浸水条件下级配弱黏结颗粒边坡稳定性研究

发布时间：2018-06-18 22:43

本文选题：岩土工程 + 弱黏结边坡　；参考：《重庆交通大学》2016年硕士论文

【摘要】：高速公路、水利水电、矿山开采等基础设施的大量修建,所形成的永久或临时性边坡历来都是岩土工程的核心问题,针对其中类土质岩体形成的弱黏结边坡,以三峡水库为背景,采用离散元软件PFC2D/3D,实施室外模型试验等方法,进行深入研究分析。对不同级配的弱黏结崩坡积层力学特性进行了三轴压缩数值试验,建立了含石量0%、20%、40%、60%、80%及100%,尺寸60×30cm、65×32.5cm、70×35cm、75×37.5cm及80×40cm共30种试样,分别在100kPa、300kPa、500kPa及1000k Pa围压下进行压缩,得出如下结论:(1)土石混合体粘聚力c随着含石量的增加而减小,近似呈线性关系,内摩擦角?在含石量小于40%时,几乎不变,当大于40%且小于60%时,内摩擦角?处于过渡阶段,开始增大,且增大程度越来越快,当含石量大于60%时,内摩擦角急剧增加。(2)同一含石量试样的粘聚力随着试样尺寸的增大而逐渐减小,且减小程度在含石量40%左右达到最大,随着试样尺寸的增大,含石量0%的试样内摩擦角?几乎不变,20%、40%和60%含石量的试样内摩擦角减小,80%、100%含石量的试样内摩擦角增大。(3)崩坡积物试样在“低含高围”情况下,破坏时出现“剪涨”现象,“高含低围”情况下,出现“剪缩”现象。采用碎石、粘土、高岭土及水泥以一定的配比试制类土质岩体,以龚家方岸坡为原型,实施了室外物理模型试验,并采用PFC3D软件建立了离散元数值模型,对两者在不同水位工况下的变形破坏、内部应力、孔隙率等进行了分析研究。结果表明:(1)碎石、粘土、高岭土、水泥按照4:2:1:0.14的体积比配制而成的试验用类土质岩体能较好替代野外大粒径不规则类土质岩体;(2)室外模型在水位上升期间前缘发生局部坍塌,在水位下降期间发生整体垮塌,且内部空隙水压力可以间接反映此时边坡的变形形态;(3)离散元模型在水位升降期间模拟边坡的变形破坏情况与室外物理模型一致,且能同时获得岸坡内部孔隙率及应力的变化情况,间接反映岸坡变形情况。运用离散元软件PFC2D,建立了三峡水库龚家方2号斜坡的离散元模型,并对其破坏问题进行模拟,模拟结果表明:(1)水库蓄水后,斜坡上覆崩坡积层会沿着岩土分界面向下滑动;(2)整个滑动过程可以分为底端变形、上段及中段垮塌、整体滑动以及固化稳定4个阶段,其中底端变形形成的“鼓包”是否破裂是斜坡启动的关键;(3)斜坡的滑动速度在初始阶段速度会迅速增大,之后缓慢减小,直至稳定。将模拟结果与观测资料对比分析,与实际破坏情况一致。运用离散元软件PFC2D,建立了三峡水库岸坡区域神女溪青石滑坡的离散元模型,并对其在145m、155m、165m和175m水位工况下的变形与破坏问题进行模拟研究,结果表明:(1)滑坡在165m水位下同等时间内坡中部分竖向位移最大,滑动速度最快,坡脚处水平方向应力以及水平方向应变速率均最先达到最大值;(2)145m水位下滑坡变形量微小,155m、165m和175m水位下滑坡的破坏过程可分为弱化蠕变、前缘变形滑动、中部失稳滑动以及固化稳定四个阶段,且滑动过程中靠近滑带上部的岩土体强度会逐渐降低,起到一定促滑作用。模拟结果中不同水位下滑坡稳定状态以及175m水位下裂缝的产生和扩展情况皆与实际情况相近。运用离散元方法及室外模型试验等手段对库区弱黏结边坡进行研究分析,丰富了离散元PFC2D/3D的应用,为工程中弱黏结边坡的防治提供了参考。
[Abstract]:The construction of the basic facilities such as expressway, water conservancy and hydropower, mine mining and so on, the permanent or temporary slope has always been the core problem of geotechnical engineering. In view of the weak bond slope formed by the soil like rock mass, the Three Gorges reservoir is taken as the background, the discrete element software PFC2D/3D is adopted to carry out the outdoor model test and so on. A three axis compression test was carried out on the mechanical properties of the weak cohesive and slop slop layers of different gradations, and a total of 0%, 20%, 40%, 60%, 80% and 100%, size 60 x 30cm, 65 x 32.5cm, 70 * 35cm, 75 x 37.5cm and 80 * 40cm were compacted under the confining pressure of 100kPa, 300kPa, 500kPa and 1000K Pa respectively, and the following conclusions were concluded: (1) The cohesive force C of the soil and rock mixture decreases with the increase of the content of the stone. The internal friction angle is almost invariable when the stone content is less than 40%. When it is greater than 40% and less than 60%, the internal friction angle is in the transition stage, and the increase degree becomes faster and faster. The internal friction angle increases sharply when the stone content is more than 60%. (2) the same stone The cohesive force of the sample size decreases with the increase of sample size, and the degree of reduction is maximum at about 40% stone content. With the increase of sample size, the friction angle in the sample with 0% stone is almost invariable, the friction angle in 20%, 40% and 60% rock content decreases, and the friction angle in the specimen with 80% and 100% is increased. (3) the landslide product Under the condition of "low high and high enclosure", the phenomenon of "shear rise" and "cut and shrink" in the case of "high low confinement" occurred in the case of "high low confinement". The rock mass was tested with gravel, clay, kaolin and cement in a certain proportion. The outdoor physical model test was carried out with the prototype of Gong Jia Fang, and the discrete PFC3D software was used to establish a discrete model. The deformation failure, internal stress and porosity of the two are studied under different water level conditions. The results show that: (1) lithotripsy, clay, kaolin, cement in accordance with the volume ratio of 4:2:1:0.14 can replace the large size irregular soil rock mass in the field, and (2) outdoor model in the field There is a local collapse in the front edge of the water level, and the whole collapse occurs during the fall of the water level, and the internal clearance water pressure can indirectly reflect the deformation form of the slope at this time. (3) the deformation and failure of the simulated slope is consistent with the outdoor physical model during the period of the water level rise and fall, and the porosity of the slope can be obtained at the same time and should be obtained at the same time. The variation of the force is indirectly reflected on the deformation of the bank slope. Using the discrete element software PFC2D, the discrete element model of the 2 slope of the Three Gorges reservoir, Gong Jia Fang, is established and its failure is simulated. The simulation results show that (1) after the reservoir is impounded, the overlying slope on the slope will slide down along the interface of the rock and soil; (2) the whole sliding process can be divided into two parts. For the bottom end deformation, the collapse of the upper and middle sections, the whole sliding and the stabilization of the 4 stages, in which the breakage of the "drum" formed by the deformation of the bottom end is the key to the start of the slope; (3) the sliding velocity of the slope will increase rapidly at the initial stage, then slowly decreases, and goes straight to the stable. The discrete element software PFC2D is used to establish the discrete element model of the Tsing Shi brook landslide in the slope area of the Three Gorges reservoir, and to simulate the deformation and failure of the landslide under the water level of 145m, 155m, 165m and 175m. The results show that (1) the vertical displacement of the landslide at the same time in the same time of the 165m water level is the largest, The sliding velocity is the fastest, the horizontal stress at the foot direction and the horizontal strain rate are the first to reach the maximum. (2) the deformation of the landslide at the 145m water level is small. The failure process of the landslides under the water level of 155m, 165m and 175m can be divided into the weakening creep, the deformation sliding of the front edge, the unstable sliding of the middle part and the solidification stability, and the sliding process is close to the sliding process. The strength of the rock and soil body in the upper part of the sliding zone will gradually decrease and play a certain role in promoting the sliding. In the simulation results, the stability of the landslides at different water levels and the occurrence and expansion of the cracks under the 175m water level are all similar to the actual conditions. The application of the scattered element PFC2D/3D provides a reference for the prevention and control of weak cohesive slopes in engineering.
【学位授予单位】：重庆交通大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TU43

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