A method for zoning a high concrete-faced rockfill dam body

Abstract

This invention belongs to the technical field of concrete-faced rockfill dams in water conservancy and hydropower engineering. Specifically, it provides a method for zoning the dam body of a high concrete-faced gravel dam, including the following steps: 1) Formulating a preliminary scheme for zoning the dam body of the high concrete-faced gravel dam and the filling standards for gravel and riprap; 2) Determining the boundary values ​​for dividing the high-stress zone and low-stress zone of the dam body; 3) Calculating and determining the stress magnitude and distribution of the dam body; 4) Dividing the dam body into low-stress and high-stress zones; 5) Adjusting the dam body zoning scheme in step 1) to determine the final dam body zoning scheme. This invention solves the problems of inconsistent deformation and poor seepage stability and safety in existing high concrete-faced gravel dams. It reduces and controls the deformation of high concrete-faced gravel dams, providing a basis for optimizing and adjusting the dam body zoning of high concrete-faced gravel dams.

Description

Technical Field

[0001] This invention belongs to the technical field of rockfill dams with concrete panels in water conservancy and hydropower engineering, and specifically relates to a method for partitioning the dam body of a high concrete-faced gravel dam. Background Technology

[0002] Gravel is a widely distributed filling material found in riverbeds and riverbank slopes, offering lower mining costs and higher resistance to deformation compared to blasted rock. Concrete-faced dams are a widely used type of dam in my country's water conservancy and hydropower engineering construction, and the practice of using gravel as filling material for high-faced dams in China is also increasing.

[0003] In high concrete-faced gravel dams (especially those exceeding 200 meters in height), there are significant stress differences between high-stress zones within the dam body and low-stress zones on the dam slope and crest. Furthermore, the mechanical properties of gravel and riprap differ considerably under different stress conditions. At lower stress levels, riprap exhibits greater deformation and shear strength than gravel, while at higher stress levels, riprap shows lower deformation parameters than gravel. Therefore, the rational design of dam body zoning and the selection of appropriate materials directly determine and influence dam deformation, stability, and seepage safety.

[0004] Chinese patent document CN113203670A, published on August 3, 2021, discloses a method for layer-by-layer superposition inversion of the permeability coefficient of the core wall soil of an earth-rock dam. This method, based on monitoring data from piezometers and weirs at different reservoir water levels, forms the actual dam body phreatic lines. Combined with known soil permeability coefficients, theoretical calculations are used to perform layer-by-layer superposition inversion analysis of the permeability coefficient of the earth-rock dam's seepage-proof core wall from low to high reservoir water levels, achieving precise layer-by-layer permeability coefficient acquisition. This document uses piezometers at different cross-sections of the dam body to accurately obtain the permeability coefficient of the seepage-proof core wall, providing a reliable basis for subsequent seepage-proofing reinforcement design of earth-rock dams. However, this document focuses on the subsequent reinforcement and maintenance of the earth-rock dam after its construction, without altering the dam's structure. Summary of the Invention

[0005] The purpose of this invention is to provide a method for partitioning the dam body of a high concrete-faced gravel dam to overcome the problems of inconsistent deformation and poor seepage stability and safety in existing high concrete-faced gravel dams.

[0006] Therefore, the present invention provides a method for partitioning the dam body of a high concrete-faced gravel dam, comprising the following steps:

[0007] 1) Draft a preliminary plan for the dam body zoning of the high concrete-faced gravel dam and the filling standards for gravel and riprap; the preliminary plan for the dam body zoning is that the upstream shell, top and middle of the dam body are gravel areas, and the downstream shell of the dam body is a riprap area.

[0008] 2) Mechanical tests were conducted on gravel and boulders under different stress conditions to obtain the E-B model parameters of gravel and boulders and to determine the boundary values ​​for dividing the high-stress zone and low-stress zone of the high concrete-faced gravel dam body.

[0009] 3) Determine the stress magnitude and distribution of the high concrete-faced gravel dam by performing finite element calculations on the E_B model parameters;

[0010] 4) Based on the boundary values ​​of the high stress zone and low stress zone of the high concrete-faced gravel dam body in step 2) and the stress distribution of the high concrete-faced gravel dam in step 3), the gravel material area is divided into low stress zone and high stress zone.

[0011] 5) Based on the low-stress zone and high-stress zone divided in step 4), the dam body zoning scheme in step 1) is adjusted. During the adjustment, the gravel and stone materials in the area that belongs to the gravel and stone material area in step 1) and is divided into the high-stress zone in step 4) are replaced with boulders. The adjusted scheme is the final dam body zoning scheme.

[0012] Preferably, the filling standard for the gravel and stone is that the relative density of the gravel is ≥0.9 and the porosity of the stone is ≤19%.

[0013] Preferably, the mechanical test in step 2) is a triaxial shear test, and the E_B model parameters of gravel and block stone under different stress conditions are obtained through the triaxial shear test.

[0014] Preferably, the different stress conditions are 50 kPa to 3000 kPa, and the 50 kPa to 3000 kPa range is divided into 6 to 10 stress levels.

[0015] Preferably, in step 3), the stress distribution of the high concrete-faced gravel dam is a stress contour distribution.

[0016] Preferably, the stress contour distribution includes contour lines that define the boundary between the high-stress zone and the low-stress zone of the high-concrete-faced gravel dam body.

[0017] Preferably, in step 4), the low-stress zone is the area within the dam body where the stress value is less than the boundary value between the high-stress zone and the low-stress zone of the high-concrete-faced gravel dam body, and the high-stress zone is the area within the dam body where the stress value is greater than the boundary value between the high-stress zone and the low-stress zone of the high-concrete-faced gravel dam body.

[0018] Preferably, the low-stress zone is filled with rubble, and the high-stress zone is filled with gravel.

[0019] Preferably, after determining the final dam body zoning scheme, steps 3) to 5) are repeated to adjust the final dam body zoning scheme, requiring that the difference between the two final dam body zoning schemes does not exceed 0.5m.

[0020] Preferably, in step 5), the dam body zoning scheme in step 1) is adjusted, specifically by replacing the gravel and stone materials in the upper upstream part of the dam body and the dam crest with boulders.

[0021] The beneficial effects of this invention are:

[0022] 1. The method for zoning the dam body of a high concrete-faced gravel dam provided by this invention fully considers the stress distribution characteristics of the dam body (stress magnitude and distribution), as well as the mechanical and deformation characteristics (mechanical and deformation parameters) of gravel and boulders. The method involves the following steps: 1) Formulating a preliminary scheme for zoning the dam body of the high concrete-faced gravel dam and the filling standards for gravel and boulders; the preliminary scheme for zoning the dam body is that the upstream shell, top, and middle parts of the dam body are gravel areas, and the downstream shell is a boulder area; 2) Conducting mechanical tests on the gravel and boulders under different stress conditions to obtain the E_B model parameters of the gravel and boulders, and determining the boundary values ​​for dividing the high-stress and low-stress zones of the high concrete-faced gravel dam body; 3) Determining the stress magnitude and distribution of the high concrete-faced gravel dam body by finite element calculation using the E_B model parameters; 4) Based on the boundary values ​​of the high-stress zone and low-stress zone of the high concrete-faced gravel dam body in step 2) and the stress distribution of the high concrete-faced gravel dam in step 3), the gravel material area is divided into low-stress zone and high-stress zone; 5) Based on the low-stress zone and high-stress zone divided in step 4), the dam body zoning scheme in step 1) is adjusted. During the adjustment, the gravel material in the gravel material area belonging to step 1) and the area divided into the high-stress zone in step 4) is replaced with block stone. The adjusted scheme is the final dam body zoning scheme. Reasonable setting of dam body zoning and selection of appropriate materials, making full use of the mechanical and deformation characteristics of the two dam construction materials, directly determines and affects the deformation and seepage stability of the dam body, reduces and controls the deformation of the high concrete-faced gravel dam body, improves the stability and safety of the dam body, and provides a basis for the optimization and adjustment of the dam body zoning of high concrete-faced gravel dams.

[0023] 2. The method for zoning the dam body of a high concrete-faced gravel dam provided by this invention involves repeating steps 3) to 5) to adjust the final dam body zoning scheme after determining the final dam body zoning scheme. The final dam body zoning schemes of the two consecutive attempts should not differ by more than 0.5m. Through repeated experiments and comparisons, the error is reduced and the accuracy of zoning is improved.

[0024] 3. The method for zoning the dam body of a high concrete-faced gravel dam provided by this invention uses triaxial shear tests for mechanical testing. The E_B model parameters of gravel and boulders under different stress conditions are obtained through these triaxial shear tests. By comparing and analyzing the relationship curves between the initial modulus Ei and stress σ3 of the gravel and boulders, the curves show that the initial modulus Ei of the gravel and boulders intersects with stress. The stress value at the intersection point is the boundary value between the high-stress zone and the low-stress zone of the high concrete-faced gravel dam body. This test provides a clear stress state and facilitates the acquisition of accurate target parameters. Attached Figure Description

[0025] The present invention will now be described in further detail with reference to the accompanying drawings.

[0026] Figure 1 This is a flowchart of the method for dividing the dam body of a high concrete-faced gravel dam;

[0027] Figure 2 This is a schematic diagram of the dam body zoning for Example 2, a high concrete-faced gravel dam.

[0028] Figure 3 The relationship between the initial modulus Ei and stress σ3 of gravel and boulders in Example 2 is shown.

[0029] Figure 4 This is a stress distribution diagram of a high concrete-faced gravel dam, as shown in Example 2.

[0030] Figure 5 This is a diagram showing the division of low-stress and high-stress zones in the high-concrete-faced gravel dam body of Example 2;

[0031] Figure 6 This is the final dam zoning scheme for Example 2. Detailed Implementation

[0032] Example 1:

[0033] like Figure 1 As shown, a method for zoning the dam body of a high concrete-faced gravel dam includes the following steps:

[0034] 1) Draft a preliminary plan for the dam body zoning of the high concrete-faced gravel dam and the filling standards for gravel and riprap; the preliminary plan for the dam body zoning is that the upstream shell and the middle of the top of the dam body are gravel areas, and the downstream shell of the dam body is a riprap area.

[0035] 2) Mechanical tests were conducted on gravel and boulders under different stress conditions to obtain the E-B model parameters of gravel and boulders and to determine the boundary values ​​for dividing the high-stress zone and low-stress zone of the high concrete-faced gravel dam body.

[0036] 3) Determine the stress magnitude and distribution of the high concrete-faced gravel dam by performing finite element calculations on the E_B model parameters;

[0037] 4) Based on the boundary values ​​of the high stress zone and low stress zone of the high concrete-faced gravel dam body in step 2) and the stress distribution of the high concrete-faced gravel dam in step 3), the gravel material area is divided into low stress zone and high stress zone.

[0038] 5) Based on the low-stress zone and high-stress zone divided in step 4), the dam body zoning scheme in step 1) is adjusted. During the adjustment, the gravel and stone materials in the area that belongs to the gravel and stone material area in step 1) and is divided into the high-stress zone in step 4) are replaced with boulders. The adjusted scheme is the final dam body zoning scheme.

[0039] Step 3) Determine the stress magnitude and distribution of the high concrete-faced gravel dam by performing finite element calculations on the E_B model parameters. Specifically, by establishing a finite element calculation model of the dam and using the EB model parameters, the stress magnitude and distribution of the high concrete-faced gravel dam can be calculated and determined by inputting the EB model parameters into the finite element calculation model of the dam. The establishment of the finite element calculation model of the dam adopts existing technology, which will not be described in detail here.

[0040] The method for zoning the dam body of a high concrete-faced gravel dam provided by this invention fully considers the stress distribution characteristics of the dam body (stress magnitude and distribution), as well as the mechanical and deformation characteristics of gravel and boulders (mechanical and deformation parameters). Through steps 1) to 5), the dam body zoning is rationally set and suitable materials are selected. The mechanical and deformation characteristics of the two dam construction materials (gravel and boulders) are fully utilized, which directly determines and affects the deformation and seepage stability of the dam body, reduces and controls the deformation of the high concrete-faced gravel dam body, improves the stability and safety of the dam body, and provides a basis for the optimization and adjustment of the dam body zoning of high concrete-faced gravel dams.

[0041] Preferably, the filling standard for the gravel and stone is that the relative density of the gravel is ≥0.9 and the porosity of the stone is ≤19%. After filling, it ensures that the deformation of the high concrete-faced gravel dam is coordinated or that the deformation is minimized, and that the seepage stability is good.

[0042] Preferably, step 2) of the mechanical test is a triaxial shear test, through which the E_B model parameters of gravel and block stone under different stress conditions are obtained. The E_B model parameters include strength parameters, shear parameters, deformation parameters, and initial modulus Ei;

[0043] The stress state of this test is clear, and it is easy to obtain accurate target parameters; the triaxial shear test is an existing test, and its test method will not be described in detail here.

[0044] Step 4) The specific method for defining the boundary values ​​between the high-stress zone and the low-stress zone of the high concrete-faced gravel dam body is as follows:

[0045] By comparing and analyzing the relationship curves between the initial modulus Ei and stress σ3 of gravel and boulders, it was found that the curves of the initial modulus Ei of gravel and boulders intersect with the stress changes. The stress value at the intersection point is the boundary value between the high-stress zone and the low-stress zone of the high concrete-faced gravel dam body. To facilitate subsequent calculation and analysis, the experimental stress value close to the intersection point can be selected as the boundary value.

[0046] In practical operation, deformation parameters include the initial modulus Ei and the modulus coefficient; the experimental data are processed according to the E_B model to obtain the parameters. By comparing and analyzing the relationship between the initial modulus Ei and the stress σ3, and comparing the modulus coefficients of gravel and boulders under different stresses, the boundary value for dividing the high-stress zone and low-stress zone of the high concrete-faced gravel dam body is determined. For example, the curves of the initial modulus Ei and stress σ3 of gravel and boulders intersect at point C, which is between stresses A kPa and B kPa. When the stress is less than A kPa, the modulus coefficient of boulders is greater than that of gravel; when the confining pressure is greater than B kPa, the modulus coefficient of boulders is less than that of gravel. Therefore, the boundary value between the high-stress zone and low-stress zone of the high concrete-faced gravel dam body is B kPa.

[0047] Preferably, the different stress conditions are 50 kPa to 3000 kPa, and the 50 kPa to 3000 kPa range is divided into 6 to 10 stress levels.

[0048] By classifying stress conditions into different levels, it is easy to partition the area.

[0049] Preferably, the stress distribution in the gravel and stone material area in step 3) is a stress contour distribution.

[0050] The calculation method for determining the stress magnitude of a high concrete-faced gravel dam adopts the existing finite element method. The stress contour distribution can well reflect the stress magnitude distribution of the dam body. Based on the contour distribution, the dam body zoning is adjusted to reduce the deformation of the dam body and improve its stability.

[0051] Preferably, the stress contour distribution includes contour lines that define the boundary between the high-stress zone and the low-stress zone of the high-concrete-faced gravel dam body.

[0052] Ensure that the dam body is clearly and accurately divided into high-stress and low-stress zones.

[0053] Preferably, in step 4), the low-stress zone is the area within the dam body where the stress value is less than the boundary value between the high-stress zone and the low-stress zone of the high-concrete-faced gravel dam body, and the high-stress zone is the area within the dam body where the stress value is greater than the boundary value between the high-stress zone and the low-stress zone of the high-concrete-faced gravel dam body.

[0054] Preferably, the low-stress zone is filled with rubble, and the high-stress zone is filled with gravel.

[0055] Under low confining pressure, riprap has higher shear strength and better permeability than gravel. This method makes full use of the high modulus coefficient of riprap under low stress and the high modulus coefficient of gravel under high stress to reduce and control the deformation of high concrete-faced gravel dams, improve the seepage stability and seismic safety of the dam slope, and has broad application and promotion value.

[0056] Preferably, after determining the final dam body zoning scheme, steps 3) to 5) are repeated to adjust the final dam body zoning scheme, requiring that the difference between the two final dam body zoning schemes does not exceed 0.5m.

[0057] By repeating experiments and making comparisons, errors were reduced and the accuracy of partitioning was improved.

[0058] Preferably, in step 5), the dam body zoning scheme of step 1) is adjusted, specifically by replacing the gravel and sand material in the upper part of the upstream dam body and the dam crest with boulders. This satisfies the hydraulic transition relationship between the cushion material and the boulders, and an additional transition material is added between the cushion material and the boulders after the adjustment.

[0059] Example 2:

[0060] Based on Example 1, a method for partitioning the dam body of a high concrete-faced gravel dam includes the following steps:

[0061] 1) Draft a preliminary plan for the dam body zoning of the high concrete-faced gravel dam and the filling standards for gravel and riprap; the preliminary plan for the dam body zoning is that the upstream shell, top and middle of the dam body are gravel areas, and the downstream shell of the dam body is a riprap area.

[0062] like Figure 2 As shown, according to the design specifications for concrete face panels, the upstream and middle sections of the dam body are gravel and sand material areas, while the downstream dam body is a rock material area. For high concrete face panel gravel dams, the relative density of gravel and sand material is ≥0.9, and the porosity of rock material is ≤19%.

[0063] 2) Mechanical tests were conducted on gravel and boulders under different stress conditions to determine the boundary values ​​for dividing the high-stress zone and low-stress zone of the high concrete-faced gravel dam body.

[0064] like Figure 3 As shown, the stress conditions of the confining pressure in the test ranged from 50 kPa to 3000 kPa. This range was divided into nine stress levels: 50 kPa, 100 kPa, 200 kPa, 300 kPa, 400 kPa, 800 kPa, 1200 kPa, 2000 kPa, and 3000 kPa. The mechanical and deformation parameters of gravel and boulders under different stress conditions were obtained through triaxial shear tests. The relationship between the initial modulus Ei and the confining pressure σ3 was compared and analyzed. The tests revealed that when the confining pressure was less than 300 kPa, the modulus coefficient of the boulders was greater than that of the gravel; when the confining pressure was greater than 400 kPa, the modulus coefficient of the boulders was less than that of the gravel. Comparative analysis determined that the boundary between the high-stress zone and the low-stress zone of the high concrete-faced gravel dam body was 400 kPa.

[0065] 3) Determine the stress magnitude and distribution of the high concrete-faced gravel dam by performing finite element calculations on the E_B model parameters;

[0066] like Figure 4 The stress distribution diagram of the high concrete-faced gravel dam shown is included. The stress distribution contour lines of the dam body include the contour line of 400 kPa, which marks the boundary between the high stress zone and the low stress zone of the high concrete-faced gravel dam body.

[0067] 4) Based on the boundary values ​​of the high stress zone and low stress zone of the high concrete-faced gravel dam body in step 2) and the stress distribution of the high concrete-faced gravel dam in step 3), the gravel material area is divided into low stress zone and high stress zone.

[0068] like Figure 5 The diagram shows the division of low-stress and high-stress zones in the high concrete-faced gravel dam body. The low-stress zone is located in the upstream top and downstream dam shell where the stress value is less than the limit value. The high-stress zone is located in the upstream lower dam shell and the interior of the dam body where the stress value is greater than the limit value.

[0069] 5) Based on the low-stress zone and high-stress zone divided in step 4), the dam body zoning scheme in step 1) is adjusted. During the adjustment, the gravel and stone materials in the area that belongs to the gravel and stone material area in step 1) and is divided into the high-stress zone in step 4) are replaced with boulders. The adjusted scheme is the final dam body zoning scheme.

[0070] like Figure 6 The final dam zoning scheme is shown. The low-stress zone of the high-concrete-faced gravel dam uses riprap, while the high-stress zone uses gravel. The upper part of the upstream dam and the dam crest shell are adjusted to use riprap. To meet the hydraulic transition relationship between the cushion material and the riprap, a transition material is added between the cushion material and the riprap after the adjustment.

[0071] Repeat steps 3) to 5) to adjust the final dam body zoning scheme, ensuring that the difference between the two final dam body zoning schemes does not exceed 0.5m.

[0072] In practice, the dam body zoning is ultimately determined by considering factors such as dam and reservoir operating conditions, construction, and investment.

[0073] The present invention provides a method for zoning the dam body of a high concrete-faced gravel dam. Based on the stress distribution characteristics of the dam body and the mechanical characteristics of gravel and riprap, the dam body is divided into two zones: a low-stress zone and a high-stress zone. Riprap is selected for the low-stress zone, while gravel is selected for the high-stress zone. This dam body zoning method fully utilizes the characteristics of high modulus coefficient of riprap under low confining pressure and high modulus coefficient of gravel under high confining pressure, thereby reducing and controlling the deformation of the high concrete-faced gravel dam body. Simultaneously, riprap exhibits higher shear strength under low confining pressure and better permeability than gravel. This method improves the seepage stability and seismic safety of the dam slope in high concrete-faced gravel dams, and has broad application and promotion value.

[0074] In the description of this invention, it should be understood that if any term indicates an orientation or positional relationship, it is based on the orientation or positional relationship shown in the drawings, and does not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the terms used to describe positional relationships in the drawings are for illustrative purposes only and should not be construed as limiting the invention.

[0075] The above examples are merely illustrative of the present invention and do not constitute a limitation on the scope of protection of the present invention. All designs that are the same as or similar to the present invention are within the scope of protection of the present invention.

Claims

1. A method of zoning a high concrete-faced rockfill dam body, characterized by: It comprises the following steps: 1) preparing a preliminary scheme of zoning of the dam body of a high concrete face sand gravel dam and filling standards of sand gravel material and block stone material; the preliminary scheme of zoning of the dam body is that the upstream dam shell and the top and middle part of the dam body are sand gravel material zones, and the downstream dam shell of the dam body is a block stone material zone; 2) performing mechanical tests on the sand gravel material and the block stone material under different stress conditions to obtain E_B model parameters of the sand gravel material and the block stone material, and determining the limit value for dividing the high stress zone and the low stress zone of the dam body of the high concrete face sand gravel dam, which is a numerical value; 3) determining the stress size and distribution of the dam body of the high concrete face sand gravel dam after the E_B model parameters are calculated by finite elements; 4) dividing the sand gravel material zone into the low stress zone and the high stress zone according to the limit value for dividing the high stress zone and the low stress zone of the dam body of the high concrete face sand gravel dam in step 2) and the stress distribution of the high concrete face sand gravel dam in step 3); 5) adjusting the dam body zoning scheme in step 1) according to the low stress zone and the high stress zone divided in step 4), and replacing the sand gravel material in the region belonging to the sand gravel material zone in step 1) and divided into the low stress zone in step 4) with the block stone material, and the adjusted scheme is the final dam body zoning scheme.

2. The method of zoning a high concrete-faced rockfill dam body as claimed in claim 1, wherein: The filling standards of the sand gravel material and the stone material are that the relative density of the sand gravel material is greater than or equal to 0.9, and the porosity of the block stone material is less than or equal to 19%.

3. The method of zoning a high concrete faced rockfill dam body of claim 1, wherein: The mechanical test in step 2) is a triaxial shear test, and the E_B model parameters of the sand gravel material and the block stone material under different stress conditions are obtained through the triaxial shear test.

4. The method of zoning a high concrete faced rockfill dam body as claimed in claim 3, wherein: The different stress conditions are 50kPa-3000kPa, and 50kPa-3000kPa is divided into 6-10 levels of stress.

5. The method of zoning a high concrete faced rockfill dam body of claim 1 wherein: The stress distribution of the high concrete face sand gravel dam in step 3) is a stress contour distribution.

6. The method of zoning a high concrete-faced rockfill dam body of claim 5, wherein: The stress contour distribution includes the contour of the limit value for dividing the high stress zone and the low stress zone of the dam body of the high concrete face sand gravel dam.

7. The method of zoning a high concrete-faced rockfill dam body of claim 1, wherein: The low stress zone in step 4) is a region in which the stress value in the dam body is less than the limit value, and the high stress zone is a region in which the stress value in the dam body is greater than the limit value.

8. The method of zoning a high concrete-faced rockfill dam body of claim 7, wherein: The low stress zone is filled with the block stone material, and the high stress zone is filled with the sand gravel material.

9. The method of zoning a high concrete faced rockfill dam of claim 1 wherein: After the final dam body zoning scheme is determined, steps 3) to 5) are repeated to adjust the final zoning scheme of the dam body, and the difference between the final zoning schemes before and after is not more than 0.5m.

10. The method of zoning a high concrete-faced rockfill dam body of claim 1, wherein: In step 5), the dam body zoning scheme in step 1) is adjusted, specifically, the sand gravel material of the upstream upper part and the dam shell of the dam top is replaced with the block stone material.

Images