饱和花岗岩水-力耦合力学特性试验研究

Experimental Research on Mechanical Properties of Saturated Granite under Hydro-mechanical Coupling

采用全应力多场耦合三轴试验仪,对饱和花岗岩开展了不同加载速率、不同围压、不同孔压下的水-力耦合三轴压缩排水试验,分别给出了饱和花岗岩在不同加载速率、不同有效围压下的应力-应变曲线,分析了峰值强度、峰值应变、弹性模量随加载速率以及有效围压的变化规律。研究结果表明:(1)在不同有效围压和加载速率的条件下,岩样的应力应变曲线均经历了非线性压密、弹性、屈服、峰后四个阶段。偏压加载初期非线性压密阶段比较明显,而随着围压的升高非线性段逐渐消失;由于花岗岩的致密性较高,因而曲线的弹性阶段较长且相对平滑;在屈服和峰后阶段,岩石呈现出明显的脆—延性转化的过程。(2)饱和花岗岩的峰值强度随着加载速率的增加而增大;且当有效围压相同时,岩石的峰值强度大致相等,抵抗外界荷载的能力大致相同。(3)缓慢加载条件下饱和花岗岩的峰值应变表现出加载速率强化效应,但强化效果是有限的;且在有效围压相同条件下,随着围压和孔压的同步增长,峰值应变也呈增长的趋势。(4)弹性模量随着加载速率的增加呈二次多项式增长,但随着围压和孔压的同步增长而逐渐降低。

Using full stress and multi-field coupling triaxial apparatus,the hydro-mechanical coupling triaxial compression drainage tests were carried out on saturated granite with different loading rates,confining pressures and pore pressures.The stress-strain curves of saturated granite under different loading rates and effective confining pressures were provided respectively,and the variation rules of peak strength,peak strain and elastic modulus were studied under the very loading rates and effective confining pressures.The results show that:(1)under the effect of different effective confining pressures and loading rates,stress-strain curves of saturated granite exhibit the nonlinear compaction,elasticity,yield and failure stages.At the initial stage of deviating stresses loading,the nonlinear compaction stage is relatively obvious,but with the increase of confining pressure,the nonlinear compaction stage gradually disappears.Due to the high density of granite,the linear elastic stage of the curve is long and relatively smooth.In the yield and failure stages,the rock shows obvious brittle-ductile transformation process.(2)The peak strength of saturated granite increases with the increase of loading rate,and when the effective confining pressure is constant,the peak strength is approximately equal,and the resistance to external load is roughly the same.(3)Under the condition of slow loading,the loading rate has obvious strengthening effect on the peak strain of saturated granite,while the strengthening effect is limited.When the effective confining pressure is constant,with the synchronous increase of confining pressure and pore pressure,the peak strain presents an increasing trend.(4)Elastic modulus and loading rate show a quadratic polynomial growth relationship.However,with the synchronous increase of confining pressure and pore pressure,the elastic modulus presents a decreasing trend.