Research On New Materials And Construction Technology Of Railway Subgrade Mud Pumping

The disasters of existing railway subgrade have become more and more serious, especially the mud pumping problem. Under the wetting-induced softening of underground water, the strength of subgrade soil decreases rapidly. Under the action of train dynamic load, the subgrade soil could be liquefied into mud, and the sleepers would vibrate up and down when the trains pass. There would be a pumping force for the mud, and the mud could be brought out through the ballast by the pumping force. The ballast would sink into the subgrade surface layer, which causes line irregularity and seriously endanger the safety of train. Based on the research background, a new glue injection material was developed, which has good properties such as high strength, impact resistance, waterproof and easy construction. This new glue can be made the gravel glued layer mixed with the gravel. The glued layer can prevent the surface water into the subgrade and prevent the mud in subgrade into the ballast. The reliability of the mixed glued layer was verified by the compressive strength tests and the bending strength tests. The in-site construction technology was determined by the analysis of advantages in different construction technologies. The treatment effect of the glue and the geotextile were comparative analyzed by testing the sleeper’s acceleration when the trains pass. The main conclusions of this research are as follows:(1) The domestic railway subgrade mud pumping mechanism and regulation measures has been summarized by data investigation and collection. Subgrade bed soil, water and train dynamic load are the three main factors of mud pumping, and they are mainly considered in mud pumping renovating. The subgrade bed soil condition is the prerequisite conditions, water is the essential factor, the train dynamic load is external factors, remediation measures mainly focus on these three factors.(2) The different contents of various components on the impact strength and compressive strength of polyurethane materials and the influence of amine based catalysts on the solidification time of the polyurethane materials has been studied by laboratory experiments, Based on influence,the formula of the glue has been determined. And the compressive strength and flexural strength of the test block were studied, which is mixed of glue and crushed stone. The feasibility of glue for mud pumping renovating in railway subgrade has been verified.(3) The diffusion and cementation of glue in gravel and different soil layers were analyzed by laboratory tests. The advantages and disadvantages of injection and spray type construction technologies were analyzed. The advantages of spray type construction technology are homogeneous mix, good operability, less material waste, and reasonable economy. The spray type construction technology costs more time than the injection type construction technology. Due to the coordination of construction time, the in-situ construction technology finally taken in Mianyang is spray type.(4) After the completion of the construction, The accelerations of sleepers glue injection treated section and paving geotextiles treated section were tested when trains pass. The range and amplitude of acceleration of glue injection treated section is much smaller than that of paving geotextiles treated section. So the effect of glue injection treated section is better and the train operation is safer.