冻结白垩系砂岩强度特性试验研究

Experimental Study on Strength Characteristics of Freezing Sandstone in Cretaceous Strata

为研究白垩系地层冻结砂岩的强度特性,采用MTS-815电液伺服岩石试验系统开展了不同温度状态下饱和中砂岩和粗砂岩的单轴压缩试验,获得冻结白垩系砂岩的力学性质与低温的相关性。试验表明：冻结白垩系中粒砂岩及粗粒砂岩,其单轴抗压强度均随温度的降低而增大,从25℃降至-30℃的过程,中粒砂岩强度提高了49.475%～64.656%,而粗粒砂岩的强度提高了59.455%～84.886%,相同温度下,饱和粗粒砂岩的单轴强度总是大于中粒砂岩;两种岩石强度的差异性较大,且差值随着温度降低而总体上不断增大;随着温度的降低冻结白垩系岩石弹性模量明显增大,应力-应变曲线的压密段和塑性变形段越来越不明显,表现出更明显的弹性和脆性特征。通过试验结果分析,可为该地区冻结法凿井冻结壁和井壁的设计参数的选取提供参考。

To study the strength characteristics of freezing sandstone in cretaceous stratum, the MTS - 815 electro hydraulic servo rock experiment system was applied to carry out uniaxial compression tests of saturated sandstone and coarse sandstone at different temperatures, obtaining the correlation of mechanical properties and low temperature. The results show that, for freezing medium - grained sandstone and cretaceous coarse sandstone, the uniaxial compressive strength increases with the decreasing of temperature, which falls from 25℃ to minus 30℃, the strength of the medium - grained sandstone increases by 49. 475% - 64. 656%, and the coarse sandstone increases by 59. 455% ～ 84. 886% ; Saturated uniaxial strength of coarse sandstone is always greater than medium - grained sandstone at the same temperature; Difference in strength of the two rocks is obvious, which becomes more obvious as the temperature falls; As temperature falls, the elastic modulus of freezing cretaceous rock increases, the pressure and plastic deformation in stress - strain curve keeps becoming less significant, showing obvious elastic and brittle characteristics. The analysis of test results can offer references for design parameters selection of freezing wall and shaft wall in this area.