含剪切带层状岩体抗剪强度参数估算及工程应用

剪切带作为一种特殊的软弱结构面，对工程建设的危害早已引起人们的广泛关注和深刻认识。本文以古贤水利枢纽坝址区含剪切带坝基岩体为研究对象，分析了剪切带的空间发育规律，并采用大型原位剪切试验方法确定其抗剪强度参数；同时，根据建立的由岩体波速估算地质强度指标GSI的计算公式，结合Hoek-Brown岩体强度准则，本文给出了估算岩体抗剪强度参数的理论计算方法。对比两者计算结果表明：采用Hoek-Brown强度准则估算的等效内摩擦角偏小，而黏聚力明显偏大，这主要是由于准则中最小主应力的取值范围引起的，据此提出公式应用中需注意的问题及相应解决方法。该方法能在试验资料不足的情况下，为含剪切带层状岩体力学参数的快速评价提供了一条新途径。

ENGINEERING APPLICATION AND SHEAR STRENGTH PARAMETER ESTIMATION OF STRATIFIED ROCK MASS WITH SHEAR ZONE

As a kind of special weak structural plane, shear zone has aroused attention and deep understanding of the influence on engineering construction. Rock mass of dam foundation with shear zone of Guxian hydro-junction project is taken as the research object, this paper analyzed the distribution characteristics of shear zone, and determined parameters of shear strength by large in-situ shear test. In the meantime, according to the established calculation formulae of geological strength index(GSI)for rock masses estimated by ultrasonic velocity of rock mass, the rock mass mechanical parameters are predicted by Hoek-Brown criterion. The result shows that equivalent fraction coefficient from Hoek-Brown criterion is lower than test value and cohesion force is far greater than that from shearing test. It is shown by error analysis that the difference between experiment values and estimated ones is mostly induced by the span of minimum principal stress used in Hoek-Brown criterion. For this situation, some cautions and corresponding resolve methods while using Hoek-Brown criterion are reminded. In addition, the proposed method provides a new approach to determine the mechanical parameters of stratified rock mass with shear zone, when test data are scant.