Determining The Effect Of Ground Improvement Using Impact Rolling For Varying Site Conditions

Deep compaction techniques have been in use for a number of years. There are a number of deep compaction techniques that can be applied in ground improvement. These range from the traditional drop weight to eccentrically shaped (impact) rollers.

It is generally accepted that either of these techniques would affect some degree of ground improvement in noncohesive soils. The depth of ground improvement would be dependent on a range of factors including mechanical characteristics of the soil i.e. PSD, Atterberg limits and the location of ground water table.

To date anyone undertaking deep ground improvement using impact rolling techniques does not have a way of predicatively determining the depth of ground improvement in different soil and ground water conditions. It is the authors‟ intent to present a series of case studies where deep ground improvement using impact rolling techniques was successfully utilised across a variety of ground and phreatic conditions. The degree of improvement was evaluated in terms of CPT Tip Resistance (Qc), Young‟s modulus (E) and bearing capacity.

The intent of these case studies is to investigate relationships between the degree of improvement and potential contributing factors including the soil properties, the weight of the impact rolling module used, the number of roller passes and the location of the water table. These relationships are developed for a series of non-cohesive soil conditions specifically well graded sand, uniformly graded sand and crushed limestone, and are presented as nomographs. These nomographs can provide a guidance to predictively determine the number of passes required to effect ground improvement to a given depth for a particular soils type in various phreatic conditions.