Stability Analysis Of The Yuanjue Cave Laminated Sandstone Enclosure

The Yuanjue Cave in Anyue County,Sichuan Province,has important historical and cultural significance,and is an important part of China's early cave chain,and the stone carvings inside the cave have great cultural and artistic value.In order to better protect Yuanjue Cave,it is urgent to solve the problem of rock instability in Yuanjue Cave as soon as possible.To solve this scientific problem,we first need to establish a three-dimensional refined numerical model of Yuanjue Cave to analyze the stability of its surrounding rock on the basis of sufficient understanding of the mechanical properties of its surrounding rock.In this paper,the fine view compression,Brazilian splitting and variable angle plate shear tests were conducted on the laminated sandstone rock samples to obtain the mechanical parameters of the laminated sandstone and analyze its mechanical properties,and the 3D refined numerical model of the cave was established by software through 3D laser scanning and aerial photography by unmanned aerial vehicle,etc.FLAC^3Dsoftware was used to analyze the stability of the surrounding rock after excavation and under the seismic dynamic state of the Yuanjue Cave,and the The following conclusions were obtained.(1)The laminated sandstone has strong anisotropy,the peak strength in the vertical laminated direction is higher than that in the horizontal direction,and the rupture mode of the laminated sandstone in the horizontal direction is mainly shear damage or shear followed by tension damage,while the rupture mode of the laminated sandstone in the vertical direction is mainly tension damage or tension followed by shear damage.(2)For the first time,the 3D refined modeling of the surrounding rock of the circular jue cave considering the structure of laminae was realized.The point cloud processing and model stitching were carried out by using Photoscan and Geomagic Studio,and the model was grouped and meshed by using Hypermesh software,and the grain layer and structural surface were established after importing into FLAC^3D.(3)The displacement of the surrounding rocks in Yuanjue cave showed a tendency of sinking at the top and bulging at the bottom,the displacement in the middle and front of the roof slab was slightly larger than the sides,the fissures had a greater impact on the stability of the roof slab,and there was a concentration of compressive stress at the front geometric abruptness of the sidewall,which might lead to the intensification of the damage,and the unstable depth of the sidewall in Yuanjue cave was 0.3 m using the unit safety factor method,and there were local unstable rocks at the connection between the roof slab and the sidewall.Based on the strength reduction method,the current safety factor of the Yuanjue cave was determined to be 2.6 through the plastic zone penetration,the displacement of key points and the percentage of plastic units at the contact surface.(4)Under the action of seismic dynamics,the relative displacement of the top slab of Yuanjue Cave is larger than that of the side walls,and the relative displacement of the front part of the top slab is larger than that of the middle and back parts,and the rock body of the top slab of the cave has a strong amplification effect on the seismic acceleration,and the acceleration amplification coefficient is higher the farther away from the critical surface.