Centrifuge Shakers and Research Overview at Home and Abroad ![]()
With the development of the similarity theory of dynamic centrifugal model tests, the shaking table model test technology has also matured. Seven centrifuge model laboratories in the United States and the United Kingdom have used their own centrifuge power test equipment to conduct a well-known test for verifying numerical analysis methods. The project name is "Verification of Centrifugal Simulation Tests for Liquefaction Analysis Methods" (VELACS) t ". The participating organizations are Davi: University of California, California Institute of Technology, Cambridge University, Colorado Buller, Massachusetts Institute of Technology, Princeton University, and Rensselaer Polytechnic Institute. The test is conducted on nine geotechnical models for vibration and liquefaction tests, and the test The results validate the numerical analysis results. During the test, sinusoidal seismic waves were input to simulate the dynamic responses of nine types of dams or strata. Before the test was completed, another group of researchers used their constitutive mathematical models to perform numerical simulation analysis on the same structure. And submit the analysis results. Since the input seismic wave in the dynamic centrifugal model test is slightly different from the seismic wave used in the calculation, after the test is completed, the input seismic wave used in the test is entered again. Numerical analysis and forecasting, and eventually compared with the test results.
The research results of Velacs prove that as long as the vibration device can produce seismic input that meets the requirements, and carefully design and make models, the existing technical level can already well achieve the repeatability of the test results between the various laboratories. Using the test results of the centrifugal model, the following dynamic analysis procedures were verified and compared: (1) equivalent linear total stress analysis procedures QUAD-4, FEDAM, LUSH and FLUSH procedures; (2) indirect accidental dynamic response procedures DESRA and TARA; (3) Dynamic response analysis programs coupled with Biot's consolidation theory, DYSACZ, DYNAFLOW and SWANDYNE programs. The results show that only the fully effective nonlinear effective stress program can predict the displacement of non-dilatable soil. For the displacement of dilatant soil, none of the above programs can be coupled, so the constitutive relationship of the soil under dynamic load, More in-depth and meticulous research needs to be done. This research result of Velacs is of great significance for using dynamic centrifugal simulation tests to recognize the defects of numerical analysis methods, modify numerical models, and improve the accuracy of data analysis.
The University of Colorado used a servo-hydraulic vibration table to carry out a dynamic centrifugal simulation test, to study and evaluate the seismic response of dams with different densities at different amplitudes and vibration frequencies, and observe the deformation and liquefaction characteristics of the soil. October 17, 1989 in Santa Cm, USA. An earthquake of magnitude 7.1 on the Richter scale occurred in the mountain area, not far from the epicenter. The 'Neill Forebay earth and rock dam was previously installed with an acceleration sensor embedded in the toe and top of the dam, and the dynamic response of the dam was recorded. The height of the dam was 18.3m, the bottom width was 122.0m, and the top width of the dam was 10.7m. The maximum horizontal acceleration at the top of the dam reaches 0.5g. The field observation data provides the conditions for verifying the centrifugal model test. Law et al. [5] used the University of Colorado 400g-t centrifuge to perform dynamic centrifugal model tests on four model earth-rock dams of different sizes. Reliable test data, these test data are compared with the prototype observation results, proving that the model test results are very close to the prototype observation results. The use of dynamic centrifugal model test can more accurately simulate the prototype earthquake situation.
The University of Cambridge in the United Kingdom used the method of bumpy roads (Bumping Road) to generate sinusoidal vibrations in centrifuges to study the seismic stability of slopes under seepage conditions la}. Steedman and Zeng also studied the effect of earthquake on cantilever beam retaining walls.11] The analysis shows that the seismic response of cantilever beam retaining walls depends largely on the rigidity of the soil and retaining wall system, and the natural vibration of flexible cantilever beam retaining walls The frequency is close to the main frequency of the earthquake. The dynamic centrifugal model test proves that the calculation results of the commonly used quasi-static analysis method will greatly underestimate the impact of the earthquake.
In recent years, Japan has become more active in the manufacture and research of geotechnical centrifuges and vibration equipment. It has successively constructed Dalin Group Geotechnical Centrifuge (700g-t), the Civil Engineering Research Institute Centrifuge (PWRI, 600g-t) and Takenaka Technology Research Institute (400-500g-t). Suzuki et al. Used a centrifuge shaker to study the dynamic response of the liquefied foundation B '. For loose sand foundations, deep cement mixing was used to solidify the grid in the field. The model test research proved that the grid was in the vibration direction The size has a great influence on the anti-liquefaction ability of the foundation. The test also shows that lowering the groundwater level can increase the anti-liquefaction ability of the foundation. Japan Nagase et al. Also studied the permanent deformation of inclined ground due to seismic liquefaction, and observed a linear relationship between the thickness of the liquefied soil layer and the permanent deformation of the ground in logarithmic coordinates. The Disaster Prevention Research Institute of the University of Tokyo in Japan used medium-sized centrifuges and shakers to study the propagation of shear waves in dry sand layers. . Due to the large number of centrifuge shakers in Japan, the range of seismic research projects in recent years has been more extensive.
The Hong Kong University of Science and Technology used a horizontal two-way centrifuge shaker in 2001. The laboratory is also equipped with two model boxes for dynamic model tests. The centrifuge shaker has been used to test the deformation and stability of weathered granite loose-filled slopes under earthquake conditions: "In the experiment, it is possible to simulate earthquakes with different amplitudes and observe vibrations under different slope heights or gradients Deformation, changes in pore water pressure and changes in vibration acceleration, etc. Using this two-way shaker, sand liquefaction tests were also carried out, and research work was carried out to verify the constitutive model of the sand.
The Nanjing Institute of Hydraulic Research in China built a small centrifuge shaker in 2002], using this shaker to complete the vibration deformation and stability study of the face rockfill dam of Xinjiang Jilintai Hydropower Station. Tsinghua University developed and installed an electro-hydraulic vibration table on its 50g-t small centrifuge in 2003, and has completed the commissioning work. Tongji University is also installing a vibrating table device on the newly built 1508-t centrifuge.
The research results of Velacs prove that as long as the vibration device can produce seismic input that meets the requirements, and carefully design and make models, the existing technical level can already well achieve the repeatability of the test results between the various laboratories. Using the test results of the centrifugal model, the following dynamic analysis procedures were verified and compared: (1) equivalent linear total stress analysis procedures QUAD-4, FEDAM, LUSH and FLUSH procedures; (2) indirect accidental dynamic response procedures DESRA and TARA; (3) Dynamic response analysis programs coupled with Biot's consolidation theory, DYSACZ, DYNAFLOW and SWANDYNE programs. The results show that only the fully effective nonlinear effective stress program can predict the displacement of non-dilatable soil. For the displacement of dilatant soil, none of the above programs can be coupled, so the constitutive relationship of the soil under dynamic load, More in-depth and meticulous research needs to be done. This research result of Velacs is of great significance for using dynamic centrifugal simulation tests to recognize the defects of numerical analysis methods, modify numerical models, and improve the accuracy of data analysis.
The University of Colorado used a servo-hydraulic vibration table to carry out a dynamic centrifugal simulation test, to study and evaluate the seismic response of dams with different densities at different amplitudes and vibration frequencies, and observe the deformation and liquefaction characteristics of the soil. October 17, 1989 in Santa Cm, USA. An earthquake of magnitude 7.1 on the Richter scale occurred in the mountain area, not far from the epicenter. The 'Neill Forebay earth and rock dam was previously installed with an acceleration sensor embedded in the toe and top of the dam, and the dynamic response of the dam was recorded. The height of the dam was 18.3m, the bottom width was 122.0m, and the top width of the dam was 10.7m. The maximum horizontal acceleration at the top of the dam reaches 0.5g. The field observation data provides the conditions for verifying the centrifugal model test. Law et al. [5] used the University of Colorado 400g-t centrifuge to perform dynamic centrifugal model tests on four model earth-rock dams of different sizes. Reliable test data, these test data are compared with the prototype observation results, proving that the model test results are very close to the prototype observation results. The use of dynamic centrifugal model test can more accurately simulate the prototype earthquake situation.
The University of Cambridge in the United Kingdom used the method of bumpy roads (Bumping Road) to generate sinusoidal vibrations in centrifuges to study the seismic stability of slopes under seepage conditions la}. Steedman and Zeng also studied the effect of earthquake on cantilever beam retaining walls.11] The analysis shows that the seismic response of cantilever beam retaining walls depends largely on the rigidity of the soil and retaining wall system, and the natural vibration of flexible cantilever beam retaining walls The frequency is close to the main frequency of the earthquake. The dynamic centrifugal model test proves that the calculation results of the commonly used quasi-static analysis method will greatly underestimate the impact of the earthquake.
In recent years, Japan has become more active in the manufacture and research of geotechnical centrifuges and vibration equipment. It has successively constructed Dalin Group Geotechnical Centrifuge (700g-t), the Civil Engineering Research Institute Centrifuge (PWRI, 600g-t) and Takenaka Technology Research Institute (400-500g-t). Suzuki et al. Used a centrifuge shaker to study the dynamic response of the liquefied foundation B '. For loose sand foundations, deep cement mixing was used to solidify the grid in the field. The model test research proved that the grid was in the vibration direction The size has a great influence on the anti-liquefaction ability of the foundation. The test also shows that lowering the groundwater level can increase the anti-liquefaction ability of the foundation. Japan Nagase et al. Also studied the permanent deformation of inclined ground due to seismic liquefaction, and observed a linear relationship between the thickness of the liquefied soil layer and the permanent deformation of the ground in logarithmic coordinates. The Disaster Prevention Research Institute of the University of Tokyo in Japan used medium-sized centrifuges and shakers to study the propagation of shear waves in dry sand layers. . Due to the large number of centrifuge shakers in Japan, the range of seismic research projects in recent years has been more extensive.
The Hong Kong University of Science and Technology used a horizontal two-way centrifuge shaker in 2001. The laboratory is also equipped with two model boxes for dynamic model tests. The centrifuge shaker has been used to test the deformation and stability of weathered granite loose-filled slopes under earthquake conditions: "In the experiment, it is possible to simulate earthquakes with different amplitudes and observe vibrations under different slope heights or gradients Deformation, changes in pore water pressure and changes in vibration acceleration, etc. Using this two-way shaker, sand liquefaction tests were also carried out, and research work was carried out to verify the constitutive model of the sand.
The Nanjing Institute of Hydraulic Research in China built a small centrifuge shaker in 2002], using this shaker to complete the vibration deformation and stability study of the face rockfill dam of Xinjiang Jilintai Hydropower Station. Tsinghua University developed and installed an electro-hydraulic vibration table on its 50g-t small centrifuge in 2003, and has completed the commissioning work. Tongji University is also installing a vibrating table device on the newly built 1508-t centrifuge.
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