Study On The Internal And External Clamping Type Marine Pile Spreader With Changeable Diameter And Analysis Of The Clamping Mechanism

The large-scale marine foundation pile is the important part of the pile foundation of the offshore oceanic structure.It is a thin-shelled steel pile with long length and smooth inner and outer shells.With these characteristics,its lifting operation has always been the major problem in the construction of marine structures.This paper compares and analyzes the structural characteristics and clamping methods of various types of spreaders of the large-scale marine foundation piles.It is found that the existing pile spreaders often hold the piles only in one side,thus the pile only sustains the one side load from the spreader and it may cause large deformation to the pile or even damage it.Moreover,the spreader is usually designed to the pile with certain inner and outer diameter,so its adaptability to the certain specific pile with different diameters is not satisfactory.In view of this situation,this paper proposes the structural scheme of “Internal and External Clamping Type Marine Pile Spreader with Changeable Diameter”,which is based on the bilateral spreader of the IHC.Co,working to improve the problems mentioned above.The research is supported by the National Natural Science Foundation of China.In view of the structure of the spreader proposed in this paper,the friction clamping method and the wedge teeth embedding clamping method were studied in depth.At the same time,the internal and external clamping method was also testified to be effective.The specific work fulfilled in this paper is as follows.According to the structural size of the pile,the design of the overall scheme of the spreader was completed.In this part,the design of the overall mechanical structure of the spreader,the work hydraulic circuit and the control system was completed,which provided the basis of the analysis of the clamping mechanism.For the friction clamping method and the clamping hydraulic cylinder initially selected,firstly,the elastic shell theory,the method of equivalent model and the finite element simulation were respectively used to calculate the deformation of the area clamped by the spreader,when the spreader only clamps the outer shell of the pile or adopts the internal and external clamping method.From the result of analysis,the internal and external clamping method was proved to be effective.Subsequently,in order to study the friction clamping force of the spreader,the maximum static friction coefficient between the spreader clamping mechanism and the outer shell of the pile was calculated.Finally,the lifting process of the pile was studied,and the safety criterias for lifting foundation piles by friction clamping method were given to testify the friction clamping force of the spreader.For wedge teeth embedding clamping method,firstly,the plastic mechanics slip line field theory and Abaqus simulation analysis were utilized to study the interaction process of the wedge teeth and the outer shell of the pile.In this part,the effect of the teeth angle on its embedding performance and the connection between single tooth embedding and multi-tooth embedding was the essential content.In this part,the structural parameters of the clamping hydraulic cylinder and the clamping wedge of the spreader were finally determined.Then,the theory of elastic mechanics and Abaqus simulation analysis was used to study the stress characteristics of wedge teeth during the lifting process.Finally,friction clamping method and the wedge teeth embedding clamping method was compared in detail.From the comparison,the advantages and limitation of the two methods were concluded.For the clamping hydraulic cylinder re-selected,the deformation of the pile was recalculated,and the necessity of using the inner and outer clamping methods of the spreader was analyzed.In order to further study the two clamping methods of the spreader,a small experimental device was designed and manufactured for related experimental research.For the friction clamping method,the bearing capacity of the method was experimentally studied,and the maximum static friction coefficient between the clamping mechanism of the experimental device and the pile specimen was obtained.For the wedge teeth embedding clamping method,the process of wedge teeth insertion with different tooth angle and number,and the bearing capacity of wedge teeth were studied experimentally.The equivalent friction coefficient between the clamping mechanism of the experimental device and the pile specimen was obtained.The friction coefficients of the two clamping methods obtained by experiments were compared quantitatively to illustrate the difference between the two clamping methods.Through the analysis of the experimental data,the correctness of the theoretical analysis and simulation in the previous content was verified.