AU2020100727A4

AU2020100727A4 - Method For Dynamic Test Of 100 m-High Earth And Rockfill Dam Under Real Stress Field

Info

Publication number: AU2020100727A4
Application number: AU2020100727A
Authority: AU
Inventors: Hongjun Li; Zeping XU; Zuwen YAN; Zhengquan YANG; Jianming Zhao; Hong Zhong; Kaibin ZHU
Original assignee: China Institute of Water Resources and Hydropower Research
Current assignee: China Institute of Water Resources and Hydropower Research
Priority date: 2019-06-25
Filing date: 2020-05-07
Publication date: 2020-06-18
Anticipated expiration: 2028-05-07
Also published as: CN110258435A

Abstract

The present invention provides an innovative approach for a centrifuge shaking table test of a 100 m-high earth and rockfill dam under a real stress field. The method includes: taking a maximum particle size allowed for a size of a model box as an upper limit, determining a model material gradation by proportionally and equally replacing an oversize part, compacting and filling a 100 cm-high model dam in layers, controlling according to a designed maximum dry density of the dam, and arranging, at an equal height, 5 acceleration sensors and a displacement meter along the dam height at a position of a dam axis; adjusting a centrifugal acceleration to five stages respectively to perform shaking table model tests, and inputting a sine wave 3 times under the corresponding centrifugal acceleration with a vibration frequency of 2 Hz, an acceleration amplitude of 0.3 g and a duration of 20 s in each test stage; using a hyperbola to perform fitting and regression analysis on acceleration peak values and subsidence displacements under different centrifugal accelerations at different heights, and extending a fitting curve to a centrifugal acceleration of 100 g to obtain evaluation indexes corresponding to the 100 m-high earth and rockfill dam under the real stress field. The present invention can quantitatively determine the key evaluation indexes such as the dynamic response acceleration distribution law, the amplitude and the dam crest seismic-induced deformation of the 100 m-high earth and rockfill dam subjected to strong earthquakes under the real stress field. paper envelope curve Average Curve Test - Lower envelope curve 0-0 1000 100 10 1 0.1 0.01 Particle size/mm

Description

METHOD FOR DYNAMIC TEST OF 100 m-HIGH EARTH AND ROCKFILL DAM UNDER REAL STRESS FIELD

TECHNICAL FIELD

The present invention belongs to the technical field of strong earthquake simulation of earth 5 and rockfill dams, and particularly relates to a method for a dynamic test of a 100 m-high earth and rockfill dam under a real stress field.

BACKGROUND

At the present stage, seismic damage data on 100 m-high earth and rockfill dams subjected to strong earthquakes is still very limited. A large-scale shaking table model test on the ground is an 10 important method to study dynamic response characteristics of the 100 m-high earth and rockfill dams. By observing stress and deformation of a model dam under a series of earthquakes, the stress and deformation of the prototype dam are obtained with a related similarity ratio. However, the large-scale shaking table model test on the ground cannot simulate real stress field of prototype. The similarity ratio of stress and strain between the model and the prototype should be 15 guaranteed, as the strength and deformation characteristics of soil materials for earth and rockfill dams are directly related to the stress levels. Therefore, the results of the shaking table model test on the ground cannot be directly adopted into the seismic design of the prototype. Nevertheless, Centrifuge shaking table model test is an innovative technology developed rapidly in recent years. It is an effective and advanced research method and test technology to study the dynamic 20 problems of high earth and rockfill dam, such as mechanism of seismic failure, verification of numerical simulation and application of seismic reinforcement measures, etc.

However, based on the present capacity of centrifuge shaking table, the volume and weight of the model of 100 m-high earth and rockfill dam has to be reduced in large proportion to conduct centrifuge shaking table model test. As the dynamic properties of rock-fill materials after 25 reducing in a large scale are quite different from those of original dam construction materials. It is difficult to quantitatively analyze the dynamic features of the prototype dam, such as acceleration distribution, dynamic amplitude and dam crest subsidence, etc. Therefore, it is necessary to find out an innovative method for dynamic model test of a 100 m-high earth and rockfill dam in centrifuge.

SUMMARY

The present invention provides a method for a dynamic centrifuge model test of a 100 mhigh earth and rockfill dam. On the basis of ensuring that the similarity rate of stress and strain between a model and a prototype dam equal to 1, a series of earthquake motions with different centrifugal accelerations are obtained to achieve dynamic response characteristics of a model dam, 35 and dynamic response characteristics of a prototype dam with a corresponding dam height can be i

2V2$\Wm 07 May 2020 obtained based on the related similarity rate (the centrifugal accelerations). Through regression analysis and curve fitting, a straight relationship between the centrifugal accelerations and the dynamic characteristics of prototype dam bodies with different dam heights could be established, and the dynamic response characteristics of the 100 m-high prototype dam subjected to strong 5 earthquakes under a real stress field can be quantitatively obtained by extending a fitting curve.

The present invention provides a method for a dynamic test of a 100 m-high earth and rockfill dam under a real stress field, including the following steps:

step 1: take a maximum particle size allowed for the centrifuge model box as the upper limit of the model material, and determine the material gradation by proportionally replacing the 10 oversize particles of the prototype material, making a model dam of 100 cm high by layered compacting and filling, where the density of the model dam is controlled according to the designed maximum dry density of the prototype dam, and acceleration sensors and displacement sensors at dam axis, with 5 layers along dam height are arranged.

step 2: operate centrifuge with the acceleration of five stages, 10 g, 20 g, 30 g, 40 g and 50 g 15 respectively, to perform shaking table model tests, and input a sine wave 3 times under the corresponding centrifugal acceleration with a vibration frequency of 2 Hz, an acceleration amplitude of 0.3 g and a duration of 20 s in each test stage.

step 3: use hyperbola function to perform fitting and regression analysis for acceleration peak values and subsidence displacements of the model dam under different centrifugal accelerations 20 at different heights, and extend the fitting curve to the centrifugal acceleration of 100 g, to obtain, on this basis, the evaluation indexes of 100 m-high earth and rockfill dam under the real stress field, where the evaluation indexes comprise acceleration distribution law, amplitude and dam crest seismic-induced deformation.

Further, the method includes:

by the application of steps 1 to 3, and with the increase of the model size and the centrifugal acceleration, the method can be directly applied to the centrifuge shaking table model tests of earth and rockfill dams with the heights of 150 m or above.

Compared with the traditional methods, the present invention has the following beneficial effects:

By using present centrifuge shaking table test device and technology, the key evaluation indexes such as the dynamic response acceleration distribution law, the amplitude and the dam crest seismic-induced deformation of the 100 m-high earth and rockfill dam under the real stress field can be quantitatively determined, which has the following advantages:

1. ft can ensure that the similarity rate of stress and strain between the model dam and the 35 prototype dam is 1, and centrifuge shaking table model tests of the 100 m-high earth and rockfill

2V2$\Wm 07 May 2020 dam under the real stress field can be finished through present existing centrifuge shaking table technology and device.

2. Through curve fitting and regression analysis, the key evaluation indexes such as the dynamic response acceleration distribution law, the amplitude and the dam crest seismic-induced 5 deformation of the 100 m-high earth and rockfill dam subjected to strong earthquakes under the real stress field can be quantitatively determined. It will provide scientific basis for aseismatic design of the dam and formulation of seismic measures.

3. The applicability and accuracy of an existing dynamic calculation and analysis model in the dynamic analysis of the 100 m-high earth and rockfill dam can be effectively estimated.

4. With the upgrading of centrifuge shaking table test device, this method can be directly extended to centrifuge shaking table model tests of a hydraulic structure with a height of 150 m or above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an arrangement of a centrifuge shaking table model test of 15 the present invention;

FIG. 2 is a curve graph of a rockfill particle gradation;

FIG. 3 is a distribution diagram of dynamic response accelerations along a dam height at a position of a dam axis under different centrifugal accelerations;

FIG. 4 is a distribution trend and fitting curve graph of dam crest peak accelerations under 20 different centrifugal accelerations; and

FIG. 5 is a distribution trend and fitting curve graph of dam crest seismic-induced deformation amplitudes under different centrifugal accelerations.

DETAILED DESCRIPTION

The present invention is described in detail below with reference to various implementations 25 shown in the accompanying drawings, but it should be noted that these implementations are not intended to limit the present invention, and functions, methods, or structural equivalent transformations or replacements made by those of ordinary skill in the field according to these implementations fall within the protection scope of the present invention.

In this embodiment, through an existing centrifuge shaking table test device and technology, 30 on the basis of ensuring that the similarity rate of stress and strain between a model dam and a prototype dam is 1, key evaluation indexes such as a dynamic response acceleration distribution law, an amplitude and dam crest seismic-induced deformation of a 100 m-high earth and rockfill dam under a real stress field are quantitatively determined.

The present invention provides a method for a dynamic test of a 100 m-high earth and 35 rockfill dam under a real stress field. On the basis of ensuring that the similarity rate of stress and

2V2$\Wm 07 May 2020 strain between a model and a prototype dam is 1, a same earthquake motion is input under a plurality of centrifugal accelerations to obtain dynamic response characteristics of a model dam, and dynamic response characteristics of prototype dams with different dam heights can be obtained based on the similarity rate relation (the centrifugal accelerations). Through regression 5 analysis and curve fitting, an internal relation between the centrifugal accelerations and the dynamic characteristics of prototype dam bodies with different dam heights is established, and a centrifuge shaking table model test method can be used to quantitatively obtain the dynamic response characteristics of the 100 m-high prototype dam subjected to strong earthquakes under a real stress field by extending a fitting curve.

The method of the present invention based on the foregoing principle includes the following steps:

a): take a maximum particle size allowed for the centrifuge model box as the upper limit of the model material, and determine the material gradation by proportionally replacing the oversize particles of the prototype material, making a model dam of 100 cm high by layered compacting 15 and filling, where the density of the model dam is controlled according to the designed maximum dry density of the prototype dam, and acceleration sensors and displacement sensors at dam axis, with 5 layers along dam height are arranged.

b): operate centrifuge with the acceleration of five stages, 10 g, 20 g, 30 g, 40 g and 50 g respectively, to perform shaking table model tests, and input a sine wave 3 times under the 20 corresponding centrifugal acceleration with a vibration frequency of 2 Hz, an acceleration amplitude of 0.3 g and a duration of 20 s in each test stage.

c): use hyperbola function to perform fitting and regression analysis for acceleration peak values and subsidence displacements of the model dam under different centrifugal accelerations at different heights, and extend the fitting curve to the centrifugal acceleration of 100 g, to obtain, 25 on this basis, the evaluation indexes of 100 m-high earth and rockfill dam under the real stress field, where the evaluation indexes comprise acceleration distribution law, amplitude and dam crest seismic-induced deformation.

Embodiment 1

The schematic diagram of a model arrangement is shown in FIG. 1. A dam construction 30 material is granite rockfill. A model dam has a bottom width of 200 cm and a height of 100 cm. Upstream and downstream dam slopes are 1:1. In the figure, there are an earth and rockfill dam 1, acceleration sensors 2 and a laser displacement sensor 3.

Solid lines in FIG. 2 are design gradation curves of an earth and rockfill dam. A centrifuge shaking table model test was performed under a reduced scale according to the method. The 35 maximum particle size was 20 mm. A broken line in FIG. 2 is a determined gradation of the

2V2$\Wm 07 May 2020 model test.

When a centrifugal acceleration rose to 10 g, a seismic wave was input along the river flow with the waveform of a sine wave and a frequency of 20 Hz, vibration was performed 3 times, a peak acceleration was 4 g, and each vibration lasted 2 s. When the centrifugal acceleration rose to 5 20 g, the seismic wave was input along the river flow with the waveform of a sine wave and a frequency of 40 Hz, vibration was performed 3 times, the peak acceleration was 8 g, and each vibration lasted 1 s. When the centrifugal acceleration rose to 30 g, the seismic wave was input along the river flow with the waveform of a sine wave and a frequency of 60 Hz, vibration was performed 3 times, the peak acceleration was 12 g, and each vibration lasted 2/3 s. When the 10 centrifugal acceleration rose to 40 g, the seismic wave was input along the river flow with the waveform of a sine wave and a frequency of 80 Hz, vibration was performed 3 times, the peak acceleration was 16 g, and each vibration lasted 0.5 s. When the centrifugal acceleration rose to 50 g, the seismic wave was input along the river flow with the waveform of a sine wave and a frequency of 100 Hz, vibration was performed 3 times, the peak acceleration was 20 g, and each 15 vibration lasted 0.4 s.

Five acceleration sensors are arranged along the height on the dam axis and one subsidence sensor is arranged on the dam crest to measure the dynamic response and seismic deformation of the dam.

Centrifuge shaking table model tests were performed on the model dam. The distribution of 20 the dam axis accelerations along the dam height, peak values of dam crest accelerations and permanent deformation amplitudes under different centrifugal accelerations are shown in FIG. 3, FIG. 4 and FIG. 5. The results of physical model analysis showed that with the increase of the centrifugal acceleration, the model dam acceleration amplitude and the dam crest subsidence had good regularity. After polynomial fitting, by extending the dam crest peak acceleration and a dam 25 crest seismic-induced deformation curve, the amplitude of the dynamic response acceleration and the dam crest subsidence corresponding to the model dam of the 100 m-high earth and rockfill dam model dam (with a centrifugal acceleration of 100 g) could be quantitatively obtained, and were 20.62 m/s² and 80.2 cm respectively, and the effect was good.

It is obvious to those skilled in the art that the present invention is not limited to the details of 30 the foregoing exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or basic features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-limiting in every respect, and the scope of the present invention is defined by the appended claims rather than the foregoing description, and all changes falling within the meaning and scope of equivalent elements of the 35 claims should be included in the present invention.

Claims

1. A method for a dynamic test of a 100 m-high earth and rockfill dam under a real stress field, comprising the following steps:

step 1: taking a maximum particle size allowed for the centrifuge model box as the upper 5 limit of the model material, and determining the material gradation by proportionally replacing the oversize particles of the prototype material, making a model dam of 100 cm high by layered compacting and filling, wherein the density of the model dam is controlled according to the designed maximum dry density of the prototype dam, and acceleration sensors and displacement sensors at dam axis, with 5 layers along dam height are arranged.

10 step 2: operating centrifuge with the acceleration of five stages, 10 g, 20 g, 30 g, 40 g and 50 g respectively, to perform shaking table model tests, and inputting a sine wave 3 times under the corresponding centrifugal acceleration with a vibration frequency of 2 Hz, an acceleration amplitude of 0.3 g and a duration of 20 s in each test stage.

step 3: using hyperbola function to perform fitting and regression analysis for acceleration 15 peak values and subsidence displacements of the model dam under different centrifugal accelerations at different heights, and extending the fitting curve to the centrifugal acceleration of 100 g, to obtain, on this basis, the evaluation indexes of 100 m-high earth and rockfill dam under the real stress field, wherein the evaluation indexes comprise acceleration distribution law, amplitude and dam crest seismic-induced deformation.

20 2. The method for a dynamic test of a 100 m-high earth and rockfill dam under a real stress field according to claim 1, further comprising:

after steps 1 to 3 are completed, directly applying the method to centrifuge shaking table model tests of earth and rockfill dams with heights of 150 m or above with the increase of the model size and the centrifugal acceleration.