The Physical Mechanism and Prevention Method of Loess Slope Failure Induced By the Coupling Effect of Earthquake and Rainfall


Abstract eng:
Earthquakes and rainfalls are the two most important factors to cause landslides. However, the coupling effect of the two factors on landslides is rarely considered in the slope stability analysis due to the lack of conclusive evidence of slope failure induced by the coupling effect. Unfortunately, some cases of massive failure of loess slopes and long distance sliding of mudflow caused by the Minxian-Zhangxian Ms6.6 Earthquake, Gansu Province, China in 2013 were seriously influenced by the persistent heavy rain before the earthquake. This should be the conclusive coupling event under earthquake and rainfall around the world. Those loess landslides induced by the Earthquake show the features associated with soil flow, among which the landslide at Yongguang Village, the largest one with more than 1.5km sliding distance, led to a serious loss of 14 households buried and 12 persons dead. In this paper, firstly, the influence laws of water content on static and dynamic shear strength of loess soil were investigated by means of triaxial tests, dynamic triaxial tests and torsional shear tests. Secondly, the shaking table tests were performed with the three coupling patterns of earthquake and rainfall, i.e. a rainfall before and after an earthquake, and liquefaction triggered mud flow. In the tests, the time histories of acceleration, pore pressure and soil pressure in the loess slope model were recorded. Based on the tested results, the mechanism of failure and sliding of loess slopes induced by the coupling effect of earthquake and rainfall was analyzed. The critical PGAs causing gentle loess slope completely failure at different rainfall conditions were provided. And then, by means of the fuzzy information processing, the methods of predicting the sliding distance and the affected region of a landslide were presented respectively. Furthermore, a method of seismic safety design for the engineering practice to prevent the disaster of loess slope failures induced by coupling effect of earthquake and rainfall was proposed. The results shown that a rainfall may predominately decrease shear strength of loess deposit, which made loess slopes more easy to lose their stability under the effect of earthquakes due to an obvious decrease of static and dynamic cohesions and internal friction angles. The saturated loess layer in slopes may liquefy under the effect of strong earthquakes, which usually trigger a long distance soil flow. Earthquakes may cause some fissures in the vertical direction in loess deposit, which may favor the down seepage of rainfall in the loess slopes. Therefore, a persistent rainfall or heavy rainfall after an earthquake may easily induce landslides in loess areas. For the above-mentioned reason, the coupling effect of earthquakes and rainfalls on stability of loess slopes should be well considered in landslides disaster mitigation and risk management of landslides.

Contributors:
Conference Title:
Conference Title:
16th World Conference on Earthquake Engineering
Conference Venue:
Santiago (CL)
Conference Dates:
2017-01-09 / 2017-01-13
Rights:
Text je chráněný podle autorského zákona č. 121/2000 Sb.



Record appears in:



 Record created 2017-01-18, last modified 2017-01-18


Original version of the author's contribution as presented on USB, paper 4783.:
Download fulltext
PDF

Rate this document:

Rate this document:
1
2
3
 
(Not yet reviewed)