【作者】 苏洁；

【导师】 张顶立；

【作者基本信息】 北京交通大学 ， 岩土工程， 2009， 博士

【摘要】 众所周知,采用浅埋暗挖法进行城市地下工程施工时,隧道开挖产生的地层变形及应力释放必然会对周边环境产生一定程度的扰动,而由于城市环境的复杂性,特别是在北京这种以立交环路为主要地面交通形式的城市中,隧道施工将会不可避免的穿越大量既有桥梁,并对其正常使用造成影响。随着北京地区地铁新线建设高潮的到来,这种现象将会越来越多,所带来的矛盾也将更加突出,因此研究浅埋暗挖法施工影响对邻近桩基的影响及其控制具有重要的现实意义。本论文在对国内外相关文献资料进行广泛调研的基础上,以北京地铁4号线、5号线、10号线相关工程以及南水北调穿越西四环主路等为工程背景,采用理论分析、数值模拟以及现场实测相结合的方法,对隧道浅埋暗挖法穿越既有桩基施工这类工程所涉及的理论基础、关键技术以及控制体系等核心问题进行了深入、系统的研究,取得了以下一系列成果:(1)针对浅埋暗挖法穿越既有桩基施工的工程特点,提出了隧道-土体-桩基-上部结构四者之间的相互作用关系,认为控制隧道施工对桩基影响的关键是控制地层变形;(2)依据桩基承载力基本理论,并结合北京地区浅埋暗挖法施工地层变形特点,研究了不同地层变形模式下,既有桩基的变形特点及受力机理,并提出了相应的计算模型以及相应的控制方法;(3)提出了隧道施工影响下桩基承载力损失的概念,认为隧道施工过程中既有桩基的沉降是由于桩基承载力损失引起的,并通过理论推导建立了桩基沉降与承载力损失之间的关系;以此证明了通过控制桩基沉降来实现桩基承载力损失控制的正确性,为其提供了理论支持;(4)通过“隧道掌子面与桩基不同纵向距离”、“隧道下穿桩基时的不同竖向与水平距离”、“隧道侧穿桩基时的不同竖向与水平距离”等五种情况下,隧道施工对桩基沉降、水平位移、轴力及弯矩等四项指标影响程度的综合分析,将桩基承载力受隧道施工的影响程度,从空间位置关系上按由重到轻划分为一级、二级、三级、四级四个区间,为采用模糊综合评价方法进行桩基承载力影响评价提供了应用基础;(5)以上述研究成果为基础,形成了系统的浅埋暗挖隧道施工影响下既有桥梁风险控制体系,控制体系的关键是以围岩动态力学原理为基础的变位分配方法。并将其在实际工程中进行了成功应用。更多还原

【Abstract】 It is well-known that surrounding environment must be disturbed by the stratum deformation and stress relieving induced by tunnel excavation when underground works are constructing in urban using shallow mining method.Especially constructing shallow depth bored tunnel in Beijing of which the main ground traffic style is based on overpass and circuit,many existing overpasses will be crossed by tunnels and the normal operation of them will be affected inevitably.As new construction climax of the metro lines is coming in Beijing now,the number of this phenomenon is increasing,and the following contradictions will become sharper.So, it’s very important to study on the effect and control method for adjacent pile foundation.In this paper,based on domestic and foreign documents,integrated existing project experience、combined theoretical analyse with numerical modeling and taking line 4、5、10 in Beijing and South-to-North water diversion engineering for example,systematic and intensive research on key technique、theoretical basis、control system and so on will be made.And a series of research findings are obtained.(1)In the light of characteristics of crossing existing pile foundations by shallow mining method,the interaction relationship of tunnel-soil-pile-superstructure are given and the key factor of controlling the influence to the pile foundations be controlling the ground deformation;(2)According to the basic theory of bearing capacity of pile foundation and considering the characteristics of stratum deformation caused by shallow mining method in Beijing,the deformation model and stress mechanism of existing pile foundation in different ground deformation mode are studied and the relevant model and control method are established.(3)Concept of bearing capacity loss of pile induced by tunnel construction is put forward,which suggested that the settlement of exiting pile foundation is caused by bearing capacity loss of pile and established the relationship between them by theoretical derivation.It is approved that the bearing capacity loss of pile can be controlled by settlement of pile foundation.(4)Through five cases including“the difference of vertical distance between the tunnel face and pile foundation,”“the different vertical and horizontal distance when the tunnel under crossing the pile foundation,”and“the different vertical and horizontal distance when the tunnel side crossing pile foundation”,and considering the influence degree of the four indicators,such as pile foundation settlement,horizontal displacement,axial force and bending moment during tunnel construction,classified the influencing degree to pile by construction as grade 1,2,3and4 from weight to light, provided application basis to using fuzzy comprehensive evaluation method to evaluate capacity influnce of pile foundation.(5)According to the research findings mentioned above,a systematic risk control system of existed bridge during the shallow mining field construction is established. The key to this system is movement allocation method base on dynamic mechanical analysis principle.And it is successfully used in practical engineering.更多还原