Study Of Subgrade Construction Technique On The Accumulations

Because of the intensively effect of the "5·12 Wenchuan Earthquake", geological hazard such as landfall, landside and debris flow etc was happened, a large quantity of soil and stone was slipped from the mountains down to stable foot, formed many friable accumulations with the ultra-large size stone and thick covering layer. In the restoration and reconstruction project of the highway of S303 between Yingxiu and Wolong in Sichuan Provence, part of the highway passes through some accumulations. So, in order to reduce the failure of the pavement and subgrade on the accumulations when the highway is in the use in the future, problems were faced in construction:How to control the settlement of the friable accumulations to built subgrade on it.Based on these situations, two test sections was set up on two accumulations in this project. The research of the treatment of accumulations and the filling of subgrade was carried out from three aspects--machinery selection, construction technology and quality testing and evaluation. Based on the current appliance situation of the construction machine, the research of the machinery selection was operated from the aspects of technique and economy to choose the optimal program, then test in the field was implemented to determine the parameter of construction machine. Based on the results of the machinery selection, the research of the construction technology was carried out to determine the control parameter of construction quality and the procedure of construction. According to present testing method of compaction quality and the work method of construction machine, the research of quality testing and evaluation was carried out to determine the appropriate index of compaction and the method of quality testing and evaluation, then made standard of quality evaluation with test in the field.For the treatment of accumulations, dynamic compaction has obviously advantage in technique and economy, when machinery selection was carried out. In the test of dynamic compaction, the energy of tamping, the distance of tamping points, the number of tamping times and the management standards values of the settlement after the last two tamping. In the construction of subgrade filling with vibratory roller, the number of compaction times, the speed of the machine, and the thickness and coefficient of the layer. Based on the test in the field, construction process, the method of quality testing and the standard of evaluation in the treatment and compaction of accumulation subgrade have been determined.