INFLUENCE OF OCCURRENCE MODE OF HYDRATE ON MECHANICAL BEHAVIOUR OF HYDRATE-BEARING SOILS
YAN Rongtao1，2，WEI Changfu2，FU Xinhui1，ZHONG Xiaobin3，XIAO Guiyuan1
(1.The Experimental Center for Minig and Metallurgy and Environmental Science of Guangxi，Guiling，Guangxi 541004，China；2. State Key Laboratory of Geomechanics and Geotechnical Engineering，Institute of Rock and Soil Mechanics，Chinese Academy of Sciences，Wuhan，Hubei 430071，China；3. Xi'an Railway Bureau，Xian，Shaanxi 710054，China)
Abstract：Based on the two synthesis methods of hydrate in soils，the unsaturation sampling(US method) and gas diffusion sampling method for saturation soil(SD method)，triaxial shear tests are performed to study the effects of occurrence mode of hydrate on the mechanical properties of hydrate-bearing soils containing CO2. The experimental results confirm that the occurrence mode and saturation of hydrate have significant impact on the mechanical behaviour of soil with hydrate. In view of the microscopic mechanism，some analysis indicate that samples formed by US method，which are called as cementation mode，exhibit some structure characteristics of cementing soil. the samples formed by SD method，which are called as pore filling mode，loading mode and lenticle mode，show the properties of the friction material significantly，and exhibit strain softening due to the crushing damage of hydrate during the shearing period. Besides，by introducing a new parameter—the effective saturation of hydrate，a formula considering the influence of hydrate synthesis methods，which can predict the shearing strength of hydate-bearing soil，is proposed.
KVENVOLDEN KA，LORENSON T D. Global occurrences of gas hydrate[C]//Proeedings of the Eleventh International offshore and Polar Engineering Conference Stavanger. Norway：[s. n.]，2001：17-22.
[2]
曾繁彩，蔡秋蓉，陈宏文，等.天然气水合物的环境效应[J]. 海洋地质，2003，(3)：1-10.(ZENG Fancai，CAI Qiurong，CHEN Hongwen，et al.Environmental effects of natural gas hydrate[J]. Marine Geology，2003，(3)：1-10.(in chinese))
[3]
SULTAN N，COCHONAT P，CANALS M，et al. Triggering mechanisms of slope instability processes and sediment failures on continental margins：a geotechnical approach[J]. Marine Geology，2004，213(1/2/3/4)：291-321.
[4]
WINTERS W J，WAITE W F，MASON D H，et al.Physical properties of sediment containing methane gas hydrate[C]// Proceedings of the 229th National Meeting of the American-Chemical-Society. San Diego，USA：Amer Chemical Soc，2005：：:234--240???-???.
[5]
WINTERS WJ，WAITE W F，MASON D H，et al. Methane gas hydrate effect on sediment acoustic and strength properties[J]. Journal of Petroleum Science and Engineering，2007，56(1/2/3)：127-135.
[6]
MASUI A，HANEDA H，OGATA Y，et al. Effects of methane hydrate formation on shear strength of synthetic methane hydrate sediments[C]//Proceedings of the Fifteenth International Offshore and Polar Engineering Conference. Seoul，Korea：The International Society of Offshore and Polar Engineering???，：???Seoul, Korea，22005：364-369.
[7]
YUN TS，SANTAMARINA JC，RUPPEL C. Mechanical properties of sand，silt，and clay containing tetrahydrofuran hydrate[J].Journal of Geophysical Research-Solid Earth，2007，112(B4)：13.
[8]
MASUI A，MIYAZAKI K，HANEDA H，et al.Mechanical characteristics of natural and artificial Gas hydrate bearing sediments[C]//Proceedings of the 6th International Conference ongas Hydrates(ICGH2008). Vancouver，Canada：British Columbia，2008：???463-470???.
[9]
DVORKIN J，HELGERUD M B，WAITE W F，et al. Introduction to
natural gas hydrate in oceanic and permafrost environments[M]. Netherlands：Kluwer Academic Publishers，2000：245-260.
[10]
张旭辉，王淑云，李清平，等. 天然气水合物沉积物力学性质的试验研究[J].岩土力学，2010，31(10)：3069-3074.(ZHANG Xuhui，WANG Shuyun，LI Qingping，et al. Experimental study of mechanical properties of gas hydrate deposits[J]. Rock and Soil Mechanics，2010，31(10)：3069-3074.(in Chinese))
[11]
KONO H O，NARASIMHAN S，SONG F，et al. Synthesis of methane gashydrate in porous sediments and its dissociation by depressurizing[J].Powder Technology，2002，122(2/3)：239-246.
[12]
邵龙潭，刘潇，郭晓霞，等.土工三轴试验试样全表面变形测量的实现[J]. 岩土工程学报，2012，34(3)：409-415.(SHAO Longtan，LIU Xiao，GUO Xiaoxiang，et al. Whole surface deformation measurement of triaxial soil sepcimen based on digital image processing[J]. Chinese Journal of Geotechnical Engineering，2012，34(3)：409-415.(in chinese))
[13]
DUNCAN M J，CHANG CY. Nonlinear analysis of stress and strain in soils[J].Journalof Soil Mechanicsand FoundationsDivision，ASCE，1970，96(5)：1629-1654.
[14]
SHIBUYA S，TATSUOKA F，ABE F，et al. A New look at stress-strain relations of soils and soft rocks[C]//Proceedings of the9th Asian Regional Conference on Soil Mechanics and Foundation Engineering. Bangkok，Thailand：Publ Thailand，1991：534???-551?.??.
[15]
EBINUMA T，KAMATA Y，MINAGAWA H，et al. Mechanical properties of sandy sediment containing methane hydrate[C]//Proceedings of the 5th international Conference on Gas hydrates. Trondheim，Norway：[s.n.]，2005：958-961.
[16]
SANTAMARINA J C，RUPPEL C. The impact of hydrate saturation on the mechanical，electrical，and thermal properties of hydrate-bearing sand，silts，and clay[C]//Proceedings of the 6th international Conference on Gas Hydrates.Vancouver，Canada：[s.n.]，2008：???324-330???.
[17]
DURHAM W B，KIRBY S H，STERN L A，et al.The strength and rheology of methane clathrate hydrate[J].Journal of Geophysical Research：Solid Earth，2003，108(B4)：2182.
2013, Vol. 32 
