Experimental simulation investigation of influence of depth on spalling characteristics in circular hard rock tunnel

Abstract

A series of true-triaxial compression tests were performed on red sandstone cubic specimens with a circular hole to investigate the influence of depth on induced spalling in tunnels. The failure process of the hole sidewalls was monitored and recorded in real-time by a micro-video monitoring equipment. The general failure evolution processes of the hole sidewall at different initial depths (500 m, 1000 m and 1500 m) during the adjustment of vertical stress were obtained. The results show that the hole sidewall all formed spalling before resulting in strain rockburst, and ultimately forming a V-shaped notch. The far-field principal stress for the initial failure of the tunnel shows a good positive linear correlation with the depth. As the depth increases, the stress required for the initial failure of the tunnels clearly increased, the spalling became more intense; the size and mass of the rock fragments and depth and width of the V-shaped notches increased, and the range of the failure zone extends along the hole sidewall from the local area to the entire area. Therefore, as the depth increases, the support area around the tunnel should be increased accordingly to prevent spalling.

摘要

为了研究埋深对圆形隧洞诱发板裂破坏的影响, 对含圆形孔洞的立方体红砂岩试样进行了一系 列的真三轴压缩试验, 并采用自制的微型视频监测设备对孔洞洞壁破坏过程进行了实时监测和记录, 得到了不同初始埋深(500、1000 和1500 m)圆形隧洞的竖直应力调整过程中洞壁破坏完整演化过程。 结果表明: 隧洞洞壁在发生应变型岩爆之前, 均形成了板裂破坏, 并最终形成V-型槽。隧洞初始破坏 所需的远场主应力与深度线性**相关。随着深度的增加, 隧洞洞壁初始破坏所需的应力明显增大, 板 裂破坏变得越剧烈, 岩片的尺寸和质量、V-型槽的深度和宽度均增大, 破坏区的范围逐渐由隧洞洞壁 局部扩大至整个洞壁。因此, 随着深度的增加, 隧洞支护区域应相应增大, 以防止板裂破坏的发生。