Well, if i am not wrong ,the dynamic replacement (DR) method that you are talking about is the one with big pounder that drop on ground. More i need to address that, the DR method have a limitation in term of treatment depth. It is also worth reading the Priebe paper, because the design concept was exactly from that. Paper, 1. "The design of vibro replacement", Heinz J.Priebe, Ground Engineering, December 1995, Technical Paper 12-61E. 2. "Ground Improvement To Accelerate The Construction Of A High Embankment", Kenny Yee & Ting Wen Hui, Proceedings of The Malaysia Geotechnical Conference 2004.

the term you want to search for is deep dynamic compaction (DDC). It works well, especially in area of high ground water (where excavation cannot be used). The effects of a 20 ton weight can reach 15 feet or more below the ground surface. A typical drop pattern in the US is a staggered 12 foot square grid with 3 to 5 drops on the first pass and 3 to 5 drop on the second pass. weights are generally 10 to 20 tons. Compaction is check with cone-pen or drilling.