In dynamic compaction, what combination of weight and drop height is typical to achieve densification to depths around 30 ft?

In dynamic compaction, what combination of weight and drop height is typical to achieve densification to depths around 30 ft?

• A. 5-ton weights and 20 ft drop
• B. 10-ton weights and 60 ft drop
• C. 30-ton weights and 100 ft drop
• D. 50-ton weights and 200 ft drop

Answer: (C)

In dynamic compaction, the depth of densification comes from the energy of each impact, which is roughly proportional to the hammer weight times the drop height. To densify soil to about 30 ft, you need a substantial energy input, typically provided by a heavy hammer dropped from a substantial height. A 30-ton weight released from around 100 ft delivers enough energy to rearrange soil particles to that depth while avoiding excessive surface disturbance or unnecessary cost. Lighter weights or shorter drops don’t furnish enough energy to reach 30 ft, while far heavier weights from much greater heights would be more energy than needed and can cause problems. So the combination of a 30-ton weight and a 100 ft drop is the most effective for achieving about 30 ft of densification.

In dynamic compaction, the depth of densification comes from the energy of each impact, which is roughly proportional to the hammer weight times the drop height. To densify soil to about 30 ft, you need a substantial energy input, typically provided by a heavy hammer dropped from a substantial height. A 30-ton weight released from around 100 ft delivers enough energy to rearrange soil particles to that depth while avoiding excessive surface disturbance or unnecessary cost. Lighter weights or shorter drops don’t furnish enough energy to reach 30 ft, while far heavier weights from much greater heights would be more energy than needed and can cause problems. So the combination of a 30-ton weight and a 100 ft drop is the most effective for achieving about 30 ft of densification.