QUANTITATIVE EVALUATION OF THE BEARING CAPACITY OF SURROUNDING ROCK MASS AND THEORETICAL CONSTRUCTION OF THE CHARAVTERISTIC CURVE OF TUNNEL SUPPORT FOR NATM

主动调动地下洞室围岩的承载能力是新奥法(新奥法)的特点。人们曾多次尝试给出这种能力的定量表达式，但从来没有人完全解决过这个问题。在本文的第一部分中，简要讨论了支护压力与隧道壁面位移之间的理论关系。给出了弹性地基中圆形衬砌隧道在完全滑移和无滑移两种情况下平面应变的简化解。这两种情况使得解释剪应力传递和相对剪切位移的影响成为可能。此解的横向自由场地应力被限制在竖向应力的固定值(σ_v*=-p，σ_H*=-Kp)。在与自由场应力对应的荷载作用下，开挖和支撑实际的隧道洞口。我们引入了一个假设…更多的实际“开挖卸载”情况发生在隧道施工过程中。通过改进这一推导，成功地利用严格解构造了隧道掘进的理论特征曲线。特征曲线以相对支撑刚度为指标，清晰地反映了隧道衬砌、围岩和整体的承载能力。隧道周围应力分布的弹性理论表明，隧道周边的偏应力最大。这里的讨论应该包括特征曲线对地面屈服区域和地面不连续面的依赖关系。我们用不同单元模型对不连续地基进行了数值模拟。用上述理论解对分析得到的实际地面反应曲线进行了检验。我们将了解到，虽然地基或多或少可以作为与自由场应力相对应的载荷的承重结构部件，但必须避免过高估计。较少

Active mobilization of bearing capacity of rock mass surrounding an underground opening characterizes the NATM (New Austrian Tunneling Method) concept of supporting. There have been many attempts to give quantitative expressions for this capacity but no one has ever completely solved the question. In the first part of this paper theoretical relations between support pressure and tunnel wall displacements are briefly discussed. We derive a simplified solution of a circular lined-tunnel in an elastic ground under the plain strain for full-slip and no-slip conditions. These two conditions at the ground-lining interface make it possible to explain the effects of shear stress transmission and relative shear displacement. The lateral free-field ground stresses for this solution are restricted to a fixed value of the vertical stresses (σ_v* = -p, σ_H* = -kp). An actual tunnel opening is excavated and supported after the load corresponding to the free-field stresses. We introduce an assumption … More of the actual "excavation unloading" conditions that occur during tunneling. By advancing this derivation, the strict solution is utilized successfully to construct a theoretical characteristic curve of tunneling. The characteristic curve shows clearly the bearing capacities of a tunnel lining, the surrounding ground and the total by using an index "relative-support-stiffness".The elastic theory of the stress distribution around tunnels demonstrates that the deviatoric stresses are maximum at the periphery of the excavation. Discussion here should include the dependence of the characteristic curve on the zone of yielded ground and the discontinuity in the ground. We have carried out numerical simulations for a discontinuous ground with Distinct Element Modeling. The realistic ground reaction curves by the analyses are examined with the theoretical solution derived above. We will learn that while the ground may work, more or less, as a load bearing structural component to the load corresponding to the free-field stresses, overestimation must be avoided. Less