Gravity offshore platform,as an oil production platform that integrates drilling,production,storage and transportation facilities,has been widely used in offshore marginal oil field.Under the multiple marine loads,offshore platform is in the complex stress state.In order to meet the structural safety operation requirements,it is necessary to analyze the stress deformation of platform structure and foundation.Based on the LD 29-1 marginal oil field development project,combined with the platform design scheme suggested in"Shallow sea gravity platform underwater oil storage technology",numerical simulation calculations and centrifuge model tests were carried out.The deformation law,foundation soil displacement law,and failure mode of shallow sea gravity platform structure were determined.Results show that the overall structure of the platform has obvious lateral deformation under the action of marine load,the deck structure warped and the vertical settlement of surface foundation is large.When there is no bucket skirt on the platform,sliding deformation mainly occurs between the platform and the foundation,and when a 5 m long bucket skirt is added to the platform,the rotational deformation around the bottom plate mainly occurs between the platform and the foundation,while the upper platform structure has inclined.The results can provide technical reference for the construction and structural optimization of gravity offshore platforms.
In the survey and design of marine geotechnical engineering,undrained shear strength is a particularly important strength parameter.In order to accurately evaluate the undrained shear strength of marine soft soil,the undrained shear strength of marine soft soil was calculated based on the data from piezocone penetration tests and vane shear tests at the expansion project site of Macao International Airport,and a linear correlation between cone tip factor Nkt and normalized effective cone tip resistance QE was proposed.The undrained shear strength predicted based on this linear relationship is more consistent with the vane shear test results.At the same time,the given cone tip factor can reflect the spatial variability of the in-situ soil well along the depth direction.For Macao marine soft soil strength parameters can be interpreted using the Nkt-QE relationship obtained from the calibration of this paper,providing a reliable geotechnical design basis for design.
Based on the time domain coupled model,the response characteristics of moored ships under the action of wave with medium to long period was studied.Considering the nonlinear characteristics of the mooring lines and fenders,a three-dimensional time domain analysis model of ship-mooring system-fender was established.The motion response characteristics of the coupled system were analyzed,and the influence rules of different periods and loading states on parameters such as six degrees of freedom motion and cable tension were discussed.The calculation results shows that,under laden and ballast conditions,except for roll motion,the motion of the other five degrees of freedom gradually increases with the increase of the wave period.At the peak period of 17 seconds,the roll motion of laden condition and ballast condition are 1.71° and 0.93°,respectively,slightly greater than the values of 15 seconds and 19 seconds.Furthermore,the tension of the mooring line gradually increases with the increase of wave period under laden and ballast conditions,and the positions where the maximum force occurs are on the breast-fore and breast-aft lines,which should be taken seriously during the operation process.In summary,the dynamic response of the mooring system is particularly sensitive to the long period waves.It is recommended to closely monitor the wave conditions in the project area to ensure the safety of port operations.
This paper analyzes the high-precision installation method for the end steel shell in the cast-in-place immersed tube based on the main structure of the north bank buried section and open section of the Dalian Bay Subsea Tunnel Construction project.The construction period of this project is tight,and the southern end of the Z13 section of the north bank buried section and open section structure serves as the docking section between the cast-in-place immersed tube and the prefabricated immersed tube.If conventional techniques are used for construction,the progress is slow and the construction quality is difficult to guarantee.In order to solve this problem,an end steel shell was installed at the docking point.Based on the structural form of the end steel shell,the method of adding a steel support system was adopted,effectively solving the problems of traditional segmented installation that cannot ensure accuracy and a long construction period.A complete set of high-precision installation methods for the end steel shell was developed.By analyzing,inventing,applying,and summarizing the high-precision installation method of cast-in-place immersed tube end steel shells,the construction quality,safety,and duration of the project meet the design requirements,while creating good economic and social benefits.
The conventional hydraulic climbing formwork method can no longer meet the requirements of safe and rapid construction of ultra-high concrete bridge towers.In order to solve this technical barrier,this project has conducted in-depth research from the aspects of new intelligent equipment,assembly design and construction,and refined process management.Solve the problem of maintenance age through new intelligent climbing formwork;ensure the accuracy of steel bar installation by adding steel bar spacers;cleverly solving the problem of variable cross-section in the interior space of the main tower through the design of telescopic brackets;through the assembly and installation of the lower crossbeam bracket and tension preloading,the technical difficulties in the construction of the lower crossbeam have been solved,which greatly improves the construction efficiency of the ultra-high concrete tower and reduces safety risks.Moreover,the practical effect of this project is good,which has great reference value for subsequent ultra-high bridge towers.
