Cone Penetration Testing Procedure
(CPT)Gregg Drilling & Testing, Inc. carries out all Cone Penetration Tests (CPT) using an integrated electronic cone system, Figure CPT. The soundings are conducted using a 20 ton capacity cone with a tip area of 15 cm2 and a friction sleeve area of 225 cm2. The cone is designed with an equal end area friction sleeve and a tip end area ratio of 0.80.
The cone takes measurements of cone bearing (qc), sleeve friction (fs) and dynamic pore water pressure (u2) at 5-cm intervals during penetration to provide a nearly continuous hydrogeologic log. CPT data reduction and interpretation is performed in real time facilitating on-site decision making. The above mentioned parameters are stored on disk for further analysis and reference. All CPT soundings are performed in accordance with revised (2002) ASTM standards (D 5778-95). The cone also contains a porous filter element located directly behind the cone tip (u2), Figure CPT. It consists of porous plastic and is 5.0mm thick. The filter element is used to obtain dynamic pore pressure as the cone is advanced as well as Pore Pressure Dissipation Tests (PPDT’s) during appropriate pauses in penetration. It should be noted that prior to penetration, the element is fully saturated with silicon oil under vacuum pressure to ensure accurate and fast dissipation. When the soundings are complete, the test holes are grouted using a Gregg In Situ support rig. The grouting procedure consists of pushing a hollow CPT rod with a “knock out” plug to the termination depth of the test hole. Grout is then pumped under pressure as the tremie pipe is pulled from the hole. Disruption or further contamination to the site is therefore minimized. | 
