软弱夹层厚度模拟实用方法及其应用

A PRACTICAL METHOD TO SIMULATE THICKNESS OF WEAK INTERBED AND ITS APPLICATION

围岩中分布的软弱夹层对地下洞室围岩稳定性、支护结构安全性有着重要的影响,以软弱夹层的变形、强度等效为出发点,基于接触面单元和软弱夹层影响带概念,提出一种在固定的有限元网格中模拟不同厚度的软弱夹层的实用化模拟方法,并初步验证该方法的合理性、正确性、实用性;利用提出的模拟方法,以奥地利岩土工程有限元分析软件FINAL为平台,系统分析地下洞室分别位于II,III,IV级3种围岩,软弱夹层分别分布在顶部、拱肩、边墙3种不同部位,软弱夹层厚度分别为0.000D,0.005D,0.010D,0.020D,0.200D5种厚度等条件下,软弱夹层对洞室围岩位移场、应力场、塑性区以及喷层结构受力的影响,着重讨论不同软弱夹层厚度条件下,围岩位移场、应力场、塑性区及喷层内力随夹层厚度的变化差异;总结当前试验条件下,软弱夹层厚度对地下洞室围岩稳定性与支护结构安全性影响的一般规律;研究成果可望为地下洞室的规划、设计、施工,尤其是遭遇软弱夹层等特殊工程条件下的设计、施工、维护等提供一定的参考与指导作用。

Such discontinuities as weak interbeds, faults, joint distributed in surrounding rock mass play an important and decisive role in the stability of surrounding rocks of underground openings and the safety of supporting system in most practical engineering cases. Based on the equal deformation and strength for discontinuities, a method is presented, which can be applied to simulate the thickness of weak interbed in the numerical test with unique FEM mesh and its validity, reasonableness and practicability are validated via some numerical tests. This method is composed by the COJO element, which is a perfect element formed in geotechnical FEM software FINAL to simulate the properties of contact, and influenced zone of interbed that is a fine mesh zone with constant thickness in FEM mesh. In this method, The mechanical parameters for influenced element are altered .in order to reflect the various thicknesses of faults. Based on this method, systematic numerical tests have been conducted to study the stability of a tunnel surrounded by different thickness weak interbed buried in surrounding rock mass and the safety of supporting structures. These different thickness weak interbeds are with the thicknesses o f0D, 0.005D, 0.010D, 0.020D, 0.200D, respectively, where D is span of underground opening; and the surrounding rock masses are graded in classes Ⅱ, Ⅲ, Ⅳ. Some qualitative and quantitive laws on the influence of weak interbeds with different thicknesses are summarized, especially the influences on the deformation, stress of surrounding rock mass, as well as the inner force of shotcrete supporting structure. These results may have reference and guide significance to the selection of location and layout of underground opening, the design of supporting system and the construction of underground openings, especially these tunnels stroken to the faults.