Abstract：The dynamic stress diffusion and the roadbed settlement after tamp are studied in four classes of tamping energy，i. e. 840，960，1 080，1 200 kN·m，respectively，in roadbed primed with large granule red sandstone. The test results show that the effective reinforcement distance ranges from 2–3 m to 3–4 m and the effective reinforcement depth ranges from 3.5–4.0 m to 5.0–6.0 m. The dynamic stress change is more markedable with the tamp time increasing，but it approaches stable when the tamping time increases 3–5 times. The deformation change markedable with the above different classes of tamping energy in depth of 4.0 to 6.0 m，but when the depth excesses 6.0 m，the settlements are almost equal，and the final deformation at depth of 5.5 m is 5.0–7.0 cm. The reliability and validity of the tamper construction design are proved by a series of tests.
