围护结构及土层在盾构始发过程中的力学行为研究

发布时间：2018-08-01 14:30

【摘要】：盾构始发在隧道施工过程中占有的空间比重很小,却是施工危险性最大的阶段,其施工力学研究显得尤为重要。本文以弹性力学和弹塑性理论为理论基础,在总结大量研究经验的基础上,利用有限元软件ABAQUS对盾构始发过程进行仿真模拟,并将模拟结果与实际案例的分析结果进行对比,验证有限元模型计算结果的可靠性。通过构建模型并分析计算结果,研究得到土质强度、隧道间距、空间作用以及注浆压力等参数与构筑物、围岩位移和应力的变化关系。具体如下:(1)土质强度越大,其对抵抗地层扰动能力越强,引起地层损失越小。地表沉降、地层位移与应力、管片位移与应力随着土质强度的增大而减小;在粉质粘土内,盾构扰动范围随着土质强度的增大而减小。(2)新建隧道对已建构筑物与围岩的位移与应力变化影响较大。隧道间距越小,在新建隧道的影响下,管片位移与应力均发生改变,位移方向由指向两侧变为向左;拱顶和仰拱呈增加趋势,拱腰与之相反;在X轴和Y轴上,围岩位移方向改变,在Z轴上,等位移线由“单驼峰”变为“双驼峰”形状;拱顶围岩地应力分布由“漏斗”变为“双漏斗”型;围护结构受新建隧道的影响范围主要分布在左侧墙角处,洞口中心应力呈减小趋势,洞口中心以下与之相反。(3)空间作用是构筑物不同部位应力分布迥异的主要因素。管片仰拱、拱顶呈受拉状态,拱腰呈受压状态,前者应力值较大;阴阳角即墙角处应力值大于墙体中部。(4)注浆压力设置过小,地层损失较大,地表沉降较为严重;设置过大引起地表大量隆起,通过模型计算结果与现场实际情况进行对比,得到膨胀系数合理值为1.E-04。通过比较实测与计算结果的管片收敛和地表沉降曲线的变化规律可知,计算模型能够真实地反映现场的实际情况,计算结果可靠。
[Abstract]:The construction mechanics of shield tunneling is very important because it occupies a small proportion of the space in the tunnel construction process, but it is the most dangerous stage of construction. Based on the theory of elastic mechanics and elastic-plastic theory, this paper makes use of finite element software ABAQUS to simulate the starting process of shield tunneling, and compares the simulation results with the analysis results of actual cases. The reliability of the finite element model is verified. By constructing the model and analyzing the results, the relationship between soil strength, tunnel spacing, space action and grouting pressure on the structure, displacement and stress of surrounding rock is obtained. The main results are as follows: (1) the stronger the soil strength, the stronger the resistance to the formation disturbance and the smaller the formation loss. Ground subsidence, ground displacement and stress, segment displacement and stress decrease with the increase of soil strength; in silty clay, The disturbance range of shield machine decreases with the increase of soil strength. (2) the new tunnel has a great influence on the displacement and stress change of the built structure and surrounding rock. The smaller the tunnel spacing, the more the segment displacement and stress change, the direction of displacement changes from pointing to both sides to the left; the arch top and inverted arch show an increasing trend, the arch waist is the opposite; on the X axis and Y axis, The displacement direction of surrounding rock is changed from "single hump" to "double hump" on Z axis, and the distribution of earth stress in arch roof is changed from "funnel" to "double funnel". The influence range of the retaining structure by the new tunnel is mainly distributed in the corner of the left wall, the stress of the center of the hole is decreasing, and the stress below the center of the opening is opposite to it. (3) the spatial action is the main factor of the stress distribution in different parts of the structure. The stress value of the former is larger, the stress at the corner of the yin-yang angle is larger than that in the middle of the wall. (4) the grouting pressure is too small, the formation loss is large, and the surface subsidence is more serious. By comparing the results of model calculation with the actual situation in the field, the reasonable value of expansion coefficient is 1.E-04. By comparing the measured and calculated results of segment convergence and the variation of surface subsidence curve, it can be seen that the calculation model can truly reflect the actual situation in the field, and the calculation results are reliable.
【学位授予单位】：石家庄铁道大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U455.43

【参考文献】