Application of shear wave velocity for evaluation of equivalent radius of penetrometers

Abstract

As a penetrometer is pushed into saturated soft soils, excess pore water pressure affected by the disturbed zone is generated. This excess pore water pressure, which dissipates radially, is related to the probe size and shape. The probe size and shape may be represented by an equivalent radius. The aim of this paper is to evaluate the equivalent radius of a penetrometer using the horizontal coefficient of consolidation. Three penetrometers including the cone penetrometer, dilatometer, and Field Velocity Probe (FVP), are used within a large laboratory calibration chamber and in the field. For the calibration chamber tests, a clay-sand mixture is prepared and consolidated under a vertical stress of 160 kPa. These dissipation tests are conducted at a depth that is equal to half the height of the chamber. For the field tests, three penetrometers are penetrated into soft soils through a gravel layer and a sand mat layer. These dissipation tests are implemented at a depth of 24 m. The cone penetrometer, dilatometer, and FVP measure the change of the pore water pressure, the closing pressure value, and the shear wave velocity, respectively. From these six dissipation tests, the equivalent radii of the dilatometer and the FVP are obtained. In addition, an empirical equation for the calculation of the equivalent radius of the penetrometer is suggested. (C) 2012 Elsevier B.V. All rights reserved.