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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。
The black cotton soil in East Africa is a kind of strong expansive soil. Its expansion and shrinkage easily lead to serious damage to the structures such as foundations, road subgrade, slope and pile foundation, and the engineering problems are outstanding. Combined with the literature research, this paper introduces the research history, classification standards and engineering characteristics of expansive soils, especially black cotton soil. According to the national standard “Code for Construction of Expansive Soil Area” (GB 50112-2013), the free expansion of black cotton soil in East Africa was tested and its microstructure was observed by scanning electron microscope. The results show that the free expansion rate of black cotton soil in East Africa reaches 205%, and the swelling property of black cotton soil decreases after the wet-dry cycle. The microstructure of black cotton soil makes it more expansive and belongs to strong expansive soil. In addition, the adverse effects of black cotton soil on the pile foundation were also investigated and analyzed, and corresponding engineering measures were put forward.