Study On Brake Performance Of Brake Bed Filler For Long Downhill Truck Escape Lane

With the continuous development of highways in mountainous areas of China,the number of long and downhill sections is increasing,and the safety situation of highways in mountainous areas is becoming increasingly severe.Escape lanes play a crucial role in ensuring the traffic safety of long and steep downhill sections.At present,the design of brake bed filler for escape lanes mainly relies on experience,and there is a lack of systematic theoretical research on the properties and evolution of filler.This article studies the filler’s optimal gradation and long-term use performance for getting the best fillers and providing scientific management suggestions.This article uses coarse-grained soil as the experimental fillers and conducts a series of loading model tests using an electronic universal testing machine.It reveals the effects of controlling particle size,non-uniform coefficient,mud content,water immersion,and reciprocating load on the braking performance of the fillers.PFC is used to simulate the reciprocating loading model test process,and a prediction formula for the sinking coefficient of fillers,reciprocating load,and reciprocating frequency is proposed.The main work and achievements are as follows:Define the sinking coefficient to characterize the braking performance of the filler.The larger the sinking coefficient,the better the braking performance.The smaller the controlling particle size and non-uniform coefficient,the greater the sinking coefficient of the filler.Combining with the deceleration characteristics of the filler,it was found that the filler with a particle size range of 0～22.5 mm,a controlled particle size of 7.5 mm,and an non-uniform coefficient of 2.6 has the best braking performance.An increase in the mud content of filler is not conducive to the stopping of large trucks.For small cars,filler with a mud content of 15% are conducive to stopping,while filler with a mud content of less than or equal to 10% are not conducive to stopping.Air drying will reduce the sinking coefficient of mud containing filler,which is not conducive to vehicle stopping.Water immersion can increase the sinking coefficient of filler,but in reality,the vehicle stopping process in this situation is complex,and further research is needed to determine whether water immersion is helpful for vehicle stopping.After experiencing a reciprocating load that is less than the ultimate bearing capacity of the filling material in the early stage,when the stress in the graded loading stage is less than the ultimate bearing capacity of the filling material,the larger the reciprocating load in the early stage,the greater the decrease in the sample trapping coefficient;When the stress is greater than the ultimate bearing capacity of the filling material,the reciprocating load in the early stage has little effect on the sample insertion coefficient.Therefore,if the weight of subsequent vehicles is less than the ultimate bearing capacity of the filler,the filler will not be able to exert good braking performance on the vehicle,and the larger the weight of the vehicle rolling the filler in the early stage,the worse the braking performance of the filler on subsequent vehicles;If the weight of the subsequent vehicle exceeds the ultimate bearing capacity of the filler,the braking performance of the filler will not be affected,and it still has a good effect on the braking and stopping of the vehicle.During the reciprocating loading stage,the porosity of the simulated sample decreases with the increase of reciprocating times,and the greater the reciprocating load,the greater the degree of porosity reduction;During the stage of graded loading,the porosity of the simulated sample decreases continuously with the increase of stress.Therefore when the vehicle first compacts the filler,a heavier vehicle will cause a greater reduction in the porosity of the filler,resulting in a smaller reduction in the porosity generated by subsequent vehicle compaction of the filler.