浅埋土洞坍塌机理的理论分析

Theoretical Analysis on Collapse Mechanism of Shallow-buried Soil Tunnel

基于霍克布朗强度准则(H-K准则)采用泛函变分法对"活塞板"试验结果进行理论分析,推导出浅埋土洞破坏时滑动面曲线方程和临界覆土厚度的解析解,并对H-K准则中材料参数B=0.5和B=1时两种特殊情况下的推导结果进行了讨论。当材料参数B=0.5时,土体破裂滑动面为抛物线。当材料参数B=1时(即莫尔库伦准则下),土体破裂滑动面为斜直线,但破裂面与水平方向的夹角与岩土工程计算中常用假定条件明显不同;当土洞埋深趋向于无限大时,活塞板上的竖向土压力趋于恒定值,该结论与太沙基理论和普氏卸荷拱理论是一致的。本文还提出了采用土工剪切试验数据计算霍克布朗准则参数的方法,并用具体的工程案例来示例了本理论在实际工程中的应用。

Based on Hoek-Brown soil failure criterion,the collapse mechanism of shallow-buried soil tunnel is analysed by means of functional calculus of variation,deriving the functional expression of the sliding surface curve and theoretical solution about the critical thickness of overlying soil when the tunnel collapses. The deduction under two special cases of Hoek-Brown criterion parameter B = 0.5 and B = 1 is discussed. When B = 0.5,the failure sliding surface curve is a parabolic,when B = 1(i. e. under the Mohr-Coulomb criterion),the failure sliding surface curve is a diagonal line,but the angle between it and the horizontal direction is different from the current assumption in geotechnical engineering calculation. When the depth of the tunnel tends to infinity,the load of the tunnel roof tends to constant value,which is consistent with the inference of Terzaghi. A method of calculating parameters of Hoek-Brown criterion is presented by means of using data obtained from geotechnical shearing test. The application of this theory in project is illustrated by an example of case.