PREDICTION OF DYNAMIC COMPACTION POUNDER PENETRATION

GRAY MULLINS, MANJRIKER GUNARATNE, PAMELA STINNETTE and SAMAN THILAKASIRI

ABSTRACT: A semi-empirical computational technique is presented for predicting the depth of craters formed by dynamic compaction (DC) pounders after the first impact. This technique utilizes a correlation developed between the initial shear strength of the soil beneath the pounder, determined by a CPT profile, and the impact energy per unit area (specific impact energy). First, the correlation is established by a series of model impact tests involving different drop heights, drop weights and impact areas. Then, the correlation is verified by the results from a full-scale field test performed by the authors. Further, data from a DC project performed elsewhere is also shown to support the predictive technique. An illustrative example is provided to demonstrate how typical CPT data can be adapted to predict the crater depths during DC projects for a given level of applied impact energy. On the other hand, this method can be used to determine the maximum impact energy that can be applied without causing excessive initial penetration of pounders and thus preclude the need for trial impacts. Hence well in advance of heavy equipment mobilization, this technique can certainly aid in effective planning of DC projects on particularly weak ground where penetration predominates heave.

Key words: CPT, crater, dynamic compaction, dynamic replacement, organic soil, pounder, specific impact energy (IGC: K3/K5)