复杂地下水环境下膏溶角砾岩隧道围岩力学性质劣化研究

A Law for Degradation of Mechanical Properties of Gypsum Breccia Surrounding Tunnels in a Complex Groundwater Environment

为研究复杂地下水环境下隧道膏溶角砾岩的劣化特征,以山西某隧道工程存在的膏溶角砾岩为研究对象,考虑流速作用(0、10、20 L/h),开展不同循环次数(1、3、6、10次)的干湿循环试验,系统分析膏溶角砾岩在不同流速及不同干湿循环次数下的溶蚀和吸水行为的演变规律;通过单轴和三轴压缩试验,进一步探究膏溶角砾岩在不同流速及不同干湿循环次数下的力学参数劣化规律。研究结果表明:1)干湿循环作用与水流共同导致了膏溶角砾岩的劣化,干湿循环对膏溶角砾岩的劣化作用主要在于降低颗粒的联结程度,而流速则会加剧膏溶角砾岩的溶蚀行为,并侵蚀剥离岩样表面的松散颗粒;2)膏溶角砾岩各力学指标(单轴抗压强度、弹性模量、内摩擦角、黏聚力)随着流速与干湿循环次数的增加呈下降趋势,当流速为20 L/h时,经历10次干湿循环后,膏溶角砾岩的单轴抗压强度降低了72.86%,弹性模量降低了75.67%,内摩擦角降低了70.69%,黏聚力降低了57.58%,其力学参数的劣化程度由高到低依次为弹性模量、单轴抗压强度、内摩擦角以及黏聚力。

To study the degradation characteristics of the gypsum breccia that surrounds tunnels in a seasonally supplemented groundwater environment,a case study on gypsum breccia is conducted for a tunnel project in Shanxi.Wetting-drying cycle tests for 1,3,6,and 10 cycles are carried out considering the effect of flow rates of 0,10,and 20 L/h.The law describing the corrosion and water absorption behavior of gypsum breccia under the action of the wetting-drying cycles at different flow rates is systematically analyzed in this paper.Based on the results of uniaxial and triaxial compression tests,the law describing the degradation of the mechanical parameters of gypsum breccia under different wetting-drying cycles and flow rates is then explored in more detail.The results show the following.(1)The wetting-drying cycle and water flow cause degradation of the gypsum breccia.The effect of the wetting-drying cycle on the gypsum breccia mainly involves a reduction in the degree of connection between particles,whereas the water flow aggravates the corrosion of the gypsum breccia and erodes the loose particles on the surface of the rock.(2)The mechanical indices of gypsum breccia including the uniaxial compressive strength,elastic modulus,friction angle,and cohesive strength show a downward trend as the flow rate and the number of wetting-drying cycle increase.When the flow rate is 20 L/h,after 10 wetting-drying cycles,the uniaxial compressive strength of the gypsum breccia is reduced by 72.86%,the elastic modulus is reduced by 75.67%,the friction angle is reduced by 70.69%,and the cohesion strength is reduced by 57.58%.The elastic modulus is degraded the most,followed by the uniaxial compressive strength,friction angle,and cohesion.