Driveability back-analyses of onshore vibratory and vibrojetting installation tests on tubular piles

This paper presents the results of driveability back-analyses for a series of piles installed onshore in sand with vibro-driving and with a new installation concept in which vibro-installation is combined with the use of water jetting (vibrojetting). The jet assisted installation is based on the reduction of the soil resistance on the inside of a pile, using a water jetting gun technique (jetring), by fluidizing the interface between the inner pile wall and soil plug. The most decisive parameters in the driveability analysis were (i) the ones related to operational data such as hammer settings and crane load and (ii) the ones related to selection of vibratory driving parameters and the method used for estimating the soil resistance to driving. The applied driveability backanalysis predicts penetration speeds that are in relatively good agreement with measurements in the field. Results have also shown that the vibrojetting technique is promising in improving installation performance.