Research On The Crushing Performance Of Submarine Non-diagenetic Gas Hydrate Mechanical Cutter Suction Cutter

As the 173rd mineral resources in China,the natural gas hydrate is rich in resources.It is a kind of efficient clean energy and also an important direction of the future global energy development.The solid fluidization development is a new idea for safe,green and efficient exploitation of seafloor non-diagenetic hydrate in China.And the seafloor mining part is the key to achieve commercial gas production.Aiming at mechanical cutter suction crushing which is one of the mining and crushing methods,the research on the crushing performance of the single pick cutter on the cutter head to hydrate deposit is carried out,which is the important foundation for the design and optimization of the next suction cutter.The main research work is as follows:(1)For these problems of indoor synthetic seabed gas hydrate—high cost,long cycle and easy to decompose when it is under the normal temperature and pressure,two similar crushed material were substituted for the average intensity level and peak intensity level of submarine non-diagenetic hydrate,which provides a quick and low cost sample for the subsequent crushing performance experiment and optimization tools.Considering the study of crushing performance,the volume,velocity and particle size distribution of hydrate fracture are mainly concerned and it is not easy to change the phase state of hydrate in the environment of the seabed in situ.In this paper,based on the similarity theory,we use the material with similar mechanical properties to replace the submarine non-diagenetic hydrates to carry out the crushing experiment.Through uniaxial compression test,three axis shear test and Brazil split test,the parameters such as uniaxial compressive strength,elastic modulus,Poisson's ratio,tensile strength,cohesion and internal friction angle of the samples were obtained.Compared with the corresponding parameters of hydrate,two kinds of formula for average intensity and peak intensity of gas hydrate were determined respectively and the corresponding preparation techniques and methods were mastered.The drawing board is made of similar materials with aggregate content and gypsum content as the variable.It provides broken samples and valuable prescription data for subsequent work.(2)Based on the preparation of hydrate crushing sample,carry out pick cutter breaking experiment and obtain the effects of single cutter cutting width,cutting depth,front edge angle,side slope angle,cutting speed and material mechanical properties on cutting load and cutting specific energy,which provides the basis for optimizing design of mechanical single cutter head.Aiming at the difficult problem of full-scale mechanical suction cutter head crushing experiment,the binomial equation of cutting depth,cutting width and cutting force is fitted.The adaptability of Evans two-dimensional tensile fracture model under the condition of large front edge angle is verified and the Goktan extrusion model is modified under the working condition of the small front edge angle,which lays a theoretical foundation for the calculation and Simulation of the cutting force of the full size mechanical winch cutter head when it is broken.(3)On the basis of single cutter crushing experiment of hydrate samples,the particle size distribution of hydrates samples under the structure of different cutting parameters and the structure of the cutter is studied so that the influence of the parameters on the particle size distribution after the fracture of hydrates was obtained.The experimental data show that the cutting depth in the parameters concerned is the most important factor affecting the distribution of the particle size after the hydrates are broken.The crushing effect is the best when the wedge tooth' side angle is 10 degrees.The maximum particle size and mass fraction of large particle size are all lower than those of other tooth types,which provides a basis for the optimum design and selection of single tooth for the mechanical winch cutter head.(4)Based on the D-P strength criterion,a numerical model for the fracture of undersea non-diagenetic hydrates is established.Based on this model,the simulation analysis of the fracture of the submarine non-diagenetic hydrates is carried out by using ABAQUS software and the model was corrected with the experimental data of hydrate sample crushing.The modified model is used to carry out the simulation study of the pick cutter breakage of the mechanical winch cutter head combination.The simulation model and method are provided for the mechanical fracture simulation study of the subsequent submarine non-diagenetic hydrates,the structural design and optimization of the mechanical winch cutter head.In this paper,two kinds of fractured samples of gas hydrate in non-diagenetic rocks of the seabed have been developed.The influence of the cutting parameters on the broken particle size and load is found through the experimental study of single cutter fragmentation.The main controlling factors affecting the size of hydrate fragmentation were found,and a simulation model for numerical simulation of seafloor non-diagenetic hydrate was established and corrected by experimental data.The research results provide a theory and method for the design and optimization of the mechanical suction cutter for the marine non-diagenetic hydrate,and play a supporting role in the study of the mechanically excavated marine non-diagenetic hydrate.