基于开挖卸荷劣化的边坡岩体宏观力学参数USMR分析评价方法及验证

USMR method for evaluating macro-mechanical parameters of slope rock mass deteriorated due to excavation unloading

为研究锦屏某边坡岩体在开挖卸荷条件下的岩体宏观力学参数,对该区砂岩进行室内卸荷试验研究,结果表明:相对于加载试验,卸荷过程中岩样的强度及变形参数发生了劣化,低、高围压下岩石变形及破裂形式也有所不同。为此,在对SMR及CSMR修正的基础上,提出了考虑开挖方式、边坡形态及卸荷损伤的边坡卸荷岩体的评价体系USMR法。基于USMR法对研究区边坡开挖岩体宏观参数(变形模量Em、岩体抗压强度cm?、岩体抗拉强度tm?、岩体抗剪强度参数cm和m?)进行了动态分析,并分别考虑了不同围压3?及卸荷损伤De条件下岩体参数的劣化规律。分析表明:开挖卸荷过程中岩体宏观参数发生了不同程度的劣化,拉应力区、低应力区和高应力区岩体参数的劣化规律有所不同,拉应力区及低应力区岩体力学参数对开挖卸荷更加敏感。研究结果对边坡开挖卸荷岩体的稳定性分析与评价具有一定指导意义。

To investigate macro-mechanical parameters of a rock mass slope in Jinping during unloading, a series of unloading experiments on sandstone is carried out in the laboratory. The results show that there is degradation effect on strength and deformation parameters of rocks in unloading process compared to loading failure, and there exist different deformation and failure characteristics under low and high confining pressure. Therefore, based on correction of slope mass rating（SMR） and conventional SMR（CSMR）, an evaluation system of unloading rock mass-USMR（Unloading Slope Mass Rating） has been proposed. In this procedure, the excavation method, slope form and unloading damage are considered. Based on USMR, a dynamic analysis of macro-mechanical parameters（deformation modulus Em, compressive strengthcm？, tensile strengthtm？, and shear strength parameters cm and m？） of unloading slope rock mass is made, the effects of different confining pressures3（？） and unloading damages（De） on deteriorating law of the parameters of rock mass are examined. The analysis results indicate that in the process of excavation unloading the macro parameters of rock mass degrade in different degrees. The degradation laws of rock mass parameters vary in tensile stress area, low stress area and high stress area. Mechanics parameters of rock mass are more sensitive to excavation unloading in the tensile stress area and low stress area. The results will benefit the stability analysis of slope unloading excavation.