层理位置对近水平软硬互层隧道变形的影响

Stability Analysis and Optimization of Primary Support on Tunnel Excavation with Soft-hard Interbed Rock

江习高速四面山隧道软硬互层围岩为近水平岩层,弹性模量比值为1∶5,黏聚力比值为1∶4,层理效应明显,且层理与隧道相对位置不一,对隧道开挖影响也不同。以砂泥互层V级围岩隧道施工段为工程依托,采用接触分析方法,研究层理与隧道相对位置关系对隧道变形影响,并进行变形预测,得出以下结论:(1)隧道开挖后,其拱顶沉降相对水平收敛变化更大,层理层间滑移相对层间剥离变化更明显。(2)隧道拱顶沉降受隧道上方层理影响最大,水平收敛受穿隧道层理影响最大,底鼓受隧道下方层理影响最大。(3)对于层理本身,隧道开挖对断面以上位置的层理影响更大,对其下方层理影响较小,层理位于隧道上方层理滑移最大,层理穿越隧道断面时层间剥离量最大。研究成果可在类似隧道提出针对性施工工艺设计建议并推广应用。

Some sections in Simianshan Tunnel,Jiangxi highway,are surrounded by of soft-hard interbed rock.The elastic modulus ratio of soft and hard rock is 1∶ 5,cohesive force ratio is 1∶ 4. The bedding effect of the rock mass is remarkable,different relative positions between the bedding and tunnel result in different influence on the tunnel excavation. Making use of contact analysis method,the relationship between bedding and its relative location with tunnel is studied,and the tunnel deformation is predicted. The results show that：（1）After the tunnel excavation,the vault sink value is larger than the level convergence of the surrounding rock. At the same time,the change of the bedding sliding is more obvious than stripping.（2）The vault sink is the largest when the bedding is above the tunnel,while the level convergence is the largest when the bedding is cross the tunnel and the tunnel floor heave is the largest when the bedding is under the tunnel.（3）For bedding itself,it has the largest effect on the above bedding deformation when the tunnel excavated,while it is smaller when the bedding is under the tunnel. Interlayer sliding is the largest when the bedding is above the tunnel,and the stripping is the largest when the bedding cross the tunnel. Research results provide a good model for the similar tunnel construction and put forward construction design suggestions.