【作者】 张毅；

【导师】 折学森；

【作者基本信息】 长安大学 ， 岩土工程， 2019， 博士

【摘要】 随着我国中西部地区基础设施建设的发展,山区高速公路规模不断增加,其中很多路段穿越膨胀土等特殊土地区和滑坡地段。当隧道进出口穿越这些地段时,由于膨胀土和滑坡的共同作用,隧道施工时往往发生地质灾害,严重影响工程的施工质量和进度。因此,研究膨胀土和滑坡共同作用下对隧道结构变形的影响,提出有针对性的防控措施,是十分有必要的。论文依托河南三淅高速公路项目,针对隧道穿越膨胀土滑坡地段工程,采用室内试验、理论分析、数值模拟和现场监测的手段对滑坡地段膨胀土隧道变形机理和防控技术进行研究,主要研究内容和成果如下:1、通过室内试验确定了膨胀土的基本力学指标、膨胀潜势、膨胀力及膨胀率等指标,研究了膨胀土围岩的物理力学特性,考虑体积变形,给出能够更好地估算非饱和土的强度、变形和渗透系数等参数、反映吸力作用下土的持水性能的土—水特征曲线。2、根据弹塑性力学的理论,推导出隧道开挖考虑土体膨胀特性的解析解,得到了不同含水率变化条件下的弱膨胀土围岩特征曲线,该曲线可以反映弱膨胀土围岩吸水膨胀后对支护受力及变形的影响。3、采用FLAC 3D有限差分软件,分析隧道洞口段围岩吸水膨胀引起的滑坡滑动对围岩及隧道初期支护结构受力和变形的影响,即隧道开挖支护后、滑坡体纵向错动位移分别为3cm、5cm、8cm、12cm时隧道围岩及初期支护的变形和受力分布情况,并研究削坡卸载对控制滑坡稳定性及隧道受力变形的效果。结果表明,围岩吸水膨胀后隧道初期支护结构沿着纵向发生较大的变形,最大纵向变形位于滑坡体的中间的隧道拱顶部位,为68mm,并随着滑坡的发展,其纵向变形逐渐向拱腰、拱脚部位延伸,位于滑坡体内的初期支护变形增长较快。对山体进行削坡卸载和基底加固方案后,得益于围岩的自重应力的降低和膨胀应力的减小,以及地基桩很大程度地限制了滑坡体向临空面的滑动,故可以大幅减小滑坡体及隧道初期支护结构的应力和变形。“削坡卸载和基底加固”方案对于控制滑坡稳定性及隧道变形具有较好的效果,可以降低工程风险,增强结构稳定性和安全性。数值计算结果和现场的施工实践证明,在不采取卸荷和隧道加固措施的条件下进行隧道洞口滑坡段施工的方案是不可行的。4、针对浅埋膨胀土隧道特征,结合现场监测数据,利用数值模拟对比分析了环形开挖预留核心土法、中隔壁导洞法、交叉中隔壁法对穿越滑坡地段的浅埋弱膨胀土隧道围岩变形的影响。结果表明,在浅埋膨胀土段隧道采用中隔壁导洞法施工可以较好地控制围岩变形及支护压力,是比较合适的施工工法。根据计算结果总结了一套适合浅埋段膨胀土隧道施工方法,为类似工程提供参考。5、通过对隧道穿越滑坡段裂缝变形发展情况及滑坡体特征的分析,认为控制或降低开挖过程中的变形是防止膨胀土隧道滑坡体系破坏的关键。结合数值计算结果,综合考虑滑坡区的地质环境、工期及环保等因素,提出“削坡卸载+基底加固+洞口挡墙支挡”的滑坡治理措施以及浅埋段隧道施工方法。通过治理,滑坡处于稳定状态。同时,通过现场施工反馈可知,采用中隔壁导洞法开挖可有效控制围岩变形及支护压力。研究成果可为类似工程提供参考。更多还原

【Abstract】 With the development of infrastructure construction in central and western regions of China,the scale of expressways in mountainous areas is increasing constantly,Many of which pass through special land areas such as expansive soil and landslide areas.When the tunnel entrance pass through these areas,geological hazards often occur in tunnel construction due to the joint action of expansive soil and landslide,which influence the construction process and quality.Therefore,it is very necessary to study the influence of expansive soil and landslide on the deformation of tunnel structure and put forward the corresponding pre vention and control measures.In this paper,the deformation mechanism and control technology of expansive soil tunnel in landslide area are studied based on the project of Sanxi Expressway in Henan Province by means of laboratory test,theoretical analysis,numerical simulation and field monitoring and the main results are as follows:1.The basic mechanical indexes,swelling potential,swelling force and swelling rate of expansive soil are determined by laboratory tests.The physical and mechanical properties,where the volume deformation is considered,of expansive soil surrounding rock are studied.the soil-water characteristic curves which can better estimate the strength,deformation and permeability coefficient of unsaturated soil and reflect the water holding capacity of soil under suction are given.2.the analytical solution of tunnel excavation considering soil swelling characteristics is deduced,and the characteristic curves of weak expansive soil surrounding rock under different water content are obtained according to the theory of elastic-plastic mechanics.The curves can reflect the influence of weak expansive soil surrounding rock swelling on supporting force and deformation.3.the influence of landslide sliding caused by water swelling of tunnel entrance on the stress and deformation of surrounding rock and initial supporting structure of tunnel is analyzed by using finite difference software FLAC 3D,and the deformation and stress of tunnel surrounding rock and initial supporting after tunnel excavation and supporting are analyzed when the longitudinal displacement of landslide body is 3 cm,5 cm,8 cm and 12 cm respectively.The effect of cutting slope unloading on landslide stability and tunnel deformation is studied.The results show that the initial support structure of the tunnel undergoes a large deformation along the longitudinal direction after the water swelling of thesurrounding rock.The maximum longitudinal deformation is 68 mm,located in the middle part of the tunnel vault.With the development of the landslide,the longitudinal deformation gradually extends to the arch waist and arch foot,and the initial support deformation in the landslide increases rapidly.The results of numerical calculation and field construction practice prove that it is not feasible to construct the landslide section at the tunnel entrance without unloading and tunnel reinforcement measures.4.The influence of reserved core soil method,CD method and CRD method on surrounding rock deformation of shallow-buried weak expansive soil tunnel passing through landslide area is analyzed by numerical simulation according to the characteristics of shallow-buried expansive soil tunnel together with field monitoring data.The results show that the deformation of surrounding rock can be well controlled by using CD method in shallow-buried expansive soil tunnel construction.And supporting pressure is a suitable construction method.According to the calculation results,a suit of construction methods for expansive soil tunnel in shallow buried section is summarized,which can provide reference for similar projects.5.It is considered that controlling or reducing the deformation in the excavation process is the key to prevent the failure of the expansive soil tunnel landslide system through the analysis of the development of the crack deformation and the landslide characteristics of the tunnel through the landslide section.Combining with the numerical results and considering the geological environment,construction period and environmental protection in the landslide area,the landslide control measures and the tunnel construction method of shallow buried section are put forward.Through the treatment,the deformation and destruction of landslides have been effectively curbed.At the same time,through the feedback of field construction,it can be seen that the CD excavation method can effectively control the surrounding rock deformation and support pressure.The research results can provide reference for similar projects.更多还原