【作者】 刘庆晨；

【导师】 郑刚；

【作者基本信息】 天津大学 ， 岩土工程， 2013， 博士

【摘要】 本文针对邻近运营地铁线路施工中所涉及到的基坑开挖、地表荷载、承压含水层减压降水扰动方式，对既有地铁结构的影响机理及保护问题，采用现场实测与数值模拟相结合的研究方法，进行研究。本文的主要内容及结论如下：（1）结合西青道下沉隧道基坑超近距离上跨运营地铁1号线既有隧道箱体结构的工程实例，分析基坑开挖对下卧隧道箱体变形的影响，对其过大的箱体结构隆沉与变形缝处的差异变形，有针对性地提出在隧道箱体两侧的土体加固、浇筑底板与抗浮桩形成“保护箍”以及分块开挖分块堆载回压的变形控制措施，并对相应的施工参数进行优化，为施工设计提供依据。根据现场实测，对实际基坑开挖过程进行动态模拟，并在此基础上，通过数值模拟对比分析，评价各项既要箱体变形控制措施的合理性与有效性。（2）对地铁1号线西站站车站与隧道连接部在地表荷载作用下产生的沉降进行现场监测与有限元分析，由于变形缝的存在，结构沉降表现为非连续性。在此基础上分析地表荷载位置、大小、面积、结构埋深以及是否进行变形缝处土体预加固因素对于存在变形缝的非连续性结构变形的影响，研究表明：变形缝削弱结构刚度，加剧结构沉降及结构间的差异变形，不同荷载位置下结构的沉降特点也各不相同。（3）通过某抽水试验的模拟，反演土体参数。在保证参数可行的基础上进行承压含水层降水对既有盾构隧道影响的仿真模拟，分析隧道周围土体应力场、隧道自身变形、横断面内力与纵向变形，研究其影响机理，指出：隧道周围土体在减压降水时，竖向总应力几乎不变，水平向总应力减小，相当于在隧道原有荷载基础上，隧道两侧受到附加拉力，导致隧道压扁加剧，对管片横断面受力不利。并对既有隧道相对承压含水层位置、隧道与减压井净距、承压含水层埋深、承压含水层不同程度截断因素的影响进行参数分析，表明：当隧道部分或全部位于承压含水层中时，减压降水对隧道横断面内力与纵向变形影响较大；当隧道位于隔水层中时，减压降水对隧道横截面内力影响较小，隧道横断面有扭转趋势，但当隧道位于上部隔水层中时，隧道随地层产生较大沉降，对隧道纵向变形不利。当既有隧道与减压井净距较小时，不能由于两者间被地下连续墙截断而忽略减压降水对隧道纵向变形的影响。更多还原

【Abstract】 This dissertation researched the influence mechanism of some related disturbance types, e.g. excavation, ground loading and dewatering of confined aquifer on the existing metro structure and corresponding protective measures. The main works and conclusions are summarized as follows:(1) According to the practice project that the open cut of Xiqing Road Tunnel was constructed closely upon the existing tunnel of the operating Metro Line1, ABAQUS is applied to analyze the effect of excavation on the existing underlying metro tunnel. In order to control the excessive upheave of the tunnel and differential displacements at the deformation joints, some deformation control measures were proposed specially, including soil improvement alongside the existing tunnel, formation of protection hoop by slab and anti-floating piles, excavation in sections and timely suppression by heaped load, and the corresponding construction parameters were optimized. These results can provide evidence for the optimization of the construction design. The practical construction procedure was simulated dynamically based on the field monitoring data. Further on, the reasonability and the effectiveness of the deformation control measures mentioned above were analyzed by contrast analysis using numerical simulations.(2) The settlement induced by ground loading was monitored in the West Railway Station subway station of the Metro Line1. Besides, the deformation characteristics of structure were analyzed by field measurements and finite element method. The results show that the settlement curve is discontinuous at the structural deformation joint. Furthermore, the effects of many factors, e.g. the loading location, magnitude, area, buried depth of the structure and weather to pre-reinforce the soil around the deformation joints on the deformation of discontinuous metro station boxes were studied. It is found that the structural deformation joint can weaken the structure stiffness and increase the settlement and differential settlement of the structure.(3) Based on a certain pumping test, the soil parameters were derived by inverse analysis. On the basis of ensuring the feasibility of parameters, simulation was performed to find out the effect of dewatering of confined aquifer on the existing shield tunnel, and afterwards, the stress field of soil around the tunnel, the sectional distortion and internal forces and the longitudinal deformation of the tunnel were analyzed to study their influencing mechanisms. The results show that during the process of depressurization dewatering, the vertical total stress is almost constant whereas the horizontal total stress decreases. This phenomenon has the same effect with that both sides of the tunnel are subjected to tensile force, and leads to the aggravated flattening of tunnel, which has adverse effects on the load carrying capacity of tunnel section segments. On this basis, the research investigated the influence factors such as the position of the existing tunnel related to the artesian aquifer, the distance between tunnel and well, buried depth of the artesian aquifer and insertion depth of water-stop curtain in the artesian aquifer. It is indicated that dewatering has higher impact on the force of cross section and the longitudinal deformation of tunnel while the tunnel is located in the confined aquifer partly or completely. And dewatering has lower impact on the force of cross section but can cause the cross section have the tendency of twisting, while the tunnel is located in the aquiclude. However, the tunnel has a greater settlement along with the stratum while the tunnel is located in the upper aquiclude, which is adverse for the longitudinal deformation of tunnel. It should be pointed out that when the tunnel is close to the dewatering well, even there is a diaphragm wall cutting off the confined aquifer, the influence of dewatering on the longitudinal deformation cannot be neglected.更多还原