海洋含气土高应力加卸载变形特征与渗流规律  

DEFORMATION AND SEEPAGE CHARACTERISTICS OF MARINE GASSY SOIL DURING HIGH-STRESS LOADING AND UNLOADING

作　　者：宋杰[1] 刘乐乐 刘涛[1] 张永超 杨磊 万义钊 Song Jie;Liu Lele;Liu Tao;Zhang Yongchao;Yang Lei;Wan Yizhao(Shandong Engineering Research Center of Marine Exploration and Conservation,Ocean University of China,Qingdao 266100,Shandong,China;Key Laboratory of Gas Hydrate,Ministry of Natural Resources,Qingdao Institute of Marine Geology,China Geological Survey,Qingdao 266237,Shandong,China;Donghai Laboratory,Zhoushan 316021,Zhejiang,China;Zhejiang Institute of Marine Geology Survey,Zhoushan 316021,Zhejiang,China)

机构地区：[1]中国海洋大学海底建设与保护山东省工程研究中心,山东青岛266100 [2]中国地质调查局青岛海洋地质研究所,自然资源部天然气水合物重点实验室,山东青岛266237 [3]东海实验室,浙江舟山316021 [4]浙江省海洋地质调查大队,浙江舟山316021

出　　处：《力学学报》2025年第2期545-558,共14页Chinese Journal of Theoretical and Applied Mechanics

基　　金：山东省自然科学基金(ZR2022YQ54);国家自然科学基金(U2006213,42277139);东海实验室开放基金(DH-2022KF0220);浙江省自然资源科技资金(2023-61);浙江省地质专项资金(2023013);中央自然灾害防治体系建设资金(2023330053);山东省泰山学者工程(tsqn202306297)资助项目。

摘　　要：含气土是一种结构特殊的土,具有力学强度低、压缩性高、膨胀性强和固结过程复杂等特点,在海洋工程建设中容易诱发多种形式的灾害.海洋含气土的力学性质变化受有效固结应力和孔隙压力的影响,但是目前针对更高有效固结应力条件下的海洋含气土力学性质试验研究还不够充分.文章首先对取自浙江舟山近海浅层气富集区的海洋沉积物进行了物理力学指标测试,然后重塑并借助沸石制备了含气土试样,最后在侧向完全受限条件下开展了循环加卸载试验,竖向载荷最高达到3200 kPa,揭示了海洋沉积物粒径级配、矿物组成、液限和塑限含水率等指标在去除盐分前后的变化机理,分析了含气量等因素对海洋含气土试样加卸载变形回弹与渗流过程的影响规律.结果表明,海洋含气土的体积压缩系数随着载荷的增加而减小,并且含气量越高则压缩指数与回弹指数均增大;孔隙水与气体主要在循环加卸载过程中的首轮排出,并且集中在首轮加载的初期;在首轮加载过程中,不含气饱和海洋土的渗透系数单调减小,而海洋含气土的渗透系数出现了明显的回升波动.Gassy soils have special inner structures(e.g.,massive gas bubbles dispersed in the pore water),and this leads to low shear strength,high compressibility,strong expansivity,and complex consolidation process.The presence of gassy soils beneath the seafloor has great potential to trigger various kinds of disasters during ocean engineering construction.Mechanical properties of marine gassy soils are inherently controlled by the effective stress for consolidation and the inner pressure of pore fluids.However,when subjected to high effective stresses for consolidation,experimental data are currently insufficient,and how marine gassy soils response remains elusive.In this study,intact marine sediments were cored from an offshore region rich in shallow gas near the city of Zhoushan,and the sediments,after indoor testing for basic physical and chemical indexes(e.g.,particle size distribution,mineral composition,liquid and plastic limit water ratios),were remolded to prepare gassy soil specimens by using the zeolite method.Cyclic loading and unloading were performed on the gassy soil specimens under laterally confined condition,and the maximum vertical stress was 3200 kPa.Basic physics behind changes of the indexes due to salt removing were unveiled,and effects of the gas content on deformation behaviors as well as seepage characteristics during cyclic loading and unloading were analyzed.It is shown that coefficient of compressibility of marine gassy soils decreases during loading,and the compression index together with the expansion index increases with increasing gas content.Pore gas and water are produced mainly during the virgin loading,and more than one half of the cumulative volumes of produced gas and water are squeezed out of gassy soils at the beginning of the virgin loading.The hydraulic conductivity of water saturated soils monotonously decreases when the soils subjected loading.However,the hydraulic conductivity of marine gassy soils firstly decreases,then changes to increase,and finally returns to decrease du

关 键 词：浅层气 含气土 固结试验 压缩指数 渗透系数 

分 类 号：TU411[建筑科学—岩土工程]