Tamping rammer is divided into ordinary hammer and replacement hammer. Common hammers are usually 2.4-2.5 meters in diameter and weigh 8-50 tons. It must have holes, the role of holes is to ventilate, so as to avoid hammer being sucked up by soil. The displacement hammer is usually 1-1.5 meters in diameter, and there is no air vent because of its small diameter. But a slot is set on the side for ventilation.

Dynamic compaction was first used by Menard Technologies in France in the late 1960s to treat foundation. In this method, the heavy hammer (usually 100-400 kN) falls freely from the height (usually 6-40 m) to give the foundation impact force and vibration, so as to improve the strength of the foundation soil and reduce its compressibility.

Selection of rammer size:

1. The weight of rammer is related to the depth and fall distance of the soil layer to be strengthened. There are formulas.

2. The material of rammer is best cast steel.

3. The bottom area of rammer: The size of the bottom area is related to the type of soil. Generally speaking, for sandy soil and gravel fill, the bottom area of 2-4 square meters is more suitable. For general Quaternary cohesive soil, 3-4 square meters are recommended. 4-6 square meters is recommended for silty soil.