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采用有限元法对隧道施工过程的支撑荷载法中的几个问题进行了详细的研究。讨论了释放荷载和支撑荷载的关系,分析了支撑荷载的大小、方向以及选取的部位对计算结果的影响;根据三维模型的计算结果确定了位移释放率,并据此得到了按平面应变模型模拟隧道施工过程时各施工阶段支撑荷载的大小。计算结果表明:在采用平面应变方法进行隧道施工过程的计算时,为了模拟开挖面的空间效应,在洞周施加的是支撑荷载而非释放荷载;在只有体积力和面力的情况下,支撑荷载可以采用被挖掉的岩土体的周边(内圈)节点的等效节点力,也可以取留下围岩周边(外圈)节点的等效节点力并反号,若洞周节点上有集中荷载,则支撑荷载必须采用前者;在台阶法施工中,采用变化后的洞周节点力作为下半断面支撑荷载的初始应力的方法,能够得到较满意的结果。
The finite element method is used to study several problems in the supporting load method of tunnel construction. The relationship between the release load and the support load is discussed. The influence of the size and direction of the support load and the selected part on the calculation result is analyzed. The displacement release rate is determined according to the calculation results of the three-dimensional model, and the plane strain model is obtained Tunnel construction process of the various stages of construction support load size. The results show that in the calculation of the tunnel construction process by the plane strain method, in order to simulate the space effect of the excavation face, the support load rather than the release load is applied at the hole circumference; in the case of only the bulk force and the face force, The supporting load can adopt the equivalent nodal forces of the nodes (inner rings) of the excavated rock mass and the equivalent nodal forces of the nodes of the surrounding (outer ring) For the concentrated method, the former must be used to support the load. In the step method construction, using the changed cavity-periphery force as the initial stress of the lower half-section supporting load can obtain more satisfactory results.