Influence factors of strong self-weight collapsibility of Ili loess
ZHANG Ai-jun1, XING Yi-chuan2, HU Xin-li3, WANG Hai-tao3, GUO Min-xia1, ZHANG Bo1, GAO Ya-ping4
1. College of Water Resources and Architectural Engineering, Northwest A& F University, Yangling 712100, China; 2. China Institute of Water Resources and Hydropower Research, Beijing 100044, China; 3. Administration of Xinjiang Ili River Basin Development and Construction, Ili 835000, China; 4. Xinjiang Investigation and Design Institute of Water Resources and Hydropower, Urumchi 830000, China
Abstract:The deposition process of the loess in Ili valley in Xinjiang is controlled by circulation of Atlantic Ocean west wind, which is different from the deposition process of East Asia monsoon-controlled loess in Loess Plateau. Based on the in-situ comprehensive soaking tests on a channel project, it is been proved that Ili loess is a kind of strong collapsible loess. Furthermore, the collapsibility is characterized by early development, fast speed and large value. According to the field measurement, the maximum self-weight settlement reaches a large value of 352 cm, and the maximum collapsibility coefficient is 0.18 (p=200 kPa). From the history of sediment, the formation age of Ili loess is young. The deposition process is drier and cooler, and it is not influenced by hot and humid climate. Thus, there is less effect of rainfall-leaching on salinity, especially on calcium carbonate. In consideration of its physical property and mineral composition, the natural density, moisture content and saturation of Ili loess are low, while the dissolved salt content is high. The micro-structure observations indicate that the Ili loess has the characteristics of point contact, aerial structure form and few cementations, which lead to a highly unstable structure and strong potential collapsibility. These are historic and internal factors that cause strong collapsibility.
[1] GB 50025—2004 湿陷性黄土地区建筑规范[S]. 2004. (GB 50025—2004 Code for building construction in collapsible loess zone[S]. 2004. (in Chinese)) [2] 邵生俊, 李 骏, 李国良, 等. 大厚度自重湿陷黄土湿陷变形评价方法的研究[J], 岩土工程学报, 2015, 37(6): 965-978. (SHAO Sheng-jun, LI Jun, LI Guo-liang, et al. Evaluation method for self-weight collapsible deformation of large thickness loess foundation[J]. Chinese Journal of Geotechnical Engineering, 2015, 37(6): 965-978. (in Chinese)) [3] 姚志华, 黄雪峰, 陈正汉, 等. 关于黄土湿陷性评价和剩余湿陷量的新认识[J]. 岩土力学, 2014, 35(4): 998-1006. (YAO Zhi-hua, HUANG Xue-feng, CHEN Zheng-han, et al. New recognition of collapsibility evaluation and remnant collapse of loess[J]. Rock and Soil Mechanics, 2014, 35(4): 998-1006. (in Chinese)) [4] 黄雪峰, 陈正汉, 哈 双, 等. 大厚度自重湿陷性黄土场地湿陷变形特征的大型现场浸水试验研究[J]. 岩土工程学报, 2006, 28(3): 382-389. (HUANG Xue-feng, CHEN Zheng-han, HA Shuang, et al. Large area field immersion tests on characteristics of deformation of self weight collapse loess under overburden pression[J]. Chinese Journal of Geotechnical Engineering, 2006, 28(3): 382-389. (in Chinese)) [5] 谢定义. 试论我国黄土力学研究中的若干新趋势[J]. 岩土工程学报, 2001, 23(1): 3-13. (XIE Ding-yi. Exploration of some new tendencies in research of loess soil mechanics[J]. Chinese Journal of Geotechnical Engineering, 2001, 23(1): 3-13. (in Chinese)) [6] 张苏民, 郑建国. 湿陷性黄土(Q 3 )的增湿变形特性[J]. 岩土工程学报, 1990, 12(4): 12-31. (ZHANG Su-min, ZHENG Jian-guo. Collapsible loess(Q3) of humidification deformation characteristics[J]. Chinese Journal of Geotechnical Engineering, 1990, 12(4): 12-31. (in Chinese)) [7] 张爱军, 邢义川. 黄土非饱和增湿的湿陷过程特性[C]// 湿陷性黄土研究与工程. 罗宇生, 汪国烈. 北京: 中国建筑出版社, 2001: 123-126. (ZHANG Ai-jun, XING Yi-chuan. The collapsible characteristics of unsaturated loess during humidifying process[C]// Research and Engineering of Collapsible Loess. LUO Yu-sheng, WANG Guo-lie. Beijing: China Architecture and Building Press, 2001: 123-126. (in Chinese)) [8] 刘保健, 谢永利, 于友成. 黄土非饱和入渗规律原位试验研究[J]. 岩石力学与工程学报, 2014, 23(24): 4156-4160. (LIU Bao-jian, XIE Yong-li, YU You-cheng. In-situ testing study on infiltration in unsaturated loess[J]. Chinese Journal of Rock Mechanics and Engineering, 2014, 23(24): 4156-4160. (in Chinese)) [9] 宋友桂, 史正涛, 方小敏, 等. 伊犁黄土的磁学性质及其与黄土高原对比[J]. 中国科学:地球科学, 2010(1): 61-72. (SONG You-gui, SHI Zheng-tao, FANG Xiao-min, et al. Loess magnetic properties in the Ili basin and their correlation with the Chinese loess plateau[J]. Science China Earth Science, 2010(1): 61-72. (in Chinese)) [10] 李传想, 宋友桂, 千琳勃, 等. 中亚昭苏黄土剖面粒度记录的末次冰期以来气候变化历史[J]. 沉积学报, 2011(6): 1170-1179. (LI Chuan-xiang, SONG You-gui, QIAN Lin-bo, et al. History of climate recorded by grain size at the Zhaosu loess section in the central asia since the last glacial period[J]. Acta Sedimentologica Sinica, 2011(6): 1170-1179. (in Chinese))