The Application Of Cone Penetration Test In Bohai Offshore Platform Site Investigation

Nowadays, following the rapid development of the offshore engineering, offshore CPT has been developed as an internationally recognized standard. CPT technology is time-saving, accurate, economical and labor-saving. Besides, because of the minimized disturbance to soil, the testing results can reflect the initial stress-strain status of the soil better than other test methods. The domestic research on CPT in offshore engineering is at initial step. In 2007, China Oilfield Service., Ltd imported the first Down-hole CPT and did the first test which done all by Chinese technicians.It is important to know the application of CPT technology and mature international test procedure, to discuss the problems during interpretation using CPT data, to verify the suitability of the interpretation of CPT data, to propose the reasonable empirical factors used to obtain soil parameters in offshore geotechnical engineering in China.Based on the Bohai offshore platform investigation, this paper introduced the basic principles of CPT test; introduced the testing points, equipment, and the method of CPT data acquisition, correction and elaboration. This paper contains discussion on the interpretation approaches using CPT data based on theories analysis and comparison between the interpretation results from CPT, drilling and laboratory soil testing results, and suitable empirical factors for studied sites are proposed.In the paper the main innovation and research harvests are as follows:1. Introduced the requirements, testing procedures and equipment of Offshore CPT Testing, pointed out the existing disadvantage which is needed to be improved;2. Based on existing soil classification method, CPT data, Drilling results and Laboratory Test results were compared and analyzed. This paper also discussed some soil behavior type classification charts and recommended a reasonable CPT classification chart ;3. Compared with the UU Triaxial test and laboratory vane test, this paper presents the interpretation for estimation of undrained shear strength in cohesive soils, over-consolidation ratio in cohesive soils, and sensitivity in cohesive soils using the adopted approaches. The correlations between the estimation results based on CPT data and laboratory testing results were discussed, and the empirical factors for the study sites are proposed;4. According to the CPTU results, made the curve of undrained shear strength of cohesive soil suggested to use that curve to calculate the pile bearing capacity.