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天津滨海地区地处渤海湾西岸,晚新生代沉积了巨厚的松散沉积物。地下水位下降、地层自然固结、地表载荷的加速增长等复合因素造成了严重的地面沉降。利用在天津滨海新区塘沽地区施工的一眼1 226 m全取芯钻孔,通过原状样品测试分析,系统研究了晚新生代土层的物理力学性质、黏性土固结特征,并结合欠固结黏性土层沉降量计算等方法阐述了土层固结状态空间特征,探讨了土层固结特征与地面沉降的相关关系。结果表明:该地区0~100 m深度土层具有低天然密度、高孔隙比、高含水率、高压缩性等特点,表现出软土的性质,在地表荷载增大的情况下,易发生地面沉降;100~550 m的黏性土大都处于超固结和微超固结状态,主要是由于过去地下水的大量开采造成的;550 m以下的黏性土多为正常固结,局部存在欠固结黏性土夹层。钻孔中存在合计约218 m的欠固结黏性土夹层,这些欠固结黏性土夹层在自重应力下的最终沉降量为1 985 mm,沉降量最大的土层对应于第1、6含水组,分别达614 mm和665 mm,这一沉降过程完成所需时间为数十年甚至上百年。
Tianjin Binhai area is located in the west coast of the Bohai Bay, Late Cenozoic deposited a huge thick loose sediments. Subsidence of groundwater level, natural stratification of strata and accelerated acceleration of surface loads have resulted in serious land subsidence. Taking a 1 226 m full coring borehole constructed in Tanggu area of Binhai New Area, Tianjin, the physical and mechanical properties of the Late Cenozoic soil and the consolidation characteristics of cohesive soil were systematically studied through the testing and analysis of the undisturbed samples. Settlement of clay and other methods to calculate the spatial characteristics of the consolidation state of the soil, discussed the relationship between soil consolidation characteristics and land subsidence. The results show that the depth of 0-100 m in this area is characterized by low natural density, high void ratio, high water content and high compressibility, which shows the properties of soft soil. Under the condition of increasing surface load, Most of the clay of 100-550 m is in overconsolidation and micro-overconsolidation state, mainly due to the massive exploitation of groundwater in the past; the clay below 550 m is mostly normal consolidation, Results cohesive soil interlayer. There are a total of about 218 m of underconsolidated cohesive interlayer in the borehole. The ultimate settlement of these underconsolidated cohesive intercalations under gravity load is 1 985 mm, The water-bearing groups, which are 614 mm and 665 mm, respectively, require decades or even centuries to complete.