中低应变率范围内花岗岩单轴压缩特性的尺寸效应研究

 利用变频动态加载岩石力学试验系统对直径为50 mm，长度分别为50，75，100，125 mm的花岗岩试样进行中低应变率范围内的加载试验。研究结果表明：(1) 试样强度具有显著的应变率依赖性，随着应变率增大，压缩强度近似以乘幂关系增大。(2) 静载和准动态加载条件下，岩石强度基本上随试样长度的增加而减小。(3) 不同应变率加载条件下，直径为50 mm的试样，长径比不小于2时，方能取得基本稳定的试验结果。(4) 峰值应变随试样尺寸的增大逐渐减小。(5) 割线模量E50和线性段弹性模量Et随试样尺寸的增大而增大，且Et＞E50。(6) 破裂形式具有显著的应变率效应，随着应变率的增高，破碎程度加大；其尺寸效应则表现为：应变率 ＜10－3 s－1时，随着尺寸的增大，破裂形式表现为劈裂–锥形破裂–剪切破裂的过程；应变率 ＞10－2 s－1时，破裂形式则直接由锥形破裂变为剪切破裂。

RESEARCH ON SIZE EFFECT OF UNIAXIAL COMPRESSION PROPERTIES OF GRANITE UNDER MEDIUM AND LOW STRAIN RATES

The static and quasi-dynamic tests on granite specimens under various strain rates are conducted by using rock dynamic loading system. The specimens are 50 mm in diameter，with the length of 50，75，100，125 mm，respectively. The research results are drawn as follows：(1) Specimen strength is significantly dependent on strain rates and increases with the growth of strain rates with a power relationship. (2) Under static and quasi-dynamic loading conditions，rock strength generally decreases with the increase in specimen length. (3) When the diameter of specimen is 50 mm，the aspect ratio should be not smaller than 2；then steady test results can be obtained under different strain rates. (4) Peak strain under each strain rate decreases with increasing specimen size. (5) Both of secant modulus E50 and elastic modulus Et increase with increasing specimen size；and Et is larger than E50. (6) Failure mode is significantly dependent on strain rates and failure is serious when the strain rate increases. When strain rate  ＜10－3 s－1，failure mode has a process of split failure-taper failure-shear failure；when strain rate  ＞10－2 s－1，the failure mode changes from taper failure to shear failure directly.