【作者】 伍毅敏；

【导师】 徐岳； 吕康成；

【作者基本信息】 长安大学 ， 桥梁与隧道工程， 2008， 博士

【摘要】 随着软弱破碎围岩隧道数量的增加,因隧道地基承载力不足而引起的工程灾害时有发生,有必要将软基隧道视为一类特殊隧道开展针对性研究。本文采用理论分析、数值模拟和现场测试等方法,对软基隧道拱脚地基荷载的计算方法、主要处治措施的作用机理与施工工艺、软基隧道病害防治方案等展开系统研究,建立了软基隧道处治的技术体系。主要研究内容及取得的成果如下:(1)从地基承载力验算的需求出发,根据软弱围岩中隧道初期支护结构的受力特点,探讨了软基隧道拱脚地基荷载的计算方法。对于浅埋软弱围岩隧道,采用荷载—结构法,将围岩对支护结构的摩阻力、锚杆对支护结构沉降的抵抗力进行适当简化,推导了无偏压和有偏压条件下浅埋隧道拱脚地基荷载的计算公式;对于深埋软弱围岩隧道,采用地层结构法,通过隧道施工的数值模拟直接评价拱脚地基承载力。通过实体工程的实际观测与理论计算结果对比,验证了计算方法的合理性。(2)根据锁脚钢管的设计施工特点和受力性状,研究了锁脚钢管的解析计算方法。将软弱围岩中的锁脚钢管视为文克尔弹性地基上的梁,建立了锁脚钢管的弹性地基梁解析模型,推导了相关公式,用Visual Basic语言编写了计算程序,绘出了锁脚钢管合理长度与钢管规格、地基弹性抗力系数的关系图。(3)采用有限元数值模拟方法,研究了锁脚钢管的承载特性和破坏模式,探讨了围岩强度和钢管几何参数对锁脚钢管承载力的影响规律。通过数值模拟对比分析得到了区别于工程经验的几点重要认识:对于不能穿透软基的锁脚钢管,其轴向承载力十分有限,合理下插角很小,一般小于5°;常用的42mm小导管直径过小,横向承载能力有限,不宜用作锁脚钢管;锁脚钢管存在一个决定于围岩强度和钢管规格的合理长度(一般为3～4m),超出合理长度后承载力不再增加;锁脚钢管应全长开孔注浆,重点加固初期支护结构附近的围岩。在此基础上,提出了锁脚钢管设计施工的方法和建议。(4)系统研究了提高隧道地基承载力和支护结构抗沉降能力的主要工程措施。在分析各种工程措施的作用机理、设计原理、施工工艺和适用条件的基础上,编制了软基隧道处治工程措施选择表。(5)结合酉水3号、4号和长干1号等软基隧道的处治,通过分析软基隧道的主要病害,提出了软基隧道处治的基本原则。针对正常施工和病害处治施工的不同要求,分别制定了软基隧道正常施工和病害处治施工的地质勘察、计算分析、措施选择和监测评估方案,建立了软基隧道处治的技术体系。更多还原

【Abstract】 With the increasing of the numbers of tunnels in soft rock, engineering disasters occur frequently due to the inefficient bearing capacity of tunnel bases. It is necessary to pay more attention and to do further researches to those tunnels. By means of theoretical analysis, numerical simulation and field tests, the load calculation method for soft bases under arch feet, supporting mechanism, main treatment measures and scheme to deal with engineering diseases have been studied. A technology system for construction of tunnels with soft bases has been set up. The main contents and conclusions are as follows:(1) In order to check base bearing capacities of tunnels in soft rock, a new analysis method to calculate the loads on soft bases is developed, in which the load-bearing characteristic of tunnel supporting structure is considered. As to shallow buried tunnel in weak and soft rocks, on basis of the theory of load & structure method, formulas to calculate base loads in symmetrical and unsymmetrical tunnel are deduced, with necessary simplifications of the friction from surrounding rock and the resistance of steel bars to the supporting structure. To deep buried tunnel with soft base, the bearing capacity can be directly evaluated through construction numerical simulation according continuous medium theory. The calculation method is verified by comparing the theoretical result with the field test.(2) An analytic model of the foot steel pipe is built, with a view to its characteristic of design and construction, and behaviors of load and deformation. Based on the Winkler’s assumption, a model of beam on elastic foundation is put forward to analyze the foot steel pipe. Formulas are deduced and software is written with Visual Basic for the calculation. Graphics of the reasonable length corresponding to size of steel pipe and elastic resistance coefficient of soft rock is brought forward for the design of foot steel pipes.(3) Bearing behavior and failure module of foot pipes are studied through numerical simulation with FEM. The influence to the bearing capacity is discussed, including the strength of surrounding rock and the parameters of steel pipe. Some important results different from engineering experiences are gained by theoretical analysis: 1) to foot steel pipe that can not penetrate the soft base, its reasonable dip angle is very small for low longitudinal bearing capacity; 2) steel pipe with diameter of 42mm is unsuitable for foot steel pipe because its low cross bearing capacity; 3) to a given geological condition and pipe parameter, the reasonable length of steel pipe is certain, extra longer pipes can’t obtain larger capacity; 4) surrounding rock near the support structure should be especially reinforced by drilling grouting holes along the whole steel pipe. Based on those results, design and construction methods are presented.(4) Main engineering measures are researched to increase the bearing capacity of soft base and the resistance of structure to settlement. On the basis of analysis of support mechanism, design theory, construction method and applicable condition, a design table is established for measure selection to treat with tunnel on soft base.(5) Combining with engineering instances of No.3 Youshui Tunnel and No.4 Youshui Tunnel, No.1 Chang’gan Tunnel, principles for treatment are raised through the analysis of common diseases in tunnel with soft base. Directed against the different demands of normal construction and diseases treatment, systematic schemes are established including the geological survey, calculation and analysis, engineering measures selection, monitoring and assessment.更多还原