初次支护结构对围岩塑性区和位移的影响研究

为了探索初期支护对隧道围岩稳定性的影响,采用岩土工程三维有限元分析软件Z_Soil3D对隧道施工中锚杆和钢架的作用进行了模拟分析。计算结果表明:增加锚杆长度或钢架惯性矩,围岩塑性区厚度和围岩位移都减小,锚杆长度及钢架惯性矩存在优化值,当锚杆长度或惯性矩超过优化值后对进一步改善围岩稳定性的作用不明显;永久钢架主要起拱的作用,其内力以轴向压力为主,在节点处存在局部弯矩,永久钢架构件内力与施工顺序相关,最早施加的构件轴力是后施加的数倍;临时钢架为压弯构件,存在较大轴力和弯矩,水平和竖向临时钢架的弯矩相差不大,2层水平钢架构件的轴力相差较大,竖向构件的轴力与上层水平构件的轴力相当,但明显大于下层水平构件的轴力。

Study on Influence of Primary Support on Plastic Zone and Displacement of Surrounding Rocks

The effects of anchors and steel frames on the surrounding rocks are studied by means of ED FEM software ZSoil3D, so as to learn the influence of primary support on the stability of surrounding rocks of tunnel. The calculation re sults show that： 1） The thickness of plastic zone and the displacement of the surrounding rock tent to decreased as the length of anchor or the moment of inertia of steel frames increased. However, there exists an optimal value of the length of anchor and the moment of inertia of steel frames, beyond which the increase of them does not have obvious influences on the stability of surrounding rocks. 2） The permanent steel frames works as arches that were mainly subject to axial com pression except for the localized bending in nodes. Furthermore, the internal force in permanent steel frames was depend ent on construction sequences. For instance, the internal force in first assembled members may be several times larger than that in members assembled later. 3） The temporary steel frames are subject to both axial compression and bending. The bending moment in the horizontal members is close to that in vertical members. However, the internal force in the upper and lower steel frames are obviously different. The axial pressure in vertical members of the lower frame is close to that in horizontal members of the upper frame but much larger than that in horizontal members of the lower frame.