【作者】 朱继良；

【导师】 李渝生； 王士天；

【作者基本信息】 成都理工学院 ， 地质工程， 2001， 硕士

【摘要】 马家河坝孤立岩体具有独特的地质背景和岩体结构类型，其潜在变形及它的稳定性问题对溪洛渡水电站工程有着重要的意义。作者在现场调研的基础上，对其进行分析，研究结果表明： （1）马家河坝断层的形成是在NW－SE方向推挤力的作用下，岩层变形而褶皱，形成NE向倾伏的那里沟背斜、马鞍山－咩咩山向斜及石板滩背斜的褶皱构造。随NW向主动力的持续作用，那里沟背斜愈来愈不对称，陡倾的SE翼剪应力高度集中并形成一组共轭剪节理面，当该部位的剪应力积累达到或超过岩体的抗剪强度时，便在那里沟背斜SE翼沿共轭剪切面发生逆冲剪断破坏，形成马家河坝断裂。随着递进变形的作用，马家河坝断层由NW向SE不断地俯冲剪切并扩展延伸，当扩展至石板滩－马家河坝一带时，由于受石板滩背斜阻挡而强烈地向上逆断爬坡，由平缓的剪切运动发展为前缘挤压逆冲叠瓦带。从而形成后部剪切逆断－中部俯冲剪胀－前部强力逆冲的推覆构造。 （2）通过对金沙江河谷岩体应力场发展演变过程及现今状态和未来发展趋势的数值模拟分析，结果表明： 随着河谷下切深度的增加，应力分异范围逐渐增大，谷底应力集中强度逐渐升高。河谷岩体应力场的发展演化进程总体上经历了两个阶段：第一阶段为金沙江下切至440m高程（即断层带发育部位），此阶段河谷侵蚀下切影响范围为断层上盘岩体，随河谷下切岩体应力的分异现象逐渐加剧，整个河谷岩体处于较强的卸荷松驰、应力释放调整发展过程；第二阶段为金沙江自440m下切至360m（现今谷底）高程，此阶段内岩体应力调整分异进程大为减缓，除谷底应力集中程度大幅度增加而形成“高应力包”现象外，其它各部位的应力－形变发展并无明显变化，整个河谷总体上处于岩体应力变异调整较平稳的发展阶段。经200年流变时步的数值模拟分析，岸坡岩体应力的变化梯度有所增大，特别在河谷左岸公路附近上方的高边坡岩体、断层带内和谷底等部位。但随着时间的推移，主应力和剪应力的大小和方向均不再发生明显的变化。说明在今后一段时期内，岩体的应力－形变作用处于缓慢的调整阶段。 （3）线弹性和流变性有限元数值模拟分析成果表明：马家河坝孤立岩体应力分异范围主要受地质构造控制。在断面附近及其所围限的岩体内，最大主应力和最小主应力速线均发生明显的偏转，形成一定范围内的应力重分布区；沿主断层带底面发育有明显的高应力带，与此形成鲜明对照的是，主断层带厚度范围内，出现一显著的低异常应力分异带。在F₁、F₂断层与F₃断层相交处及F₃断层前缘靠近地表处，主应力和剪应力均出现负值（计算值），表明这些特殊部位处于软弱的拉张应力状态，并呈长期缓慢的平稳松驰趋势。 （4）在各种工况条件下，马家河坝孤立岩体总体上具有较高的安全储备，表现出良好的稳定状态。在拟定的料场荷载作用下，这种较高的安全储备非但没有减少，反而略有增高，是因为料场荷载对抗滑力的贡献大于对下滑力的贡献。但值得注意的是，该孤立岩体NE部前缘大转山包附近的局部块体，在最不利的工况条件下（蓄水至580～590m一高程时遇Vlll度地震），处于极限平衡状态，安全储备极低。孤立岩体SW边缘局部块体也有类似情况；通过对孤立岩体前缘局部块体发生失稳破坏时的涌浪计算，所形成的涌浪冲击不会对大坝安全构成危胁。更多还原

【Abstract】 ABSTRACTMajiaheba isolated rock mass has distinctive geological background and structure of rock mass, whose potential deformation and stability are important to Xiluodu hydroelectric station. On the basis of in-situ investigation, we carefully studied it and draw some conclusions.First of all, Maj iaheba fault was formed which was the result of the NW-SE directional shove press. Under the condition, rock strata began to distort and fold so that the NE directional Naligou anticline, Maanshan-Mimishan syncline and Shibantan anticline were formed. With the NW directional continually acted, Naligou anticline became more and more asymmetric, whose steep dip SE facet’s shearing stress much accumulated and formed a group conjugated joint plane. When it continued to accumulate and was equal to or superpass the rock mass’s shearing strength, it began to overthrust and shearing destruction so that Majiaheba fault was formed. With the development of progressive deformation, Majiaheba fault continually subducted and sheared and extended from NW to SE direction. When it extended to Shibantan-Majiaheba, it began to strongly obducted and climbed because of Shibantan anticline’s resistance, and its easy movement developed to leading edge’s compressed overthrust imbricated fault zone. As a result, it formed a thrust-nappe tectonics, whose root zone sheared and obducted, whose middle zone subducted and dilated, whose front zone strongly obducted.Second, by analyzing Jinshajiang wadi’s rock mass stress field development and the development of finite element numerical modeling in the future, it shows us the following signals.With the increase of wadi’s down-cutting depth, the range of displacement of stress extended and wadi’s accumulation of stress’s strength increased. Wadi’s rock mass stress filed’s development was divided into two stages: the first stage was the wadi down-cutting the 440m altitude, that is, the fault lied. During the stage the range of being affected was the upper rock mass. With the wadi down-cutting, rock mass’s displacement of stress became wide and the whole wadi rock mass lied in the stage of load off and stress relaxation regulation. The second stage was the wadi down-cutting from 440m to 360m altitude which is today’s bottom. During the stage rock mass’s rate of the displacement of stress became slower. The whole wadi rock mass lied in slow regulation stage except that the wadi’s rock mass stress accumulation quickly increased. By analyzing the result of two hundred years rheological finite element numerical modeling, bank slope rock mass stress gradient increased, especially, the rock mass of high-slope above the highway, fault zone and wadi in the left bank and so on. With the time passing away, the principal stress and shear stress’s values and directions are no longer apparent variation. They show that rock mass stress-deformation lie in a slow regulation stage in the future.Third ,the results of linear elastic and rheological finite element numerical modeling showthat Majiaheba isolated rock mass抯 displacement of stress is mainly controlled by the geological conformation. The maximum principal stress and maximum shear stress trajectory both divert near the fault and among the rock mass which is surrounded by the fault and form some range of displacement of stress; there is a high stress zone at the bottom of the fault. On the contrary, there is a lower one in the fault zone. the principal stress and shear stress抯 values are negative in the place where the F1, F2 fault and F3 fault抯 conjunction and F3 fault抯 leading edge near the ground, which show that the special places lie in tensile stress and slow relaxation condition.Fourth, under all the condition, as a whole, Majiaheba isolated rock mass has high margin of safety and lies in a stable condition. Under the aggregate preparation ground condition, the high margin of safety not decrease but increase because it distributes resisting force more than the sliding force. Under the dangerous condition(stora更多还原