大粒径破碎岩石承压变形特性

为研究大粒径破碎岩石承压变形特性,研制了大尺寸破碎岩石承压变形试验系统,选取某矿区典型顶板砂岩,考虑垮落区破碎岩石粒径的分布特征和受力状态,进行了正态分布的粒径级配和梯形分级加载试验。试验表明:随轴向载荷增加,破碎岩石轴向变形逐渐增大,残余碎胀系数和空隙率逐渐减小,加载较恒载阶段尤为明显;恒载初期,轴向应变增长较快,而后逐渐变缓并趋于平稳,应变时间历程呈现对数关系;加载阶段,随载荷增大,破碎岩石试样轴向应变差值呈现先减小后增大,恒载阶段,随载荷增大,破碎岩石试样轴向应变差值则呈现先增大后减小;破碎岩石承压后的变形分为瞬时压缩变形和长期压缩变形两个阶段,主要由颗粒位置调整、原始或新生小颗粒滑动填充空隙引起的;破碎砂岩试样以粒径15~20 mm为承压变形过程中的稳定粒径,试验后,粒径15 mm的含量均有增加,粒径20 mm的含量则均有减小,为破碎砂岩试样总质量的16.76%。

Bearing deformation characteristics of large-size broken rock

In order to study the bearing deformation characteristics of large-size broken rock,a testing system used for bearing deformation test of large-size broken rock was developed.The typical sandstone from the roof was chosen as sample.In view of the particle size distribution characteristics and stress state of broken rock in caving zone,the size distribution of broken rock obeyed the law of normal distribution and the loading pattern was designed to step loading.The test results indicated that along with the increase of axial load,the axial deformation of broken rock increases gradually,the residual bulking coefficient and porosity decrease gradually,which are more obvious in loading stage than that in constant load stage.In the early constant load stage,the axial deformation of broken rock grows rapidly,then tends to be slow and steady gradually,the relationship between strain and time meets the logarithmic relationship.In loading stage,the D-value of axial strain decreases first and then increases,in constant load stage,which is opposite.The bearing deformation of large-size broken rock isconsisted of two parts:instantaneous compression deformation and long-term deformation,which reflects in the position adjustment of rock particles,smaller original and newborn rock particles slide and fill the gap between larger rock particles.The 15-20 mm particle size of broken rock is constant during the process of bearing deformation test,at the end of test,the content of broken rock (particle size is smaller than 15 mm) increases by 16.76% and the content of broken rock (particle size is greater than 20 mm particle size) decreases by 16.76%.The research results are of significance for forecasting and controlling the movement and deformation of overlying strata caused by mining.