高孔隙水压力对岩石蠕变特性的影响

设计3种加载方式,其中一种施加高孔隙水压力,分别进行分级加载蠕变试验,用于研究分析高孔隙水压对岩石蠕变特性的影响。首先,利用大理石加工的标准圆柱试件,按3种加载方式分别进行蠕变试验,得到轴向、横向的蠕变变形过程曲线,以及岩石破坏时的破坏形态;然后,对3种加载方式下的岩石轴向应变、横向应变、剪应变、体积应变以及破坏形态等进行比较分析;最后,在比较分析的基础上,总结高孔隙水压力对于岩石蠕变及破坏的影响。研究表明:孔隙水压力作用明显,但不是完全作用,即孔隙水压力作用系数接近于1;在高孔隙水压力作用下,岩石的强度大大降低,承载时间大大缩短,破坏时的应变也降低;虽然3种加载情况都是以剪切破坏为主,但在有高孔隙水压力作用下,岩石的破坏更具有突然性;可能不存在一个统一的等效应变阈值,使在不同的加载情况下,应变超过该阈值后即产生加速蠕变破坏;在加速破坏前,除瞬时加载产生的体积应变外,在蠕变过程中,岩石体积应变几乎不变。该成果对于进一步研究考虑孔隙水压力影响的非线性蠕变模型具有指导意义,也可对高孔隙水压力作用下的岩石结构工程处理措施提供指导。

INFLUENCE OF HIGH PORE WATER PRESSURE ON CREEP PROPERTIES OF ROCK

Three types of loading modes are designed in which a high pore water pressure is applied；and creep tests are performed respectively to study the influence of pore water pressure on creep properties of rock. Firstly，with the normal marble samples，the triaxial tests in the three loading modes are performed to get the axial and lateral creep deformation curves as well as the failure patterns of the rock samples. Then the analyses and comparisons of the test results of axial，lateral，shear and volumetric strains as well as failure patterns are performed. Finally，based on the analysis and comparisons，the influence of high pore water pressure on the creep and failure of rock is analyzed. The research shows that the effects of the pore water pressure on creep of rock are obvious with the influential coefficient of pore water pressure less than 1，but approaching to 1. Under the action of high pore water pressure，the strength，strain and the time of creep to failure are lessened greatly. Though the samples are all in shearing failure，the failure under high pore water pressure is more sudden. There might be no definite equivalent strain under which the tertiary stage of creeps under different loading conditions begin to occur. And the pore water pressure has no effect on the volumetric strain before failure occurs. The results can be applied to guide the establishment of the nonlinear creep constitutive model of rock under high pore water pressure. And it is also useful for guiding the design and construction of rock structures under high pore water pressure.