论文部分内容阅读
为了研究低孔隙水压力对砂岩卸荷力学特性的影响,在TOP INDUSTRIE多功能岩石三轴测试系统上,设计进行不同围压(5,10,15,20 MPa)和不同孔隙水压力(0,0.3,0.6,0.9,1.2 MPa)下的砂岩三轴卸荷试验。重点分析孔隙水压力对砂岩卸荷强度及变形破坏特征的影响。研究结果表明:(1)随着孔隙水压力的增大,岩样加载阶段的弹性模量逐渐减小,而且围压越小,相同的孔隙水压力增量条件下,弹性模量减小趋势越明显;(2)在卸载过程中,岩样侧向变形的增大速率明显大于轴向变形,而且,孔隙水压力越大,围压越小,侧向扩容现象越明显,岩样越容易破坏;(3)在卸载过程中,岩样的变形模量呈现先缓后陡的劣化规律,而且围压越小、孔隙水压力越大,变形模量降低幅度越大;(4)随着孔隙水压力的增大,岩样破坏时对应的围压值逐渐增大,黏聚力和内摩擦角降低趋势明显,说明孔隙水压力加速了岩石破坏的进程;(5)水对砂岩矿物颗粒的软化和颗粒间连接的弱化作用,以及孔隙水压力的水楔效应,是导致砂岩卸荷力学特性劣化的根本原因。因此,在涉水工程岩体卸荷变形稳定分析中,孔隙水压力的作用效应不容忽视。
In order to study the effect of low pore water pressure on the unloading mechanical properties of sandstone, three-axis test system of TOP INDUSTRIE multi-purpose rock was designed to conduct experiments with different confining pressure (5,10,15,20 MPa) and different pore water pressures (0, 0.3, 0.6, 0.9, 1.2 MPa) sandstone triaxial unloading test. The influence of pore water pressure on unloading strength and deformation and failure characteristics of sandstone is analyzed emphatically. The results show that: (1) With the increase of pore water pressure, the elastic modulus decreases gradually at the loading stage, and the smaller the confining pressure, the lower the elastic modulus at the same increment of pore water pressure (2) During the unloading process, the rate of increase of rock lateral deformation is obviously greater than that of axial deformation. Moreover, the larger the pore water pressure and the smaller the confining pressure, the more obvious the lateral expansion is, (3) During the process of unloading, the deformation modulus of rock samples shows the first slow and then the steep deterioration law, and the smaller the confining pressure, the larger the pore water pressure, the greater the decrease of deformation modulus; (4) With the Pore water pressure increases, the corresponding confining pressure value increases gradually when the rock sample is damaged, and the cohesion and internal friction angle decrease obviously, which indicates that the pore water pressure accelerates the process of rock failure; (5) Softening and weakening of the interparticle connection, as well as the water wedge effect of pore water pressure, are the fundamental reasons leading to the deterioration of unloading mechanical properties of sandstone. Therefore, the effect of pore water pressure can not be ignored in the stability analysis of rockfill unloading deformation.