【作者】 张健；

【导师】 黄生根；

【作者基本信息】 中国地质大学 ， 防灾减灾工程及防护工程， 2007， 硕士

【摘要】 管棚——箱涵推进工法已经成为我国地下工程中一种重要的施工方法。箱涵推进工法以其独有的智能化、安全、快捷等特点和优势,在地下工程中得到广泛的推广和运用。如何控制地层位移以及保证繁忙线路的安全,是设计和施工中必须考虑的首要问题。因此,如何总结地层的移动规律,对后续工程设计和施工具有指导意义。本文对顶进箱涵施工引起的地层位移进行了理论分析。首先研究了顶进箱涵引起的地层损失及其理论,地层损失可以分为正常地层损失和不正常地层损失两种,应采取有效措施减小地层损失;分析了土体孔隙水压力变化理论,在施工过程中,箱涵顶进对周围土体将产生附加荷载,从而引起土体扰动,在周围地层中形成超孔隙水压力,可以通过分析土体孔隙水压力的变化,对土体扰动进行评价,并且是一个灵敏的指标;在管棚法箱涵顶进工程中,管棚置于箱涵的外围,对隧道的施工起着重要的作用,在某种程度上可将其视为相当于隧道中的初期支护。正确分析管棚的作用机理具有十分重要的意义,分析了施工过程中钢管棚的力学作用等,把钢管视为置于Winkler地基上的弹性地基梁,得到了一些规律性的认识。分析了注浆对土体的扰动,包括注浆的作用机理、在土体中的渗透以及注浆的效果等,在施工过程中注浆的主要功能有润滑和支撑作用,可以减小顶进箱涵施工摩擦阻力和减小引起的土体变形,如果注入的润滑泥浆能在箱涵的外周形成一个比较完整的泥浆套,那么减摩效果将是十分令人满意的,在推进过程中需对后面的箱涵体不断补浆,以使箱涵与土层间空隙中泥浆的压力能够始终与土压力一致。本文以郑州市下穿北京至珠海高速公路立交工程为背景,根据现场工程地质条件和施工方案,结合FLAC^3D三维数值分析程序,对顶进过程中引起的地层位移进行仿真模拟。对于本工程,管棚施工引起的地层位移很小,数值模拟主要考虑箱涵顶进引起的地层位移,在数值模拟中对施工过程进行简化,并考虑开挖面土压力、注浆压力因素的影响。开挖面土压力的大小根据开挖面原始的侧向压力作为基础,按照该土压力值的1倍在数值模拟开挖过程中施加于开挖面。注浆采用等代层来模拟,分不同的注浆压力进行模拟分析。研究成果包括不同工况下,路面竖直位移、路面水平位移、管棚复合体水平位移、基底的水平位移分布情况,并对它们进行对比分析,总结数值模拟情况下,箱涵顶进引起的地层位移规律。对施工引起的地层位移进行了现场监测。测试的项目主要包括地表变形、深层土体位移、孔隙水压力、箱涵实测的顶力、地下水位的变化、土体与涵壁的接触压力、顶进偏差等。介绍了现场测试的基本原理和方法,对现场测试结果进行分析,研究施工引起的孔隙水压力、周围土体土压力等变化规律,根据监测的结果和在监测过程中发现的问题,对施工过程进行必要的指导。通过现场监测和数值模拟结果的对比分析,总结了地层的移动规律。最后讨论了箱涵顶进施工对环境影响的防治措施。通过计算分析,得到以下结果:（1）在顶进箱涵工程中,注浆对地层位移的影响较大。随着箱涵的推进,注浆的效果将明显下降,因此要对后面的箱涵不断补浆。注浆的压力需要合理控制,在数值模拟过程中,注浆压力的大小对路面的竖直位移影响较大,随着注浆压力增大,路面逐渐上升;注浆压力的大小对地层的水平位移的影响较小。（2）路面测点随箱涵顶进的影响,根据测点与开挖面的距离的不同,大致可以分为微小上升、微小沉降、沉降急剧增大、缓慢沉降四个阶段。路面发生最大沉降的位置不是轴线,而是与轴线的距离为箱涵跨度的一半,该位置应重点进行加固处理。在箱涵顶进过程中,要注意尽量减小轴线偏差,并尽量减小管棚和箱涵间的建筑空隙,以控制地层移动。（3）箱涵顶进过程中引起的路面变形范围较大,受影响的区域为距离箱涵轴线两侧100m以内,主要影响区域为距离箱涵轴线两侧25m以内;由于管棚的支撑作用,掌子面前方路面并没有出现较大的沉降,由于管棚变形的连续性,受前方管棚下沉的影响,掌子面后方钢管产生轻微的隆起,导致路面的隆起。（4）在与箱涵的中心标高一致处,掌子面正前方的深层土体发生最大的水平位移。在距离孔口15m深度以下,即距离箱涵底板6m深度以下区域,土体的位移很小,受到的扰动影响较小。孔口30m以下深度的土体基本不受箱涵顶进的影响。（5）当箱涵的顶进速度比掌子面出土速度快时,前方土体中的孔隙水压力会上升;反之,就会减小。孔隙水压力是评价箱涵顶进对土层扰动的灵敏准确的指标。对土体扰动进行评价,监测孔隙水压力比监测深层土体位移更有效,针对不同的监测方案的选取上,应优先选择监测孔隙水压力的变化。（6）随着箱涵的顶进,路面水平位移的增加速率逐渐减小;在同一施工阶段,管棚测点的水平位移最大,其次是路面测点,基底测点的水平位移最小。路面和管棚测点的水平位移较为接近。（7）采用Mohr-Coulomb准则对管棚箱涵顶进工法进行三维模拟分析,结果与实测的数据基本吻合,基本上能够反映出地层位移的变化趋势。更多还原

【Abstract】 The pipe roof box culvert jacking method has been one of the main construction methods in the underground engineering in our country. The construction technology with box culvert jacking is being widely used in building underground engineering because of its unique characteristics and advantages such as intelligence, safety and quickness, etc. The main issue considered both in the design and construction is controlling of the stratum displacement and keeping the safety of the busy expressway. So, how to summarize the stratum displacement patterns has guiding significance for the design and construction in the future.The stratum displacement induced by the box culvert jacking is researched with theoretical method in the paper. The theory of soil loss caused by the box culvert jacking is researched. The soil loss can be divided into normal loss and abnormal loss, and it is necessary to take effective measures to minish the soil loss. The theories of pore water pressures are studied. The superimposed load and soil disturbance will be induced by propulsion of box culvert jacking. The excess pore water pressure will be caused in the soil around the box culvert. The soil disturbance can be evaluated by analyzing the variety of pore water pressure, and it is a sensitive index. In the pipe roof box culvert jacking process, the pipes are installed in the soil around the box culvert, and it is important during the tunnel construction to some extent. The pipes can be regarded as the initial support in the tunnel construction. To analyze the interaction mechanism exactly has significant meaning. By analyzing the mechanics action of the pipe roof in the construction process. The steel tubes are regard as the elastic foundations above Winkler foundations. Some theories are concluded. The disturbance of soil induced by injection is studied, includes the injection mechanism, the seepage behavior of mud on soil around the box culvert and the injection effect. The grouting has lubricating and supporting function during the construction. The grouting can minish the culvert-soil contact friction and the soil deformation induced by the box culvert jacking. If the lubricative slurry can form more integrated mud layer system around the culvert, the effort of antifriction will be quite perfect. To supply mud for the latter culvert during the advancing is necessary, and the pressure of mud in the gap between the soil and culvert will be in accord with the soil pressure all the time.The paper is based on the subway project crossing under Beijing-Zhuhai expressway located in Zhengzhou. Based on the in-situ data, the numerical simulation of the stratum displacement during the whole construction process is studied systematically by using FLAC^3D computer programming. The numerical simulation will mainly consider the stratum movements induced by the box culvert jacking because the stratum movements induced by the pipe roof jacking is very small during the construction. The construction process will be simplified in the numerical simulation, and the effect of factors including the soil pressure on the face of excavation and the grouting pressure will be regarded. The earth pressure on the surface of excavation is based on the original earth pressure on the excavation face, and the force applied on the face of excavation is according to 1.0 times of the original earth pressure during the simulation process. The equivalent layer is substituted for the slurry in the numerical simulation. The simulation will regard the varied mud pressure. The research includes the vertical movement distribution of pavement, the horizontal movement distribution of pipe roof composites, and the horizontal movement distribution of the foundation. By the analysis and comparison of them, the stratum displacement patterns induced by the culvert box jacking is summarized during the process of numerical simulation.The in-situ stratum displacements induced by box culvert jacking construction are monitored. The in-situ testing includes surface deformation, sub-surface movements, pore water pressures, the total jacking forces of box culvert, culvert-soil contact stresses, under ground water levels, deviations in line and level of box culvert. The basis theory and method of in-situ testing are introduced. The results of field-testing are analyzed, and the variety of testing datum include earth pressures, pore water pressures and underground water levels during the course of the construction are studied. Base on the result of monitoring and the problem detected by the monitoring, the process of construction is guided. By combing the analysis and comparison of the site measured results and numerical simulation results, the stratum displacement patterns are summarized. The measures for protecting neighborhood circumstance and relevantly controlling measures for minishing the stratum movements during culvert box jacking are studied.By the calculation and analysis, some results are gained:（1）The grouting has great effect on the stratum movements in the process of box culvert advancing. As the advancing of the culvert box, the effort of grouting descends obviously, and it is necessary to supply mud for the latter box culvert. The grouting pressure should be controlled reasonably. During the numerical simulation, the value of grouting pressure has great effect on the vertical movements of pavement, and the pavement ascends gradually as the increasing of grouting pressure. And the value of grouting pressure has little effect on the horizontal stratum movement.（2）The patterns of the point movement on the pavement can approximately be divided into four steps including little rise, little subsidence, quick subsidence, slow subsidence. The greatest subsidence of the pavement is not on the axis but in the domain, and the distance between the domain and the axis is about half of box culvert span. Reinforcement and treatment is the key in the domain. The stratum movement is controlled by minishing the axis deviation and minishing the gap between the box culvert and pipe roof as far as possible. （3）The deformation area on the pavement induced by the box culvert jacking is very large. The distance between the effected domain and the axis is more than 100 meters. The distance between the mainly effected domain and the axis is less than 25 meters. Because of the support of pipe roof, the pavement does not appear great subsidence in front of the excavation face. The deformation of the pipe roof is continuous. Induced by the deformation of the pipe roof in front of the excavation face, steel tube behind the excavation face will generate little increase and the face of pavement heaves.（4）According with the same elevation of the box culvert axis, the soils in front of excavating face generate the biggest horizontal movements. The soil displacements become small more than 15m below the orifice, and the location is approximately 6m below the bottom of box culvert. The disturbance of the soil at the location is very slight. The box culvert jacking has slight effect on the disturbance of the soil more than 30m below the orifice.（5）The pore water pressure in the front soil will ascend when the advancing velocity of box culvert is larger than the velocity of excavating on the working face, or the pressure will descend. The pore pressure is a sensitive and exact index for monitoring the vibration of soil in the process of box culvert jacking. To evaluate the vibration of soil, monitoring pore water pressure is more effective than monitoring the sub-surface movement. Monitoring the variation of pore water pressure is the first choice regarding different choices of monitoring scheme.（6）The increase velocity of horizontal movements on the pavement descends gradually in the process of the box culvert jacking. During the same step in the construction, the point movements of the pipe roof composites are the biggest. The movements of pavement are the second, and the movements of foundation are the smallest. The horizontal movements of pavement are equal to the composites approximately.（7）The pipe roof box culvert jacking is studied by 3-dimension simulation considering Mohr-Coulmb criterion. The result of the simulation is the same as measurement on the whole. The results can reflect the trend of the stratum movement on the whole.更多还原