Jack-up Rig Footing Penetration Prediction And Punch-through Analysis And Research

At present under the tense energy situation in the world, the offshore oil and gasexploration and mining appears to be more important. And our country is a largeenergy-consumption country, with the fast development of economy and people’sliving condition, it would ask for higher requirement to oil and gas production, suchas industry and civil consumption. It is in the ascendant for offshore oil and gasexploration and mining. At present the most widely used drilling platform at homeand abroad is Jack-up rig, which is the main force for offshore oil and gas explorationand mining. Since the jack-up rig was put into use at home and abroad, the accidenthappened constantly, among them “punch-through” would accounted for53%. Andthe forecast of “punch-through” of Jack-up rig, actually is solving problem of ultimatebearing capacity of layered soil. The ultimate bearing capacity of surface foundationresting on a single layered of homogeneous undrained clay has been studied bynumerous investigators. In realiaty,however, soil strength profiles beneath footings arenot homogeneous but may increase or decrease with depth or consit of distinct layershaving significantly different properties. While the effect of increasing strength withdepth on bearing capacity has been addressed by several researchers, however,rigorous solution to the problem of footing resting on layered clays do not appear toexist.Through the predecessors about stratified soil foundation bearing capacityformula of experience summary analysis, case analysis, this paper discussesapplication research of the jack-up rig in the south area of China seaFirst of all, this paper introduces predecessors about stratified soil foundation ofthe ultimate bearing capacity of solving methods, including SNAME recommendedabout all kinds of circumstances solving principle, Skempton, Terzaghi, Meyerhof andothers propose calculation formula. And then to use Skempton formula calculationlaminated clay foundation ultimate bearing capacity analyzed methods of correction,and the ultimate bearing capacity of the foundation a sea area is analyzed.Secondly this paper will introduce the characteristics and applicability of finiteelement software PLAXIS for this subject, and in the PLAXIS model, through a lot ofcalculation examples, simulation rig "offshore oil941" pile shoe in the layered clay,especially middle clamp hard clay layers of stratified soil of the situation.Finally, the author will pick out the calculation results: displacement nephogram,stress nephogram, strain nephogram to carry on the analysis, and draw the variouscases of the corresponding foundation ultimate bearing capacity-inserted deep curve,this paper reveals stratified soil foundation bearing capacity with soil undrained shearstrength, soil thickness change and the characteristics of change. This paper also willthen through calculating the ultimate bearing capacity of foundation bearing capacityfactor for Nc, through with Chen (1975), Meyerhof and Hanna (1978) and thecomparison of the Nc value, the paper further stratified soil characteristics of thebearing capacity of foundation.