. When simulating fluid dynamics during the import of the mud structure model into the construction environment model, the DiFelice resistance model is used to simulate particle blockage behavior. The simulated fluid dynamics includes fluid phase simulation and particle phase simulation; The fluid phase was simulated using the Navier-Stokes equations and conventional continuous medium methods; the mass conservation equations and momentum conservation equations in the Navier-Stokes equations were solved using the finite volume method. Particle phase simulation is implemented based on Newton's laws of motion of DEM; After importing the mud structure model into the construction environment model, a mud skin structure is generated. The softening problem of the mud skin structure is treated as a two-dimensional problem. Then, a three-dimensional constitutive model of the contact is simulated through shear law to obtain the mud wall protection model.
2. The method for analyzing the stability of seepage-proof wall trench mud slurry wall protection according to claim 1, characterized in that, The method for constructing the discrete element model includes: The particle size distribution of the soil samples was determined, and the particle size distribution was preprocessed using the particle size amplification method. Based on the preprocessed particle data, a soil sample model was constructed. A wall is built around the soil sample model as a fixed boundary, and the top wall is deleted as a free boundary. Based on the layered filling method, soil sample particles with fixed gradation are randomly generated in the boundary area to obtain a discrete element model.
3. The method for analyzing the stability of seepage-proof wall trench mud slurry wall protection according to claim 1, characterized in that, The conditions for determining whether a stable state has been reached include: Under gravity conditions, when the ratio of the forces acting on each soil particle in the relative directions reaches 1e... -5 When the time is right, the discrete element model reaches a stable state.
4. The method for analyzing the stability of seepage-proof wall trench mud slurry wall protection according to claim 1, characterized in that, The method for performing trenching and generating guide walls includes: Based on the target depth, soil particles are removed from the center of the stratum model to obtain a trench, and a concrete guide wall is generated on top of the trench.
5. The method for analyzing the stability of seepage-proof wall trench mud slurry wall protection according to claim 2, characterized in that, When constructing a discrete element model using soil sample particles, a parallel cementation model is used to simulate the cementation effect of silt and clay particles.