基于二维正态分布的岩体抗剪强度参数取值范围确定

针对以往研究中岩体强度参数确定具有较强人为随意性的缺点,对同一类型岩体直剪试验中的正应力、剪应力进行统计分析,并对其开展联合分布的拟合研究,得到了正应力、剪应力联合分布的概率分布模型。在给定的正应力条件下,通过不同概率保证率,可以利用概率分布模型得到剪应力的上下限值,然后在一组不同正应力、剪应力数值中回归得到岩体抗剪强度参数取值范围。以二滩水电站中蚀变玄武岩与混凝土胶结面的直剪试验数据为例,计算得到了在80%保证率下的混凝土与基岩胶结面抗剪强度参数的取值范围分别为f∈(0.68,0.91)与c∈(0.25,1.78)。通过实际工程算例表明,所提出的基于二维正态分布的岩体抗剪强度参数取值的方法可为实际工程中确定岩体抗剪强度参数提供参考。

2-D normal distribution based study on parameter selecting range for shear strength of rock mass

Aiming at the defect of strong artificial randomness in the determination of the parameter of rock mass shear strength in the previous studies，the normal stress and shear stress in the direct shear test made on the same type of rock mass are statistically analyzed herein，and then the relevant joint distribution fitting is studied，from which the probability distribution model for the joint distribution of normal stress and shear stress is obtained. Under the condition of the given normal stress，both the upper limit and the lower limit of the shear stress can be got with the probability distribution model through various probability guarantee rates，thus the parameter selecting range for shear strength of rock mass can be obtained through the regression made in a set of different values of normal stress and shear stress. By taking the data got from the direct shear test made on the cemented interface between the altered basalt and concrete during the construction of Ertan Hydropower Station as the study case，the value selecting ranges of f∈（0.68，0.91）andc∈（0.25，1.78） for the parameter of the shear strength of the cemented interface between the concrete and the foundation rock are respectively obtained from the calculation made under the probability guarantee rate of 80%. Through the actual calculation case，it is indicated that the 2-D normal distribution based method for the value selection of the rock shear strength parameter can provide a reference for the determination of rock shear strength in an actual construction project.