Study On The Compaction Characteristic And Construction Control Of Red Clay And Gravel Mixed Fill Subgrade

This paper relies on the red clay and gravel mixed filling subgrade construction of Extension Project in Zun-Gui Highway.Systematically studied the compaction characteristics and construction control of this kind of subgrade through the ways of laboratory experiment,field test and numerical simulation.Some important conclusions drawn from this study are as follows:(1)Compared with the maximum dry density and the optimal water content of Heavy Compaction Test which used dry process of preparing red clay and wet process of preparing red clay,It is considered that the results by wet process are more beneficial to the engineering practice.And it is found that the compaction curve of red clay has two peaks,the second peak was regarded as the ture maximum dry density,its corresponding water content was regraded as the true optimal water content.(2)Through the vibration compaction experiment,it is found that there is an optimal collocation for the content of red clay and gravel.When 30% gravel was added to the rea clay,the compacting effect of the filler is the best.In the optimal clay-gravel mixture ratio,there is an optimal vibration parameter in the vibration compaction test of mixture.After experimental analysis,while the vibration frequency is 45 Hz and the vibration time is 5 min,the compaction efficiency is the best.(3)Through the on-site test section,it was clarified that the rolling water content of red clay should be between 26% and 48%;the thickness of loose paving should be controlled between 25 cm and 35 cm according to different moisture content,and the sheep foot roller can be used for vibratory pressure.Then,use an optical roller to level it.(4)The "sandwich" type that is applied to the red clay and gravel mixed roadbed is proposed.It is a layer of soil and a layer of stone.The influence of different soil and stone thickness on the stability of roadbed was simulated by Flac3 D software.The simulation results showed that the subgrade settlement was the smallest under the layer thickness of 2m gravel+ 2m red clay.(5)According to the results of indoor test and field test section analysis,a complete roadbed construction method,process and drainage prevention plan were proposed.Two representative sections were selected for post-construction monitoring.The monitoring results showed that the roadbed was basically stable and the subgradesettlement control standards were met.The rationality and feasibility of layered filling methods for soil and rock and construction control schemes are well established.In summary,this paper mainly focuses on red clay and gravel as the subgrade filler to carry out experimental research and field measurement.The research ideas,research methods,and experimental data will provide a reliable reference for the study of similar subgrade fillings in the future.The research results will be directly applied to the construction of red clay soil-stone mixed subgrade for the high-speed expansion project under construction in Xi’an,which will help us understand the high liquid limit red.The basic characteristics of clay,compaction characteristics and construction control as a roadbed filler have positive significance.At the same time,a complete set of construction control methods for red clay block-stone mixed roadbed was established,which accelerated the construction schedule,reduced the construction cost,saved costs,and further improved the design and construction level of the highway subgrade in China.