Mechanical Characteristics Of Bucket Foundation In Sand During Static Pressure Penetration

Bucket foundation is a common foundation type in marine engineering,most of the bucket foundation taking suction penetration.Hence,reasonable negative pressure can reduce sinking resistance on the precondition of bucket foundation stability,and sinking in place.The estimation method of negative pressure of bucket sinking adopted actual CPT field data,and the CPT data is the soil resistance characteristic parameters in the process of bucket foundation static pressure penetration.Therefore,research on static pressure penetration of bucket foundation can provide relevant parameters for the negative pressure estimation of sucking penetration.Based on the existing research results of the bucket foundation suction and static penetration.Using the method of combining theoretical analysis with discrete element method and model test,soil displacement and earth pressure in static pressure penetration process were studied,then the penetration resistance,earth pressure,reason for soil plug were obtained.The main contents of this thesis are as follows:(1)The model tests of different diameter of bucket foundation in the sand under static pressure penetration were carried out,and the development of tube-soil plug,displacement field of soil body and external stress in the bucket were monitored.The bucket of the soil arching effect are confirmed by the laws of displacement field changing,while the bucket soil stress state changes is to verify that the soil arching effect has a significant impact on the development of the soil plug,and the soil arching effect and soil plug in bucket revealed the mechanism of penetration resistance increment.(2)According to the large deformation characteristics of the soil in the penetration process,a bucket foundation static penetration model using discrete element method was established,then the dynamic penetration of bucket foundation in sandy soil in the whole process of simulation was carried out.The change characteristics of soil displacement and force chain in the process of sedimentation were analyzed,the soil particles position and force chain were studied on soil arching effect on micro forming mechanism.(3)Based on the theory of static three hinge arch under uniformly distributed load stress mechanism,the soil arch stress pattern was put forward according to the principle of static three hinged arch.And the arch axis is parabolic under uniformly distributed load,the soil arch appears axisymmetric space.Therefore,the calculation method of penetration resistance,earth pressure inside bucket wall is established considering soil arch effect,based on the theory of computational mechanics when the soil arching was simplified to a plane problem.In a word,according to the displacement characteristics in the process of bucket foundation static pressure penetration in sand,the soil arching influence on penetration resistance was studied,then calculation methods of penetration resistance and earth pressure inside bucket wall were put forward.Afterwards,the theoretical calculation result of soil plugging effect,frictional resistance of bucket-soil and penetration resistance were compared with the test data of different diameter bucket under static pressure penetration,in order to testify the rationality of this method.This paper’s method can provide a reference for reasonable prediction of penetration resistance of bucket foundation.