冻融循环条件下层理砂岩卸荷力学特性试验研究

研究层理砂岩在两种含水状态（自由饱水与真空饱水）、不同冻融循环次数（0次、20次、40次、80次、120次）条件下的三轴卸荷力学特性.研究表明：砂岩的强度随着冻融循环次数的增加而降低，真空饱水组的劣化程度较自由饱水组剧烈，外观损伤破坏主要出现在岩样端部边缘和层理面附近.加载与残余变形阶段产生轴向应变；卸荷阶段，围压降低与变形增长具有良好的相关性，随着冻融次数增加，卸荷阶段应变量减少，冻融作用对卸荷效应更敏感.冻融次数对破坏模式的影响有一定规律但不显著，试样破坏以剪切破坏为主，但随着冻融次数的增加，张拉破坏有增强的趋势.

The bedding sandstone unloading mechanical properties experimental study in the freeze-thaw cycle conditions

It studies the triaxial unloading mechanical properties of bedding sandstone under two kinds of mois-ture contents including free water-saturation and vacuum saturation and different freeze-thaw cycle times from 0 to 120 times).It shows that the strength of the sandstone decreases with the increase of freeze-thaw cycle times, and the degree of degradation of vacuum saturation group is more radical than that of free water-saturation group. Appearance damage occurs mainly in the edge of the rock′s end and the vicinity of the bedding plane.The axial strain is produced in the stage of loading and residual deformation;and it has good correlation between the reduce of confining pressure and the growth of deformation in the unloading stage.The strain produced in the unloading stage is reduced with the increase of the freeze-thaw times,and unloading effect under the action of freeze-thaw becomes more sensitive.There are certain rules,but no significant,of the effect of the freeze-thaw times to fail-ure mode,and sample destructions are mainly shear failure,but the tensile failure has a tendency to increase with the increase of freeze-thaw times.