Driven cast-in-situ (DCIS) piles are classified as a large displacement pile, despite sharing certain aspects of their construction with replacement pile types. However, there are relatively few case histories of load tests on DCIS piles in the literature to verify the assumption that they behave as large displacement piles. In particular, the shaft resistance of DCIS piles in sand is uncertain due to the complex interaction between the freshly cast concrete and surrounding displaced soil after extraction of the steel installation tube. This paper describes the installation, curing, and maintained compression load testing of three temporary-cased DCIS test piles at a uniform sand site near Coventry, United Kingdom. The piles were instrumented with vibrating wire strain gauges to enable accurate measurement of the local shear stress generated on the pile shaft during maintained compression loading. The tests showed that the peak average and local shear stresses tended to mobilize at greater shaft displacements than traditional preformed displacement piles during loading. A clear reduction in normalized local shear stresses (and hence radial effective stress) at failure with distance from the pile base, i.e., friction fatigue, was evident for all piles, implying that radial stresses generated during driven installation of the steel tube are not erased upon concreting and tube withdrawal. Furthermore, the inferred normalized radial effective stresses at failure were remarkably similar to those reported for traditional preformed displacement piles in the literature.

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The effects of sample holding times, sample storage, and sample preservation in the laboratory have considerable effects on the final results of standard SRA (source rock analysis). This research was primarily directed to determine the potential effects of delay in processing and analysis. For example, over time; will the volatile hydrocarbon content (S1) and hydrocarbon generative potential (S2) [which is used to calculate Hydrogen Index (HI) and Production Index (PI)] show consistent results? In total fifteen samples were analysed for source rock analysis using the industry standard SRA-TPH/TOC instrument to test the effect of wait time on SRA results. Results from experiments conducted for variations in the sample holding time in shale rock samples show statistically meaningful changes. The samples that were processed and analyzed within one to three days show significant S1 and S2 values whereas the same samples analysed after four weeks and subsequently after three months show declining trends. The change between the four week and three month analysis is almost negligible. The noted average change in S1, S2 and S3 values ranges between 2% to 14%, 1% to 9% and 0% to 12%, respectively. Since the HI and PI are calculated from the S1 and S2 values, they also show lower values, averaging 5.26% and 3.75%, respectively. The same samples were also analyzed for clay contents and brittleness. The samples with high clay content and lower brittleness index show greater decline in the S1 and S2 values, and conversely, low clay content at higher brittleness show less decline in the S1 and S2 values. Therefore, more lithified/cemented samples show less variability over long holding times. In addition, the experimental results obtained indicate that sample holding time also demonstrate there are considerable effects on the final results when the S1 and S2 values are especially high. In order to avoid the sample degradation and data consistency issues, there is an industry-wide need to reassess sample collection, storage, processing, and analysis time. Although the data set analyzed may not be sufficient to make broad conclusions concerning the changes in the data, as there are several other confounding factors to take into account. However, the approaches demonstrated in this study will assist future researchers with more comprehensive data sets.

Driven cast-in-situ (DCIS) piles are classified as large displacement piles. However, the use of an oversized driving shoe introduces additional complexities influencing shaft resistance mobilisation, over and above those applicable to preformed displacement piles. Therefore, several design codes restrict the magnitude of shaft resistance in DCIS pile design. In this paper, a series of dynamic load tests was performed on the temporary steel driving tubes during DCIS pile installation at three UK sites. The instrumented piles were subsequently subjected to maintained compression load tests to failure. The mobilised shear stresses inferred from the dynamic tests during driving were two to five times smaller than those on the as-constructed piles during maintained load testing. This was attributed to soil loosening along the tube shaft arising from the oversized base shoe. Nevertheless, the radial stress reductions appear to be reversible by the freshly-cast concrete fluid pressures which provide lower-bound estimates of radial total stress inferred from the measured shear stresses during static loading. This recovery in shaft resistance is not recognised in some European design practices, resulting in conservative design lengths. Whilst the shaft resistance of DCIS piles was underpredicted by the dynamic load tests, reasonable estimates of base resistance were obtained.