不同溶蚀程度灰岩巴西劈裂力学性能及能量演化特征

Mechanical Properties and Energy Evolution Characteristics of Brazilian Splitting of Limestone with Different Dissolution Degrees

岩体在溶蚀作用下形成溶隙,导致岩体内部结构发生改变,进而影响其力学性质和破坏特征。为研究不同溶蚀程度灰岩的应力-应变关系、力学参数、破坏模式和能量的变化规律,借助数字图像处理技术和颗粒流离散元方法,构建了不同溶蚀程度灰岩的数值计算模型,开展了一系列不同溶蚀程度灰岩的巴西劈裂离散元数值试验。研究表明:不同溶蚀程度的灰岩在巴西劈裂试验过程中的应力-应变曲线均出现明显的多峰特征和脆性破坏特征;当溶蚀程度较低时,应力传递及破坏产生的裂隙在溶蚀灰岩中分布较为均匀,随着溶蚀程度的增大,灰岩的峰值抗拉强度呈指数减小的变化趋势,应力-应变曲线的多峰形态明显,裂隙在灰岩内的分布也越分散且呈“S”形分布的特征越显著;试样在孔洞周围处出现应力集中现象,从而使灰岩易发生结构性破坏;溶蚀灰岩破坏过程中,大部分输入的应变能首先转化为弹性应变能,只有小部分转化为耗散应变能,溶蚀程度的增加显著降低了岩溶灰岩巴西劈裂破坏过程中的总应变能输入和弹性应变能的储存极限,加快了能量耗散速度。研究成果对岩溶地层隧道围岩稳定性研究具有指导意义。

The dissolution of rock mass leads to the formation of dissolution gap, which changes the internal structure of rock mass, and then affects its mechanical properties and failure characteristics. In order to study the stress-strain relationship, mechanical parameters, failure mode and energy variation of limestone with different degrees of dissolution, the numerical calculation model of limestone with different degrees of dissolution was constructed by means of digital image processing technology and particle flow discrete element method, and a series of Brazilian split discrete element numerical tests of limestone with different degrees of dissolution were carried out. The results show that the stress-strain curves of limestone with different degrees of dissolution in the Brazilian splitting test show obvious multi-peak characteristics and brittle failure characteristics. When the dissolution degree is low, the cracks produced by stress transfer and failure are evenly distributed in the dissolved limestone. With the increase of the dissolution degree, the peak tensile strength of the limestone decreases exponentially, and the multi-peak shape of the stress-strain curve is obvious. The distribution of cracks in the limestone is more dispersed and the distribution of S shape is more significant. The stress concentration occurs around the hole, so that the limestone is prone to structural damage. During the failure process of dissolved limestone, most of the input strain energy is first converted into elastic strain energy, and only a small part is converted into dissipative strain energy. The increase of dissolution degree significantly reduces the total strain energy input and the storage limit of elastic strain energy in the Brazilian splitting failure process of dissolved limestone, and accelerates the energy dissipation rate. The research results have guiding significance for the study of tunnel surrounding rock stability in dissolved strata.