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| Shake table model test study on dynamic response and damage mechanism of slopes with thin and thick rock combination |
| GUO Mingzhu,WANG Chen,GU Kunsheng,WANG Zhiying |
| (Key Laboratory of Urban Security and Disaster Engineering of Ministry of Education,Beijing University of Technology,
Beijing 100124,China) |
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Abstract A shaking table model test was designed and completed to study the dynamic response and damage mechanism of counter-bedding slopes with thin and thick rock combination,taking the pre-slide slope of the “Gongzha” landslide in the Xuelongnang area of the Jinsha River basin on the Qinghai—Tibet Plateau as a prototype. The test results show that the PGA amplification coefficient increases significantly above 1/2 slope height of the slope,that the PGA amplification coefficient changes differently from inside to surface at different elevations of the slope,and that the PGA amplification coefficient increases in the high-steep area but decreases at the foot of the slope. The input seismic wave frequency,amplitude and time compression ratio all have a relatively large effect on the slope dynamic response. When the input wave amplitude is relatively large,the PGA amplification coefficient increases significantly under high-frequency wave excitation. When the input wave frequency is less than the slope natural frequency,the PGA amplification coefficient increases with increasing the input wave frequency,and after exceeding the slope natural frequency,the PGA amplification coefficient decreases at the surface while decreases first and then increases at the inside of the slope with the input wave frequency. The effect of input wave amplitude on the slope dynamic response is related to the type of input wave,and the slope dynamic response law is different under different types of input wave excitation. Comprehensive analysis of the slope dynamic response and high-speed camera photo records indicates that the PGA amplification coefficient in the high-steep area of the slope surface is the largest while that the variation law of PGA amplification coefficient along the elevation inside the slope basically follows the elevation effect. The natural frequency of the slope drops significantly at 0.2 g amplitude seismic wave excitation,and at this time the slope structure changes under seismic action. The damage mode is:cracks initiating in the upper shoulder of the high-steep area→the crack area expanding downward→local instability of the upper right side of the high-steep area→the instability zone expanding to the whole high-steep area→the rock in the high-steep area being shaken down from top to bottom along with part of the lower thin rock block,and the damage process is accompanied by a slight uplift of the lower part of the slope. The test reveals the dynamic response law and damage mechanism of counter-bedding slope with thin and thick rock combination under the action of earthquake,which provides a basis for the prevention and control of such slopes.
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