弱胶结砂质泥岩渐进性破坏力学特性试验研究
Experimental investigations on mechanical characteristics of weakly cemented sandy mudstone under progressive failure
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摘要: 为深入揭示弱胶结砂质泥岩渐进性破坏力学特性,对干燥与自然状态砂质泥岩试样进行渐进性破坏单轴压缩试验研究。结果表明:与硬脆性岩石相比,该类岩石裂纹密度低,自稳能力差,峰前岩石体积膨胀变形过程延长,峰后变形破坏呈现局部阶段性塑性流动特征和延时效应,渐进性变形破坏过程持续时间显著缩短;岩石弱胶结特性表现为:① 峰前重要应力门槛值与峰后残余应力明显劣化;② 岩石刚度与抗变形能力弱化显著;③ 岩石宏观破坏特征是环向剪切破坏面、张性破坏面、剪切滑移面共同作用的结果,与裂纹渐进性演化特征、层理密集程度及强度相关;④ 干燥状态岩样力学特性与硬脆性岩石近似相同,含水状态岩样峰前重要应力门槛值、弹性模量、峰后残余应力具有不同程度劣化, 侧向膨胀变形程度提高。巷道围岩治理应加强初次支护强度并及时补强,控制围岩张拉破坏与剪切破坏,提高围岩刚度和抗变形能力。Abstract: The experimental investigations on uniaxial compression of weakly cemented sandy mudstone samples under dry and natural conditions were conducted respectively to uncover the mechanical characteristics of weakly cemented sandy mudstone.The results indicate that compared with hard and brittle rocks, such rock has some characteristics including low crack density, weak self-stability; the course of volume dilatancy deformation is prolonged at the pre-peak; the delay effect and plastic flow trait can be showed in some stages at the post-peak; and the time of progressive failure is obviously short.The weakly cemented characteristics of such rock are primarily reflected in following three aspects:(1) the significant stress thresholds before the peak and the residual stress after the peak are obviously deteriorated; (2) the stiffness and anti-deformation of such rock are weak conspicuously; (3) the macroscopic failure characteristics of rock specimen are primarily result from three types of surface including tensile fracture surface, shear slip surface, and hoop shear failure surface, which have close relationship with some factors such as the crack progressive evolutionary characteristics, the density and the strength of bedding surfaces.(4) the mechanical characteristics of weakly cemented sandy mudstone in dry condition is similar to hard and brittle rocks, while the mechanical characteristics of such rock in natural condition are deteriorated in different degrees, including the important stress thresholds at pre-peak, elastic modulus, the residual stress at post-peak, and the degree of lateral expansion deformation is enhanced.It is essential to strengthen the initial support strength and consolidate strength timely to keep the tensile and shear failure in control and to enhance the rigidity and anti-deformation capability of surrounding rock masses.