Method of Analysis for Seismic Force of Debris Flows Induced by Landslides

 

Dian Xu

School of Civil Engineering in Chongqing University of Science & Technology, China; Address: college town of Shapingba District in Chongqing, Postal code: 401331; Tel: 0086-15223412478; e-mail: xudian2000@126.com

Chang-xi Mao

Hydraulic Engineering Department in Nanjing Hydraulic Institute, Nanjing Postal code: 210029

Chang-ming Bu

School of Civil Engineering in Chongqing University of Science & Technology, China; Address: college town of Shapingba District in Chongqing, Postal code: 401331; e-mail: buchangming45@163.com

 

 ABSTRACT

Recently geologic disasters of landslides with debris flows have frequently occurred, which closely relate to earthquakes and rain storms. Thus it is desired to develop a modified calculation method for seismic force. That is, besides the original consideration of the inertia force of earthquake acceleration, another term of the excess seepage force due to the successive vibration of earthquake waves should be added. This additional force can reduce the effective weight of soil mass and make the slope easier to slide. Here an “infinite slope” type landslide with a parallel straight line plane on the weathered mountain slope is analyzed. The formulas for shallow slide under rainy saturated and unsaturated conditions are derived. By comparing the calculated results under different slope gradient earthquake accelerations and excess seepage forces, the calculated safety factor has been found to be in error by 25% if the excess seepage force is not considered, and it decreases further one half during saturation of the slope by rain

Keywords: debris flow; earthquake force; excess seepage force; calculated formulas

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