Abstract：Research purposes: The Q2 overlapping clay soil is widely distributed in Ningxiang along the Changsha －Yiyang Railway and it is hardly found in other regions． To choose the proper method to treat this type of soil is the key problem because the subgrade settlement of intercity railway must be controlled strictly． Through the in － situ investigation，drilling exploration，in － situ test and indoor experiment，etc，the study is done on the soil＇s morphology and genesis，physical property，strength characteristics，deformation consolidation and expansive property to know the engineering characteristics of the overlapping clay soil for providing the reliable basis for the subgrade design．
Research conclusions: The overlapping soil is formed from the red clay caused by the effect of leaching and depositing under the warm and wet environment，and it is a typical unsaturated soil with void ratio being bigger than red clay and saturation degree always being less than 90%． The overlapping soil with high liquid limit and high liquidity index is a high liquid limit soil． This soil is generally in plastic － hard status with strong strength and its bearing capasity can reach to 200kPa in natural condition． The overlapping soil belongs to the medium compressible soil，and the compressibility of the overlapping soil in the low layer is bigger than the soil in the upper layer． This soil is a typical over － consolidated soil with the over consolidation ratio of surface soil up to 15． 4 and the overlapping soil belongs to weak expansive soil．
Kong Lingwei，Guo Aiguo，Lv haibo， etc． Fundamental Property and Microstructure Model of Red Clay［J］．CHINESE Journal of Rock Mechanics and Engineering，2001( S1) : 973 －977．
Yang Qing，He Jie，Luan Maotian． Comparative Study on Shear Strength of Unsaturated Red Clay and Expansive Soils［J］． Rock and Soil Mechanics，2003( 1) :13 －16．
Yang Guolin，Wang Liangliang． Statistics Analysis of Physical and Mechanic Parameters about Red Clay along Passenger Dedicated Line ［J］． Journal of Railway Engineering Society， 2009( 3) : 1 －6．
Wu Shanyang． Study on the Engineering Geological Properties of Plinthitic Soil in Changsha ［J］． Site Investigation Science and Technology， 1992( 5) : 20 －22．
Wang chunlin． On the Origin of Quaternary Worm －like Net － veined Red ( laterite) Soil in Hunan Province and Its Significant in Neotectonic Studies［J］． Natural Sciences Journal of Hunan Normal University， 1986( 1) :100 －106．
Zheng Yanming，Zhou Shangzhe，Kang Jiancheng，etc．On the Southern Vermicular Red Soil and Its Forming Environment［J］． Journal of Jiaying University，2005( 3) : 79 －83．
Li Zhenyu． Numerical and Experimental Research on Red Clay Foundation Settlement of Wuhan －Guangzhou Passenger Line ［D］． Changsha: Sentral South University，2007．
2011, Vol. 28 
版权所有 © 2014 《铁道工程学报》编辑部