Suction foundations are generally installed with negative pressures to overcome the resistance of soils and complete the penetration,but excessive negative pressures are also avoided to cause seepage damages.In this p...Suction foundations are generally installed with negative pressures to overcome the resistance of soils and complete the penetration,but excessive negative pressures are also avoided to cause seepage damages.In this paper,the model test method was used to analyze the movement characteristics of multi-bucket foundations in the process of sinking in sand,and the common calculation methods of sinking resistances are verified.The critical negative pressure corresponding to the seepage failure of foundation was determined under the action of increasing negative pressure step by step and the characteristics of soil failure were studied.The calculation formula of critical suction in sand was verified in application,and according to the test results,the value of seepage coefficient was modified,which provides an example for the study of suction foundation in sand soils.展开更多
The penetration of the composite bucket foundation(CBF)is crucial in its construction process.In actual projects,the foundation is inevitably subjected to eccentric load caused by towers and turbines,as well as wind,w...The penetration of the composite bucket foundation(CBF)is crucial in its construction process.In actual projects,the foundation is inevitably subjected to eccentric load caused by towers and turbines,as well as wind,wave,and flow,during the one-step installation.Moreover,the eccentric load is bound to affect the penetration method and penetration resistance of the foundation.To examine the above-mentioned issues,the penetration resistance of CBF with eccentric load was calculated and analyzed based on model tests,and the seepage field of the CBF under eccentric load was analyzed using ABAQUS.The influence of different magnitudes of eccentric load and various offset strategies on penetration resistance was analyzed,and the theoretical and measured values were compared.The result indicated that the negative pressure of the offset room was found to be smaller than that of other rooms when the CBF penetrated the soil under eccentric load.The penetration resistance of CBF under eccentric load was larger than that without eccentricity,and the larger the eccentric load is,the greater the penetration resistance.The influence of different eccentric load offset strategies on penetration resistance was found to be negligible.The calculated penetration resistance under eccentric load was in good agreement with the measured value.展开更多
To investigate the natural frequencies and towing behaviors of a 3-bucket foundation platform at different drafts, the decay and towing experiments were carried out in a towing tank on a scale of 1:20. The air pressur...To investigate the natural frequencies and towing behaviors of a 3-bucket foundation platform at different drafts, the decay and towing experiments were carried out in a towing tank on a scale of 1:20. The air pressure inside the bucket foundations, the water pressure at the bottom of the bucket foundations, the acceleration of the platform and the towing force were determined in the test process. The time-history curves of the measured parameters were obtained, and the frequency responses of the parameters at different drafts were analyzed by means of fast Fourier transform(FFT). The results showed that the platform natural frequency of heave decreased slightly with the rise of draft. The natural frequencies of roll and pitch are much lower than that of heave, and they increased slightly with the increase of draft. When towing in the following sea, the maximum acceleration of surge, sway and heave has downward trends with the increase of draft, but the change range decreased gradually with the increase of draft. When the draft is 5.0 m(the ratio of draft to bucket height is 0.56), the towing dynamic responses achieve the maximum, which is not conducive to the towing of the platform. When the draft is 6.0 m(the ratio of draft to bucket height is 0.67), the towing dynamic responses are the most stable.展开更多
This paper describes the model tests for determining the axial friction and the lateral resistance of sand to pipeline by using fine sand and prototype pipeline, and the calculation method based on limit analysis theo...This paper describes the model tests for determining the axial friction and the lateral resistance of sand to pipeline by using fine sand and prototype pipeline, and the calculation method based on limit analysis theory is verified. The effect of cyclic loading is considered in the test.展开更多
With the rapid development of large-scale development of marginal oilfields in China,simple wellhead platforms that are simple in structure and easy to install have become an inevitable choice in the process of oilfie...With the rapid development of large-scale development of marginal oilfields in China,simple wellhead platforms that are simple in structure and easy to install have become an inevitable choice in the process of oilfield development.However,traditional simple wellhead platforms are often discarded after a single use.In pursuit of a more costeffective approach to developing marginal oilfields,this paper proposes a new offshore oil field development facility—an integrated bucket foundation for wellhead platform.To verify the safety of its towing behavior and obtain the dynamic response characteristics of the structure,this paper takes a bucket integrated bucket foundation for wellhead platform with a diameter of 40 m as the research object.By combining physical model tests and numerical simulations,it analyzes the static stability and dynamic response characteristics of the structure during towing,complete with the effects of the draft,wave height,wave period,and towing point height,which produce the dynamic responses of the structure under different influence factors,such as roll angle,pitch angle,heave acceleration and towing force as well as the sensibility to transport variables.The results show that the integrated bucket foundation for wellhead platform is capable of self-floating towing,and its movement is affected by the local environment,which will provide a reference for actual projects.展开更多
The breakwater with top sealed, shallow and wide penetrating box foundations is a new type of structure, applicable to deep water and soft seabed. The relations of horizontal and vertical bearing capacities of the bo...The breakwater with top sealed, shallow and wide penetrating box foundations is a new type of structure, applicable to deep water and soft seabed. The relations of horizontal and vertical bearing capacities of the box foundation structure as well as the instability induced failure modes to its dimensions and external loads are discussed through static model tests and wave tests. The mechanical properties of the stability of the box foundation are similar to those of embedded rigid foundations, i.e. the vertical stresses at the bottom of the box are distributed in a linear pattern under the action of vertical loads, and passive and active soil pressures are developed at the front and back sides of the box under the action of horizontal loads; there are two instability induced failure modes of the foundation structure-horizontal slide along the box base and tilting due to insufficient local vertical bearing capacity of the soil beneath the box base. The stability of box foundations can be analyzed by use of the methods applied to analysis of the embedded rigid foundations. To increase the width of the box is the most effective way to improve the stability of box foundations.展开更多
基金The authors would like to acknowledge the support from the National Natural Science Foundation of China(No.52171274).
文摘Suction foundations are generally installed with negative pressures to overcome the resistance of soils and complete the penetration,but excessive negative pressures are also avoided to cause seepage damages.In this paper,the model test method was used to analyze the movement characteristics of multi-bucket foundations in the process of sinking in sand,and the common calculation methods of sinking resistances are verified.The critical negative pressure corresponding to the seepage failure of foundation was determined under the action of increasing negative pressure step by step and the characteristics of soil failure were studied.The calculation formula of critical suction in sand was verified in application,and according to the test results,the value of seepage coefficient was modified,which provides an example for the study of suction foundation in sand soils.
基金support from the National Natural Science Foundation of China(No.52171274).
文摘The penetration of the composite bucket foundation(CBF)is crucial in its construction process.In actual projects,the foundation is inevitably subjected to eccentric load caused by towers and turbines,as well as wind,wave,and flow,during the one-step installation.Moreover,the eccentric load is bound to affect the penetration method and penetration resistance of the foundation.To examine the above-mentioned issues,the penetration resistance of CBF with eccentric load was calculated and analyzed based on model tests,and the seepage field of the CBF under eccentric load was analyzed using ABAQUS.The influence of different magnitudes of eccentric load and various offset strategies on penetration resistance was analyzed,and the theoretical and measured values were compared.The result indicated that the negative pressure of the offset room was found to be smaller than that of other rooms when the CBF penetrated the soil under eccentric load.The penetration resistance of CBF under eccentric load was larger than that without eccentricity,and the larger the eccentric load is,the greater the penetration resistance.The influence of different eccentric load offset strategies on penetration resistance was found to be negligible.The calculated penetration resistance under eccentric load was in good agreement with the measured value.
基金Supported by the National Natural Science Foundation of China(No.51309179)Tianjin Municipal Natural Science Foundation(No.14JCQNJC07000)the State Key Laboratory of Hydraulic Engineering Simulation and Safety(Tianjin University)
文摘To investigate the natural frequencies and towing behaviors of a 3-bucket foundation platform at different drafts, the decay and towing experiments were carried out in a towing tank on a scale of 1:20. The air pressure inside the bucket foundations, the water pressure at the bottom of the bucket foundations, the acceleration of the platform and the towing force were determined in the test process. The time-history curves of the measured parameters were obtained, and the frequency responses of the parameters at different drafts were analyzed by means of fast Fourier transform(FFT). The results showed that the platform natural frequency of heave decreased slightly with the rise of draft. The natural frequencies of roll and pitch are much lower than that of heave, and they increased slightly with the increase of draft. When towing in the following sea, the maximum acceleration of surge, sway and heave has downward trends with the increase of draft, but the change range decreased gradually with the increase of draft. When the draft is 5.0 m(the ratio of draft to bucket height is 0.56), the towing dynamic responses achieve the maximum, which is not conducive to the towing of the platform. When the draft is 6.0 m(the ratio of draft to bucket height is 0.67), the towing dynamic responses are the most stable.
文摘This paper describes the model tests for determining the axial friction and the lateral resistance of sand to pipeline by using fine sand and prototype pipeline, and the calculation method based on limit analysis theory is verified. The effect of cyclic loading is considered in the test.
基金supported by the National Natural Science Foundation of China(Grant No.52271287).
文摘With the rapid development of large-scale development of marginal oilfields in China,simple wellhead platforms that are simple in structure and easy to install have become an inevitable choice in the process of oilfield development.However,traditional simple wellhead platforms are often discarded after a single use.In pursuit of a more costeffective approach to developing marginal oilfields,this paper proposes a new offshore oil field development facility—an integrated bucket foundation for wellhead platform.To verify the safety of its towing behavior and obtain the dynamic response characteristics of the structure,this paper takes a bucket integrated bucket foundation for wellhead platform with a diameter of 40 m as the research object.By combining physical model tests and numerical simulations,it analyzes the static stability and dynamic response characteristics of the structure during towing,complete with the effects of the draft,wave height,wave period,and towing point height,which produce the dynamic responses of the structure under different influence factors,such as roll angle,pitch angle,heave acceleration and towing force as well as the sensibility to transport variables.The results show that the integrated bucket foundation for wellhead platform is capable of self-floating towing,and its movement is affected by the local environment,which will provide a reference for actual projects.
文摘The breakwater with top sealed, shallow and wide penetrating box foundations is a new type of structure, applicable to deep water and soft seabed. The relations of horizontal and vertical bearing capacities of the box foundation structure as well as the instability induced failure modes to its dimensions and external loads are discussed through static model tests and wave tests. The mechanical properties of the stability of the box foundation are similar to those of embedded rigid foundations, i.e. the vertical stresses at the bottom of the box are distributed in a linear pattern under the action of vertical loads, and passive and active soil pressures are developed at the front and back sides of the box under the action of horizontal loads; there are two instability induced failure modes of the foundation structure-horizontal slide along the box base and tilting due to insufficient local vertical bearing capacity of the soil beneath the box base. The stability of box foundations can be analyzed by use of the methods applied to analysis of the embedded rigid foundations. To increase the width of the box is the most effective way to improve the stability of box foundations.
