Rammer hammer weight can be taken 8 ~ 40t, to improve the durability and safety of the building, the bottom form is usually round or polygonal. The material of the rammer is cast steel, in the case of limited conditions may use steel plate shell filled with concrete. The bottom surface of the rammer is symmetrically equipped with a number of uniform 4~6 vent holes with diameters of 250mm~500mm running up and down, which is conducive to discharging the air from the bottom of the pit when the rammer hits the ground and reducing the suction at the bottom of the pit when the hammer is lifted. The area of the bottom of the hammer should be confirmed according to the nature of the soil. For sandy soil and gravel fill, it is generally suitable to use the bottom area of 2~4 square meters; for general clay soil, it is recommended to use 3~4 square meters; for silty soil, it is recommended to use 4~6 square meters. Hammer bottom static grounding pressure value is generally between 25 ~ 40kPa, for fine-grained soil hammer bottom static grounding pressure to take the smaller value.