Initial rise of bubbles in cohesive sediments by a process of viscoelastic fracture
Initial rise of bubbles in cohesive sediments by a process of viscoelastic fracture
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DOI：
10.1029/2010jb008133
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发表时间：
2011-04
影响因子：
--
通讯作者：
C. Algar;B. Boudreau;Mark A. Barry
中科院分区：
文献类型：
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作者：
C. Algar;B. Boudreau;Mark A. Barry
[1]了解沉积物中气泡上升的机理是至关重要的，因为气泡在向大气中释放甲烷以及天然气水合物的形成和融化方面起着重要作用。以往描述和预测其他浮力地质体通过周围固体(如岩浆和水力裂缝)抬升的模型似乎不适用于软沉积物中的气泡，本文提出了一个新的软质细粒粘性沉积物中气泡抬升的模型。这种沉积物中的气泡基本上是“干的”(如果有游离水的话也很少)，并通过弹性膨胀和断裂的过程生长，这可以用线弹性断裂力学原理来描述，该原理假定沉积物组构中存在一系列缺陷。通过推广这一理论，我们预测气泡最初是通过裂缝在(次)垂直方向上的优先扩展而上升的。我们给出了初始气泡上升的判据。一旦上升开始，上升的速度由沉积物对应力的粘弹性反应控制。使用这个新的气泡上升模型，我们估计上升速度约为每秒厘米级。我们再次表明，毛细压力在控制气泡的生长或上升方面没有实质性的作用。
[1] An understanding of the mechanics of bubble rise in sediments is essential because of the role of bubbles in releasing methane to the atmosphere and the formation and melting of gas hydrates. Past models to describe and predict the rise of other buoyant geological bodies through a surrounding solid (e.g., magmas and hydrofractures) appear not to be applicable to bubbles in soft sediments, and this paper presents a new model for gas bubble rise in soft, fine-grained, cohesive sediments. Bubbles in such sediments are essentially “dry” (little if any free water) and grow through a process of elastic expansion and fracture that can be described using the principles of linear elastic fracture mechanics, which assume the existence of a spectrum of flaws within the sediment fabric. By extending this theory, we predict that bubbles initially rise by preferential propagation of a fracture in a (sub) vertical direction. We present a criterion for initial bubble rise. Once rise is initiated, the speed of rise is controlled by the viscoelastic response of the sediments to stress. Using this new bubble rise model, we estimate rise velocities to be of the order of centimeters per second. We again show that capillary pressure plays no substantive role in controlling bubble growth or rise.