【作者】 李结全；

【导师】 欧孝夺；

【作者基本信息】 广西大学 ， 结构工程， 2018， 博士

【摘要】 在岩溶地区修建地铁会遇到诸多技术难题。在地铁盾构隧道建设中,如果岩溶处治不当,容易造成盾构机“栽头”、“陷落”、隧道突水、突泥、地面沉降、坍塌等事故,影响隧道的正常建设,严重时甚至出现伤亡事故。盾构隧道施工成败很大程度取决于地质条件和盾构设备两个因素,既相辅相成又互相制约,尤其是岩溶地区的盾构隧道施工,对两个因素的要求更为严格。在岩溶给地铁隧道建设带来困扰的同时,反过来,隧道建设也会对周边环境产生影响,导致新的岩溶问题。因此,本文以南宁市轨道交通2号线岩溶区段的工程建设为依托,通过理论分析、数值模拟、现场试验等研究方法,开展岩溶地区地铁隧道盾构掘进安全控制技术研究,主要的研究内容和成果如下:(1)运用数值模拟的方法,以溶洞与隧道的相对位置、溶洞大小等参数为主要变量,分析了溶洞位于隧道顶部、底部及正侧部时盾构隧道施工时围岩、管片的应力应变以及地表沉降的变化规律。并总结出三种工况下隧道周边岩溶处治范围不应小于外扩0.5倍盾构隧道洞径。(2)根据南宁市轨道交通2号线岩溶区段施工经验及数值模拟结果,总结出以地面和盾构机预处理为主、洞内预留措施为辅,先地面处理后掘进岩溶的处治原则;其处治范围是:隧道底部地层为灰岩时隧道结构外扩2m范围内,为粘土或者粉质粘土时外扩3m范围内,底部下放5m范围内的溶(土)洞应处治,且处治范围不应小于外扩0.5倍盾构隧道洞径。(3)针对不同形态溶洞提出了相应的处治技术,通过现场试验芯样的抗压强度、注浆段标贯击数平均值及渗透系数等方面对处治效果进行了检测,检测结果表明处治后的岩土体均能满足设计要求。(4)在盾构施工中地质条件是基础,盾构设备是关键。为保证盾构隧道掘进能够顺利通过岩溶地区的复杂地质情况,选用土压平衡式盾构机,并对关键部位进行优化设计。优化结果如下:1))刀盘的基本结构为辐条面板式,4个主梁+4个副梁,开口率为40%;2)针对灰岩类地层,应加强刀盘强度和耐磨性,并提供与之匹配的驱动功率;3)针对泥饼问题,分别采用在刀盘设计6个改良剂注入口、配置加强型刮刀并增大间距、设置土仓搅拌系统等措施来防止形成泥饼;4)针对复杂地层容易产生喷涌问题,螺旋输送机设计须为防喷涌形式,并采用9.5°的小倾角皮带机,增强输送稀渣的能力;5)在盾尾顶部增设2个注浆口,同步优化注浆设计;6)在掌子面不稳定及涌水地层,对盾构机开挖面前方进行超前地质加固。(5)结合岩溶地区盾构施工引起的地表沉降数据,采用灰色关联分析方法对盾构参数进行敏感性分析,并对其影响程度大小进行排序。分析认为敏感性由大到小排序为:刀盘扭矩、盾构总推力、注浆压力、掘进速度、注浆量、土仓压力。这为以后此类地区盾构参数的合理设定以及盾构隧道地表沉降控制措施的制定提供了理论依据。(6)结合岩溶地区盾构隧道施工过程的现场实际情况,通过掘进参数和监测数据的分析,综合考虑经济、技术和社会效益,针对地铁盾构隧道穿越岩溶地区的黏土(粉质黏土)层、强风化硅质岩层和碎石土层、以及中风化灰岩层,分别提出了相应的盾构参数控制标准和措施,对今后类似工程提供参考依据。更多还原

【Abstract】 During constructing the subway in karst area,many problems spring out.If the karst is not handled properly,it is easy to cause the head felling of shield,water and mud inrush in tunnel,land subsidence and other accidents,affecting the normal construction of the tunnel,and even leading to casualty accidents.The success or failure of the shield tunnel construction depends largely on the geological conditions and the shield equipment,which both complement and restrict each other.Especially,the construction of the shield tunnel in the karst area is more stringent for the two factors.While karst brings troubles to subway tunnel construction,in turn,tunnel construction will also have an impact on the surrounding environment,leading to new karst problems.Therefore,based on the construction of the karst section of the metro line 2 in Nanning,this paper carries out the safety control technology of metro shield tunnel construction in karst area through theoretical analysis,numerical simulation,field test and other research methods.The main research contents and results are as follows:(1)Though change the relative positions between the karst caves and the tunnels,and the size of karst cave,the numerical simulation method is used to analyze the stress and strain of the surrounding rock and segments,the law of settlement during the construction of shield tunnels under three conditions(The three conditions refer to the cave is above,below and on the side of the tunnel).It is concluded that the scope of karst treatment around the tunnel under three conditions should not be less than 0.5 times the tunnel diameter of the shield tunnel.(2)According to the construction experience and numerical simulation results of the karst section of the metro line 2 in Nanning,this paper summarizes the treatment principles of treating karst:1)The pretreatment on the ground and by the shield machine is main,the supplemental measures in the cave as a supplement;2)Karst treatment after ground treatment.The scope of treatment is as follows:When the bottom stratum of the tunnel is limestone,the caves within 2m of the tunnel structure and 5m below the tunnel structure should be treated.When it is clay or silty clay,the caves within 3m of the tunnel structure and 5m below the tunnel structure should be treated.Meanwhile,the scope of treatment should not be less than 0.5 times the diameter of the shield tunnel.(3)Different treatment modalities were proposed for different types of karst caves.The treatment effect is tested by the field test of the compressive strength of the core sample,the average number of strokes in the grouting section,and the permeability coefficient.The test results show that the rock and soil after treatment can meet the design requirements.(4)Geological conditions are the basis for shield construction and shield equipment is the key.In order to ensure that the tunnel boring mashine can smoothly pass through the complex geology of the karst area,an earth pressure balance tunnel boring machine is selected and the key parts are optimized.The optimization results are as follows:1)The basic structure of the cutterhead is a spoke panel type,with 4 main beams and 4 sub beams,and the opening ratio is 40%;2)For the limestone stratum,the strength and wear resistance of the cutterhead should be strengthened,and the matching drive power should be provided;3)Designing 6 improver injection port in the cutter head,configuring enhanced spatula with large the spacing,seting up the soil tank mixing system and other measures to prevent the mud cake;4)In view of the spewing problem of the complex stratum,the design of the screw conveyor must be in the form of anti-sloshing,and a small 9.5° angle conveyor should be used to enhance the ability to transport slag;5)Two grouting openings are added at the top of shield tail to optimize the grouting design;6)Advance the geological reinforcement in front of the excavation surface of the shield machine at the unstable face and gushing stratum.(5)Based on the surface settlement data caused by the shield construction in the karst area,the grey correlation analysis method was used to analyze the sensitivity of the shield parameters and rank the impact degree.According to the analysis,the sensitivity is ranked as follows:cutterhead torque,shield total thrust,grouting pressure,driving speed,grouting amount,and earth pressure.This provides a theoretical basis for the rational setting of shield parameters in such areas and the development of surface settlement control measures for shield tunnels.(6)Combining with the actual site conditions during the construction of the shield tunnel in the karst area,through the analysis of the boring parameters and monitoring datas,comprehensively consider the economic,technical and social benefits,the corresponding shield parameter control standards and measures for clay(silty clay)layer,strong weathering siliceous rock layer and gravel soil layer,and the weathering limestone layer in karst area are proposed respectively,which will provide reference for similar projects in the future.更多还原