Study On Uniaxial Compression Properties And Resistivity Of Aqueous Soils

Natural gas hydrate mainly occurs in the bottom sediments of the sea,with the characteristics of high energy density,large scale,large amount of resources,Shallow burial,clean,etc.,which is described as the most promising strategic new energy in the 21 st century.At the same time,as natural gas hydrate requires a strict occurrence environment,its exploitation has become a worldwide hot spot and difficulty.Improper exploitation can lead to serious environmental and geological problems.Therefore,it is particularly important to understand the mechanical properties of hydrate-bearing sediments for the stability of its exploitation.Resistivity method can efficiently and conveniently reflect the relevant characteristics of NGH deposits.If it can be applied to the engineering practice of NGH,it will bring about great economic effects.Therefore,this paper mainly explores the influence of hydrate saturation on the mechanical properties of hydrate samples and the changes in the resistivity during the hydrate formation process.In this paper,tetrahydrofuran hydrate samples formed by mixing silt,xiamen standard sand and self-prepared south China sea sedimentary soil with tetrahydrofuran solution were studied,and Triaxial samples were prepared by compaction method.The samples were induced to form tetrahydrofuran hydrate by freezers.Through special unconfined compression test and resistivity observation test under low temperature environment,the influence rule of different soil mass,different hydrate saturation and different sample dry density control on its unconfined compressive strength was discussed,and the variation rule of the resistivity of samples before and after the formation of tetrahydrofuran hydrate was explored.Research findings:(1)Under the same dry density,the unconfined compressive strength of tetrahydrofuran hydrate samples compacted by three soils increases with the saturation of the hydrate,the reason is that the cementation between the particles will affect the strength of the sample.With the increase of hydrate saturation,the hydrate crystals generated in the pores will increase,and the cementation between the hydrate particles will be more obvious.(2)At the same hydrate saturation,the unconfined compressive strength of tetrahydrofuran hydrate samples compacted by three soils was strengthened with the increase of dry density control,which is because the control of dry density directly affects the density of the samples,and the density increases with the increase of dry density.(3)In the case that the dry density and hydrate saturation of the samples are the same,the unconfined compressive strength of the tetrahydrofuran hydrate samples changes due to different soil properties.The sequence of unconfined compressive strength is: Xiamen standard sand > self-mixing south China sea sedimentary soil > silt.(4)The resistivity of tetrahydrofuran hydrate powder decreased with the increase of dry density.The reason is that the higher the dry density is,the smaller the pores are,and the more closely the hydrate crystal particles are connected with each other,which reduces their resistivity.(5)With the formation of tetrahydrofuran hydrate in the sample,its resistivity gradually increased and reached the maximum value at 24 hours,at which time tetrahydrofuran hydrate was almost completely formed.