【摘要】：在四川藏區(qū)公路（汶九高速、雅康高速、綿九高速和汶馬高速）和麗香高速公路設計中，發(fā)現隧道洞口段巖堆分布廣泛，這些塌落巖體在坡腳的堆積物結構松散、強度較低、穩(wěn)定性較差，給隧道的設計、施工帶來極大困難。本文依托“重慶交通大學交通土建工程材料國家地方聯合工程實驗室開放基金《基于離散元理論的松散堆積體高邊坡穩(wěn)定性研究》（編號：LHSYS-2013-007），總結了國內外專家學者對處于堆積體區(qū)隧道相關研究成果，建立洞口段邊坡評價方法，并從常規(guī)的開挖方式中尋找一種快速、經濟、安全的開挖方式，通過對走馬嶺隧道邊坡穩(wěn)定性評價和模擬出口段隧道開挖，得出了以下幾點結論。 ①采用室內大型直剪儀對重慶地區(qū)典型堆積體試樣進行直剪試驗，測取不同密實度下的抗剪強度。當松散堆積體密實度由0.3增大到0.6時，內摩擦角由25.67°增大到32.53°，而粘聚力則由5.13Kpa增大到32.29Kpa。 ②通過對堆積體區(qū)隧道邊坡的失穩(wěn)進行分析，，提出堆積體邊坡的兩種滑動失穩(wěn)模式：基巖深埋情況下的圓弧滑動和基巖淺埋的界面滑動，并用公式推導了在隧道開挖擾動情況下仰坡失穩(wěn)機理。 ③采用了三維有限元程序ANSYS對隧道常規(guī)開挖方式（全斷面開挖、臺階法、導坑法），來模擬堆積體隧道開挖，通過比較得出三種開挖方式中臺階法對圍巖和邊坡穩(wěn)定性影響最小，而全斷面開挖影響最大。 ④運用傳統(tǒng)的極限平衡法和有限元程序Plaxis2D對走馬嶺隧道洞口邊坡進行穩(wěn)定性綜合分析，兩種方法得出相同結果；并采用離散元顆粒流程序PFC2D對洞口邊坡開挖進行數值模擬，通過對顆粒位移的比較，得到了錨桿技術對于堆積體邊坡加固可以起到明顯效果。 ⑤運用三維有限元程序ANSYS，模擬在不同剛度的初期支護，通過監(jiān)測隧道開挖后拱頂圍巖應力，得到了隧道最佳支護剛度。 ⑥運用三維有限元程序ANSYS，采用臺階法預留核心土開挖方式，分析圍巖和邊坡的位移及塑性區(qū)變化。結果表明：該方式在第一步環(huán)形開挖后，拱頂圍巖和仰坡產生一定位移；第二步左側臺階開挖后，位移變��；隨后圍巖和坡頂處于基本穩(wěn)定狀態(tài)。
[Abstract]:In the design of Sichuan Tibetan Highway (Wen-Jiu Highway, Ya-Kang Highway, Mian-Jiu Highway and Wen-Ma Highway) and Lixiang Highway, it is found that the rock mass at the entrance of the tunnel is widely distributed, and the rock mass at the foot of the slope is loose in structure, low in strength and poor in stability, which brings great difficulties to the design and construction of the tunnel. Open Fund of National Laboratory of Transportation and Civil Engineering Materials of University (No. In this way, a quick, economical and safe excavation method is found. Through the slope stability evaluation of the Taumaling tunnel and the simulation of the tunnel excavation in the exit section, the following conclusions are drawn.
(1) The shear strength of typical accumulations in Chongqing area was measured by direct shear test with a large-scale direct shear apparatus. When the density of loose accumulations increased from 0.3 to 0.6, the internal friction angle increased from 25.67 degrees to 32.53 degrees, while the cohesion increased from 5.13 Kpa to 32.29 Kpa.
(2) Based on the analysis of the instability of the tunnel slope in the accumulation area, two kinds of sliding instability modes of the accumulation slope are put forward, i.e. the circular sliding under the condition of deep bedrock buried and the interface sliding between shallow bedrock buried, and the instability mechanism of the slope under the condition of tunnel excavation disturbance is deduced by the formula.
Thirdly, the three-dimensional finite element program ANSYS is used to simulate the excavation of the accumulative body tunnel by using the conventional excavation method (full-section excavation, step method, pilot pit method). The results show that the step method has the least influence on the stability of surrounding rock and slope, and the full-section excavation has the greatest influence.
(4) The traditional limit equilibrium method and the finite element program Plaxis 2D are used to analyze the stability of the entrance slope of the Zhumaling tunnel, and the same results are obtained by the two methods; and the discrete element particle flow sequence PFC2D is used to simulate the excavation of the entrance slope. Slope reinforcement can play a significant role.
_The initial support with different stiffness is simulated by using the three-dimensional finite element program ANSYS. The optimum support stiffness of the tunnel is obtained by monitoring the surrounding rock stress of the arch roof after excavation.
_By using the three-dimensional finite element program ANSYS, the displacement and plastic zone of the surrounding rock and slope are analyzed by using the step method with reserved core soil. This stable state.
【學位授予單位】：重慶交通大學
【學位級別】：碩士
【學位授予年份】：2014
【分類號】：U455.4

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