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| Excess interstitial water pressure within sliding zone induced by strong seismic shaking：An initiation model of the DGB landslide |
| CUI Shenghua，PEI Xiangjun，HUANG Runqiu，ZHU Ling |
(State Key Laboratory of Geohazard Prevention and Geoenvironment Protection，Chengdu University of Technology，
Chengdu，Sichuan 610059，China) |
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Abstract Daguangbao(DGB) landslide，formed within a saturated bedding fault 400 m in depth，is the largest landslide triggered by the 2008 Wenchuan earthquake. To study pore and crack water pressures (i.e.，interstice water pressure) responses within weak layers，a series of shaking table tests were conducted on a geological model with a saturated weak interlayer. The results show that the excess interstice water pressure within the weak layer is much larger than that in both the upper and lower layers and that the excess water pressure of the weak layer is characterized by transient generation and gradual accumulation. It was proposed that compression-tension and shear behaviors of the model depending on uncoordinated deformation and dynamic damage depending on uncoordinated deformation within the weak layer respectively induce transient excess water pressure and accumulation of the excess water pressure. An effective stress model for earthquake-inducted landslides under both horizontal and vertical shaking conditions，containing the interstice water pressure ration rw and the effective area index of interstice water pressure η，was developed. For the DGB landslide，site investigations show that η is in the range of 0.7-0.9 and that the effective stress of the sliding zone decreases to zero while rw ranges from 0.73 to 1.04. The shaking table tests also show that the seismic parameters in the landslide area during the Wenchuan earthquake can make rw reach the above range. Finally，the failure mechanism of the DGB landslide mechanism from strong seismic action，damage and expansion of dislocation interface resulted from dynamic uncoordinated deformation，excitation of the excess interstitial water pressure to initiation of landslide was concluded.
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2020, Vol. 39 
