东非地区黑棉土工程特性和桩基病害处理*
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(1 清华大学土木工程系，北京 100084；2 清华大学土木工程安全与耐久教育部重点实验室，北京 100084；3 中国路桥工程有限责任公司，北京 100011)［摘要］东非地区黑棉土是一种强膨胀性土，它的胀缩变形易导致建筑物地基、道路路基、边坡、桩基础等结构受到严重破坏，工程问题突出。结合文献调研，对膨胀土尤其是黑棉土的研究历史、分类标准、工程特性进行了综合介绍。根据国家标准《膨胀土地区建筑技术规范》(GB 50112—2013)对东非地区黑棉土的自由膨胀率进行了测试，并采用扫描电子显微镜对其微观结构进行了观测。结果表明，东非地区黑棉土的自由膨胀率可达205%，干湿循环后黑棉土的膨胀性能下降；黑棉土微观结构使其具有更强的膨胀性，属于强膨胀土。另外，也调研并分析了黑棉土对桩基的不利影响，提出了相应的工程处理措施。［关键词］黑棉土; 工程特性; 电镜扫描; 桩基; 工程措施中图分类号：TU473.1 文献标识码：A 文章编号：1002-848X(2015)01-0072-05Engineering properties of black cotton soil in East Africa and pile foundation disease treatmentZhang Dafeng1, Yang Jun1,2, Li Lianyou3, Shen Zhaopu3(1 Department of Civil Engineering, Tsinghua University, Beijing 100084, China; 2 Key Laboratory of Civil Engineering Safety and Durability of China Education Ministry, Beijing 100084, China; 3 China Road and Bridge Corporation, Beijing 100011, China)Abstract: Black cotton soil in East Africa is one kind of strong expansive soil. Its swelling and shrinkage deformation can damage building foundations, road embankment, slope, pile foundation and other structures easily.The engineering problems are very prominent. Combining literature study, the research history, classification criteria, engineering properties of expansive soil expecially black cotton soil were introduced in detail. Referring to national standard of Technical specifications for construction ground in expanding soil areas (GB 50112—2013), the free expansion ratio of black cotton soil in East Africa is tested, and its microstructure is observed by scanning electron microscopy. The result shows that the free expansion ratio of black cotton soil in East Africa can reach 205% and the expansion capability decreases after dry-wet cycle. The special microstructure of black cotton soil contributes to strong expansion characteristic. Black cotton belongs to the strong expansive soil. In addition, the adverse impacts on pile foundation were analyzed and corresponding treatment measures were given.Keywords: black cotton soil; engineering property; electron microscope scanning; pile foundation; treatment measure*国家重点基础研究发展计划（2014CB047004）。通迅作者：杨军，博士，副研究员，博导，Email:junyang@mail.tsinghua.edu.cn。参考文献［1］ORIOLA F，MOSES G. Groundnut shell ash stabilization of black cotton soil［J］. Electronic Journal of Geotechnical Engineering, 2010, 15(D): 415-428.［2］FREDLUND D G，RAHARDJO H. Soil mechanics for unsaturated soils［M］. New York: John Wiley & Sons, Inc., 1993: 1-19.［3］JONES D, HOLTZ J. Expansive soils: hidden disaster ［J］. Civil Engineering, 1973, 43(8):54.［4］FREDLUND D G, RAHARDJO H. 非饱和土力学［M］. 陈仲颐,张在明，陈愈炯，等译. 北京:中国建筑工业出版社, 1997: 15-18.［5］GB 50112—2013膨胀土地区建筑技术规范［S］. 北京:中国建筑工业出版社, 2013.［6］Earth Manual［M］. Denver: United States Bureau of Reclamation, 1973.［7］Indian Standard classification and identification of soils for general engineering purposes［S］. New Delhi: Bereau of Indian Standards, 1970.［8］WILLIAMS A B, DONALDSON G W. Building on expansive soils in South Africa［C］//Proceedings of 4th International Conference on Expansive Soils. Denver: ASCE, 1980.［9］张爱军，哈岸英，骆亚生. 压实膨胀土的膨胀变形规律与计算模式［J］. 岩石力学与工程学报, 2005, 24(7): 1236-1241.［10］郑健龙, 杨和平. 公路膨胀土工程 ［M］. 北京: 人民交通出版社, 2009.［11］郭爱国，刘观仕，孔令伟，等. 高速公路建设中膨胀土特性的试验研究［J］. 岩土力学, 2005, 26(3): 397-403.［12］杨宏伟,赵鹏程,吴超,等. 扫描电子显微镜在摩擦学研究中的应用［J］. 合成润滑材料, 2011, 38(2): 23-27.［13］李生林, 施斌, 杜延军.中国膨胀土工程地质研究［J］.自然杂志, 1997, 19(2): 82-86.［14］王年香，顾荣伟，章为民，等. 膨胀土中单桩性状的模型试验研究［J］. 岩土工程学报, 2008, 30(1): 56-60.［15］(苏) 索洛昌 E A (Сорочан Е А). 膨胀土上建筑物的设计与施工［M］. 徐祖森,等译. 北京: 中国建筑工业出版社, 1982.［16］陈善雄, 李伏保, 孔令伟. 弱膨胀土工程特性及路基处治对策［J］. 岩土力学, 2006, 27(3): 353-359.［17］YADU L, TRIPATHI R K, SINGH D. Comparison of fly ash and rice husk ash stabilized black cotton soil［J］. International Journal of Earth Sciences and Engineering, 2011, 4(6): 42-45.［18］OSINUBI K J, OYELAKIN M A, EBEREMU A O. Improvement of black cotton soil with ordinary portland cement-locust bean waste ash blend［J］. Electronic Journal of Geotechical Engineering, 2011, 16(E): 619-627.［19］MILLER D J. Expansive soils: problems and practice in foundation and pavement engineering［M］. New York: John Wiley & Sons, Inc., 1997
