بهمن نیرومند

Basically, in the most of the civil engineering projects and structures which are built on the weak soils, improvement and subgrade compaction are inevitable. Dynamic compaction is one of the effective ways of improving the loose and intermediate subgrades, where different methods and technologies are adopted to compact these subgrades based on the different status of the site and environment. The rammed impact compaction is one of the methods which can be used to compact layers with low to average thickness and can be useful as an alternative for excavation and replacing with engineering embankment. This method is based on impacting the masses of the soil with high frequency on points of a meshwork with different patterns and by using a hydraulic hammer assembled on a mechanical excavator. With respect to this method, the compaction of layers with low to average thickness is possible for improvement of the uncompacted soil layers with higher rate and instead of layer to layer compaction. The important factors to evaluate this method include some parameters such as effective depth of the rammed impact system, compaction pattern, spaces between the impact points, the amount of required energy for impacting each point, dry density of the soil before and after the impaction and calculating the young modulus of the soil after the impaction. In order to investigate the effects of the above-mentioned parameters on the process of impaction and compaction, after physical modeling, the impact compaction were conducted in the form of field and experimental tests with medium scale. These three tests were carried out as a pilot tests in three silty-sands located on new city of Aalishahr, Niyayesh district in Bushehr and Shilat cross-intersection in Bushehr. Therefore, three rammers with 12, 16 and 20 centimeters diameter and installable on an electrical hammer were designed. Also, the impact tests were conducted with different patterns including single point, squared (four-poin