Abstract

The elasto-plastic behavior of the Fontainebleau sandstone is studied from experimental and numerical points of view on the basis of a series of conventional triaxial compression tests. Five distinct stages of the axial strain curve are quantified in terms of four stress thresholds (crack closure stress σ_cc, crack initiation stress σ_ci, crack damage stress σ_cd and short-term peak strength σ_p). The onset of dilation and total volumetric strain reversal occur at axial stress level 30–50% and 50–80% of σ_p, respectively. A refined continuous strain deviation (RCSD) method is proposed to more accurately define the elastic parameters. Other internal state variables are determined accordingly. Some important information are gained as follows: (1) the Poisson’s ratio decreases with the increase of the confining pressure; (2) at the same stress level, the higher of the confining pressure, the smaller of the negative plastic volumetric strain (dilatancy); (3) the evolution of the friction-like coefficient and the plastic volumetric strain can be described with an exponential function and a hyperbolic function, respectively. A strictly experimental based constitutive model is proposed to study the elasto-plastic behavior of the Fontainebleau sandstone. All numerical aspects including formulations, algorithms and experimental validations, are presented in detail.

摘要

在一系列常规三轴压缩试验的基础上，从实验和数值的角度研究了枫丹白露砂岩的弹塑性行为。轴向应变曲线的五个不同阶段根据四个应力阈值（裂纹闭合应力σ _cc、裂纹起始应力σ _ci、裂纹损伤应力σ _cd和短期峰值强度σ _p）进行量化。在σ _p的 30-50% 和 50-80% 的轴向应力水平下发生膨胀和总体积应变反转的开始， 分别。为了更准确地定义弹性参数，提出了一种改进的连续应变偏差（RCSD）方法。其他内部状态变量相应确定。得到的一些重要信息如下： (1)泊松比随着围压的增加而减小；(2)在相同应力水平下，围压越高，负塑性体积应变(剪胀)越小；(3) 类摩擦系数和塑性体积应变的演变可以分别用指数函数和双曲线函数来描述。提出了一个严格的基于实验的本构模型来研究枫丹白露砂岩的弹塑性行为。所有数值方面，包括公式、算法和实验验证，