PFC Dynamic Response Simulation And Test On Impacting Subgrade With Rapid Impact Compactor

In the construction process of backfill and compaction, quality of compacted subgrade affects the service life of highway or railway. It is reported that in most subgrade backfill projects nationwide, the test of compaction quality remains traditional outcome sample testing, which doesn’t correspond with mechanized construction of high efficiency. For the purpose of realizing synchronization of subgrade compaction technology and testing methods, more and more scholars studied and developed vehicle-mounted compaction quality real time testing system. This paper studied RHIC rapid hydraulic tamp machine, discussed intra-disciplinary fundamental theory of compaction quality real time testing system,with mathematical analysis, numerical simulation and field test, and established mathematical relations of dynamic response of mechanical action components, primarily accelerations, and testing indices of soil compaction quality in the tamping process. The main contents of the study involve:1. RHIC dynamics model of tamping process was set up according to RHIC structure and operating principles, and elastic semi-space theory, which innovatively simplified the action from tamper to tamping plate into vibration force F(t) and built the formula of dynamic response of tamper and tamping plate, and equivalent lumped mechanical parameters of soil system.Proved the dynamic response of the ram plate and rammer can reflect the mechanical properties of soil in the process of tamping.2. It is the first time that grain flow discrete element software PFC2 d was used to simulate the process of tamping cohesive backfill with RHIC, and to To study theacceleration chancing of the ram plate and rammer, law of soil particle displacement and development of the Force chain network in the process of tamping. Found that the order of the compacted soil is top-down, the effective compaction depth is 1.5 m, ram plate and rammer peak acceleration and the dense degree of soil was significantly positive correlation.3. After analyzing the tendency of all regression curves, it is concluded that the acceleration peak of tamping plate represents the soil compaction condition more. There exists one-to-one correspondence between acceleration peak of tamping plate and all compaction indices, and the looser the soil is, the more typically the relation shows, but the correspondence relation becomes ambiguous as soil gets denser with tamping.4. With the simulation outcome verified with field tests, test results and the numerical simulation results are basically identical, show that the simulation results with good reliability.