南海神狐峡谷群海底沉积物摩擦特性  

Frictional characteristics of the submarine sediments in the Shenhu Canyons,South China Sea

作　　者：陈顺 杨小秋[1,2,3] 何昌荣 徐子英[2,6] 林為人[5] 姚文明 施小斌 许鹤华[1] 孙珍[1] CHEN Shun;YANG XiaoQiu;HE ChangRong;XU ZiYing;LIN Weiren;YAO WenMing;SHI XiaoBin;XU HeHua;SUN Zhen(Key Laboratory of Ocean and Marginal Sea Geology,South China Sea Institute of Oceanology,Chinese Academy of Sciences,Guangzhou 511458,China;Key Laboratory of Marine Mineral Resources,Ministry of Natural Resources,Guangzhou Marine Geological Survey,Guangzhou 511458,China;University of Chinese Academy of Sciences,Beijing 100049,China;State Key Laboratory of Earthquake Dynamics,Institute of Geology,China Earthquake Administration,Beijing 100029,China;Graduate School of Engineering,Kyoto University,Kyoto 615-8540,Japan;National Engineering Research Center for Gas Hydrate Exploration and Development,Guangzhou 511458,China)

机构地区：[1]中国科学院边缘海与大洋地质重点实验室,南海海洋研究所,广州511458 [2]自然资源部海底矿产资源重点实验室,广州海洋地质调查局,广州511458 [3]中国科学院大学,北京100049 [4]中国地震局地质研究所地震动力学国家重点实验室,北京100029 [5]Graduate School of Engineering,Kyoto University,Kyoto 615-8540,Japan [6]天然气水合物勘查开发国家工程研究中心,广州511458

出　　处：《地球物理学报》2023年第11期4705-4720,共16页Chinese Journal of Geophysics

基　　金：自然资源部海底矿产重点实验室开放基金课题(KLMMR-2022-K01);国家自然科学基金项目(41874099,41776078,U20A20100);中国科学院南海海洋研究所自主部署项目(SCSIO2023QY06);国家重点研发计划重点专项(2021YFC3100604,2022YFC2807900)资助。

摘　　要：海底滑坡区沉积物的摩擦特性对滑坡发育具有控制作用,是海底边坡稳定性评估、滑坡过程中温压场演化及与滑坡相关的水合物成藏规律研究的基础参数.我国南海北部陆坡区不仅赋存着丰富水合物资源,而且在地质历史上也曾多次发生滑坡作用,目前仍是潜在的海底滑坡区.为了尽可能了解南海北部滑坡区沉积物的原位摩擦特性,本文在围压Pc=20 MPa、孔隙压Pp=10 MPa及温度T≈20℃条件下,对采自南海神狐峡谷群的4个沉积物样品开展了三轴准静态摩擦滑动实验.实验结果表明神狐峡谷群浅层沉积物:(1)均呈现速度强化及位移强化特征;(2)最大静摩擦系数μmax为0.460~0.510,稳态摩擦系数μss为0.455~0.554,二者的变化趋势较一致;(3)内聚力c为0.30~0.57 MPa、摩擦角φ为24.5°~27.0°.而神狐峡谷群地形坡度较缓(<6.8°).现今神狐峡谷群仅在沉积物自重作用下不会发生失稳,总体上比较稳定.结合峡谷群多期次的滑坡特征以及滑坡体与水合物稳定域底界(通常与似海底反射层(Bottom simulating reflector,简写BSR)重叠)、气烟囱等构造的空间分布关系,我们推测:神狐峡谷群滑坡的形成主要是由于BSR附近地层孔隙压升高、强度降低,进而导致失稳.BSR附近地层孔隙压升高则可能是由于深部热成因游离气的聚集、BSR附近的水合物在地震等对其温、压场的扰动下分解所致.The frictional characteristics of sediments control the development of landslides in submarine landslide areas.They are the basic parameters for the evaluation of submarine slope stability,and the study of the geothermal-pressure field evolution,and the law of gas hydrate hosting during the landslide process.The continental slope areas of the northern South China Sea are not only rich in gas hydrate resources,but also have many landslides in geological history.They are still potential submarine landslide areas.In order to understand the in situ frictional characteristics of the sediments in the landslide areas of the northern South China Sea as much as possible,we carried out the triaxial quasi-static frictional sliding experiments for four sediment collected from the Shenhu Canyons,under the conditions of confining pressure Pc=20 MPa,pore pressure Pp=10 MPa and temperature T≈20℃.The experimental results show that:(1)all the four shallow sediments show the characteristics of velocity strengthening and displacement strengthening.(2)The maximum static friction coefficient(μmax)and steady-state friction coefficient(μss)of these four sediments range from 0.460 to 0.510,and from 0.455 to 0.554,respectively.Moreover,there is a positive relationship betweenμmax andμss.(3)The ranges of cohesion(c)and friction angle(φ)are 0.30~0.57 MPa and 24.5°~27.0°,respectively.In fact,the topographic slope usually lower than 6.8°in the Shenhu Canyons.It means that the unstable slip could not be induced only by the sediments weight in this area.In addition,based on the multi-stage landslide characteristics of the Shenhu Conyons,the spatial distribution relationship between the landslide bodies and the bottom boundaries of the hydrate stability domain which usually overlap with the bottom simulating reflectors(BSRs),gas chimneys and other structures,we infer that the landslides are predominantly caused by the increase of pore pressure which reduces the formation strength near the BSRs.The increase of pore pressure may be cau

关 键 词：南海神狐峡谷群 摩擦系数 速度依赖性 位移依赖性 水合物 海底滑坡 

分 类 号：P736[天文地球—海洋地质] P738[天文地球—海洋科学]