摘要
为解决广西玉湛高速公路中高液限红黏土难以作为路基填料的技术难题,本文对该地区红黏土的物理力学性质进行了试验研究,并且开展了掺加河砂、山脚砂和消石灰的3 种红黏土改良试验研究.研究结果表明:随着掺砂量的增大,掺河砂改良红黏土的液限、塑限、塑性指数和毛细管水上升高度都随之降低,而加州承载比CBR值随之增大;当掺砂量为 15%时,掺河砂改良红黏土的液限和CBR值都满足规范要求,可以作为高速公路下路堤填料,但是如果作为高速公路上路堤和路床的填料,则需要进一步提高掺砂量.随着掺砂量的增大,掺山脚砂改良红黏土的最优含水率、液限、塑限、塑性指数随之降低,而最大干密度和CBR值随之增大;掺砂量为 30%时,掺山脚砂改良红黏土的CBR值、液限和塑性指数都满足规范要求,可以作为路基填料.掺加4%消石灰时,红黏土的 CBR 值、液限和塑性指数虽都满足相关规范关于路基填料的要求,但是液限已非常接近规范限值,因此建议消石灰掺量取 6%.现场填筑试验段结果表明,掺山脚砂或掺加消石灰改良高液限红黏土的方案都是可行的,改良土的液限、塑限、塑性指数和CBR值都有明显的改善,均可作为高速公路路基的填料.
Abstract
To solve the technical challenges of using high liquid limit red clay as subgrade filler in the Yuzhan Expressway in Guangxi,this paper carried out experimental research on the physical and mechanical properties of the local red clay,and conducted three kinds of red clay improvement experiments by adding river sand,sand at the foot of mountain,and slaked lime.The research results show that as the sand content increases,the liquid limit,plastic limit,plasticity index,and capillary water rising height of the river sand improved red clay all decrease,while the CBR value increases.When the sand content is 15%,both the liquid limit and CBR value of the river sand improved red clay meet the standard requirements,making it suitable as subgrade filler for the lower embankment of the expressway.However,higher sand content is required if used in the upper embankment and subgrade.With the increase of the sand content,the optimal water content,liquid limit,plastic limit,and plasticity index of the red clay improved by sand at the foot of mountain decrease,while the maximum dry density and CBR value increase.When the sand content is 30%,the CBR value,liquid limit,and plasticity index of the red clay improved by sand at the foot of mountain all meet the standard requirements,and the improved red clay can be used as subgrade filling.When 4%slaked lime is added,although the CBR value,liquid limit,and plasticity index of the improved red clay all meet the standard requirements,the liquid limit is very close to the specification limit,so it is recommended to take the amount of slaked lime as 6%.Field construction tests indicate that the schemes of improving the high liquid limit red clay by adding sand at the foot of mountain or adding slaked lime are feasible.The liquid limit,plastic limit,plasticity index,and CBR value of the improved soil have all been significantly improved.Two kinds of improved red clay can all be used as the filler of expressway subgrade.
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