本文選題：巖土工程 + 弱黏結邊坡��； 參考：《重慶交通大學》2016年碩士論文

【摘要】：高速公路、水利水電、礦山開采等基礎設施的大量修建,所形成的永久或臨時性邊坡歷來都是巖土工程的核心問題,針對其中類土質巖體形成的弱黏結邊坡,以三峽水庫為背景,采用離散元軟件PFC2D/3D,實施室外模型試驗等方法,進行深入研究分析。對不同級配的弱黏結崩坡積層力學特性進行了三軸壓縮數(shù)值試驗,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種試樣,分別在100kPa、300kPa、500kPa及1000k Pa圍壓下進行壓縮,得出如下結論:(1)土石混合體粘聚力c隨著含石量的增加而減小,近似呈線性關系,內摩擦角?在含石量小于40%時,幾乎不變,當大于40%且小于60%時,內摩擦角?處于過渡階段,開始增大,且增大程度越來越快,當含石量大于60%時,內摩擦角急劇增加。(2)同一含石量試樣的粘聚力隨著試樣尺寸的增大而逐漸減小,且減小程度在含石量40%左右達到最大,隨著試樣尺寸的增大,含石量0%的試樣內摩擦角?幾乎不變,20%、40%和60%含石量的試樣內摩擦角減小,80%、100%含石量的試樣內摩擦角增大。(3)崩坡積物試樣在“低含高圍”情況下,破壞時出現(xiàn)“剪漲”現(xiàn)象,“高含低圍”情況下,出現(xiàn)“剪縮”現(xiàn)象。采用碎石、粘土、高嶺土及水泥以一定的配比試制類土質巖體,以龔家方岸坡為原型,實施了室外物理模型試驗,并采用PFC3D軟件建立了離散元數(shù)值模型,對兩者在不同水位工況下的變形破壞、內部應力、孔隙率等進行了分析研究。結果表明:(1)碎石、粘土、高嶺土、水泥按照4:2:1:0.14的體積比配制而成的試驗用類土質巖體能較好替代野外大粒徑不規(guī)則類土質巖體;(2)室外模型在水位上升期間前緣發(fā)生局部坍塌,在水位下降期間發(fā)生整體垮塌,且內部空隙水壓力可以間接反映此時邊坡的變形形態(tài);(3)離散元模型在水位升降期間模擬邊坡的變形破壞情況與室外物理模型一致,且能同時獲得岸坡內部孔隙率及應力的變化情況,間接反映岸坡變形情況。運用離散元軟件PFC2D,建立了三峽水庫龔家方2號斜坡的離散元模型,并對其破壞問題進行模擬,模擬結果表明:(1)水庫蓄水后,斜坡上覆崩坡積層會沿著巖土分界面向下滑動;(2)整個滑動過程可以分為底端變形、上段及中段垮塌、整體滑動以及固化穩(wěn)定4個階段,其中底端變形形成的“鼓包”是否破裂是斜坡啟動的關鍵;(3)斜坡的滑動速度在初始階段速度會迅速增大,之后緩慢減小,直至穩(wěn)定。將模擬結果與觀測資料對比分析,與實際破壞情況一致。運用離散元軟件PFC2D,建立了三峽水庫岸坡區(qū)域神女溪青石滑坡的離散元模型,并對其在145m、155m、165m和175m水位工況下的變形與破壞問題進行模擬研究,結果表明:(1)滑坡在165m水位下同等時間內坡中部分豎向位移最大,滑動速度最快,坡腳處水平方向應力以及水平方向應變速率均最先達到最大值;(2)145m水位下滑坡變形量微小,155m、165m和175m水位下滑坡的破壞過程可分為弱化蠕變、前緣變形滑動、中部失穩(wěn)滑動以及固化穩(wěn)定四個階段,且滑動過程中靠近滑帶上部的巖土體強度會逐漸降低,起到一定促滑作用。模擬結果中不同水位下滑坡穩(wěn)定狀態(tài)以及175m水位下裂縫的產(chǎn)生和擴展情況皆與實際情況相近。運用離散元方法及室外模型試驗等手段對庫區(qū)弱黏結邊坡進行研究分析,豐富了離散元PFC2D/3D的應用,為工程中弱黏結邊坡的防治提供了參考。
[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.
【學位授予單位】：重慶交通大學
【學位級別】：碩士
【學位授予年份】：2016
【分類號】：TU43

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