A centrifugal model test method for core wall deformation of 300m-high earth-rock dam

Abstract

The invention discloses a centrifugal model test method for the deformation of the core wall of a 300m-class extra-high earth-rock dam, which is suitable for the study of the deformation of the core wall of a 300m-class extra-high earth-rock dam that cannot be simulated as a whole by conventional geotechnical centrifugal model tests, and belongs to the field of soil mechanics test technology and application. The steps are as follows: (1) for an extra-high earth-rock dam with a dam height of H (>300m), n (≥4) local parts are selected on the axis of the core wall dam, and a centrifugal model test is performed under the condition of Ng according to the geometric scale 1 / N (N≤H / n); (2) an overweight substitute material (such as lead sand, iron sand, etc.) is arranged on the upper boundary of the local model so that the model bears the self-weight stress of the prototype level under the hypergravity field; (3) a semi-logarithmic fitting is performed on the n core wall local test data obtained in the test to obtain the relationship between the soil deformation increment Δs and the vertical height y; (4) an integral is performed from bottom to top along the height direction of the dam axis to obtain the distribution law of the core wall deformation.

Description

Technical Field

[0001] The present invention relates to a centrifugal model test method for the deformation of the core wall of a 300m-class extra-high earth-rock dam, which belongs to the field of soil mechanics test technology and application. The test method can effectively study the deformation characteristics of the core wall of a 300m-class extra-high earth-rock dam, which cannot be simulated as a whole by conventional geotechnical centrifugal model test methods. Background Art

[0002] A number of major water conservancy projects that have been built or are under construction in my country have adopted ultra-high core wall dams, such as Xiaolangdi (160m), Nuozadu (261.5m), Lianghekou (295m), Shuangjiangkou (314m), Changheba (240m), Maoergai (147m), Miaowei (139.8m), Quxue (164m), Dashimen (128.8m), Rumei (315m), etc. For ultra-high dams, especially 300m ultra-high dams, there is not much engineering experience at present, and physical model tests are an important means of studying the stress and deformation characteristics of dam bodies. However, using conventional geotechnical centrifuge model test methods, the ability to study ultra-high dams is generally below 200m, and dams exceeding 200m cannot be simulated as a whole.

[0003] Clarifying the deformation law of the core wall is the key to building a core dam, and it is even more important for extra-high core dams. However, at present, the deformation law of the core wall of 300m-class extra-high core dams is mostly studied by numerical simulation, and there is no direct and effective physical simulation method. Summary of the invention

[0004] The purpose of the present invention is to establish a new centrifuge model test method, by integrating the results of several local centrifuge model tests on the core wall, so as to obtain the deformation law of the core wall of a 300m-class super-high earth-rock dam.

[0005] The technical solution to achieve the purpose of the present invention is a centrifugal model test method for the deformation of the core wall of a 300m-class ultra-high earth-rock dam, comprising the following steps:

[0006] Step 1: for the 300m-class extra-high earth-rock dam project (the dam height is H) to be simulated, select n (n is not less than 4) core wall parts from bottom to top along the axis of the core wall dam, and conduct centrifuge model tests under Ng conditions according to the geometric similarity ratio 1 / N (N is not greater than H / n);

[0007] Step 2: The bottom boundary of each local model of the core wall is selected as the bottom surface of the model box, that is, the deformation of the bottom boundary of all local models of the core wall is limited to 0, so that the deformation increment is obtained by the test; the surface of the upper boundary of each local model of the core wall is arranged with super-heavy substitute materials (such as lead sand, iron sand, etc.), so that the self-weight stress of the local model of the core wall under the action of the super-gravity field is equal to the self-weight stress of the prototype;

[0008] Step 3, after obtaining the deformation of n core wall local model soils through experiments, semi-logarithmic fitting analysis is performed to obtain the relationship between the core wall deformation increment and the self-weight stress: Δs(y)=a*lg[ρ*g*(Hy)]+b, where y is the vertical height, which is the prototype value converted according to the similarity law of the centrifugal model;

[0009] Step 4: Integrate from bottom to top along the height direction of the dam axis to obtain the overall core wall deformation distribution law The h in the formula is the height from the current calculation point to the riverbed, which is the prototype value converted according to the similarity law of the centrifugal model, 0≤h≤H.

[0010] The beneficial effects of the present invention are as follows: the boundary conditions of the local model test of the core wall can be accurately controlled; the semi-logarithmic relationship between the core wall deformation increment and the self-weight stress can be obtained; and the overall deformation law of the core wall of a 300m-class ultra-high earth-rock dam can be obtained by integration.

[0011] By adopting the method of the present invention, the geotechnical centrifuge model test technology can be used to effectively carry out experimental research on the deformation law of the core wall of a 300m-class ultra-high earth-rock dam project. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 Taking a 300m-high core dam as an example, several schematic diagrams of the core walls are selected;

[0013] Figure 2 This is the layout diagram of the local test model of the core wall;

[0014] Figure 3 is the relationship curve between the core wall deformation increment and self-weight stress obtained from the test;

[0015] Figure 4 is the integral distribution law of the core wall deformation. DETAILED DESCRIPTION

[0016] Example 1

[0017] A 300m-class extra-high core rockfill dam with a maximum dam height of 315m needs to study the deformation law of its core wall. The usual geotechnical centrifuge model test can only fully simulate the situation where the dam height is not more than 200m. The "A 300m-class extra-high earth-rock dam core wall deformation centrifuge model test method" was adopted to carry out 4 groups of local tests and integrate to obtain the overall deformation law of the dam core wall, including the following steps:

[0018] Step 1: Collect the core wall soil and upstream and downstream dam shell materials from the project site, transport them to the laboratory, remove impurities and prepare them according to the density, moisture content, gradation and other parameters of the project site;

[0019] Step 2, such as Figure 1, select four core wall parts from bottom to top along the dam axis, and the model layout is as follows Figure 2 (unit: mm), centrifugal model test was carried out, and the test conditions are shown in Table 1; the geometric scale of the local test of the core wall is 1 / 50, and the centrifugal acceleration is 50g;

[0020] Table 1 Test conditions of local core wall model

[0021]

[0022]

[0023] Step 3: According to the results of the local test of the core wall, the relationship curve between the core wall deformation increment and the self-weight stress is fitted, as shown in Figure 3 ;

[0024] Step 4: Integrate from bottom to top to obtain the overall deformation law of the core wall at the dam axis, as follows: Figure 4 .

Claims

1. A centrifugal model test method for core wall deformation of a 300m-class extra-high earth-rock dam, comprising the following steps: Step 1: For the 300m-high earth-rock dam project to be simulated, the height of the earth-rock dam is H, and n core wall parts are selected from bottom to top along the axis of the core wall dam. According to the geometric similarity scale 1 / N, a centrifuge model test is carried out under the condition of Ng, where N≤H / n, n≥4; Step 2: The bottom boundary of each local model of the core wall is selected as the bottom surface of the model box, that is, the deformation of the bottom boundary of all local models of the core wall is limited to 0, so that the deformation increment is obtained by the test; the super-heavy replacement material is arranged on the upper boundary surface of each local model of the core wall, so that the self-weight stress of the local model of the core wall under the action of the super-gravity field is equal to the self-weight stress of the prototype; Step 3, after obtaining the deformation increment Δs of the n core wall local model soils through experiments, and then through semi-logarithmic fitting analysis, the relationship between the core wall deformation increment Δs and the self-weight stress is obtained: Δs(y)=a*lg[ρ*g*(Hy)]+b, where y is the vertical height, which is the prototype value converted according to the similarity law of the centrifugal model; Step 4: Integrate from bottom to top along the height direction of the dam axis to obtain the distribution law of the overall core wall deformation s along the height The h in the formula is the height from the current calculation point to the riverbed, which is the prototype value converted according to the similarity law of the centrifugal model, 0≤h≤H.

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