软弱围岩段隧道施工过程中围岩位移的三维弹塑性数值模拟

3D ELASTOPLASTIC NUMERICAL SIMULATION OF SURROUNDING ROCK DISPLACEMENT IN SOFT SURROUNDING ROCK SECTION DURING CONSTRUCTION PROCESS

以渝黔二期工程笔架山隧道埋深最大的软弱围岩段实体建模,应用有限元程序对其施工全过程进行三维弹塑性数值模拟,从而得出该段某一指定横断面上各点围岩沉降及水平位移随开挖过程的变化规律和数值大小。计算结果表明:对沉降和水平位移影响最大的是在指定段前后各3m的范围内,约占其总量的2/3,而上台阶开挖的影响又明显大于下台阶开挖;在掌子面未开挖之前,围岩沉降和水平位移均已完成40%左右;从横断面上看,围岩位移比较明显的区域主要集中在距洞壁3～5m处。另外,现场实际量测拱顶下沉数据和拱腰水平收敛值与计算数据的相互比较表明,两者变化规律吻合较好。

The tunnel in soft surrounding rock with maximum buried depth was modeled based on Bijiashan Tunnel of the 2nd Project of Yuqian Expressway; and three-dimensional elastoplastic numerical simulation is conducted for construction process. Variation laws and magnitudes of settlement and horizontal displacement in designated cross section are attained. Computing results show that the maximum range of influence on the settlement and horizontal displacement is within 3 meters before and after the designated section and magnitudes account for two-third of gross amount, and the influence of upper bench excavation is obviously greater than that of lower bench; and the settlement and horizontal displacement have accomplished 40% before heading face is excavated; and the area with concentrated displacement is 3 -5 m away from the tunnel wall. In addition, comparison of arch crown settlement and horizontal convergence of haunch between in-situ testing data and computing ones shows that the variation laws fit preferably.