中文摘要：

风化是云冈石窟目前所面临的严重的地质病害之一,温度和水分的变化是造成石窟岩体风化的重要原因,尤其是在循环冻融条件下岩体更易风化,因此,利用室内试验研究循环冻融条件下云冈石窟砂岩的物理力学性质,对于石窟岩体的稳定性评价和保护具有重要的意义。将取自云冈石窟的砂岩岩样分为饱水组、干燥组和对比组3组,通过对饱水组和干燥组岩样进行35次循环冻融试验,模拟云冈石窟砂岩的风化过程。在冻融循环开始前以及每5次冻融循环结束后,量测岩样的质量、体积,并利用超声检测分析仪对各岩样进行超声纵波测试;利用INSTRON-1346岩石伺服试验机对上述3组砂岩岩样进行单轴压缩试验,并对试验后的岩样进行SEM微观结构分析。通过试验研究,得到不同含水状态下云冈石窟砂岩岩样的冻融破坏特征以及不同循环冻融次数后岩样体积、质量、超声波纵波波速、砂岩的单轴应力-应变全过程曲线、抗压强度、抗冻系数以及微观结构的变化,分析归纳出循环冻融条件下云冈石窟砂岩的主要物理力学特性。

英文摘要：

Weathering is one of serious geological diseases that the Yungang grottos have been faced with. The changes of the temperature and water in the rock masses are the main causes of weathering,especially under the condition of freezing-thawing cycles. Therefore, to research the physico-mechanical characteristics under the condition of freezing-thawing cycles by laboratory test have important significance to the stability evaluation of the rock masses in Yungang grottos. The sandstone specimens taken from Yungang Grottos are separated into three groups：saturated, dry and control groups. Laboratory tests are conducted on saturated group and dry group which have experienced 35 cycles of freezing-thawing to simulate the weathering process of sandstone. Before freeze-thaw test and after every 5 cycles of freezing-thawing,the mass and volume of specimens are measured, the ultrasonic P-wave velocities of specimens are tested using ultrasonic testing instrument;and the uniaxial compression tests of sandstone specimens are performed by INSTRON-1346 rock mechanics test system. After freeze-thaw test, the microstructures of the sandstone specimens are seen by scanning electron microscope. Through above-mentioned tests,the failure forms of the specimens under different water contents and the changes of the mass and volume,ultrasonic velocities,the complete stress-strain curves,uniaxial compressive strengths,frost resisting coefficients and microstructures of the sandstone specimens after different freeze-thaw cycles are obtained. Consequently, the main physico-mechanical characteristics of sandstone under the condition of freezing-thawing cycles are summed up.