【作者】 胡俊；

【导师】 杨平；

【作者基本信息】 南京林业大学 ， 森林工程， 2012， 博士

【摘要】 随着越江跨海交通隧道的不断兴建，大直径长距离盾构隧道工程越来越多。盾构隧道断面越大给盾构进出洞施工所带来的风险也就越高，特别是在高水压砂性土层中，如何选取合理的端头加固方式以确保大直径盾构进出洞施工的安全性是需要解决的新课题。本文以南京地铁十号线过江隧道盾构始发工程为依托，采用室内试验、数值模拟、理论研究及工程应用与实测相结合的综合研究方法，对该工程盾构始发端头加固方式及其安全性展开研究。首先对始发端头典型的两种土质进行了水泥改良前后土体热物理、力学特性的室内试验；接着对该工程盾构始发拟采用的三种加固方式及其关键问题进行了数值分析；对这三种加固方式进行比选，提出了宜采用的加固方式；最后结合实际采用的加固方式，对不同工况下盾构始发掘进进行了数值模拟分析，对垂直冻结施工进行了现场实测研究。本文主要研究工作及结论如下：（1）对始发端头典型的两种土质进行了水泥改良前后土体热物理、力学特性的室内试验，给出了数值分析时端头土体热物理、力学参数的建议取值。（2）对盾构隧道端头常用土体加固方式及设计方法进行了对比分析，运用解析解验算了当采用三轴深搅+高压旋喷加固方式时土体加固尺寸及其稳定性，从位移场和应力场出发在封门拆除工况下对不同加固范围的始发掘进进行了数值模拟分析，给出了该加固方式具体加固范围。（3）结合数值模拟，确定了当采用杯型水平冻结加固方式时的加固范围，设计了该冻结加固方案及工艺，分析了大直径杯型冻土壁的温度场发展与分布规律以及盐水温度、导热系数、容积热容量、相变潜热和原始地温等因素对杯型冻土壁温度场的影响，比较研究了不同土层下该温度场发展规律的差异性，得出温度下降速度由快到慢和形成冻土帷幕厚度从大到小为砂土水泥土＞砂土＞粘土水泥土＞粘土，砂土水泥土与砂土比粘土水泥土与粘土的冻土壁交圈时间早4天。（4）确定了当采用三轴深搅+垂直冻结加固方式的设计方案，对垂直冻土墙的温度场发展与分布规律进行了分析，比较研究了不同冻结管直径和间距下该温度场发展规律的差异性，得出随着冻结管直径的增大和间距的减小，冻结壁交圈时间线性减小，最终形成的垂直冻土墙也越厚，在冻结前期影响尤其明显。（5）对三种加固方式进行比选，提出了宜采用的加固方式和实际工程采用的加固方式及工艺，并结合实际采用的加固方式对不同工况下盾构始发掘进进行了数值模拟分析。（6）结合实际采用的加固方式，对垂直冻结施工进行了现场实测研究，详细分析了始发端垂直冻土墙在积极冻结和维护冻结阶段的温度变化规律，以判断冻土墙是否达到设计要求及确定洞门凿除和盾构始发时机，得出水泥土加固后比未加固时的原始地温高出17℃～23℃且可大大拟制冻胀变形。更多还原

【Abstract】 With the increasing accomplishments of numerous crossing-sea transportation tunnels, there aremore and more large-diameter-long-distance shield tunnel projects under construction. Inpractice, the larger the tunnel section is, the higher the risk of tunnel’s entering and exiting willface. Especially in the condition of sandy soil with high water pressure, it is a big issue how toscreen out the optimal method to enhance the tunnel end and guarantee the security when largediameter shield enter and exit during construction. Based on the shield launching project ofcrossing-river tunnel construction of Nanjing Subway Line10, my dissertation, by combiningthe execution of lab tests, numerical simulation, theory study, engineering application andpractical measurements, studied and compared reinforcement methods and evaluate theirsecurity in the project. First, two typical soils, collected on the site of shield launching project,were tested in terms of thermo-physical property and the mechanical characters before and afterthe cement improvement, respectively. Second, numerical analysis and comparison among threefrequently employed reinforcement methods were carried out. The relative data were analyzedand the optimal method was then proposed. Third, combined with the adopted method inpractice, numerical simulation to shield launching was made under different constructioncircumstances. Additionally, onsite measurement research was conducted on the vertical frozenconstruction. This paper mainly focused and drew the conclusions as follows:1. Lab tests were conducted to study the thermo-physical property and the mechanicalcharacters of the two typical types of soil collected at the tunnel ends, before and aftercement improving, respectively. The thermo-physical and mechanical parameters of the soilat the ends used in the numerical analysis are suggested.2. The common used methods of soil reinforcement at the ends of shield tunnel and theirdesign procedures are compared and analyzed. The reinforcement sizes of the soil under themethods of triaxisal deep mixing and high-pressure rotary spray and its stability is checkedby analytical solution algorithm; the initial excavation of different reinforcement areas isnumerically analyzed in terms of displacement and stress field with the door demolished,and the specific reinforcement scope of these methods and related reinforcement techniquesare given.3. Combined with the numerical simulation, the scope for cup-shaped horizontal freezingreinforcement was determined. The design and operational technologies of the freezingreinforcement were explored, consisting of the analysis for the temperature fielddevelopment and distribution pattern of the big-diameter-cup-shaped frozen soil wall, andthe impact from the surrounding factors, including the temperature of saline water,coefficient of heat conductivity, the thermal capacity of the volume, the latent heat of phasechange and the original earth temperature. Research is carried out to compare thedevelopment and distribution of this temperature fields in different circumstances such ascement sandy soil, sandy soil, cement clay and clay.4. The design scheme is determined, in which the reinforcement methods of triaxial deep mixing and vertical freeze are adopted. The development and distribution of the temperaturefields of the vertical frozen soil wall is studied. Research is conducted to compare thedevelopment and distribution of this temperature field in different diameters of freezingpipe and spacings between freezing pipes.5. Comparisons are made among the three reinforcement methods studied above, andadoptable reinforcement methods are put forward; the reinforcement method applied in realproject as well as its operational techniques were introduced; and combined with adoptedreinforcement methods, numerical analysis is conducted upon the initial shield excavationunder different construction circumstances.6. Combined with reinforcement methods adopted in practice, onsite measurement research iscarried out on vertical freezing construction; the rules of the temperature change of verticalfrozen soil wall in the launching project during the phases of positive freezing andmaintained freezing are analyzed in detail to judge whether the vertical frozen soil wall hasmet the demand of design and determine the timing of hole excavation and shieldlaunching.更多还原