The paper describes the vetting process to validate a new free-fall cone penetration test (CPT) tool. First, the analytical model to calculate the dynamic embedment of the tool is described, and the model predictions are compared with laboratory and field tests results. Then the tip resistance and pore pressure measured with the new tool are compared to those measured with conventional methods at two Gulf of Mexico deepwater sites. The paper demonstrates that the dynamic embedment depth of the new CPT tool can be reliably predicted and that the tool measurements compare well with those of conventional seabed-based methods.

1. Introduction
1.1 Purpose of the new tool

An innovative cone penetration test (CPT) rig was recently developed, and is extensively described in Young et al. (2011). The tool is deployed from nondrilling vessels and dynamically inserted into the seabed using conventional jumbo piston coring (JPC) deployment techniques. A CPT rod, which is located inside the JPC core barrel during deployment, is then monotonically pushed into the seabed below the CPT barrel. In 2011, the suite of tools was further expanded to include a seabed unit. For this unit, the CPT is not penetrated dynamically into the seabed but starts a monotonic push at the seafloor (Figure 1). Because the CPT rod is entirely housed inside the barrel, the depth interval to which CPT data can be acquired cannot be greater than the length of the barrel. However, by carefully planning the dynamic penetration of the tool, overlapping CPT profiles can be obtained down to a depth of about 40m, thereby generating a composite continuous CPT profile from the seafloor to the depth of interest. The CPT data can then be calibrated in the top 15–18m with shear strength measurements from JPC samples.

This content is only available via PDF.
You can access this article if you purchase or spend a download.