随着地下空间设施的日益拥挤，地下结构的建设深度不断增大，对深层土体的研究显得越发重要.通过研究末次冰期以来中国东海海平面和大气温度的变化，分析上海深层土(⑥～⑨层)的沉积环境，发现⑥～⑨层土沉积环境依次为：湖泊、河流-滨海、湖泊和河流-滨海、河流.通过运用Becker能量法分析高压固结试验结果得出⑧层土超固结比在3.0左右；通过全自动控制静力三轴仪三轴固结不排水试验发现土样破坏时的孔压力系数为负值，且呈现出强超固结土的性状.分别从应力和非应力的角度分析⑧层土产生超固结的原因：应力原因包括地下水位下降、土体孔隙水消散，导致土体中的有效应力有所增加；非应力原因包括长时间的次固结作用和土体的胶结作用.
With the increasing congestion of underground space facilities, the depths of underground structures are increasing. And the study of deep soils is becoming more and more important. The sedimentary environment of deep soil (the 6th—9th layer clays) in Shanghai was analyzed by studying the sea level and atmospheric temperature changes in the East China Sea since the late Pleistocene. The sedimentary environments of the 6th to the 9th layer clays were found to be lakes, rivers-marinas, lakes and rivers-marinas, rivers. By using the Becker energy method to analyze the results of the high-pressure consolidation test, the over-consolidation ratio of the 8th layer clay was about 3.0. Through the triaxial consolidated undrain test, it was found that the pore pressure coefficient while soil sample failure was negative, showing the characteristics of strong over-consolidated soil. From the perspective of stress and non-stress, the causes of over-consolidation of the 8th layer clay were analyzed. With the groundwater level decreasing, the pore water in the soil dissipated. And the increase of effective stress in the soil was the cause of stress. The long-term secondary consolidation and cementation were the reasons of non-stress.
［1］刘映晶, 陈锦剑, 王建华, 等. 逆作土方通道式施工工艺对基坑变形的影响［J］. 上海交通大学学报, 2012, 46(1): 89-93.
LIU Yingjing, CHEN Jinjian, WANG Jianhua, et al. Effect of channel-type transport technology of earthwork on the deformation of top-down deep foundation pit ［J］. Journal of Shanghai Jiao Tong University, 2012, 46(1): 89-93.
［2］TORRANCE J K. On the role of chemistry in the development and behavior of the sensitive marine clays of Canada and Scandinavia［J］. Canadian Geotechnical Journal, 1975, 12(3): 326-335.
［3］CHUNG C K, FINNO R J. Influence of depositional processes on the geotechnical parameters of Chicago glacial clays［J］. Engineering Geology, 1992, 32(4): 225-242.
［4］OHTSUBO M, EGASHIRA K, KASHIMA K. Depositional and post-depositional geochemistry, and its correlation with the geotechnical properties of marine clays in Ariake Bay, Japan［J］. Geotechnique, 1995, 45(3): 509-523.
［5］邵光辉, 刘松玉. 连云港海相粘土的沉积化学及其对土基本性质的影响［J］. 工程地质学报, 2006, 14(Sup): 86-91.
SHAO Guanghui, LIU Songyu. The influence of depositional chemistry on geotechnical properties of Lianyungang marine clays［J］. Journal of Engineering Geology, 2006, 14(Sup): 86-91.
［6］LIU S Y, SHAO G H, DU Y J, et al. Depositional and geotechnical properties of marine clays in Lian-yungang, China［J］. Engineering Geology, 2011, 121(1/2): 66-74.
［7］魏道垛, 胡中雄. 上海浅层地基土的前期固结压力及有关压缩性参数的试验研究［J］. 岩土工程学报, 1980, 2(4): 13-22.
WEI Daoduo, HU Zhongxiong. Experimental study of preconsolidation pressure and compressibility parameters of Shanghai subsoil［J］. Chinese Journal of Geotechnical Engineering, 1980, 2(4): 13-22.
［8］魏道垛, 杨熙章. 上海软土的静止侧压力系数K0的分布和变化规律的研究［J］. 大坝观测与土工测试, 1988(3): 36-43.
WEI Daoduo, YANG Xizhang. Variation of K0-values of Shanghai soft soils［J］. Dam Observation and Geotechnical Testing, 1988(3): 36-43.
［9］武朝军, 叶冠林, 王建华. 上海莲花路浅部土层超固结特性试验研究［J］. 上海交通大学学报, 2016, 50(3): 331-335.
WU Chaojun, YE Guanlin, WANG Jianhua. Experimental study of overconsolidation behavior of the upper Shanghai clays in Lianhua road［J］. Journal of Shanghai Jiao Tong University, 2016, 50(3): 331-335.
［10］严学新, 史玉金. 上海市工程地质结构特征［J］. 上海地质, 2006(4): 19-24.
YAN Xuexin, SHI Yujing. Structure characteristic of engineering geology in Shanghai［J］. Shanghai Geology, 2006(4): 19-24.
［11］邱金波, 李晓. 上海市第四纪地质与沉积环境［M］. 上海: 上海科学技术出版社, 2007: 124-125.
QIU Jinbo, LI Xiao. Shanghai quaternary geology and sedimentary environment ［M］. Shanghai: Shanghai Scientific & Technical Publishers, 2007: 124-125.
［12］王靖泰, 汪品先. 中国东部晚更新世以来海面升降与气候变化的关系［J］. 地理学报, 1980, 35(4): 299-312.
WANG Jingtai, WANG Pinxian. Relationship between sea-level changes and climatic fluctuations in East China since late Pleistocene［J］. Acta Geographica Sinica, 1980, 35(4): 299-312.
［13］王张华, 丘金波, 冉莉华, 等. 长江三角洲南部地区晚更新世年代地层和海水进退［J］. 海洋地质与第四纪地质, 2004, 24(4): 1-8.
WANG Zhanghua, QIU Jinbo, RAN Lihua, et al. Chronostratigraphy and transgression/regression during late Pleistocene in the southern Changjiang (Yangtze) River delta plain［J］. Marine Geology & Quaternary Geology, 2004, 24(4): 1-8.
［14］BECKER D E, CROOKS J H A, BEEN K, et al. Work as a criterion for determining in situ and yield stresses in clays［J］. Canadian Geotechnical Journal, 1987, 24(4): 549-564.
［15］王建华, 张璐璐, 陈锦剑. 土力学与地基基础［M］. 北京: 中国建筑工业出版社, 2011: 136-137.
WANG Jianhua, ZHANG Lulu, CHEN Jinjian. Soil mechanics and foundation ［M］. Beijing: China Architecture & Building Press, 2011: 136-137.
［16］张阿根, 魏子新.上海地面沉降研究的过去、现在与未来［J］. 水文地质工程地质, 2002, 29(5): 72-75.
ZHANG Agen, WEI Zixin. Past, present and future research on land subsidence in Shanghai city ［J］. Hydrogeology and Engineering Geology, 2002, 29(5): 72-75.
［17］BJERRUM L. Engineering geology of Norwegian normally-consolidated marine clays as related to settlements of buildings［J］. Geotechnique, 1967, 17(2): 83-118.
［18］钱家欢, 殷宗泽. 土工原理与计算［M］. 第2版. 北京: 中国水利水电出版社, 1996: 269-285.
QIAN Jiahuan, YIN Zongze. The earthwork principle and calculation ［M］. 2nd ed. Beijing: China Water and Power Press, 1996: 269-285.
［19］王冠英, 肖树芳, 习春飞. 海积软土先期固结压力与结构强度的关系及成因分析［J］.世界地质, 2004, 23(1): 69-74.
WANG Guanying, XIAO Shufang, XI Chunfei. Relationship between preconsolidition pressure and structural strenth of marine soft clay and the cause analysis ［J］. Global Geology, 2004, 23(1): 69-74.
