循环荷载作用下脆性材料剪切性能试验研究

在自制的MTS振动台试验设备上对混凝土、岩石类脆性材料（砂浆材料）进行静力和动力剪切试验,试验结果表明,（1）动力荷载情况下位移-剪力包络线形状同静力荷载情况下曲线破坏形状相似,均可划分为相同的4个阶段;（2）在相同垂直压力作用下试件的动力抗剪强度与静力抗剪强度相比有明显的增大趋势,强度较低的试件强度增加较大;（3）在相同频率情况下,随着垂直压力的增大,峰值剪切强度、残余抗剪强度随之增大;（4）静力荷载情况下其破坏处水平位移要大于动力荷载情况下破坏处的水平位移,其他条件相同时破坏处水平位移值随峰值抗剪强度的增大而增大;（5）剪切过程中有明显的剪胀现象出现。最后根据试件的破坏形状,初步分析混凝土、岩石类脆性材料的动静态剪切特性的机制。

EXPERIMENTAL STUDY ON SHEAR BEHAVIORS OF BRITTLE MATERIALS UNDER CYCLIC LOADING

Shear tests under static and cyclic loadings were performed with direct shear equipment in order to explore the shear behaviors of brittle materials such as concrete,rock,etc.under different loadings.The direct shear equipment that allows static and dynamic shear tests,was designed based on MTS in the Vibration Laboratory of Hohai University;and brittle materials were modeled by mortar.Test results under static and cyclic loadings including 1,2,3 and 5 Hz show:(1)shear stress-displacement curves under static loading are similar to the strength envelope curves under cyclic loading that can be divided into four parts;(2)the peak strength and residual strength under cyclic loading are larger than those under static loading when other conditions were same,but they change inconspicuously with the frequency changes;(3)peak strength and residual strength increase with normal stress increase under both loading conditions;(4)failure strains under static loading are larger than those under dynamic loading and both increase with the normal loading increasing;and(5)shear dilatancy is obvious during the shearing process.The failure mechanism was described simply at last.