不同围压下灰岩三轴压缩过程能量分析

Energy analysis of limestone during triaxial compression under different confining pressures

对灰岩岩样进行了不同围压下的三轴压缩试验,得到了峰值应力和弹性模量与围压的线性关系式。利用应力-应变曲线拟合了3种围压下应变能与应变的关系式,从而可以求得灰岩在任一轴向应变时的能量值。在考虑岩样对液压油做功的前提下,分析了压缩过程中几个阶段的能量转化方式,解释了高围压条件下岩石破坏更加剧烈的原因。基于裂缝扩展程度影响弹性模量大小的情况,提出了裂缝发展系数F的概念,给出了3种围压下利用轴向应力求取F的经验公式,从而可以获得灰岩压缩破坏过程中各阶段的实际岩石力学参数,并且用F值的变化趋势解释了高围压时峰值强度附近出现塑性平台的原因。

Linear equation between peak stress and Young＇s modulus with confining pressure is obtained from triaxial compression for limestone under different confining pressures. The relationships between strain energy and strain under three confining pressures are fitted by using stress-strain curve, which can obtain the energy value of limestone in anyone axial strain. Several energy changing equations of several stages in the compression process are analyzed, so as to explain the more several rock failures under higher confining pressure in consideration of the rock sample doing work to hydraulic oil. Based on crack extension degree affects the value of the Young＇s modulus, the concept of crack development coefficient F is proposed; and the empirical formula to strike F using under the three confining pressures is given; and the real rock mechanical parameters of various stages during the limestone compression are got; the plastic platform appearing near the peak intensity under high confining pressure with changing tendency of F is explained.