Impacts of Consolidation Time on the Critical Hydraulic Gradient of Newly Deposited Silty Seabed in the Yellow River Delta

• Main Authors: Meiyun Tang, Yonggang Jia, Shaotong Zhang, Chenxi Wang, Hanlu Liu
• Format: Article
• Language: English
• Published: MDPI AG 2021-03-01
• Series: Journal of Marine Science and Engineering
• Subjects: seepage failure; critical hydraulic gradient; excess pore pressure; fluidization degree; resuspension
• Online Access: https://www.mdpi.com/2077-1312/9/3/270

The silty seabed in the Yellow River Delta (YRD) is exposed to deposition, liquefaction, and reconsolidation repeatedly, during which seepage flows are crucial to the seabed strength. In extreme cases, seepage flows could cause seepage failure (SF) in the seabed, endangering the offshore structures. A critical condition exists for the occurrence of SF, i.e., the critical hydraulic gradient (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>i</mi><mrow><mi>cr</mi></mrow></msub></mrow></semantics></math></inline-formula>). Compared with cohesionless sands, the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>i</mi><mrow><mi>cr</mi></mrow></msub></mrow></semantics></math></inline-formula> of cohesive sediments is more complex, and no universal evaluation theory is available yet. The present work first improved a self-designed annular flume to avoid SF along the sidewall, then simulated the SF process of the seabed with different consolidation times in order to explore the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>i</mi><mrow><mi>cr</mi></mrow></msub></mrow></semantics></math></inline-formula> of newly deposited silty seabed in the YRD. It is found that the theoretical formula for <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>i</mi><mrow><mi>cr</mi></mrow></msub></mrow></semantics></math></inline-formula> of cohesionless soil grossly underestimated the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>i</mi><mrow><mi>cr</mi></mrow></msub></mrow></semantics></math></inline-formula> of cohesive soil. The <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><msub><mi>i</mi><mrow><mi>cr</mi></mrow></msub></mrow></semantics></math></inline-formula> range of silty seabed in the YRD was 8–16, which was significantly affected by the cohesion and was inversely proportional to the seabed fluidization degree. SF could “pump” the sediments vertically from the interior of the seabed with a contribution to sediment resuspension of up to 93.2–96.8%. The higher the consolidation degree, the smaller the contribution will be.