Research On The Uplift Performance Of Suction Bucket Foundation Of Offshore Platform In Sandy Soil Stratum

In the field of offshore engineering,suction bucket foundations are attracting more and more attention because of their excellent structural performance and cost-effectiveness.Among them,the pullout performance of the suction bucket foundation under various working conditions is one of the key factors for the stability and safety of offshore platforms.For this reason,this paper conducts a systematic study on the pullout performance of the suction bucket foundation of the offshore platform in sandy soil stratum,aiming to reveal the characteristics of the pullout performance of the suction bucket foundation in the sandy soil stratum and its influencing factors,which will be useful for practical projects.Application provides theoretical basis and technical support.The main research work and conclusions are as follows:(1)Through laboratory tests,the pullout performance of the suction bucket foundation in sandy soil is studied.By adjusting the experimental conditions such as loading speed and loading angle,the pullout performance and failure mode of the suction bucket foundation were analyzed.The research results show that:in the case of 0° and 15°,the speed change has little effect on the failure mode,and the main performance is the horizontal load failure;at the loading angle of 30° and above,at lower loading speed,the low angle The bucket shows an obvious uplifting process.The sandy soil away from the displacement direction of the bucket body is less deformed and remains in its original shape;during the uplifting process of the high-angle bucket body,partial drainage and non-drainage damage forms appear;The soil is deformed in a large range of influence due to slow loading;when the speed is fast,the failure form is that the interaction between the bucket foundation and the surrounding sand is strong,but the damage area is relatively small;at a small uplift angle,the effect of speed on the uplift performance of the suction bucket foundation is more obvious;while at a larger uplift angle,the effect of speed on the uplift performance is relatively small.(2)Use finite element software to numerically simulate the suction bucket foundation,consider the time effect of dynamic load,and study the effects of different drainage conditions,loading speeds,loading angles and loading methods on the surrounding soil during the pulling process of the suction bucket foundation The influence of stress change and bearing performance,the numerical simulation results were compared with the test data to verify the rationality of the calculation,and the time-load curves of the bucket foundation under different conditions were drawn.The research results show that the drainage conditions have a significant impact on the soil pressure distribution and the uplift bearing capacity of the bucket foundation;under the partially drained state,the soil pressure distribution is significantly different from that in the fully drained state,which is manifested in the tension of the soil in the bucket and the soil pressure.characteristics such as plugging effect;with the increase of the uplift angle,the distribution of earth pressure shows a significant change trend in different regions,and the maximum and minimum values of earth pressure gradually decrease;Simulation,partial drainage simulation and test data)were compared and analyzed,and it was found that the ultimate bearing capacity of the complete drainage simulation was higher overall;at the initial stage of loading,the displacement and bearing capacity under the sinusoidal loading mode increased rapidly,resulting in sandy soils Larger deformation;Oscillatory loading with rapid displacement in a short period of time has a greater destructive ability to the suction bucket foundation.Even if the loading disappears,the ultimate bearing capacity will decrease accordingly.The displacement of sand and bucket increases with the increase of velocity;under partially drained conditions,the sand in the bucket and the bucket foundation move together,while under the fully drained condition,the sand and bucket foundation can move independently of each other.(3)Using the explicit dynamic numerical analysis method,the sensitivity analysis of the uplift performance of the suction bucket foundation is carried out,taking into account factors such as the mechanical parameters of sand and soil,the mechanical parameters of the bucket foundation,and the differences in mooring points.The research results show that the elastic modulus of sandy soil has a great influence on the initial bearing capacity,and the slope will change with the elastic modulus in the approximate linear growth process of the initial period;when the elastic modulus is small,the displacement bearing capacity curve has no obvious The inflection point of;when the internal friction angle increases,the ultimate bearing capacity shows an upward trend,but the shape of the curve is different;the area with a large slope change increases first,and reaches the maximum value at 25°.As the internal friction angle continues to increase,the slope The maximum change gradually decreases;increasing the cohesion parameter has a significant effect on the ultimate bearing capacity and the bearing capacity curve.When the displacement/diameter is 0.08,different plastic development trends appear in the bucket foundation.With the increase of the elastic modulus of the bucket,the bearing capacity curve gradually increases,and the difference is relatively small.When the friction coefficient is low,the increase of the pull-out bearing capacity is relatively slow;when the friction coefficient is high,the increase of the bearing capacity gradually decreases,and the shape of the curve changes;The bearing capacity is low;under the condition of complete drainage,the friction of the bucket wall is the main contribution to the uplift bearing performance.When the friction coefficient is large,the friction provides most of the total bearing capacity;The uplift bearing capacity has a significant impact;it is found that the bucket foundation has a higher uplift bearing capacity at the loading position at 2/3 of the buried depth,and the bearing capacity will continue to rise as the displacement increases.The loading position has a significant impact on the uplift displacement of the bucket foundation,and loading at the bottom of the bucket can minimize the overall displacement.(4)Using backpropagation neural network to predict the pullout performance of the suction bucket foundation,and confirm the rationality of the numerical calculation by correcting with the indoor experimental data,expand new situation analysis,and carry out the pullout performance of the suction bucket foundation Prediction,combined with relevant research to verify the rationality of the prediction results.The research results show that:sample calculation and data set construction are carried out on the uplift angle and uplift prediction based on the bucket shape,and the data is divided into training set,verification set and test set to train the backpropagation neural network model;the model is fitted through iterative calculation Analysis with the predicted results shows that the correlation coefficient is very close to the theoretical maximum value of 1,which shows that the fitting effect of the model is excellent.In summary,aiming at the pullout performance of the suction bucket foundation of the ocean platform in sandy soil,this paper comprehensively uses laboratory tests,numerical simulations,sensitivity analysis and BP neural network methods,and deeply discusses the effect of the suction bucket foundation on sandy soil.The characteristics of the pullout resistance and its change rule under the joint action of many factors.The research results will provide theoretical basis and technical support for the design and optimization of suction bucket foundations in practical engineering applications,and also provide new ideas and means for further research and prediction of the pullout performance of suction bucket foundations.