海底沉积物中气囊产生过程超孔隙水压力变化特征分析  

Analysis of characteristics of excess pore water pressure changes in the process of gasbag formation in marine sediments

作　　者：雷诗芸 刘慧芳 郭秀军[1,2] 孙浩 邢程 LEI Shiyun;LIU Huifang;GUO Xiujun;SUN Hao;XING Cheng(College of Environmental Science and Engineering,Ocean University of China,Qingdao 266100,China;Key Lab of Marine Environmental Science and Ecology,Ministry of Education,Qingdao 266100,China)

机构地区：[1]中国海洋大学环境科学与工程学院,山东青岛266100 [2]山东省海洋环境地质工程重点实验室,山东青岛266100

出　　处：《海洋湖沼通报》2024年第2期51-61,共11页Transactions of Oceanology and Limnology

基　　金：自然科学基金(41977234);国家重点研发计划(2017YFC037701)。

摘　　要：在外部因素的作用下,海底沉积物中向上运移的深源气体在浅层粗-细沉积物界面处形成气囊,气囊中的气体逸出将带来一定危害。对气囊进行实时监测,能有效判定其发展规律并预测后续相关灾害发生。本研究利用多点孔隙水压力监测技术,通过数学模拟实验和物理模拟实验两种方式模拟饱和细粒沉积物中气囊的发生和消散过程,重点讨论裂缝产生、气囊形成、气体释放的典型超孔隙水压力变化特征和变化机制。在理论分析的基础上,根据数学模拟和物理模拟实验的结果,将气囊的形成-生长-消散过程分为横向裂缝产生、气囊纵向膨胀、斜/竖向裂缝产生三个阶段,对应的超孔隙水压力时间序列呈“凹”字形。气囊形成始于粗-细沉积物界面处横向裂缝产生,此时超孔隙水压力值迅速衰减;之后气囊纵向腔膨胀发育,超孔隙水压力保持相对稳定;气囊演化末期出现斜/竖向裂缝,超孔隙水压力再次累积与消散。气体释放阶段的超孔隙水压力变化曲线呈锯齿状波动,可根据压力锯齿状波动的差异性区分气体是间歇性释放还是连续性释放。土层经历气体释放过程后,再次注气时超孔隙水压力能够累积的极值降低,这意味着较小的压力就能产生裂缝再次打开气体通道,破坏沉积物使气体逸出。Under the action of external factors,the deep gas in seafloor sediments moves upward,which is easy to accumulate at the interface of shallow coarse-fine sediments and form gasbags.When the gas in the gasbag escapes,it will induce a variety of submarine geological disasters and bring harm to human engineering construction.Therefore,real-time monitoring of the formation-growth-dissipation process of gasbags is of great significance for effectively judging its development law and predicting the occurrence of follow-up potential disasters.In this study,the multi-point pore water pressure monitoring technique was used to simulate and monitor the forming and dissipation of gasbags in saturated fine-grained sediments by mathematical simulation and physical simulation experiments.The variation characteristics and mechanism of typical excess pore water pressure of fracture formation,gasbag formation and gas release were discussed in detail.According to the results of mathematical simulation and physical simulation experiments,combined with theoretical analysis,the formation-growth-dissipation process of gasbag was divided into three stages:transverse crack generation,gasbag longitudinal expansion and oblique or vertical crack generation,and its corresponding excess pore water pressure was concave.The formation of gasbag began with the transverse cracks at the interface of coarse and fine sediments,and excess pore water pressure attenuated rapidly.The gasbag showed the expansion of longitudinal cavity,and excess pore water pressure remained almost unchanged;oblique or vertical cracks appeared at the end of the evolution of gasbag,and excess pore water pressure accumulated and dissipated again.The variation curve of excess pore water pressure in gas release stage had obvious saw-tooth fluctuation characteristics,and it could be used to distinguish whether the gas was released intermittently or continuously.The accumulated extreme value of excess pore water pressure could be reduced during gas reinjection,which meant that a

关 键 词：孔隙水压力监测 超孔隙水压力 气囊 裂缝 气体运移 

分 类 号：X21[环境科学与工程—环境科学]