Seepage analysis method for synergistic effect of water gate foundation diaphragm wall and cast-in-place pile

Abstract

The invention relates to a seepage analysis method for a synergistic effect of a water gate foundation diaphragm wall and a cast-in-place pile, which comprises the following steps of: analyzing and converting a seepage field according to a Darcy permeation law and a water flow continuity equation to obtain an equation for solving the seepage field by a finite element method; establishing a model, and after the finite element model is established, defining material parameters of the model, and setting seepage working conditions corresponding to different water gate upstream water level conditions, so as to simulate seepage field characteristics of the water gate under different operation working conditions and comprehensively evaluate seepage conditions of the water gate under different water levels; and analyzing and calculating the water gate seepage under the synergistic effect of the anti-seepage wall and the cast-in-place pile.

Description

Technical Field

[0001] This invention relates to a seepage analysis method for the synergistic effect of a sluice gate foundation anti-seepage wall and cast-in-place piles. Background Technology

[0002] Steady-state seepage is a seepage pattern in which physical quantities such as pressure and velocity change only with spatial location and are independent of time when a fluid flows in a porous medium. Its core characteristics are a constant upstream and downstream head difference and the medium being in a saturated laminar flow state. It is commonly seen in scenarios such as oil reservoir development driven by rigid water pressure and seepage in earth dams.

[0003] The infiltration flow rate, seepage velocity, water head and pressure distribution, and hydraulic gradient vary depending on the materials and structures used. Currently, there is no existing technology for analyzing seepage under the combined action of the cutoff wall and cast-in-place piles in the foundation of a sluice gate.

[0004] Traditional gate foundation seepage prevention design mainly focuses on vertical cutoff walls (such as sheet piles and diaphragm walls) or horizontal cutoff covers, with the core purpose of extending the seepage path and reducing the hydraulic gradient. However, in many practical projects, the foundation treatment of sluice gates is not limited to seepage prevention. To meet requirements such as bearing capacity, settlement control, and anti-sliding stability, pile foundations such as cast-in-place piles or mixing piles are usually arranged within a large foundation area.

[0005] These downstream pile foundations objectively alter the permeability of the foundation soil, forming a second "invisible" seepage prevention or water-blocking barrier. Ignoring their existence and performing seepage analysis based solely on a natural foundation or a simplified model with only a seepage barrier wall will lead to the following problems:

[0006] Overestimating seepage risk: Ignoring the water-blocking effect of pile foundations may result in calculated seepage flow, velocity and hydraulic gradient that are significantly higher than the actual values, leading to an overly conservative design and unnecessary investment in seepage prevention.

[0007] Underestimating synergistic effectiveness: The inability to quantitatively assess the true effect of the "wall-pile" combined seepage prevention system may lead to missed opportunities to optimize the design scheme (such as appropriately reducing the depth of the seepage prevention wall), thus making it difficult to achieve the best balance between safety and economy;

[0008] Analysis model distortion: This causes deviations between the calculated seepage flow field, isohyet lines, and pore water pressure distribution under the gate foundation and the actual working conditions, affecting the accurate judgment of seepage stability.

[0009] Therefore, conducting synergistic seepage analysis of the anti-seepage wall and cast-in-place piles is to simulate the actual working state of the sluice gate more realistically, accurately and economically, which is an inevitable requirement for engineering design to move from "experience-based" to "precision-based". Summary of the Invention

[0010] The purpose of this invention is to provide a seepage analysis method for the synergistic effect of the anti-seepage wall and cast-in-place piles in the foundation of a sluice gate. This method can perform seepage analysis on the synergistic effect of the anti-seepage wall and cast-in-place piles in the foundation of a sluice gate, and can simulate the actual working state of the sluice gate more realistically, accurately and economically.

[0011] The technical solution of this invention is: a seepage analysis method for the synergistic effect of a sluice gate foundation anti-seepage wall and cast-in-place piles, comprising the following steps:

[0012] (I) Calculation Principles

[0013] According to Darcy's law of permeability and the continuity equation of water flow, the basic differential equation for steady seepage can be expressed as:

[0014] Equation 1-1

[0015] In the formula, is the partial differential symbol, x, y, z are spatial coordinates used to describe the position of any point in the seepage field, k is the permeability coefficient, and H is the hydraulic head in meters;

[0016] When deriving the rock mass permeability tensor, the expression for the seepage energy in a certain seepage region can be obtained as follows:

[0017] Formula 1-2

[0018] In the formula, I is the energy dissipation rate density (or hydraulic power density), and d is the volume element.

[0019] (1). For steady seepage, the boundary conditions of the basic differential equation are only the boundary conditions. Common boundary conditions are as follows:

[0020] (a) First type of boundary condition: When the head of water on a certain part of the boundary of the seepage region is known and the normal velocity is unknown, the boundary condition can be expressed as:

[0021] Formula 1-3

[0022] In the formula, Let S1 be the head function, and S1 be the known head boundary.

[0023] (b) Second type of boundary condition: When the normal velocity on a certain part of the boundary of the seepage region is known and the hydraulic head is unknown, the boundary condition can be expressed as:

[0024] Formula 1-4

[0025] In the formula, n is the outward normal direction, q is the inflow / outflow rate per unit area on the boundary of the seepage region, and S2 is the known flow boundary.

[0026] (c) Boundary conditions for free surfaces and overflow surfaces:

[0027] The boundary conditions for an unpressurized seepage free surface can be expressed as:

[0028] Formula 1-5

[0029] Formula 1-6

[0030] In the formula, S3 is the boundary of the free surface;

[0031] The boundary conditions for the overflow surface are:

[0032] Formula 1-7

[0033] Formula 1-8

[0034] In the formula, S4 is the overflow surface boundary.

[0035] (2) In seepage field analysis, three conditions must be met: existence of boundary conditions, uniqueness of solutions, and stability. Problems that satisfy these three conditions are called well-posed problems. Based on the above, the three-dimensional steady-state seepage problem can be reduced to the following boundary condition problem:

[0036] Formula 1-9

[0037] Formula 1-10

[0038] Formula 1-11

[0039] (3). According to the variational principle, the above boundary value problem is equivalent to finding the extremum of the energy functional:

[0040] Formula 1-12

[0041] Based on the hydrogeological structure of the study area, the seepage field is discretized, that is:

[0042] Formula 1-13

[0043] Taking the variation of equation 1-12 to zero and superimposing it over each sub-region, we obtain the equations for solving the seepage field using the finite element method:

[0044] Formula 1-14

[0045] In the formula: —Overall penetration matrix, —Head values ​​at each node, —Equivalent node flow column vector;

[0046] (ii) Based on the above calculation principles, a finite element numerical model containing the anti-seepage wall and cast-in-place piles and including the permeability parameters of each soil layer and structural material is established;

[0047] (III) By setting the upstream water level conditions under different working conditions, the key seepage parameters corresponding to the model, such as seepage flow rate, velocity distribution, head field and hydraulic gradient, are calculated based on the calculation principle, and the seepage situation of the sluice gate under different water levels is comprehensively evaluated.

[0048] Furthermore, in step (iii), the three operating conditions are as follows: Operating condition A corresponds to the highest water level of 4.08m under normal operating conditions; Operating condition B corresponds to the design flood level of 7.48m; and Operating condition C corresponds to the check flood level of 8.36m.

[0049] Furthermore, in step (iii), the permeability coefficient and specific yield parameters of the anti-seepage wall and cast-in-place piles involved in the model are 0.

[0050] Compared with the prior art, the present invention has the following advantages:

[0051] This method facilitates the analysis of seepage under the synergistic effect of the cutoff wall and cast-in-place piles in the foundation of a sluice gate, and can more realistically, accurately, and economically simulate the actual working state of the sluice gate. Through the synergistic effect of the cast-in-place piles and the cutoff wall, the seepage characteristics of the sluice gate can be effectively improved, the seepage flow can be significantly reduced, the water flow velocity can be further slowed down, the distribution of water head and water pressure isopleths is the most sparse, the hydraulic gradient is minimized, and the seepage prevention effect is most significant when the cutoff wall and cast-in-place piles are used together. Attached Figure Description

[0052] Figure 1 This is a schematic diagram of the finite element mesh and water level conditions for the present invention with a seepage barrier wall and cast-in-place piles.

[0053] Figure 2 This is a vector diagram of the flow velocity under normal flood level (H=4.08m) for the present invention, which includes a seepage barrier wall and cast-in-place piles.

[0054] Figure 3 This is a contour map of the normal flood level (H=4.08m) for the present invention, which includes a seepage barrier wall and cast-in-place piles.

[0055] Figure 4 This is a contour map of water pressure at the normal flood level (H=4.08m) for the present invention, which includes a seepage barrier wall and cast-in-place piles.

[0056] Figure 5 This is a contour map of the hydraulic gradient at the normal flood level (H=4.08m) for the present invention, which includes a seepage barrier wall and cast-in-place piles.

[0057] Figure 6 This is a vector diagram of the flow velocity at the design flood level (H=7.48m) for the present invention, which includes a seepage barrier wall and cast-in-place piles.

[0058] Figure 7 This is a contour map of the design flood level (H=7.48m) for the present invention, which includes a seepage barrier wall and cast-in-place piles.

[0059] Figure 8 This is a contour map of water pressure at the design flood level (H=7.48m) for the present invention, which includes a seepage barrier wall and cast-in-place piles.

[0060] Figure 9 This is a contour map of the hydraulic gradient at the design flood level (H=7.48m) for the present invention, which includes a seepage barrier wall and cast-in-place piles.

[0061] Figure 10 This is a vector diagram of the flow velocity at the flood level (H=8.36m) for the verification of the working conditions of the anti-seepage wall and cast-in-place piles in this invention.

[0062] Figure 11 This invention includes a flood head contour map of the water level (H=8.36m) for the verification of the working conditions of the anti-seepage wall and cast-in-place piles.

[0063] Figure 12 The water pressure contour map of the flood level (H=8.36m) for the verification of the working conditions of the anti-seepage wall and cast-in-place piles in this invention;

[0064] Figure 13 This invention provides a hydraulic gradient contour map of the flood level (H=8.36m) for the verification of the anti-seepage wall and cast-in-place pile working conditions. Detailed Implementation

[0065] To make the above features and advantages of the present invention more readily understood, specific embodiments are described below in conjunction with the accompanying drawings, but the present invention is not limited thereto.

[0066] refer to Figures 1 to 13

[0067] A seepage analysis method for the synergistic effect of a sluice gate foundation seepage-proof wall and cast-in-place piles includes the following steps:

[0068] (I) Calculation Principles

[0069] According to Darcy's law of permeability and the continuity equation of water flow, the basic differential equation for steady seepage can be expressed as:

[0070] Equation 1-1

[0071] In the formula, is the partial differential symbol, x, y, z are spatial coordinates used to describe the position of any point in the seepage field, k is the permeability coefficient, and H is the hydraulic head in meters.

[0072] When deriving the rock mass permeability tensor, the expression for the seepage energy in a certain seepage region can be obtained as follows:

[0073] Formula 1-2

[0074] In the formula, I is the energy dissipation rate density (or hydraulic power density), and d is the volume element;

[0075] (1). For steady seepage, the boundary conditions of the basic differential equation are only the boundary conditions. Common boundary conditions are as follows:

[0076] (a) First type of boundary condition (Dirichlet condition): When the head of water on a certain part of the boundary of the seepage region (such as S1) is known and the normal velocity is unknown, the boundary condition can be expressed as:

[0077] Formula 1-3

[0078] In the formula, Let S1 be the head function, and S1 be the known head boundary.

[0079] (b) Second type of boundary condition (Neumann condition): When the normal velocity on a portion of the boundary of the seepage region (e.g., S2) is known, and the hydraulic head is unknown, the boundary condition can be expressed as:

[0080] Formula 1-4

[0081] In the formula, n is the outward normal direction, q is the inflow / outflow rate per unit area on the boundary of the seepage region, and S2 is the known flow boundary.

[0082] (c) Boundary conditions for free surface and overflow surface: The boundary conditions for the free surface in unpressurized seepage can be expressed as follows:

[0083] Formula 1-5

[0084] Formula 1-6

[0085] In the formula, S3 is the boundary of the free surface;

[0086] The boundary conditions for the overflow surface are:

[0087] Formula 1-7

[0088] Formula 1-8

[0089] In the formula, S4 is the overflow surface boundary;

[0090] (2). In seepage field analysis, three conditions must be met: existence of boundary conditions, uniqueness of solutions, and stability. Problems that satisfy these three conditions are called well-posed problems. Based on the above, the three-dimensional steady seepage problem can be reduced to the following boundary condition problems:

[0091] Formula 1-9

[0092] Formula 1-10

[0093] Formula 1-11

[0094] (3). According to the variational principle and Equation 1-1, the above boundary value problem is equivalent to finding the extremum of the energy functional:

[0095] Formula 1-12

[0096] Based on the hydrogeological structure of the study area, the seepage field is discretized, that is:

[0097] Formula 1-13

[0098] Taking the variation of equation 1-12 to zero and superimposing it over each sub-region, we obtain the equations for solving the seepage field using the finite element method:

[0099] Formula 1-14

[0100] In the formula: —Overall penetration matrix, —Head values ​​at each node, —Equivalent node flow column vector;

[0101] (ii). Based on the above calculation principles, a finite element numerical model containing the anti-seepage wall and cast-in-place piles, and including the permeability parameters of each soil layer and structural material, is established;

[0102] The model involves seven materials, and their respective permeability coefficients and specific yield parameters are shown in Table 1.

[0103] Material Name Kx(m / s) Ky(m / s) Water supply Gate body 1e-05 1e-05 0 Soil layer 1 8e-05 8e-05 0 Soil layer 2 0.0008 0.0008 0 Soil layer 3 5e-07 5e-07 0 Soil layer 4 2e-05 2e-05 0 seepage barrier wall 0 0 0 Cast-in-place piles 0 0 0

[0104] Table 1. Permeability parameters of various soil layers and structural materials

[0105] (III) By setting the upstream water level conditions under different working conditions, the key seepage parameters such as seepage flow, velocity distribution, head field and hydraulic gradient corresponding to the model are calculated based on the calculation principle, and the seepage situation of the sluice gate under different water levels is comprehensively evaluated.

[0106] This seepage analysis is a steady-state seepage analysis, with three seepage scenarios set up to simulate the seepage field characteristics of the sluice gate under different upstream water levels. These three scenarios are: Scenario A, corresponding to the highest water level of 4.08m under normal operation; Scenario B, corresponding to the design flood level of 7.48m; and Scenario C, corresponding to the check flood level of 8.36m. Through the analysis of these three typical scenarios, the seepage situation of the sluice gate under different water levels can be comprehensively evaluated.

[0107] The table below shows the seepage flow rate of the sluice gate under different water levels, with both a cutoff wall and cast-in-place piles in place. Compared to the previous two conditions, the seepage flow rate is further reduced, indicating that the combined effect of the cast-in-place piles and the cutoff wall results in a more significant seepage prevention effect.

[0108] Operating conditions Highest water level (m) <![CDATA[Flow rate (m 3 / d)]]> Seepage A H=4.08 1.55 Seepage B H=7.48 2.92 seepage C H=8.36 3.34

[0109] Table 2. Statistics of seepage flow of sluice gates under various working conditions with seepage barriers and cast-in-place piles.

[0110] See Figures 1 to 13 The paper presents a finite element mesh model of the working condition with anti-seepage wall and cast-in-place piles, as well as seepage calculation results under three working conditions: normal flood level, design flood level and check flood level.

[0111] Therefore, it can be seen that in the case of the cutoff wall and the cast-in-place pile: the synergistic effect of the cast-in-place pile and the cutoff wall further reduces the seepage flow, further slows down the water flow velocity, makes the distribution of the water head and water pressure is the most sparse, the hydraulic gradient reaches the minimum, and the seepage prevention effect is the best.

[0112] In conclusion, by comparing and analyzing the seepage calculation results under different working conditions, it can be concluded that seepage prevention measures such as cutoff walls and cast-in-place piles can effectively improve the seepage characteristics of sluice gates, significantly reduce seepage flow, slow down water flow velocity, and reduce hydraulic gradient. Therefore, the seepage prevention effect is most significant when cutoff walls and cast-in-place piles are used in combination.

[0113] The above description is only a preferred embodiment of the present invention. For those skilled in the art, designing seepage analysis methods for the synergistic effect of different forms of sluice gate foundation anti-seepage walls and cast-in-place piles based on the teachings of the present invention does not require creative labor. All equivalent changes, modifications, substitutions and variations made in accordance with the scope of the patent application of the present invention without departing from the principles and spirit of the present invention shall be covered by the present invention.

Claims

1. A seepage analysis method for the synergistic effect of a sluice gate foundation anti-seepage wall and cast-in-place piles, characterized in that, Includes the following steps: (I) Calculation Principles According to Darcy's law of permeability and the continuity equation of water flow, the basic differential equation for steady seepage can be expressed as: Equation 1-1 In the formula, is the partial differential symbol, x, y, z are spatial coordinates used to describe the position of any point in the seepage field, k is the permeability coefficient, and H is the hydraulic head in meters. When deriving the rock mass permeability tensor, the expression for the seepage energy in a certain seepage region can be obtained as follows: Formula 1-2 In the formula, I is the energy dissipation rate density or hydraulic power density, and d is the volume element; (1). For steady seepage, the boundary conditions of the basic differential equation are only the boundary conditions. Common boundary conditions are as follows: (a) First type of boundary condition: When the head of water on a certain part of the boundary of the seepage region is known and the normal velocity is unknown, the boundary condition can be expressed as: Formula 1-3 In the formula, Let S1 be the head function, and S1 be the known head boundary. (b) Second type of boundary condition: When the normal velocity on a certain part of the boundary of the seepage region is known and the hydraulic head is unknown, the boundary condition can be expressed as: Formula 1-4 In the formula, n is the outward normal direction, q is the inflow / outflow rate per unit area on the boundary of the seepage region, and S2 is the known flow boundary. (c) Boundary conditions for free surface and overflow surface: The boundary conditions for the free surface in unpressurized seepage can be expressed as follows: Formula 1-5 Formula 1-6 In the formula, S3 is the boundary of the free surface; The boundary conditions for the overflow surface are: Formula 1-7 Formula 1-8 In the formula, S4 is the overflow surface boundary; (2). In seepage field analysis, three conditions must be met: existence of boundary conditions, uniqueness of solutions, and stability. Problems that satisfy these three conditions are called well-posed problems. Based on the above, the three-dimensional steady seepage problem can be reduced to the following boundary condition problems: Formula 1-9 Formula 1-10 Formula 1-11 (3). According to the variational principle, the above boundary value problem is equivalent to finding the extremum of the energy functional: Formula 1-12 Based on the hydrogeological structure of the study area, the seepage field is discretized, that is: Formula 1-13 Taking the variation of equation 1-12 to zero and superimposing it over each sub-region, we obtain the equations for solving the seepage field using the finite element method: Formula 1-14 In the formula: —Overall penetration matrix, —Head values ​​at each node, —Equivalent node flow column vector; (ii). Based on the above calculation principles, a finite element numerical model containing the anti-seepage wall and cast-in-place piles, and including the permeability parameters of each soil layer and structural material, is established; (III) By setting the upstream water level conditions under different working conditions, the key seepage parameters corresponding to the model, such as seepage flow rate, velocity distribution, head field and hydraulic gradient, are calculated based on the calculation principle, and the seepage situation of the sluice gate under different water levels is comprehensively evaluated.

2. The seepage analysis method for the synergistic effect of the anti-seepage wall and cast-in-place piles in the foundation of a sluice gate, as described in claim 1, is characterized in that... In step (iii), the three operating conditions are as follows: Operating condition A corresponds to the highest water level of 4.08m under normal operating conditions; Operating condition B corresponds to the design flood level of 7.48m. Operating condition C corresponds to a check flood level of 8.36m.

3. A seepage analysis method for the synergistic effect of a sluice gate foundation anti-seepage wall and cast-in-place piles according to claim 1 or 2, characterized in that, In step (iii), the permeability coefficient and water yield parameters of the anti-seepage wall and cast-in-place pile involved in the finite element numerical model are 0.

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