【摘要】 针对汶川震区国道213线都江堰-映秀段道路边坡崩滑和岩土损伤深度所表现的地震扰动浅表动力效应现象,通过大型振动台模型试验,对浅表效应产生机理及防护工程锚固控制机制进行了初步研究。试验采用高2.1m的砂粘土单面坡模型和3种地震波形,定量分析对比了0.253g、0.471g强震作用下3种典型高度原型边坡坡表与坡体内部的加速度放大率、动应变、振动主频等动力学响应量。由试验结果知,坡表的加速度放大率和振动主频平均较同高程坡体内部约大40%和45%,坡表的动剪应变及其与坡体内部间的动拉压应变量值显著,0.471g地震下峰值甚至高达6.5×10-3和2.2×10-3,均接近土体的极限应变。边坡浅表动力效应体现于浅表层与坡体内部间的不协调运动,拉-压动应变将产生剥离拉应力;同时与浅表层岩土动剪应变的反复揉搓作用相叠加,浅表层损伤积累及触发崩滑。对此,进一步通过锚固边坡与自然边坡的振动台模型试验对比,初步探讨了浅表动力效应的锚固控制机理,发现锚固结构能有效抑制坡表的加速度放大,提高坡体自振频率,试验中锚固边坡坡顶处加速度放大率较自然边坡小约15%～35%,自振频率提高近39%。分析锚固控制机理得:锚固后坡表自振频率提高,减轻地震波激励下的共振作用;锚固结构穿过浅层损伤破坏面将坡体内部与坡表连成整体,消除两者的不协调运动;锚固力抵消地震波在坡表反射造成的拉裂。论文研究可为汶川震区震后次生崩滑物源条件分析及边坡灾害防范深度提供一定的参考。更多还原

【Abstract】 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 × 10-3 and 2.2 × 10-3 respectively 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.更多还原