【作者】 雷晗；

【导师】 王建华； 陈锦剑；

【作者基本信息】 上海交通大学 ， 岩土工程， 2012， 硕士

【摘要】 随着新技术和设备的不断开发和采用,顶管逐渐向直径大型化的趋势发展。大直径顶管施工对土体的影响与小口径的顶管必然有所不同,因此传统的管道设计方法已不再适用,并且对提供顶力的工作井也提出了更高的要求。本文结合上海市污水治理南线工程,采用数值模拟方法,对顶管施工中管土相互作用、沉井工作井与土的相互作用进行研究。主要工作和研究成果如下:(1)考虑上海软粘土的弹塑性特性,对内径4m的大直径钢筋混凝土顶管管道的受力特性进行了分析。研究了施工过程中管土接触压力的变化及土体参数对管道外土压力的影响,并与现有的计算方法对比,总结管土界面土压力的变化规律。计算结果表明:在上海软土地基中,钢筋混凝土顶管属于刚性管,施工过程中的土拱效应使管道上方和下方土体应力减小,而左右两侧应力增大;土拱效应随覆土厚度的增加逐渐增强,管土接触压力分布比较平均;规范中对侧向土压力采用主动土压力计算偏于保守,将主动土压力系数改为静止土压力系数计算较为合理。(2)对顶力作用下的矩形和圆形沉井的受力特性进行了分析,指出现有计算方法的不足,并研究不同受力状态下的土压力分布规律。计算结果表明:矩形沉井后座墙在顶进力反力作用下的变形表现为抛物线形,墙后土体全部受压,对后背土体采用考虑位移的土压力计算方法来计算土体反力;在极限状态时,沉井后背土体产生整体位移,全部达到被动状态,土体反力按朗肯被动土压力计算。矩形沉井后背滑动体呈圆弧状楔形体,平面形状为椭圆;圆形沉井后背和前壁的滑动破坏体形状也为楔形体,平面形状为半圆。(3)对比各种国内外设计方法的不同之处及其设计依据,并结合有限元分析结果,对直线顶管施工过程中管道和沉井的土压力计算方法进行优化。在中国顶管设计规范的基础上,分别对垂直土压力、侧向土压力和地基反力的取值和土压力分布模式进行调整,提出了两种新的管道设计模式。两者都更符合管道受力的实际性状,并使管道的计算弯矩大为减小,配筋也能相应减小。提出在极限状态时,矩形和圆形沉井水平方向上的土压力分布为:矩形沉井在偏心受力时后背反力呈梯形分布,圆形沉井后背反力增量呈向心余弦分布。更多还原

【Abstract】 With the development and adoption of new technique and equipment, the diameter of jacking pipe grow up to be large scale gradually. It’s inevitable that the influence of construction of large diameter jacking pipe was different with narrow pipe. So the traditional design methods of pipe was not suitable, and the working well which provided jacking force asked for higher requirement. Based on the South Line project of sewage treatment, the interaction between soil and pipe, between soil and caisson working well, were investigated respectively by numerical simulation in this dissertation. The major works and results of this dissertation were as follows:(1) Considering the characteristic of elastoplasticity of Shanghai soft clay, the performance of DN4000 jacking pipe was studied firstly. The variation of contact pressure between pipe and soil during construction was analyzed, and then the influence of soil parameters were discussed. At the same time, the existing computing methods were compared with results of numerical simulation, and the variation laws of earth pressure of the interface were summarized. The computed results were as follows: Reinforced concrete jacking pipe was belong to rigid pipe in Shanghai soft clay. Soil arch effect in the construction would decrease soil stress above and below pipe, while increased soil stress of two sides. Soil arch effect was strengthened with increasing of cover depth, and the distribution of contact pressure was very uniform. Active earth pressure was conservative to calculate lateral pressure in Chinese standard, so it’s more reasonable to change the active earth pressure coefficient to be at rest.(2) Then the performance of rectangular and circular caisson under impellent were studied. The shortages of existing computing methods were pointed out, and the regularities of earth pressure distribution under different stress state were analyzed. The computed results were as follows: Under the counterforce on the rectangular caisson working well during pipe jacking, the displacement curve of back wall showed as parabolic while the soil was compressed all behind the back wall. The relation between displacement and earth pressure was used to calculate the earth counterforce. The soil behind back wall deformed entirely and reached to passive state at limiting state, and the vertical earth counterforce was calculated according to Rankine’s passive earth pressure theory. The slide mass behind back wall of rectangular caisson was like a cambered sphenoid, and its flat shape was elliptic. While the slide mass behind back wall of circular caisson was like a sphenoid, and its flat shape was semi-circle.(3) The differences and reasons of various design methods was compared at home and abroad finally. Combined with results of finite element, the computing methods of earth pressure of pipe and caisson are optimized in rectilinear pipe line construction. Based on Chinese jacking pipe standard, the value and load model of vertical and lateral earth pressure, and subgrade counterforce were adjusted, which induced two new design models of jacking pipe. Both of the two models were more corresponding with field practice of pipe, and they could minish computed bending moment of pipe. Accordingly, the ratio of reinforcement could be reduced. At the limiting state, horizontal distribution of earth pressure was proposed for rectangular and circular caisson: The counterforce distribution of back wall was ladder-shaped for rectangular caisson, while the increment distribution of counterforce of back wall was centripetal cosine-shaped for circular caisson.更多还原