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岩石强度是工程岩体稳定性评价和结构优化设计的前提和基础,通过岩石真三轴试验分析了岩石强度演变特征:(1)随着最小主应力的增加,岩石强度逐渐增大,但增幅逐渐减小并趋于零;(2)岩石广义压拉强度比随静水压力的增大呈先增大再减小的规律,并最终趋于1,即在π平面上呈三角形向圆形转变的过程;(3)岩石强度随中间主应力增大表现为先增大再减小的过程。三参数型指数函数完全符合岩石强度在子午面上的基本特点,而LWW、LMN和LYMH三个罗德函数准确反映了中间主应力对岩石强度的影响,且无条件满足拉压子午面区间光滑、连续、外凸性要求。利用π平面广义拉压强度比和罗德函数将指数型拉压子午面结合,构建了指数型真三轴强度准则,分析了强度参数对岩石强度的影响及其空间包络特征。最后采用14种岩石的真三轴试验数据对指数型真三轴强度准则进行了最优拟合误差分析,结果表明指数型真三轴强度准则均具有良好的拟合精度,可正确描述软-硬不同性质岩石的强度特征。
Rock strength is the prerequisite and foundation of engineering rock mass stability evaluation and structural optimization design. The rock triaxial test analyzes the evolution of rock strength: (1) With the increase of the minimum principal stress, the rock strength gradually increases, but the increase Gradually decreases and tends to zero; (2) The generalized compressive strength ratio of rock first increases and then decreases with the increase of hydrostatic pressure and finally approaches 1, that is, the transition from triangle to circle in the π plane (3) The rock strength shows the process of first increasing and then decreasing with the increase of intermediate principal stress. The three-parameter exponential function fully complies with the basic characteristics of rock strength in the meridian plane. The three Rhodes functions of LWW, LMN and LYMH accurately reflect the influence of the intermediate principal stress on the rock strength and unconditionally satisfy the smoothing of the meridional zone, Continuous, convex requirements. By using the generalized tensile strength ratio of π plane and the exponential tension-compression meridional by Rhodes function, the exponential true triaxial strength criterion is constructed, and the influence of intensity parameters on the rock strength and its spatial envelope characteristics are analyzed. Finally, the true triaxial strength test of 14 kinds of rocks is used to analyze the fitting error of the exponential true triaxial strength criterion. The results show that the exponential true triaxial strength criterion has a good fitting accuracy and can correctly describe the soft- Strength characteristics of hard and rocky rocks.