Study On Red Sandstone Roadbed Construction Technology Of Expressway With Damp-heat Mountain Climate

The red sandstone is widely distributed in Jiangxi province. A number of expressways in Jiangxi province use the red sandstone as the roadbed filler. Since red sandstone shows an property of slaking, some problems would arise if it used as embankment filling material without modified.On the one hand, it’s hard to achieve compaction, on the other hand, it may even cause the subgrade settlement and instability which would bring structural damage to the pavement.To solve this Problem, considering the characteristics of mountain climate in Jiangxi province and combined with the subject "Research on Quality Appraisal System of Red Sandstone Roadbed Filling with Damp-heat Mountain Climate" put forward by Jiangxi Province Communication Science and Technology Development Fun,the paper made an specific research on the aspects of red sandstone roadbed disease, engineering properties and modification which is based on the RuiXun expressway through a synthetically adoption of survey on the road in red sandstone,laboratory experiment, in-site test and numerical calculation methods.Taking the already built red sandstone embankment expressways in Jiangxi province as the research objects, The research involved on-site investigation on the type and degree of the pavement disease and analysed the main cause of red sandstone roadbed disease through excavation as well as the reference of the previous repair record.Based on the disintegration testing of red sandstone, whose conditions are constant natural conditions, interval sprinkling and water immersion test and the analysing of the grading of red sandstone crumbling pellets, the solubility of ions in hydrolysate and quality change, deep research on disintegration mechanism causing by cementation weakened has been made. Studies on modification of red sandstone used as roadbed filler found that adding7%lime could effectively inhibit the disintegration of red sandstone and Manual sprinkler combining with mechanical crushing is the most economical and reasonable method to accelerate disintegration. In order to have a quantitative evaluation of the slaking degree of red sandstone filling, the fractal dimension has been used as a filler control index. Meanwhile compactness, gas content, moisture content, California Bearing Ratio (CBR)has been used as filling quality control indexes. This paper puts forward a method to control the filling gradation by detecting the packing fractal dimension of red sandstone in the rolling process and marks it qualified when the fractal dimension reach more than2.6, while controlling the compaction degree≥95%, the moisture content of10%-12%. gas rate≤2%.According to the engineering properties of the red sandstone in Jiangxi province, the paper puts forward considerable way to maintain the section of expressway which would services as powerful guideline for the repairing of the red sandstone roadbed theoretically and practically.