Improvement Of Fully Weathered Red-Layered Siltstone Fill In Roadbed And Compaction Test Research

As the most widely distributed and representative red layer in China,the southwestern red layer is mainly distributed in Sichuan,Yunnan and Guizhou.The red layer forms a certain depth of weathering zone under the action of internal and external agencies over a long time.Due to the different degrees of weathering,there are large regional differences in the engineering properties of the red layer weathered material filler.This thesis is based on the Yibin Transit Expressway project,where the red-layered siltstone with fully weathered materials are widely distributed along the highway.The gradation of the filler is uniform and the compaction degree is not up to the engineering requirement.So it is not suitable for directly using as filler for roadbed construction.If we can use the red-layered weathering materials for filling construction in the southwest mountainous area,we will save a lot of high cost for filling material extraction and long-distance transportation,and avoid environmental problems caused by excavation and disposal.Therefore,in this thesis,a series of indoor geotechnical tests were conducted on the fully weathered red-layered siltstone filler that were taken from the Yibin Transit Expressway.The weathered material was improved by using the method of mixing with gravel to study the effect of physical improvement.Based on the constructed mini-sandbox model,fixed-point impact simulated compaction tests were carried out on the model fill with different bottom surface areas of press plates.According to the test results,the influence of compaction machinesoil contact area on the compaction effect of the model fill was analyzed to provide some reference for the improvement of the compaction process of the red-layered siltstone with fully weathered material fill.The main work and results of the study are as follows:(1)Based on indoor geotechnical tests,a series of indoor geotechnical tests such as water content,particle analysis,limiting water content and standard compaction test were conducted on soil samples of fully weathered red siltstone to obtain the basic physical and mechanical indexes of the soil samples and to clarify the filler category of fully weathered red siltstone.(2)In view of the problem that the filler is not easy to be compacted,by comparing the advantages and disadvantages of physical improvement and chemical improvement,the design of physical improvement of the red-layered siltstone with fully weathered material filler is studied,and standard compaction tests are conducted on the improved filler mixed with different proportions of gravel to investigate the influence of the gravel mixing ratio on the compaction performance of the improved filler.(3)Based on the constructed small sandbox model,indoor simulated compaction tests for compaction and compaction testing of roadbed construction of red-layered siltstone with fully weathered materials were carried out to analyze the effect of compaction machine-soil contact area on the compaction effect of red-layered siltstone with fully weathered materials fillers.The red layer is widely distributed in China,and the research results of this thesis can be promoted and applied to the construction of new highway projects in other areas where red layer weathering materials are widely distributed,such as Hunan,Gansu and Jiangxi,which not only saves engineering investment in terms of economy,but also protects the environment and has good application prospects.