隧道压力拱动态演变机制及规律分析

隧道开挖后形成的压力拱是随着围岩的渐进性破坏而动态发展的。以毛洞情况下隧道的最终状态为依据将动态压力拱分为稳定无塌落拱、稳定有塌落拱和不稳定无塌落拱三类,将围岩压力拱的动态发展分为原始应力状态、雏形压力拱状态、初始压力拱状态、塌落压力拱状态4个典型的时间段,从而对动态压力拱理论进行了完善。对初始压力拱和塌落压力拱的拱体厚度进行了理论推导,从理论上揭示了围岩压力拱动态发展的影响因素。通过实例计算得到了隧道埋深、侧向土压力系数与初始压力拱拱体厚度的关系以及塌落压力拱随塌落高度发展的动态演化规律。结果表明:初始压力拱拱体厚度与侧压力系数呈线性负相关,与隧道埋深呈正相关;侧压力系数对初始压力拱拱体厚度的影响随隧道埋深的增加而增大;随着塌落高度的增加,围岩压力拱范围先增大后逐渐趋于稳定,而拱体厚度则先增大后减小;若塌方在拱体厚度达到最大时仍无法稳定,则最终会发展为塌穿型塌方。

Analyze on the Dynamic Evolution Mechanism and Rule of Pressure Arch in Tunnel

The pressure arch in tunnel develops dynamically with the progressive failure of surrounding rock. Based on the final state of the unsupported-tunnel in weak surrounding rock, the dynamic pressure arch was divided into three types including stable type without collapse arch, stable type with collapse arch and unstable type without collapse arch, and the development of dynamic pressure arch was divided into four typical states including the original stress state, the miniature pressure arch state, the initial pressure arch state and the collapsed pressure arch state, which improves the dynamic pressure arch theory. The thickness of the initial and collapsed pressure arch was deduced, and the factors which affect the dynamic development of pressure arch were revealed theoretically. By a case study, the relationship among cover depth, lateral pressure coefficient and thickness of initial pressure arch was gained, and the regular pattern of the dynamic evolution of collapsed pressure arch varying with the collapse height was also analyzed. The results show that the thickness of the initial pressure arch is negatively correlated with lateral pressure coefficient and positively correlated with cover depth. The influence of lateral pressure coefficient on the thickness of the initial pressure arch increases with cover depth increasing. With the increasing of the collapse height, the range of pressure arch tends to be stable after increasing, while the thickness of pressure arch decreases after increasing to a maximum value. The collapse will develop to earth surface if the stable collapse arch can’t occur before the thickness of pressure arch reach a maximum value