【作者】 高燕；

【导师】 介玉新；

【作者基本信息】 清华大学 ， 土木工程， 2008， 硕士

【摘要】 随着城市建设的快速发展,由于大规模城市建设所造成的地面沉降日益显著。论文主要从地基附加应力特点和地基土压缩特性两方面研究城市建设对地面沉降的影响。首先在建筑物均匀分布的情况下,将建筑物分别等效为线荷载、条形荷载、集中荷载、矩形荷载,进行了地基中附加应力特点的分析。在此基础上,统计了北京部分建筑物间距,运用数理统计的方法得到了建筑物间距的随机分布规律。并且在该随机分布下,将建筑物分别等效为线荷载和集中荷载,进行了地基中附加应力特点的分析。论文同时分析了地基土层压缩特性对地面沉降的影响,对大量建筑物作用下沉降影响范围进行了初步探讨。结合某开发区的规划建设,研究了软土地基上开发区建设对邻近堤防的影响。论文主要得到如下结论:1)对北京部分建筑物的统计分析表明,建筑物间距在东西方向上服从Gamma分布,在南北方向上服从对数正态分布;2)建筑物无论是均匀分布还是随机分布,在大量建筑物荷载作用下,地基中附加应力特点与单体建筑物下附加应力特点明显不同。大量建筑物下地基中附加应力相互叠加,在深度约等于建筑物平均间距处可以近似等效为大面积均布荷载,并且该荷载集度在很大深度范围内不衰减;3)地基土模量按照指数函数规律变化时,地基沉降是有限值;按照幂函数规律变化时,只有幂指数大于1,才能使得沉降为有限值。对给定压缩层厚度h0有影响的建筑物的范围是有限的,如果以附加应力σ_h0≤0.01q（q为大面积均布荷载的集度）作为标准,那么在距离该点3.5 h₀水平范围外的建筑物荷载的影响可以忽略。4)随着建筑物与堤防距离的增加,堤防的沉降值逐渐减小。这种减小的效果在距离较近时比较显著。当建筑物与堤防距离较近时,将地表荷载转移至地下较硬土层中能明显减小沉降,当距离较远时,这种方法对沉降减小作用不明显。对于相对均质地基,荷载移入土层深度足够大时,才会有沉降的减小。更多还原

【Abstract】 With the rapid development of cities, the land subsidence caused by large-scale construction has been more and more obvious. The dissertation presents a study of land subsidence under bulk loads of buildings in respects of additional stress in foundation and soil compressive characteristics. First, under the uniform distribution, the buildings are equivalent to line load, strip load, point load and rectangular load, respectively. The characteristics of the additional stress are analyzed on each condition. And then, the distances of some of buildings in Beijing are measured. The buildings’distribution is analyzed by means of statistics. Based on this, under the random distribution, the characteristics of the additional stress are analyzed on conditions of line load and point load, respectively. What’s more, the effects of soil compressibility on land subsidence are studied. The effecting scale of land subsidence is also discussed under large-scale buildings. According to the construction of a development area, the effects of buildings on nearby dike are studied. The main conclusions are as follows.1) It is indicated by statistical analysis of some buildings in Beijing that buildings on the pitch in the east-west direction obey Gamma distribution, while in the north-south direction are in obedience to lognormal distribution.2) Whether the buildings are uniformly or stochastically distributed, the characteristics of the additional stress in foundation under large-scale buildings are significantly different from that under single building. The additional stresses are superposed. It seems large-scale uniform loads when the depth is equal to the mean distance between buildings. And the magnitude of the large-scale effecting loads does not decay in a large depth below.3) The subsidence is finite when the modulus of compressibility varies in exponential function way, while it is limited only in the condition of power index greater than 1 in power function way. The scale of buildings affecting the additional stress in a certain depth h0 is limited. If the standard that additional stress can be ignored isσ_h0≤0.01q, then the scope of the buildings from the center to 3.5 h₀ can cause impacts.4) As the distance between buildings and the dike increases, the settlement of the dike is gradually reduced. And the settlement decrease is significant nearby the dike through this method. The settlement can be also reduced by means of transferring surface load to underground where soil is hard when the buildings are closer to the dike. For the homogeneous foundation, it is not useful unless the depth is enough deep.更多还原