【摘要】：近年來,滑坡地質(zhì)災害頻發(fā),有必要建立其監(jiān)測預警體系。而滑坡的變形破壞過程與變形破壞特征的研究對于監(jiān)測預警該類滑坡具有重要意義。為了研究均質(zhì)土坡的變形破壞過程與變形破壞特征,本次研究采用大型土工離心模型試驗與數(shù)值模擬相結(jié)合的方式,先通過離心模型試驗模擬特定尺寸條件的均質(zhì)土坡,分析其變形破壞過程、變形破壞特征、變形破壞機理。在完成離心模型試驗后,運用FLAC3D軟件模擬不同尺寸條件(坡角、坡高的變化)下均質(zhì)土坡的變形破壞規(guī)律,在一系列模擬的基礎(chǔ)上對均質(zhì)土坡的變形破壞過程、變形破壞特征、變形破壞機理進行分析總結(jié)。綜合論文研究工作,得到以下幾點結(jié)論:(1)在離心試驗過程中,均質(zhì)土坡的變形破壞過程可總括為:①局部變形破壞階段;②變形破壞擴展階段;③變形破壞發(fā)展貫通階段。區(qū)別在于不同坡型條件的均質(zhì)土坡局部變形開始的部位、變形的影響區(qū)域、變形的力學性質(zhì)等的不同。具體的:當坡高較高、坡角較大(H40cm,α40°)時,坡體最先于后緣坡頂出現(xiàn)變形,在此出現(xiàn)的變形由拉性力造成。隨著離心加速度的增大,坡頂受拉區(qū)域?qū)⒊霈F(xiàn)拉裂縫,拉裂縫向Y方向和Z方向同時擴展,與此同時,前緣坡腳出現(xiàn)一定的應力集中現(xiàn)象。加速度進一步增大,變形破壞區(qū)域由坡頂沿坡面向坡腳處擴展,坡腳處出現(xiàn)少量剪切破壞。最終,拉裂區(qū)域與前緣剪切變形區(qū)域貫通;當坡高較低、坡角較小(H40cm,α40°)時,坡體最先于前緣坡腳處發(fā)生變形,變形主要由剪性力造成。隨著離心加速度,剪切變形加大,拉動后面的土體變形,隨著離心加速度的進一步增大,影響的變形區(qū)域逐漸增大至坡頂。整體上模型破壞的離心加速度值均在100~150g之間。(2)均質(zhì)土坡的應力分布特征為:坡表應力值較大,易發(fā)生變形破壞;最小主應力的集中幾乎都在坡體頂部;最大主應力的集中出現(xiàn)于坡體頂部或坡腳處;坡腳處出現(xiàn)應力集中的情況發(fā)生于大坡角或高坡高的坡型條件下。(3)均質(zhì)土坡的變形破壞特征:前緣坡腳處發(fā)生較大的剪出變形(X方向),而在Y方向上幾乎沒有位移;在坡頂近坡面處,則主要發(fā)生Y方向上的位移,X方向發(fā)生相對較小由拉性力造成的位移;從坡頂?shù)狡履_,X方向上的位移呈增加趨勢,Y方向的位移呈減小趨勢;隨著坡高增大、坡角變陡,整體的位移量增大,受拉性力而產(chǎn)生的變形區(qū)域增大,坡頂可見沿Z方向發(fā)育的裂縫,坡腳出出現(xiàn)剪切破壞。坡體內(nèi)出現(xiàn)剪應變增量帶,成為潛在的滑動面(帶)。(4)通過監(jiān)測點的位移變化分析可知:坡表最先出現(xiàn)明顯變形,當坡高較低、坡角較小時,變形主要發(fā)生在坡體淺表層;隨著坡高、坡角的增大,坡表位移繼續(xù)增大,坡體的變形的深度加大繼續(xù)向坡體內(nèi)擴展;隨著坡高、坡角的進一步增大,坡體后緣的變形破壞深度加深,坡體內(nèi)部分區(qū)域的變形發(fā)生較大調(diào)整。(5)通過對均質(zhì)土坡的變形破壞機理分析,可歸類為兩類變形破壞模式:①“拉裂—蠕滑—剪斷”型,主要發(fā)生在坡高較高、坡角較大的坡型中。該類型的變形破壞過程為先在后緣坡頂形成拉裂縫、而后在坡腳處發(fā)生蠕滑剪切作用、最后“剪斷”中部土體,形成完整滑面,坡體完全失穩(wěn)。由于坡頂裂縫向坡體內(nèi)擴展較深,這類坡破壞時規(guī)模相對較大,屬于中型滑坡,從力學機制上看類似于推移式滑坡。②“蠕滑—拉裂—剪切”型,主要發(fā)生在坡高較低、坡角較小的坡型中。即先在前緣坡腳處發(fā)生蠕滑剪切作用、而后帶動或拉裂后面坡體、最后再發(fā)生剪切破壞,形成連續(xù)滑面,坡體整體失穩(wěn)。
[Abstract]:In recent years, geological hazards of landslides occur frequently, so it is necessary to establish a monitoring and early warning system. The study of deformation and failure process and deformation and failure characteristics of landslides is of great significance for monitoring and early warning of such landslides. First, centrifugal model test is used to simulate the deformation and failure process, deformation and failure characteristics, and deformation and failure mechanism of homogeneous soil slope with specific size conditions. Based on a series of simulations, the deformation and failure process, deformation and failure characteristics, deformation and failure mechanism of homogeneous soil slope are analyzed and summarized. The difference lies in the position where the local deformation begins, the area affected by the deformation and the mechanical properties of the deformation of the homogeneous soil slope under different slope types. With the increase of centrifugal acceleration, tensile cracks will appear on the top of the slope, and the tensile cracks will expand in the direction of Y and Z at the same time. At the same time, there is a certain stress concentration phenomenon at the front foot of the slope. When the slope height is low and the slope angle is small (H40cm, alpha40 degrees), the deformation first occurs at the foot of the leading edge slope, which is mainly caused by shear force. (2) The stress distribution characteristics of homogeneous soil slopes are as follows: the surface stress value is large, and it is easy to occur deformation and failure; the minimum principal stress concentration is almost at the top of the slope; the maximum principal stress concentration occurs at the top or foot of the slope; and the stress concentration occurs at the foot of the slope. (3) Deformation and failure characteristics of homogeneous soil slopes: large shear deformation (X direction) occurs at the foot of the leading slope, but almost no displacement in the Y direction; displacement mainly occurs in the Y direction near the top of the slope, and displacement caused by tensile force relatively small in the X direction; From the top to the foot of the slope, the displacement in the X direction tends to increase, while the displacement in the Y direction tends to decrease; with the increase of the slope height, the slope angle becomes steeper, the overall displacement increases, and the deformation area caused by the tensile force increases. The cracks along the Z direction can be seen on the top of the slope, and the shear failure occurs at the foot of the slope. (4) Through the analysis of the displacement variation of monitoring points, it can be seen that the surface of the slope first appears obvious deformation, when the slope height is low and the slope angle is small, the deformation mainly occurs in the superficial layer of the slope; with the increase of the slope height and the slope angle, the displacement of the slope surface continues to increase, and the deformation depth of the slope body continues to expand to the slope body with the slope height and the slope angle further. (5) By analyzing the deformation and failure mechanism of homogeneous soil slope, it can be classified into two types of deformation and failure modes: (1) tensile-creep-shear type, which mainly occurs in the slope with higher slope height and larger slope angle. The process is to form tensile cracks at the top of the leading edge slope, then creep shear at the foot of the slope, and finally "shear" the middle soil, forming a complete sliding surface, and the slope is completely unstable. (2) Creep-slip-tension-shear type occurs mainly in the slope with low slope height and small slope angle, i.e. creep-slip shearing occurs at the foot of the leading slope, then drives or pulls the back slope, and finally shear failure occurs, resulting in continuous sliding surface and overall instability of the slope.
【學位授予單位】：成都理工大學
【學位級別】：碩士
【學位授予年份】：2015
【分類號】：P642.22

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