【作者】 孙谋；

【导师】 刘维宁；

【作者基本信息】 北京交通大学 ， 桥梁与隧道工程， 2011， 博士

【摘要】 针对盾构隧道进出洞端头土体稳定性及加固尺寸精细化设计等工程实际难题,本论文结合南京地铁TA15标盾构隧道始发及到达进出洞端头的加固工程实例,基于从建立微观模型到宏观对比、并通过工程实例再验证的思路,建立南京地铁沿线低山丘陵及淤积平原区典型粉细砂层颗粒流细观模型及加固模型、并基于微观颗粒流——宏细观剪切带——宏观工程失稳——工程加固精细化设计实例的研究思路,对盾构隧道进出洞端头土体的破坏模式、稳定性计算方法及进出洞端头土体加固尺寸的确定做进一步的参数校核、比较分析和现场验证,取得的相关研究成果如下：(1)基于南京地铁沿线低山丘陵及淤积平原区的特殊地貌及穿越地质条件,建立了南京盾构隧道进出洞穿越端头土体颗粒流细观模型,对伴随盾构穿越土层扰动破坏过程进出洞端头土体的特殊渐进性破坏特征及破坏模式进行了分析,初步确定该地区盾构掘进过程中细观参数的影响范围及其对土性特性的影响规律。南京地区原状土体受盾构刀盘切削、抓刨、振动、冲击、压实、挤密、剥离等动静荷载作用,伴随孔隙水压力的消散和局部激增过程,内摩擦角随颗粒摩擦系数的增大呈现类线性增加趋势；粘聚力也随颗粒间粘结强度的增大表现为线性增大关系。(2)给出盾构进出洞端头土体的稳定系数、进出洞端头土体的理论加固系数及范围。通过从微观到宏观,由浅入深的分析比较方法,对南京地铁盾构进出洞端头土体稳定性及参数敏感性做进一步分析认为：设计能否增加盾构隧道埋深取决于是否能有效控制或提高进出洞端头土体的稳定性,隧道埋深越浅,进出洞端头土体的稳定性相对越差,风险越大,越需提高掘进土体的内摩擦角和粘聚力指标。内摩擦角和粘聚力变化对进出洞端头土体的稳定性影响最显著,而泊松比变化对进出洞端头土体稳定性的影响相对并不明显。(3)通过分析南京地铁盾构进出洞穿越土体位移场的发展变化规律可知,该地区盾构进出洞穿越时端头土体呈现较明显的颗粒定向性运动趋势,刀盘推进中土体颗粒流的运动变化规律从无明显定向到呈现明显颗粒位移定向等特征,土体被挤密、重构、剥离等的过程中快速形成明显的剪切滑移带并发展贯通成滑裂(动)面,最终形成进出洞端头土体滑动面较集中在两部分挤压区域出现：洞门上边缘以上位置,滑动面基本呈斜直线分布,洞门上边缘以下位置的滑动面基本呈对数螺旋线或近似圆形的分布规律。实测土体损失体积与现场地表动态沉降槽体积基本吻合,为此规律提供了一例理论佐证。(4)建立盾构进出洞端头土体弹性薄板的修正极限平衡分析模型,计算了进出洞端头土体的加固厚度,通过与实例进行对比,对建议理论进行了条件修正。分析可知：在取相同计算参数和安全系数的条件下,经典极限平衡模型的计算加固厚度为4.68m,修正弹性薄板模型计算的加固厚度为5.15m,传统弹性薄板模型计算的加固厚度为7.54m,实际南京地铁工程中选取加固厚度6.0m、并实现成功进出洞。通过与实际工程的应用对比可看出,经典极限平衡模型和修正弹性薄板模型的计算结果略小并接近南京地铁实际工程取值,而传统弹性薄板模型的计算结果明显偏于安全。(5)基于塑性松动圈理论计算横断面加固厚度并拓展其到工程应用范畴。基于轴对称／非轴对称塑性边界方程求取进出洞端头土体横断面加固厚度理论值。安全系数等取相同计算参数条件下,在λ=1.0、λ=0.33及λ=0.25时的横断面加固计算厚度分别为2.21m、2.26m及3.17m,南京地铁TA15标盾构隧道进出洞进出洞端头加固实际工程的横断面加固宽度最终选取3.0m,并实现安全成功穿越,取得与建立计算模型吻合较好的实际验证。更多还原

【Abstract】 Research on the soil stability and refined reinforcement design problems of in-out head-hole for the practical shield tunnel project is investigated systematically in this thesis. A reinforcement instance of Nanjing Metro tunnel sect of No.TA15 is used to illustrate the propositional principle. Based on the idea of comparing the micro-based model to the macro phenomena, and then modified method through the practical engineering example, Nanjing subway microscopic particle flow model and the reinforcement model are established along the typical fine sand silt layer of hilly and plain areas. Corresponding to the research way in which Microscopic particle flow-Shear zone-Macro failure- Refined reinforcement design example, this paper do further parameter calibration, comparative analysis and field verification for failure mode analyse of shield tunnel in-out head-holes, stability calculation method and reinforcement size determination. The relevant research results are obtained as follows:(1) The micro-sandy particle flow model of Nanjing tunnel in-out head-hole is established based on Nanjing subway deposition along the hilly plain area of special geological features and geological conditions. The special progressive destruction characteristics and gradually failure mode analysis is carried out across the soil disturbance and damage process with shield advance. Micro soil parameters and effective properties are initially identified. Undisturbed soil are operated by the shield cutter cutting, grasping, planning, vibration, shock, compaction, peeling and other dynamic and static loads. The pore water pressure appears the processes of dissipation and local sharp increase. The internal friction angle showed a linear increasing trend with particle friction coefficient increase; Cohesion among the particles also shows a linear increase relationship with the increase of bond strength.(2) The soil stability factor, parameters and the scope of reinforcement theory of in-out head-hole for shield tunnel are given. Through angle of view from micro to macro and comparison methods, stability and parameter sensitivity analysis is carried out more detail in Nanjing shield tunnel. Some points are gained as follow:It should find out whether the tunnel design can increase the effective depth depends on control or improve the stability of the soil in-out head-hole or not; The risk is greater with the tunnel depth is more shallow, or the stability of soil in-out head-hole is relative more poorer; It need to improve indicators of the internal friction angle and cohesion to lower the risk of collapse. In this case study, the change of internal friction angle and cohesion had the most significant effect on the stability of the soil in-out head-hole, and Poisson’s ratio change has not obvious affect the stability of the soil in-out head-hole. (3) Through analysis of the development and changes of the displacement field for the soil in-out head-hole of Nanjing subway shield tunnel, it shows that more pronounced trends in regional and directional movement is appeared. The particles motion law express themselves obviously characteristics from non-directional to directional under specific shield cutter working conditions. The sands and granules are pushed closer. With the process of reconstruction, stripping, rapid reformation of distinct slip bands and the shear slip went through the surface are developed. Finally, two concentrated squeeze regions and sliding surfaces appear more obviously in the head-hole:the basic sliding surface distribution was oblique lines above the top edge position; and the sliding surface approximate appear the logarithmic spiral or circular distribution below the top edge location. The measured volume of soil loss is consistent with the volume size of dynamic surface settlement; it provides a theoretical support case for the law.(4) A modified elastic plate limit equilibrium analysis model is proposed for shield tunnel in-out head-hole. The reinforcement of soil thickness is calculated. The conditions amendment of the theory is done compared with the examples,The analysis shows:In the condition of taking the same parameters and the safety factor, the calculation of the classical reinforcement thickness of the limit equilibrium model get 4.68m, the reinforced thickness of the modified elastic plate model get 5.15m, the reinforced thickness of the traditional elastic plate model get 7.54m. Nanjing subway project select the actual reinforcement thickness of 6.0m, and achieve success out of holes.It can be seen that the reinforced thickness of the calculation result of the classical limit equilibrium model and modified elastic plate model results slightly smaller and close to the value of the actual project of Nanjing subway, but the traditional calculation of elastic plate model results significantly safer by contrast with the practical engineering applications.(5) Based and expand the classical theory of plastic zone around lining to the engineering application areas, the calculation value of the reinforcement width and thickness can be gotten based on the plastic theory and the axial symmetry/non-axisymmetrical boundary equation.In the same calculation conditions of taken the same safety factor and other parameters, the calculated reinforcement thickness of cross-section were 2.21m,2.26m and 3.17m corresponding condition ofλ=1.0,λ=0.33 andλ=0.25, Nanjing subway tunnel sect of No.TA15 engineering finally attributed success in across reinforcement section of 3.0m. It achieves the safe and successful crossing with good agreement between the established model and the actual verification.更多还原