关键词: 砂岩, 加卸载试验, ms级损伤预测, 正弦波, 动态泊松比, 体积应变

Abstract: An accurate (millisecond level) prediction method for sandstone damage by determining the dynamic Poisson’s ratio is put forward in this paper. First of all, axial loading and unloading tests are performed on rock specimens under different waveforms at varied frequency on the prerequisite that failure does not occur. Tests reveal asynchronous lateral strain and axial strain, which give rise to dynamic Poisson’s ratio under cyclic loading and unloading. The time intervals of such asynchronous phenomenon are defined. The linear relations of dynamic Poisson’s ratio against instantaneous load, instantaneous transverse length, and instantaneous axial height under different load peaks are acquired without considering the asynchronous time. Hence, the fitting formula between relational coefficients and peak load can be obtained. Through only a small amount of test data at the peak of loading force, the linear relationship between dynamic Poisson’s ratio and relevant parameters at any peak load can be predicted. Furthermore, according to the linear relation between Poisson’s ratio and instantaneous lateral length, the equations and methods for volumetric strain and damage variable can be derived within allowable error range. The present model could precisely (at millisecond level) predict volumetric strain and damage variable of rock under cyclic loading and unloading with no need to measure displacement values when load type is known.

Key words: sandstone, loading and unloading test, damage prediction at millisecond scale, sine wave, dynamic Poisson’s ratio, volumetric strain