渗透-应力耦合作用下灰岩压缩破坏及声发射特性分析

Analysis of compression failure and acoustic emission characteristics of limestone under permeability-stress coupling

富水隧道围岩体挖掘过程中,复杂的渗透-应力耦合作用经常导致岩体内部结构演化具有不稳定性,进而诱发围岩体的劣化与失稳,这对地下渗流岩体稳定性的研究提出了更高的要求。为研究贵阳下麦西隧道进口区灰岩的宏观力学和声发射特性,利用自主研发的渗透-应力耦合试验装置进行了不同渗透水压下的单轴压缩破坏、声发射和压汞试验,分析了灰岩的应力-应变、峰值强度、特征应力、破裂和声发射特性以及劣化机制等。研究结果表明:随渗透水压力增大,灰岩压密阶段延长而弹性阶段相对缩短,峰值应力为指数衰减;闭合应力和损伤应力均随渗透水压力增加呈线性减小,而随峰值应力增大而增加,表明溶蚀作用增加了灰岩损伤敏感程度;渗透水压力对灰岩破裂形式未造成较大影响,以劈裂破坏为主,且碎块均匀度与渗透水压力、峰值应力均为指数关系;不同渗透水压力下,灰岩声发射振铃计数大致经历了“平静-发展-突增-跌落”过程,水岩作用弱化了灰岩结构稳定性,导致应变能提前释放;渗透水对灰岩具有溶蚀和引裂作用,随渗透水压力增加,单位质量孔隙体积呈指数增加,起裂应力呈线性衰减。研究结果可为地下富水岩体的开挖的稳定性及减防灾分析提供理论基础。

In order to investigate the macro-mechanics behavior and acoustic emission characteristics of limestone with different osmotic pressures,the compression failure test,acoustic emission test and mercury injection test of limestone under different osmotic pressure conditions were carried out by permeability-stress coupling apparatus.The stress-strain curves,peak strengths,characteristic stresses,characteristics of failure and acoustic emission and degradation mechanism were analyzed.Results show that with the increase in osmotic water pressure,the compression phases and elastic phases of stress-strain curves are prolonged and shortened,respectively,and the peak strengths attenuate exponentially.The strength degradation coefficients,elastic modulus and deformation modulus all decrease linearly with the increase in osmotic water pressure,indicating the damage sensitivity of limestone is increased.Osmotic water pressures have no great influence on fracture forms and the splitting failure is dominant,the limestone fragment uniformity is exponential with osmotic water pressure and peak strength.Due to the structural stability of limestone is weaken by the water-rock interaction,resulting in the early release of strain energy.Osmotic water (pressure) has the effect of dissolution and crack on limestone,the pore volume per unit mass increases exponentially and the crack initiation stress decreases linearly with the increase in osmotic water pressure.