【作者】 周青春；

【导师】 白世伟； 杨春和；

【作者基本信息】 中国科学院研究生院（武汉岩土力学研究所） ， 岩土力学， 2006， 博士

【摘要】 南水北调西线工程位于青藏高原东北部,从长江上游经巴颜喀拉山输水入黄河,是我国水资源优化配置,解决北方地区缺水的一项战略性基础设施工程,直接关系到我国北方地区社会经济的可持续发展和生态环境的改善。西线工程输水线路主要为深埋隧洞,所经过的区域存在高地温、高孔隙裂隙水压力及高地应力。研究高地温、高孔隙裂隙水压力及高地应耦合作用下岩石的力学特性是岩石地下工程开挖、支护设计及围岩稳定性分析不可或缺的基本依据。本文通过温度、应力及孔隙水压力、应力耦合下的三轴试验,对输水线路的主要岩性之一-砂岩的强度特性和变形特性进行了研究,并通过应力路径试验对砂岩在地温作用下的本构模型进行探讨。研究表明,在高孔隙水压力作用下,砂岩的强度和变形模量会发生变化。相同孔隙水压力作用下,砂岩的强度受围压控制,表现为围压越高,岩石的强度越高;相同围压条件下,孔隙水压力越高,岩石强度越低。孔隙水对岩石强度的影响主要表现在岩石的c值明显降低,?值变化虽然不如c值明显,但与c值趋势是一致的,即孔隙水压力越大,?值越低。岩石的变形模量与围压有关,低围压时,孔隙水压力的存在使岩石的变形模量增大;高围压条件下,岩石的变形模量随孔隙水压力的增加而降低。在孔隙水压力作用下砂岩的破裂模式多种多样,既有剪切破坏模式,也有轴向劈裂破坏模式。由于岩石致密等因素,孔隙水压力主要对岩石试件起劈裂作用,因此随着孔隙水压力的增大,岩石脆张性破坏特征明显。砂岩的强度与围压和温度间呈现出复杂的关系。在不同的温度条件下,砂岩的强度均随围压增加而增加。低围压时,强度随温度升高而增加,较高围压时,强度随温度升高有降低的趋势。温度对岩石强度的影响主要反映在粘聚力提高的幅度很大,而摩擦角变化不明显。砂岩的平均弹性模量与温度有关,较高温度条件下的弹性模量均高于室温的弹性模量,虽然不同围压下的表现形式不同。砂岩的压延性与围压和温度有关。围压增加破坏时的变形增加;温度升高时,其压延性与围压有关:单轴压缩状态下,压延性随温度线性增加,围压在25MPa以上时,压延性低于单轴压缩状态,且呈现较复杂的关系。通过不同温度下的应力路径试验,得到砂岩经验弹塑性本构关系,并确定了模型的参数与温度间的关系,说明岩石的弹性和塑性行为对温度的敏感性存在差别。更多还原

【Abstract】 The west route of south-to-north water transfer project is situated in the north-east of Qingzhang plateau, which aims at accounting for the lackage of water in north China by transferring water from the upper of Yangtze River to the upper of Yellow River via the mountain of Bayangela. In the engineering deep tunnels will be excavated to transfer water. According to the plan, the tunnels will pass through the region existing high geotemperature, high ground water and high geostress. The study of coupling behavior of three fields (high geothermal field, high hydraulic field and high geostress field) is very important for the excavating, bolting design and stability analyzing for tunnels. In the thesis, the mechanical behaviors of the sandstone from the project have been studied through a series of coupled triaxial tests of confining pressures (from 0 to 60MPa ) and temperatures (room temperature to 70℃) as well as confining pressures (from 25 to 60MPa ) and pore pressure (from 0 to 10MPa ), and an empirical constitutive law concerning geotemperature has been researched.The results of the study show that the strength of the rock sample increases clearly with the increasing confining pressure at the same pore pressure, and decreases with the increasing pore pressure under the same confining pressure. The main reason of the influence is the clear decreasing of cohesion of the sandstone, although the friction angle doesn’t change clearly comparing to the cohesion, but it has the same tendency as the cohesion. It is also shown that the Young’s modulus of dry rock is affected slightly by the confining pressure. Nevertheless, it is revealed that under the lower pore pressure, the Young’s modulus of rock samples increases with the increasing confining pressures, but under higher pore pressure, it decreases with the increasing pore pressures. The failure state of the sandstone under pore pressure exhibits brittle-tensile feature.The relation between the strength of the sandstone and temperature is complex.The strength of the rock is higher under the higher confining pressure regardless the temperature, while the influence of temperature reveals difference: the strength increases with the temperature when the confining pressure is lower than 40MPa; however, when the confining pressure is higher than 40MPa, the strength tends to decrease with increasing temperature. It also exhibits that the cohesion increased greatly with the temperature. Moreover, it reveals that the Young’modulus doesn’t change distinctly with confining pressures, but it is higher than that in room temperature when temperature increases. The ductile feature increase with confining pressure, but it is complex under temperature.Moreover, an empirical constitutive law considering geotemperature is proposed, which parameters are related to temperature.更多还原