【作者】 吴占瑞；

【导师】 漆泰岳；

【作者基本信息】 西南交通大学 ， 桥梁与隧道工程， 2013， 博士

【摘要】 当今,在城市里面修建地铁车站,由于周围环境条件的限制,城市地铁大多要在复杂条件下修建,高楼林立、管线密集,传统的修建地铁车站施工方法受到约束,在这种情况下结合国内工程实际,提出在盾构隧道基础上进行扩挖的方法修建地铁车站。这样不仅可大幅缩短盾构的停机等待时间,确保施工期间的安全,也很好的解决了多年来城市地铁盾构不具备设置接收井的复杂条件下如何修建地铁车站、同时又提高地铁盾构一次掘进效率的难题。本文以广州地铁六号线东山口车站为工程背景,采用理论分析、数值模拟、三维模型试验以及现场监测等研究手段,针对盾构扩挖施工对周边地层和房屋的影响进行研究,论文主要从以下几个方面进行展开,并得到相关结论：1.盾构扩挖施工过程中,不同围岩级别对地层和房屋的影响方面可以看出,在从围岩和房屋安全角度出发,Ⅳ2级围岩基本上处于临界范围,在高于Ⅳ2级围岩的条件下,盾构扩挖施工对周边影响基本上处于安全状态,随着围岩级别的继续降低,当低于Ⅳ2级时,地层沉降迅速增大,当围岩处于V级围岩时,地层整体变形量较大,基本上不适合进行盾构扩挖修建地铁车站,在施工过程中,假如出现这种地层时,需要提前进行相关的超前预加固措施,提高洞周围岩的强度,确保施工和周边环境的安全。2.房屋对地表沉降范围和量值上的影响主要从房屋与盾构隧道和扩挖隧道不同距离、房屋不同重量和不同角度进行分析,在不同距离方面,总体上房屋每隔两倍洞径,地表无论是影响范围即沉降槽宽度还是总体沉降方面的发展趋势都会稍有不同,一般当房屋大于5倍洞径距离时,房屋对洞周地表沉降影响已经很小；对于影响宽度一定的房屋,房屋自重越大,房屋垂直于影响方向的宽度越短,对地表沉降的影响就越大,对于都不确定的情况,地表沉降的大小与房屋自重在基础底面上形成的均布力呈正相关关系,房屋自重在基础底面造成的均布力越大,则地表沉降量和沉降范围即越大,反之亦然；房屋最大影响宽度为房屋基础对角线的长度,此时房屋与隧道轴线的夹角为θ=90-αrctanc/l。3.盾构扩挖工序的完成中,不论是先开挖(左线)还是后开挖(右线),其盾构部分所引起的沉降量约占总体沉降量的30%；随着围岩强度的降低,左线盾构开挖造成沉降占总沉降量的比例波动不大,基本稳定在30%左右,而右线盾构开挖造成沉降占总沉降量的比例则随着围岩强度的降低而稍有增大。4.总体来看,在盾构扩挖施工过程中,房屋的相对变形对房屋受力及安全系数的影响较大,房屋突增的相对变形由于房屋结构自身的调节滞后性必然会导致房屋局部应力的增长,这从右扩挖一半时房屋受力变化中明显可以看出。所以,可以认为房屋逐渐增大的相对变形对于房屋受力的影响相对较小,突增的局部相对变形对于房屋应力的影响较大。施工中应重点控制左、右线扩挖一半时的房屋局部相对沉降量。5.盾构扩挖过程中房屋的应力从上到下逐渐增大,而且开挖引起的房屋应力变化主要集中于第一层；房屋90度方向墙体的安全系数在开挖阶段一直较小,对于这种工况需要采用辅助工法施工并对房屋及其基础进行提前加固,预防房屋的开裂破坏；45度角房屋需要重点预防右盾构开挖到联络通道开挖阶段的房屋开裂；房屋0度时需要重点控制左线扩挖和第二条联络通道的开挖阶段。6.房屋与隧道不同距离时,盾构和扩挖阶段房屋的受力总体上都经历了随着距离的逐渐增大房屋的受力先逐渐增大然后逐渐减小,最后恢复到自重作用下的房屋自然受力状态。盾构开挖时房屋的最大应力大约出现在沉降槽曲率最大处,即3i处,此处房屋水平变形最大,房屋为受力最不利状态；7.在工程实例部分,针对传统的施工方法与盾构扩挖较为新型的施工方法,从施工工期、经济效益以及投资成本进行了较为全面的对比分析,分析表明,盾构扩挖法修建地铁车站不仅能够大大缩短施工工期,同时大大减少了工程的投资成本,提高了该项工程的经济效益,对于今后类似工程起到了很好的参考和借鉴作用,值得大力提倡。8.通过模型试验和优化计算,结合工程地质水文条件,提出了该工法下穿建筑物的最优工序和地层加固方案,即在实施盾构扩挖之前打超长大管棚和袖阀管注浆加固双重地层加固措施,并成功运用于实际工程。9.根据Peck和随机介质理论,通过对相对较安全的盾构开挖阶段进行反分析得到相关的对应参数,并结合所得到盾构阶段和扩挖阶段之间的沉降比例关系,实现盾构开挖沉降参数向扩挖阶段沉降参数的转化,通过这一方法实现了从较为安全的盾构开挖阶段到相对较危险的扩挖阶段的地表沉降预测,并取得了良好的预测效果,对于扩挖阶段的开挖具有重要的指导意义。更多还原

【Abstract】 Nowadays, a great number of subway stations have been building in the cities. However, as a result of the limitation from ambient environment condition, the urban subway’s construction is performed under the complicated conditions. Especially, in some places, where there are plenty of tall buildings standing and underground pipelines covering densely, traditional excavation methods for metro station’s building are under restrictions. In this case, this dissertation put forward a new excavation method of metro station that is expanding excavation on the base of shield tunnel through the station. In this way, not only can it drastically reduce halt waiting time of shield machine and ensure construction security, but also solve a toughest problem existed for many years that is how to build a metro station and increase the efficiency of metro shield’s primary driving in some cities where there don’t meet the requirement of setting shaft out of complicated conditions.Taking Dong shankou station from the6th line of Guangzhou subway as engineering background,This dissertation synthetically adopts a variety of study means, such as theoretical analysis, numerical simulation,3-dimensional model tests and field monitoring etc. For the study of surrounding stratum and houses effect induced by the enlarging shield tunnels, this dissertation mainly relate and analyze from following parts and arrivals at some conclusions:1. In the process of enlarging shield tunnels, different surrounding rock grades have distinct influence on the surrounding stratum and houses, from which we can see:at the level of surrounding rock and houses safety, surrounding rock of Grade Ⅳ2is basically the critical range; in the case that surrounding rock grade is higher than IV2, it will remain as safe on the whole when the shield machine conducts expanding excavation and affects the surroundings; with the grade of surrounding rock continuously decreased,untill lower than IV2, the ground settlement increase rapidly; when the surrounding rock grade is V in some areas, whose whole stratum deformation is comparatively large, well then it is not rational to build the metro station through enlarging shield tunnels; Once this kind of strata happened to appear, it need to take some advance strengthening measures ahead of time, improve the strength of surrounding rock in the tunnel, and ensure construction and surrounding environment security.2. About the influence that houses have on the range and value of ground settlement, it mainly make some analysis from the buildings’weight and the relative position of houses to shield tunnel or enlarging shield tunnels, including the distance and angle. In terms with the different distance, if the distance is twice as long as the tunnel diameter, the growing trend about the whole settlement and the width of settling tank, namely the influence scope to the earth’s surface, will be slightly distinctive, only when the house is5tunnel diameters far away from the tunnel, will the influence that the house have on the earth surface have been very small. Regard the distance as constant, the more heavy the house’s dead weight is and the shorter the width to its influence direction, the greater the influence having on the earth surface’s settlement will be. To the situation that all is not clear, the value of ground settlement will have a positive correlation with the uniform force which the house dead load imposes on the foundation base, that is the bigger the uniform force is, the greater the value and range of the ground settlement will be and vice verse. The biggest influence width caused by the house is the house’s diagonal length, meanwhile the angle between the house and tunnel axis will be calculated by θ=90-arctan c/1.3. During the process of the enlarging shield tunnels, no matter which one will be firstly excavated between the left line and the right line, part of the settlement value caused by the shield approximately make up30%of the overall settlement. With the strength of surround rock decreasing, the rate of settlement that is caused by the left shield driving has little change, which is basically stable at30%. However, the rate of settlement that is caused by the right shield driving will be some higher along with the strength of surround rock increasing.4. On the whole, in the course of enlarging shield tunnels, the house’s relative deformation has a great effect on its own loads and safety factor. The jumping of house’s relative deformation must lead to its local stress increasing due to its structure own lagging in the adjustment, which is clearly demonstrated on the changes of house stress when the right expanding excavation is halfway. Therefore, the part that the house’s relative deformation gradually increasing has on the house stress is comparatively little, but the jumping of house’s relative deformation has a bigger influence on the house stress. So it should focus on controlling house’s value of local relative settlement.5. When the shield is ongoing expanding excavation, the house’s stress will increase gradually from top to bottom, moreover, its variety concentrate mainly on the ground floor. The security coefficient of wall,90degrees to the direction of house, is always smaller in the driving period. Specific to this working condition, it should take auxiliary construction method and reinforce the house and its foundation base in advance in order to protect it from crack destruction. The45degrees angle house requires focus on prevent crack destruction from the stage of the right shield working to the stage of connecting passage’s cutting through. It is necessary that the house that is parallel to the tunnel axis to control the stage between the left lines’s expanding excavation and the second connecting passage’s cutting through. 6. With the distance between the house and tunnel increasing, the house’s stress will rise at first and then descend, finally return to natural stress state under the action of deadweight in the stage of shield and expanding excavation. In the process of shield driving, the maximum of house stress approximately appear on the biggest curvatureof settlement trough, where the house’s horizontal deformation is the biggest and the stress state is the worst.7. At the part of engineering project, this dissertation makes a more comprehensive contrastive analysis from some aspects, including the construction period, economic benefit and cost of investment, to the traditional construction method and the new method of enlarging shield tunnels. It indicates that the new method not just reduce greatly the construction time, more than enormously lower capitalized cost of project and raise the economic benefit, which have a good role as reference of similar project in the future and worth to advocate.8. Through model tests and optimal computation, together with engineering geological condition and hydrogeology conditions in construction site area, this dissertation pro-pose an optimal process of shield under-passing buildings and ground consolidation scheme. In other words, it is double stratigraphic reinforcement measure that includes both setting long and large pipe shed or sleeve valve pipe and grouting reinforcement, which is applied to the actual projects.9. Based on the Peck formula and random medium theory, in the relatively safe stage of shield working, it could get the related corresponding parameter by inverse analysis, combining with the rate of settlement relation between the stage of shield and expanding excavation, in order to realize the transform of settlement parameters between the stage of shield and expanding excavation. By this way, it could take advantage of comparatively safe shield stage achieving an accurate forecast of ground settlement to the dangerous expanding excavation stage, which turn out that it has been made a good predictive effect and can have an important guiding significance to the working of expanding excavation stage.更多还原