软岩浅埋连拱隧道施工围岩变形特征分析

为研究软弱破碎围岩浅埋连拱隧道施工过程中围岩变形特性，依托陕北某连拱隧道实际工程，通过现场布设监测仪器系统开展了拱顶沉降、围岩变形长期测试，获得了随施工过程拱顶沉降及围岩径向变形规律。结果表明：地表沉降近似于Peck沉降曲线，越靠近隧道中心地表沉降越大，最大沉降值产生于左线隧道开挖落底后，约为12.1 mm;拱顶沉降沿隧道纵向变化规律为：中导洞>正洞>左右侧导洞，中导洞表现为拱顶下沉，侧导洞则是水平收敛，上台阶施工因未临时仰拱封底而其收敛变形显著大于下台阶施工；随距隧道壁面距离增加，测点累计变形量逐渐减小，K21+970测试断面围岩松动区约2 m,因测线布置限制，K21+970测试断面松动区超过4 m。

Deformation Characteristics of Surrounding Rock During Construction of Shallow Multi Arch Tunnel with Soft Rock in Seasonal Frozen Area

Based on the actual project of a multi arch tunnel in Northern Shaanxi, to study the deformation characteristics of surrounding rock during the construction of shallow buried multi arch tunnel with weak and broken surrounding rock, the long-term tests of vault settlement and surrounding rock deformation were carried out by laying certain monitoring instrument on site, while the laws of vault settlement and surrounding rock radial deformation during the construction process were obtained. The results show that: the surface settlement is similar to peck settlement curve. The closer to the center of the tunnel, the greater the surface settlement is. The maximum settlement value is about 12.1 mm after the excavation of the left tunnel, and the variation of vault settlement along the longitudinal direction of tunnel is as follows: middle pilot tunnel > main tunnel > left and right pilot tunnel. The middle pilot tunnel shows a vault settlement, while the side pilot tunnel shows a horizontal convergence. The convergence deformation of the upper step construction is significantly greater than that of the lower step construction because of no temporary invert bottom sealing. With the increase of the distance from the tunnel wall, the cumulative deformation of the measuring point decreases gradually. The surrounding rock loose area of K21+970 test section is about 2 m, and the loose area of K21+970 test section is more than 4 m due to the limitation of the layout of the measuring line.