Test Study On Railway Subgrade Reinforced By Sand Compacted Pile And Geocell

Combined with the treatment of the subgrade disease in K238 section of Guiyang-Kunming railway. Two plan for the treatment of surface course of subgrade bed of soft soil have been adopted: one is sand compactedpile combined with geocell, the other is bed course of which geocell is located in the middle of stray sand. Three typical cross section of subgrade has been chosen to test, one of which is near the rail gap. The dynamic characteristic test of subgrade bed including part of subballast and the long-period settlement test of subgrade surface including geocell base and sleeper base of the three typical cross sections have been conducted.According to the test results of each cross under train load including dynamic stress, dynamic deformation, vibrating velocity, acceleration, cumulative settlement and so on, this paper has analyzed the relationship between the dynamic characteristics of subgrade bed and its influencing rules, and the long-period settling characteristic of different treatment plan and the railway near rail gap. The following basal conclusions have been drawn:(1) The treatment plan of sand compacted pile combined with geocell can effectively improve the bearing capacity of surface course of subgrade bed and the dynamic characteristics of subgrade bed, and reduce cumulative settlement and settling velocity.(2) It is greater that the test data including subgrade dynamic stress, dynamic deformation, vibrating velocity, vibrating acceleration and cumulative settlement which are induced by striking of wheel axle. So it should be controlled that the smooth of railway at the rail gap.(3) The treatment using geocell only is adopted in the cutting section of which subgrade bed has softened deep, the test data including dynamic deformation, vibrating velocity, acceleration,subgrade cumulative settlement and settling velocity are larger and the time of stabilization for subgrade is longer, the soft ground under subgrade bed should be also treated.(4) Gross rail load on axle is one of main influencing factors of the dynamic characteristics of subgrade bed including the dynamic stress, dynamic deformation and vibrating velocity. Train velocity has little influence on the dynamic stress and dynamic deformation of subgrade bed, but has obvious influence on vibrating velocity and vibrating acceleration.(5) The long-period cumulative settling characteristic and the dynamic characteristic including dynamic stress, dynamic deformation , vibrating velocity, vibrating acceleration reduced with the increasing of height under train load.(6) The subgrade bed treatment plan can be applied to the treatment for subgrade bed disease in old railway and also can be used to the treatment of subgrade bed in the railway, the velocity of which is improving.railway subgrade; sand compacted pile; geocell; subgrade bed treatment; dynamic characteristics; cumulative settlement;...