Study on the Damage Characteristics during Stable Crack Propagation Stage for Sandstones with Different Moisture Condition
The dry,natural and water-saturated sandstones were adopted to gain some insights into the damage state dur-ing stable crack propagation stage.The crack initiation stress and crack damage stress were first computed from the volumetric strain method,and the incremental cyclic loading and unloading test was used to reveal the evolutions of residual strain,deform-ation modulus and energy terms.It shows that the residual strain in axial direction increases with the increase of axial stress level,of which the growing rate firstly decreases,then stabilizes and then increases,and the stabilization phase corresponds to the stable crack propagation stage.During this stage,the deformation modulus under loading and unloading phases both de-crease linearly,while the dissipative energy density increases.These evolution laws are applicable for the sandstones with dif-ferent moisture condition,though the absolute values are related to the moisture content.Further,the deformation modulus dur-ing loading phase could be an effective index for the damage state during the stable crack propagation stage,and the linear mathematical model based on the moisture content and axial stress level may be used to evaluate the damage state of engineer-ing rock mass.
stable crack propagationresidual straindeformation modulusenergy evolutiondamage state
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