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Investigation into the effect of backpressure on the mechanical behavior of methane-hydrate-bearing sediments via DEM analyses

Lookup NU author(s): Professor Stefano Utili

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Abstract

Backpressure has been extensively applied in experimental tests to improve the water saturation of samples,and its effect on the strength of saturated soils has been traditionally regarded as trivial in SoilMechanics. However, a non-negligible influence of backpressure on the macro mechanical propertiesof methane-hydrate-bearing-sediments (MHBS) has been surprisingly observed in several recent experimentsreported in the literature. This paper aims to shed light on this phenomenon. A theoretical analysison the microscopic interaction between soil grains and inter-particle methane hydrate (MH) wascarried out to highlight how backpressure affects the mechanical properties of the inter-particle MHwhich in turn affect the macroscopic mechanical behavior of MHBS. The influence of backpressure isaccounted for in a new bond contact model implemented into the Distinct Element Method (DEM).Then, a series of DEM biaxial compression tests were run to investigate the link between mechanicalproperties of MHBS and backpressure. The DEM numerical results show that shear strength, small strainstiffness and shear dilation of MHBS increase with the level of backpressure. As the critical state isapproached, the influence of backpressure ceases. Moreover, the elastic modulus and cohesion ofMHBS increase linearly while the internal friction angle decreases at a decreasing rate as the backpressureincreases. Simple analytical relationships were achieved so that the effect of backpressure on themechanical properties of MHBS can be accounted in the design of laboratory tests to characterize themechanical behavior of MHBS.

Publication metadata

Author(s): Jiang MJ, Zhu F, Utili S

Publication type: Article

Publication status: Published

Journal: Computers and Geotechnics

Year: 2015

Volume: 69

Pages: 551-563

Print publication date: 01/09/2015

Online publication date: 06/07/2015

Acceptance date: 23/06/2015

ISSN (print): 0266-352X

ISSN (electronic): 1873-7633

Publisher: Elsevier

URL: http://dx.doi.org/10.1016/j.compgeo.2015.06.019

DOI: 10.1016/j.compgeo.2015.06.019

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