Research On Construction Technique Of The Polyurethane-detritus Mixture For The Treatment Of Railway Subgrade Mud Pumping

Mud pumping is a common subgrade disease of ballasted track.It is caused by the subgrade softening when the water accumulation on the top of the subgrade,and then the sleeper moves up and down under the action of the train cyclic load,which causes the fine soil and water in the subgrade soil to be repeatedly pumped to form mud,and the mud will occupy the track bed and turn out of the track bed.This disease is prone to recurrence and difficult to eradicate.The influence caused by mud pumping is firstly,the ballast particles sank into the subgrade,then cause the deformation of track structure and the irregularity of the line,this will seriously affect the safety of train operation.Secondly,the mud pumping makes the track bed hardening,this causes wheel rail impact force increases,and further aggravates the track and subgrade diseases.The waterproof technology of the mixing and stirring of polyurethane and graded detritus were studied in view of this problem.This technology is mixing and stirring of polyurethane and graded detritus form a waterproof layer of polyurethane-detritus mixture,which is spread it on the top of the subgrade,and form an isolation layer between the subgrade and the ballast bed,from this to prevent mud pumping.According to the numerical simulation research,technological test research,research on site construction technology and dynamic test verification,the following research conclusions are as follows:(1)The finite element model of polyurethane-detritus mixture was established for numerical simulation,the stress distribution is analyzed,the mechanical characteristics and dynamic response characteristics are analyzed.The results show that the polyurethanedetritus mixture is increased,the stress distribution in the subgrade bed structure is more favorable,the stability of the bed is enhanced,the vibration response of the bed is further weakened,after comparative analysis,the economical and reasonable thickness of polyurethane-detritus mixture should be controlled in 5cm～8cm.(2)The technological test of polyurethane-detritus mixture was carried out,it is shown that the waterproof property of polyurethane adhesive is of impermeable magnitude when the amount of polyurethane adhesive is 9%,its mechanical properties meet the strength requirements,and it is a more reasonable scheme for setting the content of polyurethane adhesive.(3)Through the research on the construction technology of the polyurethane-detritus mixture,it is proposed to add a pair of jacks under every 5～7 sleepers,in order to improve the efficiency of construction and ensure the construction quality.Through the construction technology research,the correctness of construction procedure design of the polyurethanedetritus mixture was verified,the feasibility of using the section construction method of "flat trolley + labour",the measures to prevent polyurethane adhesive from sticking to the pot are effective.In conclusion,the construction technology is worthy of reference and promotion.(4)Through the train running dynamic detection and evaluation,it is known that through the polyurethane-detritus mixture treatment of heavy-haul railway mud pumping,the average vibration acceleration and velocity of sleeper are obviously reduced.After two years of actual operation of heavy haul railway,the project has been further tested,after the rectification,there is no mud pumping again.Therefore,it is concluded that the method is effective in the treatment of subgrade mud pumping,and the train operation safety.