Development And Application Of Polyurethane For Repairing Mud Pumping Of Subgrade Of Ballastless Track

After completing the construction of the "Four Vertical and Four Horizontal" backbone network,China's high-speed railway gradually entered the period of safe operation and maintenance from the period of large-scale construction.With the increase of operation time,the mud pumping disease of subgrade bed surface layer of ballastless track gradually appears.At present,the research results on the mechanism of mud pumping of subgrade bed surface layer of ballastless track have been reported frequently,but there are few studies on the materials and technology of mud pumping disease treatment.Therefore,this paper takes the mud pumping disease of subgrade bed surface layer of ballastless track of high-speed railway as the research object,and develops a kind of polyurethane grouting material which is specially used to treat the the mud pumping disease of subgrade bed surface layer of ballastless track.And the environmental adaptability of polyurethane grouting material was studied through the water resistance test,temperature resistance test and operation performance test of low temperature.Finally,combined with the specific situation,a set of perfect rectification techniques for repairing mud pumping of subgrade of ballastless track is developed.The main research results are as follows:1)Based on the investigation and analysis of raw materials and additives,synthesis mechanism and synthesis process of polyurethane,polyether polyols,PM200,1,4-butanediol and xylene were identified as the main raw materials for the formulation of polyurethane grouting material,and one-step process was selected as the synthesis method of polyurethane grouting material.2)The effects of polyether polyol A,polyether polyol B,PM200,BDO and xylene on the gelling time,viscosity and basic mechanical properties of polyurethane grouting material were studied by the method of single factor control variable.And obtained the optimal mass ratio of main raw materials was 150:50:90:27:25.Under this mass ratio,the gelling time of polyurethane grouting material is 30 min,the viscosity is 287 mPa·s,the compressive and tensile strength are 36.3 and 22.9 MPa,and the elongation at break is 94.3%.3)According to the indoor simulation tests of polyurethane grouting materials under different operating conditions,it was found that: When water reacts with polyurethane grouting material,its mechanical properties will be seriously reduced;When the cured polyurethane grout(polyurethane elastomer)is immersed in water,the properties of the elastomer have little effect.The mechanical properties of polyurethane elastomer can be reduced by no more than 7% when it is in the high-low temperature cycling environment of-30?~50? or in the humid-hot environment of 40?and 93% humidity for a long time.While the mechanical properties of polyurethane elastomer can still be maintained at about 83% under the hot air environment of 100? for 96 hours,which indicates that the service life of polyurethane elastomer in the ordinary environment is at least 5 years.When polyurethane grouting material is used at low temperature(<5?),it is necessary to heat the grouting material to about 30?,so that it can quickly solidify in fine cracks.At the same time,grouting pressure should be increased appropriately to reduce the heat loss of grouting material in the process of flowing.4)The treatment of mud pumping of subgrade of ballastless track should follow the principle of "Prevention,Blockage,Injection and Drainage".Before the grouting,the water in the mud pumping area should be cleaned as far as possible to reduce the influence of water on the performance of polyurethane grouting material;after the grouting,the expansion joints and sockets of the upper track structure should be repaired,especially the weak joints between the expansion joints of the supporting layer and the sealing layer of the shoulder,and multi-layer waterproofing treatment should be carried out.