堆积体区隧道开挖与边坡稳定及处治

发布时间：2018-09-14 08:43

【摘要】：在四川藏区公路（汶九高速、雅康高速、绵九高速和汶马高速）和丽香高速公路设计中，发现隧道洞口段岩堆分布广泛，这些塌落岩体在坡脚的堆积物结构松散、强度较低、稳定性较差，给隧道的设计、施工带来极大困难。本文依托“重庆交通大学交通土建工程材料国家地方联合工程实验室开放基金《基于离散元理论的松散堆积体高边坡稳定性研究》（编号：LHSYS-2013-007），总结了国内外专家学者对处于堆积体区隧道相关研究成果，建立洞口段边坡评价方法，并从常规的开挖方式中寻找一种快速、经济、安全的开挖方式，通过对走马岭隧道边坡稳定性评价和模拟出口段隧道开挖，得出了以下几点结论。 ①采用室内大型直剪仪对重庆地区典型堆积体试样进行直剪试验，测取不同密实度下的抗剪强度。当松散堆积体密实度由0.3增大到0.6时，内摩擦角由25.67°增大到32.53°，而粘聚力则由5.13Kpa增大到32.29Kpa。 ②通过对堆积体区隧道边坡的失稳进行分析，，提出堆积体边坡的两种滑动失稳模式：基岩深埋情况下的圆弧滑动和基岩浅埋的界面滑动，并用公式推导了在隧道开挖扰动情况下仰坡失稳机理。 ③采用了三维有限元程序ANSYS对隧道常规开挖方式（全断面开挖、台阶法、导坑法），来模拟堆积体隧道开挖，通过比较得出三种开挖方式中台阶法对围岩和边坡稳定性影响最小，而全断面开挖影响最大。 ④运用传统的极限平衡法和有限元程序Plaxis2D对走马岭隧道洞口边坡进行稳定性综合分析，两种方法得出相同结果；并采用离散元颗粒流程序PFC2D对洞口边坡开挖进行数值模拟，通过对颗粒位移的比较，得到了锚杆技术对于堆积体边坡加固可以起到明显效果。 ⑤运用三维有限元程序ANSYS，模拟在不同刚度的初期支护，通过监测隧道开挖后拱顶围岩应力，得到了隧道最佳支护刚度。 ⑥运用三维有限元程序ANSYS，采用台阶法预留核心土开挖方式，分析围岩和边坡的位移及塑性区变化。结果表明：该方式在第一步环形开挖后，拱顶围岩和仰坡产生一定位移；第二步左侧台阶开挖后，位移变小；随后围岩和坡顶处于基本稳定状态。
[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.
【学位授予单位】：重庆交通大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U455.4

【参考文献】