By means of a series of large-scale shaking model tests, the mechanism of side slope’s superficial dynamic effect under earthquake disturbance and its anchoring prevention were experimentally studied to the typical pattern of small collapse-slide and shallow soil damage along Dujiangyan to Yingxiu section of national highway No.213 in Wenchuan earthquake region. Using a 2.1 m height single-side model slope built by sand blended with clay and excited by three typical earthquake waves of 0.253g and 0.471g accelerations separately, the different quantitative dynamic response characteristics between the superficial and deep position of slope body were analyzed comparatively. These response analysis included magnification factors of acceleration, dynamic strain value and predominant frequency corresponding with three height prototype single-side slopes of 2.1 m, 10.7 m and 21.5 m. The result showed that the accelerate response of slope body’s surface was approximately 1.4 times of the deep position averagely, and predominant frequency of vibration was increased around 45 percent accordingly. In particularly, it presented significant dynamic shear strain of superficial stratum and dynamic tension-compression strain between the superficial and deep position, which reached 6.5×10^-3and 2.2×10^-3respectively and averages about soil’s failure limit strain. Due to the stress superposition of the stripping action conducted by tension-compression strain of incompatible response movement between superficial and deep position and the kneading action deduced by shear strain, slope’s superficial failure or damage were occurred. Furthermore, with comparative shaking table model tests between anchored slope and natural slope, the mechanism of superficial failure prevention effect of anchoring structures was preliminary studied. It was found that, anchoring structures could remarkably reduce superficial accelerate response by about 15 to 35 percent and increase natural frequency by 39 percent compared with the original natural slope at slope top in experiments. Anchoring prevention mechanism included as follows: firstly, earthquake resonant interaction was reduced due to higher natural frequency of anchored slope; secondly, the incompatible movement was diminished by anchoring structures which joined the slope’s superficial and deep position into a whole; thirdly, stripping action induced by stress wave reflection on slope’s surface was counteracted by the anchoring force. These results can provide references for road reconstruction and hazards prevention after earthquake.
