The Optimization And Simulation Analysis With Cement-Soil Compaction Piles Strengthening The Existing Railway Subgrade

This paper is based on the background of speed increase reform project of Ningqi existing railway, combined with the program of reinforcing subgrade by cement-soil compaction pile, study on the influencing factors of the characteristics of compaction piles using cement and silty clay, and optimizes the compaction constructing technique. The main contents are as follows:Firstly, experimental studied on effects of hammer bottom shape on the compaction effect. According to the bottom shape of the hammer, three cases of flat bottom, conical and circular were considered. The relationship between the shape, the distance,the compaction times and the compaction force of the hammer was determined by the soil pressure box arranged on the bottom and side of the pile. Through the comparison of experiments, the effect of the flat bottomed hammer has the largest vertical compaction force, and cone bottom hammer has the largest lateral compaction force. Different tamping hammer effects of soil compaction were detected by electron micro penetrometer. After electronic micro penetrometer testing degree of compaction standard is obtained, the different rammer’s effects of soil compaction were detected. According to the test results of the density and compaction force, the optimum shape and compaction times were put forward.Secondly, the indoor subgrade reinforcement model using 0.8m cement soil pile which contains 10% cement content was established. Using cone bottom hammer selected by rammed earth test, the strengthening process of cement soil compaction pile was simulated in model box. Through experiments, the construction method of cement-soil compaction pile affect pile-surrounding soil’s compaction degree in the range of about 1.0D, and the pile compaction force can reach about 300 kPa under optimal compaction times, and the ability of the pile body to bear the dynamic load is gradually strengthened with the strength of cement soil strengthened.Finally, the model was simulated and analyzed by using ABAQUS finite element software. On the one hand, the bearing capacity of single pile composite foundation with different lateral compaction force and different pile length was simulated. By analyzing, it is known that 1.5m pile length is optimal length. On the other hand, the reinforcement effect under the static load of the train in different length of pile arrangement was simulated. By comparison, it can be known that the reinforcing effect of the reinforcing piles on both sides of the steel rail is important to the strengthening effect of the subgrade, which can not be shortened and the line center and the outside of the rail can be properly reduced.This paper optimized correlative constructing technique of strengthening existing railway subgrade by cement-soil compaction pile by means of experiment and numerical simulation, expected to play a certain role in the future construction.