须弥山石窟5号窟窟檐的地震动力响应模拟

Seismic Dynamic Response Simulation of the Eaves of Cave No.5 of Xumishan Grottoes

受自然环境的影响,宁夏须弥山石窟5号窟窟檐周边岩体风化严重,构造裂隙和卸荷裂隙发育,岩体的力学性质变差,直接威胁石窟窟檐和大佛的安全。为研究须弥山石窟5号窟窟檐的地震动力响应,根据现场勘察和倾斜摄影数据,建立了须弥山石窟5号窟的三维实体数值模型,并利用通用有限元软件ABAQUS对石窟造像及窟檐的地震动力响应进行了数值模拟计算,重点分析了石窟窟檐整体在地震作用下的应力场和位移场,进而利用应力等值线图结合现场调查判断了石窟窟檐整体可能产生的破坏模式。结果表明:在静力条件下,石窟窟檐局部产生应力集中,位移及应变都较小;在极端地震荷载作用下,石窟窟檐整体发生较大的不均匀沉降和滑动,威胁大佛的安全;石窟窟檐上的最大主应力和最小主应力数值都较大,石窟窟檐整体的破坏模式为拉张-倾倒破坏;在地震荷载作用下,地震波在混凝土中经过折射、反射、叠加,导致石窟窟檐中部的加速度放大系数比窟檐两侧的大,且石窟窟檐左侧的加速度放大系数大于右侧。该研究结果可为须弥山石窟5号窟窟檐加固设计提供科学依据。

Affected by the natural environment,the rock mass around the eaves of cave No.5 of Xumishan Grottoes in Ningxia is seriously weathered.Structural cracks and unloading cracks are developed,and the mechanical properties of the rock mass become worse,which directly threatens the safety of the eaves and the Giant Buddha.To study the seismic dynamic response of the eaves of cave No.5 in Xumishan grottoes,this paper establishes a three-dimensional solid model of cave No.5 in Xumishan Grottoes according to the field survey and tilt photography data.Then the paper carries out the seismic dynamic simulation calculation of cave statues and eaves by using the general finite element software ABAQUS,focusing on the analysis of the stress field and displacement field of the whole eaves under the action of earthquake,and based on the stress patterns and field investigation,determines the possible failure mode of the whole cave eaves.The results show that under the static condition,the stress concentration and displacement of the cave eaves are small.Under the extreme earthquake load,the cave eaves have large uneven settlement and sliding,which threatens the safety of the Giant Buddha.The maximum principal stress and minimum principal stress on the eaves are large.The overall failure mode of the eaves is tension-collapse failure.Under the action of seismic load,the seismic wave is refracted,reflected and superimposed in the concrete,resulting in the acceleration amplification coefficient in the middle of the cave eaves being greater than that at both ends of the cave eaves.The acceleration coefficient on the left side of the cave eaves is greater than that on the right side.The research results provide a scientific basis for the reinforcement design of the eaves of cave No.5 in Xumishan Grottoes.