Settlement Property And Dynamic Compaction Improvement Parameters Study For Red Sandstone Embankment

Red sandstone can not be used as good filler in roadbed, because it is prone to swell-collapse under water conditions and the strength will be reduced significantly, but also the compactness is hard to control. Therefore, how to solve the property of swell-collapse under water conditions of red sandstone and improve the compactness of the red sandstone gravel soil roadbed, reduce the post-construction settlement and uneven settlement of the roadbed, have been the urgent problems in roadbed construction of mountainous expressway. The dynamic compaction has been widely used in expressway embankment reinforcement due to its characteristics of simple device, convenient construction and low cost, but there is no corresponding standards or theoretical basis for the dynamic compaction reinforcement of the red sandstone gravel soil roadbed. Therefore, to carry out the research of red sandstone gravel soil roadbed treated by dynamic compaction and its settlement characteristics has important theoretical and practical significance.Changsha ring expressway is used as a backing project in the article, based on the results analysis of swell-collapse test and uniaxial compressive test on red sandstone under dry-wet cycle condition, the strength of red sandstone will have a significantly reduction after several dry-wet cycles. In order to make full use of red sandstone as roadbed filler, the red sandstone roadbed should be fully slaked, improved by mixing or coved and dynamic compacted in advance; based on the summary of dynamic compaction mechanism, the dynamic compaction mechanism of red sandstone roadbed is analyzed, and on the basis of analysis of roadbed deformation and roadbed settlement during the process of dynamic compaction, methods of combination of dynamic compaction and rolling to control the roadbed settlement and the control of soil deformation modulus by settlement of single dynamic compaction are proposed, thus the control of post-construction settlement can be realized; based on the analysis of field test results of red sandstone gravel soil roadbed before and after the dynamic compaction, it can be concluded that red sandstone gravel soil after the dynamic compaction can be filled in roadbed; on the basis of field monitoring of roadbed settlement and deformation of test section in Changsha ring expressway, the change law of the monitoring results is analyzed, and the monitoring results are predicted by the grey prediction model, a prediction model which is more suitable for the dynamic compaction roadbed is proposed at last.