黄土地区明挖隧道施工对相邻地表建筑影响分析

发布时间：2018-03-05 22:22

本文选题：黄土地区　切入点：明挖法　出处：《长安大学》2017年硕士论文　论文类型：学位论文

【摘要】：在城市交通等基础设施的新建与改建工程中,明挖法广泛应用于下穿隧道及其引线工程、地铁车站等的施工。在城市商业区,隧道明挖施工引起的基坑周围被支挡土体的变形及其对周围建筑的影响是明挖隧道设计与施工关注的重点之一。本文在分析黄土地区明挖基坑施工引起的被支挡土体的地表沉降特征及其与基坑开挖深度和基坑支护结构体系类型相关性的基础上,探讨了西安地区以黄土为主的明挖基坑施工对相邻建筑物的影响。以西安黄土地区一工程实例为背景,采用Midas/GTS有限元分析软件,研究在黄土地层条件下明挖基坑施工过程中,建筑物距基坑距离、基坑内支撑形式和基坑开挖深度对支护结构、周围地表以及建筑物变形的影响规律。在本算例的条件下,主要结论如下:(1)桩体水平位移曲线呈现为中间大两头小的“内凸式”变形,水平位移最大处在距桩顶12m(0.75倍基坑开挖深度)处;地表沉降曲线呈“凹槽形”,地表沉降最大处在距离基坑边缘12m(0.75倍基坑开挖深度)处,且在距离基坑32m(2倍基坑开挖深度)外,土体沉降趋于稳定,变化幅度较小。(2)建筑物的荷载作用会使桩体水平位移和坑外地表沉降增大,但作用并不显著,且这种作用会随建筑物距基坑距离的增大而减小。(3)第一层混凝土支撑对基坑开挖产生的变形可以起到一定的控制作用。对架设位置处及桩体水平位移最大处的桩体变形有较为明显的控制作用;对紧邻基坑边缘处以及地表沉降最大处的土体变形有较为明显的控制作用;当建筑物靠近基坑一侧的端点恰好在沉降槽最低点(0.75倍基坑开挖深度)时,混凝土支撑对建筑物差异沉降的控制最为明显,此时可考虑将第一道钢支撑替换为混凝土支撑。(4)随着建筑物距基坑边缘距离的不断变化,建筑物绝对沉降的曲线形式也在不断变化,且建筑物绝对沉降曲线形式均与相应地表沉降相似,并略小于地表沉降;建筑物差异沉降在建筑物跨过沉降槽时较小,当建筑物靠近基坑一侧的端点恰好在沉降槽最低点时差异沉降最大,之后随着距基坑距离的不断增大,差异沉降逐渐减小,最终变为均匀沉降。
[Abstract]:In the construction and reconstruction of urban traffic and other infrastructure facilities, the method of open excavation is widely used in the construction of underpass tunnel and its lead project, subway station and so on. The deformation of the supported soil around the foundation pit and its influence on the surrounding buildings is one of the key points in the design and construction of the open excavation tunnel. This paper analyzes the supported soil caused by the construction of the open excavation foundation pit in the loess area. On the basis of the characteristics of soil surface settlement and its correlation with the excavation depth and the type of foundation pit supporting structure, This paper discusses the influence of open excavation foundation pit construction in Xi'an area on adjacent buildings. Taking an engineering example in Xi'an loess area as a background, using Midas/GTS finite element analysis software, this paper studies the construction process of open excavation foundation pit under the condition of loess layer. The influence of the distance from the building to the foundation pit, the form of bracing inside the foundation pit and the depth of excavation on the supporting structure, the surrounding surface and the deformation of the building. The main conclusions are as follows: (1) the horizontal displacement curve of the pile presents a "convex" deformation with two small ends in the middle, and the maximum horizontal displacement is located at a depth of 0.75 times from the top of the pile to the excavation depth of the foundation pit. The surface settlement curve is "grooved", the maximum settlement is located at a depth of 0.75 times from the edge of the foundation pit, and the settlement of the soil tends to be stable outside the depth of 32 m ~ 2 times the excavation depth of the foundation pit. The load action of the building will increase the horizontal displacement of the pile body and the settlement of the outside surface of the pit, but the effect is not significant. This effect will decrease with the increase of the distance from the building to the foundation pit.) the first story concrete bracing can play a certain role in controlling the deformation of foundation pit excavation. The deformation of the body can be controlled obviously. The deformation of the soil near the edge of the foundation pit and the maximum settlement of the ground surface is obviously controlled, when the end of the building near the foundation pit side is exactly 0.75 times the depth of the excavation of the foundation pit at the lowest point of the settlement trough. The concrete bracing controls the differential settlement of the building most obviously. At this time, we can consider replacing the first steel bracing with concrete bracing. 4) with the continuous change of the distance from the building to the edge of the foundation pit, The curve form of the absolute settlement of the building is also changing, and the curve form of the absolute settlement of the building is similar to that of the corresponding surface settlement, and is slightly smaller than the surface settlement, and the differential settlement of the building is smaller when the building crosses the settlement trough. When the end point of the building near one side of the foundation pit happens to be at the lowest point of the settlement trough, the differential settlement becomes the largest, and then with the increasing distance from the foundation pit, the differential settlement gradually decreases and finally becomes uniform settlement.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U456.3;TU433

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