关键词: 汶川地震, 陡倾顺层斜坡, 离心振动台试验, 动力响应, 失稳机制

Abstract: The stability of steep bedding slope is generally better under static force condition, but lots of instable fracture phenomena occurred in this type of slop during “5.12” Wenchuan earthquake. A special dynamic deformation failure mode, toppling deformation, is found in steep soft-hard alternative bedding slope by field investigation. Based on existing knowledge and a failure case, i.e. Shuimogou soft-hard alternative bedding of steep slope in Wenchuan County, Sichuan, the mechanism of toppling deformation and the characteristics of dynamic response of this type of slope under strong earthquake are studied by centrifugal shaking table test. On slope surface, acceleration amplification factor increases first, then decreases, and finally increases with the increase of elevation. The dynamic response shows two peak values at 1/3 of slope height and slope shoulder. At the same horizontal height, the closer to the slope surface, the greater the magnification factor of acceleration, which means that the free face effect of slope rock-soil body is more significant. Experiment reveals the instability mechanism of this slope: under the repeated actions of strong earthquake loads, differential shear failure occurs between soft rock and hard rock, rock-soil body sliding along the dominant layer is hindered, the rock-soil body nearby slope toe bends and uplifts; the potential sliding surfaces are not connected completely, under the tremendous horizontal inertia force of earthquake, shattered rock stratum at slope shoulder generates cantilever beam bending toppling toward free face, so that the entire slope undergoes tension fracture slippage?lower bending?upper toppling instable fracture.

Key words: Wenchuan earthquake, steep bedding slope, centrifugal shaking table test, dynamic response, instability mechanism