柱状节理岩体侧向变形特性单轴压缩试验研究

Experimental Study on Lateral Deformation Properties of Columnar Jointed Rock Masses under Uniaxial Compression

由于柱状节理网络的存在,柱状节理岩体在单轴压缩下沿柱状节理的滑移、松弛或局部破裂将产生较大的外观侧向变形,相应的侧向应变与轴向应变之比(以下简称侧向应变比)将大大超出连续介质泊松比上限值0.5。正确把握柱状节理岩体较大侧向变形特性,是地下洞室等大型柱状节理岩体工程设计需要解决的关键问题之一.为此,以石膏混合材料制作柱体与σ1具有不同夹角β的模拟柱状节理岩体试件,通过单轴压缩试验得到了模拟柱状节理岩体侧向应变比νr随β的变化曲线,曲线近似为倒"U"型,并在β=30°时取得最大值,在此基础上根据模拟柱状节理岩体的破坏模式对其侧向变形力学机理进行了分析。最后,参照Ramamurthy各向异性经验模型构建了预测柱状节理岩体侧向应变随夹角β变化的经验公式,将经验预测值与试验实测值进行比较发现两者吻合较好,该经验公式可以较好地预测侧向应变随夹角β的变化趋势。

Due to the columnar joints network, the slipping, relaxing or rupturing locally along these columnar joints, may result in large lateral deformation of columnar jointed rock mass and the ratio of lateral strain to corresponding axial strain （ hereinafter referred to as lateral strain ratio ） will greatly exceed the upper limit of Poisson ＇ s ratio. Correct understanding the large lateral deformation characteristics of columnar jointed rock mass is one of the key problems that should be solved for the design of large scale columnar jointed rock mass projects such as underground caverns. Therefore, simulated columnar jointed rock mass specimens with dip anglesβ different from σ1 are prepared by using plaster mixtures. Uniaxial compression tests are performed on these specimens and the curve of variation of lateral strain ratio with 13 has been obtained. The shape of the curve resembles as inverted U-typed and the maximum of lateral strain ratio occ.urs atβ= 30°. Then the mechanism of large lateral deformation is analyzed in light of the failure modes. According to the empirical anisotropy model proposed by Ramamurthy, an empirical expression is presented to predict the variation of lateral strain ratio with ft. Comparing the predicted curve with experimental data,it is found that the predicted curve agree reasonably well with experimental data and the empirical expression can predict the lateral strain ratio well.