【作者】 刘寒鹏；

【导师】 杜东菊； 李同录；

【作者基本信息】 长安大学 ， 地质工程， 2010， 博士

【摘要】 地面沉降是在自然和人为因素作用下,地面标高降低的一种环境地质现象,是一种不可补偿的永久性环境和资源损失。二十世纪中期,由于工业化的需要,开始大量开采地下水资源,导致了地下水位持续大幅度下降,产生地面沉降现象,造成了巨大的经济损失,迫使人们对地面沉降开始进行分析和研究。而目前随着全球变暖,海平面上升,使得全球沿海城市的安全受到威胁,人们对于地面沉降的研究和重视提升到了一个新的高度。上海浦东新区随着各种高层建筑不断建造,已经得到控制的地面沉降变得迅速发展。天津滨海新区内规划和建筑的高层建筑密集、数量多,与浦东新区相比有过之而无不及；同时分布有厚层海积软土为两者同样具有的工程地质特征,因此,高层建筑荷载引发的地面沉降会随着建设的推进逐步显现。高层建筑荷载作用下的地面沉降也是城市地面沉降灾害研究的新方向、新问题。而针对滨海新区高层建筑荷载作用下的地面沉降研究,以指导滨海新区的规划和建设,有益于天津滨海新区科学、快速、可持续发展。本文围绕着滨海新区这一新的地面沉降影响因素,主要从以下三个方面进行研究工作：(1)收集天津滨海新区沉降资料,对近年来塘沽、汉沽、大港的地面沉降情况进行了详尽的分析、总结,研究表明,天津滨海新区地面沉降的防控形势依然严峻。(2)制作天津滨海新区离心试验地层模型,进行了单体高层建筑施工过程中及相邻高层建筑工后长期作用的地面沉降试验研究。(3)结合离心机实验成果,利用相关计算理论及有限元软件就离心机实验成果进行分析及补充。研究取得创新性成果有：(1)离心机模型试验发现,研究区建筑加载期间,地表会发生局部隆起现象。在离心机模型试验中,100g离心加速度条件下,通过液压装置施加建筑荷载段实测沉降曲线与原有沉降趋势预测曲线相比,发现在高层建筑施工过程中,地面局部地区发生隆起的现象,对应原型建筑设计荷载,原型地面最大隆起量达到68.9mm。借鉴预制桩软土地区挤土效应理论及利用有限元软件对此现象进行了分析,分析得到隆起区域随建筑物施工发展而变化,研究模型中与建筑物中心距离2.0～5.0倍建筑物宽度范围内局部地面发生隆起,隆起部位分布受周围建筑物边界影响。(2)揭示了建筑荷载作用下,地面沉降在平面上的分布特点及剖面上的分布规律。由于高层建筑施工期间,地表局部发生隆起、地基土在高层建筑荷载引起的附加应力作用下使得距离建筑物较近部位土体沉降量大,较远处沉降量逐渐衰减的特点、海积软土自重固结产生沉降,而桩基—软土相互作用,桩基约束距离建筑物较近软土的沉降,三种因素作用下使得滨海新区高层建筑作用下的地面沉降平面分布规律复杂,地面沉降平面分布复杂性具有时间效应。剖面上研究高层建筑施工过程中,海积软土中分布的沉降量占据总地面沉降量的70%～77.8%。(3)揭示了高层建筑物作用下孔隙水压力变化规律。滨海新区高层建筑荷载在海积软土中引发超孔隙水压力平面分布大于建筑物周围2倍建筑物宽度的范围。实测建筑荷载引起的超孔隙水压力沿深度增大而增大,距离建筑物较近处,深部超孔隙水压力与浅部超孔隙水压力的比值小于距离建筑物较远处。影响范围内,超孔隙水压力具有随建筑物距离增大而减小的分布规律,土体中浅层超孔隙水压力随着与建筑物的距离增加衰减快。在高层建筑周围,由于已有建筑荷载在土体中产生附加应力随建筑物距离增大而衰减,其长时间作用导致土体工程性质具有差异性,距离已有建筑物较近的土体工程性质好,因此试验中相邻建筑物间超孔隙水压力具有比新建建筑物另一侧对应位置小的特点。与超孔隙水压力分布对应,新建建筑物引发的地面沉降具有在已有建筑物一侧沉降量小的特点。滨海新区高层建筑荷载在厚层软土中引发的超孔隙水压力消散缓慢,试验对应原型两建筑物中间观测点土体经过11.81年尚未完全固结,固结度为97.6%,天津滨海新区高层建筑荷载作用下具有地面沉降持续时间长的特点。更多还原

【Abstract】 Land subsidence is a Environmental geological phenomenon which is caused by the natural and human and it is permanent environmental and resource loss. Mid-twentieth century, as the needs of industrialization, groundwater resources has been extracted extremely, the groundwater level continued to decline significantly and the phenomenon of land subsidence happened, it has caused enormous economic losses so the Governments and experts started on the ground subsidence analysis and research. Currently with global warming and sea level rising, global coastal cities security is threatened, so the phenomenon of the land subsidence is caused the Attention of worldwide again.With the high-rise building continuously building in the Shanghai Pudong New Area, the land subsidence that has been controlled is developing rapidly. In Tianjin Binhai New Area, as same as Shanghai Pudong New Area, a large number of dense high-rise buildings are building and planned. At the same time, it is also distribute thick layer of marine soft soil, so with the development of the urban construction, the land subsidence caused by the high-rise building gradually appeared. The land subsidence caused by the high-rise building is a new directions and new problems of the hazards study on urban land subsidence. And the study for Tianjin Binhai New Area will guide the planning and construction of Binhai New Area, it can benefit Binhai New Area sciencely, rapidly, sustainable developing.Around the problem that Binhai New Area is coming, research works has been done as the follow:(1) The settlement data of Binhai New Area was collected, the recent land subsidence of Tang-gu, Han-gu and Da-guang were analysised and concluded in detail. The result proved that the prevention and control of land subsidence situation remains grim in Tianjin Binhai New Area.(2)Fitted the characteristics of the Tianjin Binhai New Area stratum, Toyoura sand and Kaolin clay composed the pile bearing stratum and soft soil around the pile separately. The course of construction was simulated by loading one of the pile groups in-flight.(3)The theoretical calculation and finite element software were used for analysis the results of centrifuge experiments and some result were added. Innovative research results obtained as follow:(1)During the high-rise building construction of Binhai New Area, uplift will occurred in somewhere of surface.Contrast the measured settlement curves during the period construction loads imposed by hydraulic equipment and the deduced curves based on the past period of 100g in-flight, the partial uplift was found, it is analysised by the principle of soil compaction effect in soft soil and the finite element software, the partial uplift is mainly happened during the period of the time of the building construction, the location changed with the period of construction, the approximate range of uplift is about 2.0-5.0 fold breadth of building from the center of the building, at the same time the uplift part is effected by the border of building nearby.(2) The land subsidence distribution in plain face of the high-rise buildings is obtained, and in cross section it is mainly happened in mine soft soil.During the high-rise building construction, uplift will occurred, the subsidiary stress caused by the loading of high-rise building decide that the land subsidence fade down with the distance increasing from the building, also with the marine soft soil consolidate by its sole weight, the piles and the soil interact each other, the settlement of soft soil around the piles is restrained by the piles, based on the three factors, the land subsidence distribution in plain face of the high-rise buildings in Binhai New Area is complex.During the period of high-rise building construction, the settlement in the marine soft soil occupy 70%-77.8% of total.(3)As the high-rise building construction, the regularity of excess pore water pressre and earth pressure is obtained.The sphere of influence of excess pore water pressure caused by study high-rise building is greater than 37.5m from the center of the building. In the marine soft soil, the excess pore water pressure increases along the depth and decreases with increasing distance from the building. The excess pore water pressure in 27.0m is 2.2-4.0 times bigger than 8.5m.The subsidiary stress caused by the old building fade down with the distance increasing, so it cause the engineering properties of soil differences, when a new high-rise building is setup around an old one, because the engineering properties of soil closer old buildings is better. So the excess pore water between adjacent buildings is smaller than the corresponding position which located the other side of the new building, and also the settlement is smaller than the other side.Fitted with the low permeability and the excess pore water pressre increasing along the depth, with the influence of study prototype buildings, the observation points in the middle of the two Buildings considerate 11.81 years, the degree of consolidation gets 97.6%, and the soil need 7.8cm settlement happen to finish the final settlement. Land subsidence caused by the high-rise building has the long duration characteristics.更多还原