循环加、卸载条件下岩石类材料变形特性的实验研究

EXPERIMENTAL STUDY ON ROCK DEFORMATION CHARACTERISTICS UNDER CYCLING LOADING AND UNLOADING CONDITIONS

从不同位移速率、不同载荷水平和不同岩石孔隙性(如坚硬致密的细粒砂岩和软弱多孔的混凝土加气砖等)3个角度对岩石类材料在循环加、卸载条件下所形成的封闭塑性滞回环的演化规律进行探讨。通过对其实验结果的分析发现:(1)岩石类材料在循环加、卸载条件下的卸载曲线与加载曲线不重合,确实将形成一封闭的塑性滞回环;(2)循环加、卸载条件下,加载曲线段的位移变化量在第1次循环期间变化较大,但从第2次循环开始,其位移变化量的变化并不明显,而卸载曲线段的位移变化量在整个循环加、卸载过程中的变化似乎都不明显;(3)一般而言,位移速率越大纵向载荷–纵向位移曲线的斜率就越大,载荷水平越高第1次循环中载荷卸载至零时所残余的位移量也越大;(4)从第2次循环开始,在每次循环加、卸载完成之后,加载曲线段的起点与卸载曲线段的终点几乎是重合的,即从第2次循环实验开始几乎不再产生新的残余位移量;(5)针对具有不同孔隙性的岩石,在不同位移速率和不同载荷水平时其循环加、卸载条件下的变形响应程度将有所不同。

The evolvement way of the plastic-loop closed by the deformation curve under the cycling loading and unloading conditions from the different displacement rates and the different load levels,and the different rock porosity(the compact fine-sandstone and the incompact aerated-concrete-brick) are introduced.The experimental results are analyzed,and the following phenomena are discovered:(1) rock deformation curve would form the plastic-loop under the cycling loading and unloading conditions because the deformation curve in loading zone differs from the deformation curve in unloading zone;(2) though the displacement change in the loading zone was more larger in the first circulate loading,the contrast of the displacement change in the loading zone of every cycling load would remain unchangeable since the second circulate loading,otherwise the contrast of the displacement change in the unloading zone would be un-conspicuous in the loading zone of every cycling load;(3) the slope of the load-displacement curve would increase when the displacement-rate increase,and the residual displacement after the first circulate loading and unloading would increase when the load-level increase;(4) in the load-displacement curve,the ending point of the unloading zone would be approximate the same as the starting point of the loading zonei,.e.new residual displacement from the second cycling load would not be generated;and(5) the response of the rock deformation to the different rock porosities under the cycling loading and unloading conditions would be different.