Numerical Simulation of Mechanical Compaction of Deepwater Shallow Sediments  

作　　者：SUN Jin WU Shiguo DENG Jingen LIN Hai ZHANG Hanyu WANG Jiliang GAO Jinwei 

机构地区：[1]Laboratory of Marine Geophysics&Geo-Resources,Institute of Deep-Sea Science and Engineering,Chinese Academy of Sciences,Sanya 572000,China [2]Qingdao National Laboratory for Marine Science and Technology,Qingdao 266237,China [3]College of Earth Sciences,University of Chinese Academy of Sciences,Beijing 100049,China [4]State Key Laboratory of Petroleum Resources and Prospecting,China University of Petroleum,Beijing 102249,China [5]CNOOC China Limited Tianjin Branch,Tianjin 300451,China

出　　处：《Journal of Ocean University of China》2018年第1期53-64,共12页中国海洋大学学报（英文版）

基　　金：funded by the National Key Basic Research Program of China (973 Program) (No. 2015 CB25 1201);NSFC-Shandong Joint Fund for Marine Science Research Centers (No. U1606401);Key Science & Technology Foundation of Sanya (Nos. 2017PT13 and 2017PT14)

摘　　要：To study the compaction law and overpressure evolution in deepwater shallow sediments, a large-strain compaction model that considers material nonlinearity and moving boundary is formulated. The model considers the dependence of permeability and material properties on void ratio. The modified Cam-Clay model is selected as the constitutive relations of the sediments, and the deactivation/reactivation method is used to capture the moving top surface during the deposition process. A one-dimensional model is used to study the compaction law of the shallow sediments. Results show that the settlement of the shallow sediments is large under their own weight during compaction. The void ratio decreases strictly with burial depth and decreases more quickly near the seafloor than in the deeper layers. The generation of abnormal pressure in the shallow flow sands is closely related to the compaction law of shallow sediments. The two main factors that affect the generation of overpressure in the sands are deposition rate and permeability of overlying clay sediments. Overpressure increases with an increase in deposition rate and a decrease in the permeability of the overlying clay sediment. Moreover, an upper limit for the overpressure exists. A two-dimensional model is used to study the differential compaction of the shallow sediments. The pore pressure will still increase due to the inflow of the pore fluid from the neighboring clay sediment even though the deposition process is interrupted.To study the compaction law and overpressure evolution in deepwater shallow sediments, a large-strain compaction model that considers material nonlinearity and moving boundary is formulated. The model considers the dependence of permeability and material properties on void ratio. The modified Cam-Clay model is selected as the constitutive relations of the sediments, and the deactivation/reactivation method is used to capture the moving top surface during the deposition process. A one-dimensional model is used to study the compaction law of the shallow sediments. Results show that the settlement of the shallow sediments is large under their own weight during compaction. The void ratio decreases strictly with burial depth and decreases more quickly near the seafloor than in the deeper layers. The generation of abnormal pressure in the shallow flow sands is closely related to the compaction law of shallow sediments. The two main factors that affect the generation of overpressure in the sands are deposition rate and permeability of overlying clay sediments. Overpressure increases with an increase in deposition rate and a decrease in the permeability of the overlying clay sediment. Moreover, an upper limit for the overpressure exists. A two-dimensional model is used to study the differential compaction of the shallow sediments. The pore pressure will still increase due to the inflow of the pore fluid from the neighboring clay sediment even though the deposition process is interrupted.

关 键 词：mechanical COMPACTION DEEPWATER SHALLOW SEDIMENTS COMPACTION LAW SHALLOW water flow OVERPRESSURE evolution 

分 类 号：P7[天文地球—海洋科学]