Determination of relative density of sand using dynamic cone resistance data

Abstract

Sand fill beneath the structure and surrounding area should be well compacted to make it non liquefiable. Once a structure is constructed on liquefiable soil, mitigation measures become very expensive. Therefore, it is very important to control the quality of sand fill so that structure would not be vulnerable to damage induced by seismic liquefaction. Compaction control of sand fill is generally done by determining field density using Sand Cone Method in Bangladesh. Sand Cone Method is expensive and cumbersome to do after completion of compaction in every single layer. The present study was aimed at developing an alternative indirect method which can be used to determine Relative Density easier and faster for clean sand of any particle size. The study consists of three stages. To know the height of fall and hole diameter of sand discharging bowl for a desired Relative Density of a specific sand, the air pluviation method was calibrated in the first stage. Then in the second stage sand deposits of different relative densities were prepared in calibration chamber and Dynamic Probing Light (DPL) and Dynamic Cone Penetrometer (DCP) tests were performed on the prepared sand deposit. Correlation between Penetration Index (rate of penetration in mm/blow, P;odcx)and Relative Density was made from the test results in calibration chamber. At the last stage, the correlation was verified for two dredge fill sites where DCP and DPL results were compared with the result from Sand Cone Method. A generalized correlation between P;odcxand Relative Density for clean sand of any particle size was found from this study. To determine in situ Relative Density of sand deposit, it is concluded that the proposed method (DCP and DPL) can be used as an alternative indirect method which is suitable up to 2 m depth.