This paper presents Class-A and Class-C predictions of the behaviour of an embankment built on soft Ballina clay improved with prefabricated vertical drains. Predictions were carried out using hand calculations and the finite-difference method. The latter approach allowed the variation of soil parameters and stress levels with depth to be considered in the analyses. An alternative systematic procedure for estimating soil parameters based on high-quality laboratory data is described. Class-A predictions highlighted some disagreement with the measured total settlements and pore pressure dissipation rates. For Class-C predictions, the choice of geotechnical parameters used in the analyses was guided by a systematic assessment of the stress states undergone by soil elements underneath the embankment centreline. This led to a better agreement between predicted and measured data, which demonstrates the potential of the proposed procedure for future analyses of embankment behaviour on soft Ballina clay

This paper describes an experimental study of the effects of sampling disturbance in an Australian natural soft clay and the consequences of different sample quality on the representativeness of soil parameters used in geotechnical designs. The paper is divided into three sections. Laboratory test results obtained from specimens retrieved using three different tube samplers as well as the Sherbrooke (block) sampler are first described. Then, the sample quality assessment, using available indices proposed for soft soils, is presented. It is shown that sample quality varies with the stress paths and boundary conditions applied in laboratory tests. Finally, mechanical soil properties derived from specimens retrieved using the different samplers are used in the prediction of two classical problems in soil mechanics: the settlement and excess pore pressure response underneath an embankment as well as the settlement and bearing capacity of a shallow footing. These two examples are used here to highlight the consequences of poor sampling in practice.

A small-scale physical modelling program using particle image velocimetry and digital image correlation (PIV/DIC) techniques was designed to obtain a refined understanding of the disturbance experienced by calcareous silt during tube sampling. The influence of the sampler wall thickness (diameter to thickness ratio, B/t) and the tube penetration rate were evaluated by estimating displacement and strain fields around the tube sampler. The results indicate that sampling with a thin tube leads to a relatively narrow undisturbed zone located at the center of the tube, with a width slightly smaller than the tube radius. Opposite to what is suggested for soft clays, tube sampling tends to densify the calcareous silt. This aspect has an important influence on the assessment of sample quality in calcareous silt for offshore and onshore projects.

In March of 2002, a depression was discovered in the eastbound lane of SC22 near Conway, South Carolina. Within hours, a hole developed that revealed a void beneath the asphalt pavement approximately 8 feet deep by 10 feet wide. As a safety precaution, the SCDOT filled the void with flowable fill and patched the asphalt while further investigations were conducted. Further investigation revealed that a collapse type sink hole had developed beneath the relatively new roadway. Geophysical testing data along with several Soil Test Borings were performed to evaluate the potential cause of the sinkhole as well as potential for future sinkhole development in the area. Although the potential for sinkhole development has always existed in the area due to the Coquina Limestone that underlies the relatively thin overburden, the absence of large-scale development has limited the occurrence of sinkholes in the area to subsidence type. As many of these sinkholes go unreported or unnoticed, this phenomenon is not well understood in the immediate area. Using the field investigation tools available, potential solutions to this sinkhole have been developed as well as precautionary measures to reduce the risk exposure as largescale infrastructure projects continue to be constructed throughout the area.