Abstract
Geological disasters of seabed instability are widely distributed in the Yellow River Delta, posing a serious threat to the safety of offshore oil platforms and submarine pipelines. Waves act as one of the main factors causing the frequent occurrence of instabilities in the region. In order to explore the soil failure mode and the law for pore pressure response of the subaqueous Yellow River Delta under wave actions, in-lab flume tank experiments were conducted in this paper. In the experiments, wave loads were applied with a duration of 1 hour each day for 7 consecutive days; pore water pressure data of the soil under wave action were acquired, and penetration strength data of the sediments were determined after wave action. The results showed that the fine-grained seabed presented an arc-shaped oscillation failure form under wave action. In addition, the sliding surface firstly became deeper and then shallower with the wave action. Interestingly, the distribution of pores substantially coincided with that of sliding surfaces. For the first time, gas holes were identified along with their positioning and angle with respect to the sediments. The presence of gas may serve as a primer for submarine slope failures. The wave process can lead to an increase in the excess pore pressure, while the anti-liquefaction capacity of the sediments was improved, causing a decrease in the excess pore pressure resulting from the next wave process. Without new depositional sediments, the existing surface sediments can form high-strength formation under wave actions. The test results may provide a reference for numerical simulations and engineering practice.
Highlights
The Yellow River Delta is one of largest-scale deltas with the fastest progradation rate in the world
It is estimated that the average annual sediment transport volume exceeds 800 million tons from 1950 to 2005 [1], and over 70–90% of the sediments were deposited in the sea area within 30 km from the estuary [2], gradually forming the modern subaqueous Yellow River Delta
The cylinder was moved up and down the water surface to produce the second wave as shown in Figure 3b; when two waves collided in the middle of the flume, a superposition occurred (Figure 3c); the two waves continued to advance in their respective directions (Figure 3d), and a reflected wave was formed simultaneously at each side wall of the flume
Summary
The Yellow River Delta is one of largest-scale deltas with the fastest progradation rate in the world. It is estimated that the average annual sediment transport volume exceeds 800 million tons from 1950 to 2005 [1], and over 70–90% of the sediments were deposited in the sea area within 30 km from the estuary [2], gradually forming the modern subaqueous Yellow River Delta. With respect to the studies on the instability of the seabed under wave action, especially in the subaqueous Yellow River Delta, plenty of field surveys, numerical analyses, laboratory tests, and in situ observation studies have been carried out [16,17,18,19,20,21]. The presence of gas may serve as a primer for submarine slope failure
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