Geomechanical model testing of surface rupture and bridge damage produced by discontinuous reverse faults

Abstract

通过地质力学模型试验研究了共线型和阶梯型两种非连续逆断层的运动引起上覆松散沉积层的破裂特征、沉积层与断层基岩之间的相互关系,并以汶川地震中受损的高原大桥为背景,通过改变桥梁与以上两种断层之间的布置关系研究了断层运动引起桥梁破坏的原因。引进数字散斑相关方法和高速摄像系统进行观测和记录试验过程。试验结果表明,非连续逆断层的破坏过程可分为4个不同的阶段,依次为弹性变形阶段、贯通阶段、滑移阶段和破坏阶段;结合观测系统解释说明了上述变化过程;分析了断层倾角和运动速度对断层基岩破坏形态和地表破裂带的影响;统计了地表破裂带宽度、断层基岩和沉积层抬升高度的关系,对比结果发现:共线型断层在破坏前聚集的能量较大、其地表破裂带宽度和抬升高度均大于阶梯型断层的;沉积层的抬升高度小于基岩的抬升高度;当桥梁模型垂直断层走向布置时均发生破坏,而平行断层走向布置时并没有破坏。 Coplanar and stepped buried reverse faults were carried out to study the relationship between faults movement and surface rupture appearing in soil layer using geomechanical model test.Furthermore,the Gaoyuan Bridge damaged during Wenchuan Earthquake was taken as an example to study the effect of fault propagation on bridge foundation by changing the arrangement of the bridge to these two types of faults.Digital speckle correlation method and high speed camera were used to observe and analyze the process of the fault movement.We have studied the effect of fault dip angles and loading rates.The research results indicated that the failure process of discontinues reverse faults can be divided into four stages:elastic stage,fault coalescence stage,sliding stage and failure stage.The width of surface rupture zone,the uplifts of bedrock and sediment layer were statistics,which indicated the width of surface rupture zone and the uplift of the coplanar type were greater than the stepped one.The larger the fault dip angle,the wider the surface rupture zone was resulted.The uplift of bedrock was greater than the uplift of soil layer.The bridge perpendicular to the fault was damaged and no damage to the parallel one.