地铁运营期杭州地区粉砂质黏土的长期沉降问题研究

发布时间：2018-03-20 00:30

本文选题：黏性土　切入点：动三轴试验　出处：《浙江科技学院》2017年硕士论文　论文类型：学位论文

【摘要】：为了解决城市交通拥堵问题,我国修建了许多地铁隧道工程。在东部软黏土地区修建的地铁隧道,在车辆振动荷载作用下会产生较大运营期沉降,引起衬砌管片开裂,上部结构沉降等问题。本文针对软黏土地区地铁隧道长期沉降问题开展研究,首先对杭州地区黏土通过室内动三轴试验研究了动力特性,其次采用电镜扫描试验和PCAS图像处理技术,对该黏土三轴试验前后的土体微观结构进行了定性、定量的分析,阐述了土体宏观变形和微观孔隙变化的关系。通过把室内动力学试验结果、数值建模与沉降经验拟合公式相结合,分别计算了土体累计塑性变形引起的沉降和累计孔压消散引起的沉降。得到了一些关于杭州地区黏土和地铁运营期长期沉降有意义的结论:(1)杭州地区饱和黏土的动应变属于稳定发展型;在动荷载作用下累计应变曲线随振动次数的发展呈现先快速发展后趋于稳定的状态。当围压和振动频率一定时,相同振次,动应变随着动荷载的增加而增加,最终稳定发展,动孔压在不同动应力情况下也存在随动应力增长的现象。(2)对地铁列车作用于钢轨上的荷载进行了简化和分析,得到与时间相关的振动荷载曲线。(3)将杭州地铁隧道运营期长期沉降,分成累计塑性变形引起的长期沉降和累计孔压消散引起的长期沉降两部分。运营期总沉降量在前五年发展较快,运营十年之后总沉降量随着时间的增加仍然在增加,但增长速度非常缓慢,可以认为达到了稳定状态。这时,累计塑性变形所引起的沉降量占总沉降量的85%以上。(4)分析SEM照片,发现土体微观颗粒的尺寸、排列、相互位置和形态,会随着动荷载的不同而发生变化,循环荷载的频率和动应力幅值对土体微观单元结构的影响十分明显,并有较强的规律性,且该规律性和室内动三轴试验土样的应变发展规律相吻合。
[Abstract]:In order to solve the problem of urban traffic congestion, many subway tunnel projects have been built in our country. In this paper, the long-term settlement of subway tunnel in soft clay area is studied. Firstly, the dynamic characteristics of clay in Hangzhou are studied by dynamic triaxial test. Secondly, the microstructure of the clay before and after triaxial test was analyzed qualitatively and quantitatively by scanning electron microscopy and PCAS image processing technology. The relationship between the macroscopic deformation of soil and the change of micro-pore is expounded. By combining the results of indoor dynamic test, the numerical modeling and the empirical fitting formula of settlement are combined. The settlement caused by accumulated plastic deformation of soil and the settlement caused by cumulative pore pressure dissipation are calculated, respectively. Some meaningful conclusions on the long-term settlement of clay in Hangzhou area and subway operation period are obtained. The dynamic strain belongs to the stable development type; Under the action of dynamic load, the cumulative strain curve develops rapidly first and then tends to stable with the development of vibration times. When the confining pressure and vibration frequency are fixed, the same vibration times and dynamic strain increase with the increase of dynamic load, and finally develop stably. Dynamic pore pressure also exists the phenomenon of following dynamic stress growth under different dynamic stress.) the load of subway train acting on rail is simplified and analyzed. The time-dependent vibration load curve. It is divided into two parts: the long-term settlement caused by accumulative plastic deformation and the long-term settlement caused by accumulative pore pressure dissipation. The total settlement in the first five years develops rapidly, and after ten years of operation, the total settlement is still increasing with the increase of time. But the growth rate is very slow and can be considered stable. At this time, the settlement caused by the cumulative plastic deformation accounts for more than 85% of the total settlement.) by analyzing the SEM photos, we found that the size, arrangement, position and shape of the soil microscopic particles. The frequency of cyclic load and the amplitude of dynamic stress have obvious influence on the micro-element structure of soil, and have strong regularity. And the regularity is consistent with the strain development law of the dynamic triaxial test soil.
【学位授予单位】：浙江科技学院
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U456.3;U231;TU433

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