水下收缩裂隙形成过程及裂缝充填模式研究

Genesis of underwater shrinkage cracks and geological models of their filling

通过野外实地考察测试,对水下收缩裂隙整体形成过程、裂隙内充填物沉积模式、影响因素等进行了详细讨论,并且建立了相应的地质理论模型。水下收缩裂隙的形成共分4个阶段,依次为:泥水混合物进入低洼地带的初始混浊状态;沉积压实稳定阶段;水位线下降,盐度增大,裂隙形成阶段;沉积裂隙充填阶段。其中“异常高压作用”,对于初始裂隙的形成、沉积物孔隙水的有效排出以及主要渗流通道的发育起到了重要作用。单一泥质地层裂隙内充填物沉积模式与沙泥互层的多旋回地层略有差异,主要表现为沙层的润滑作用以及对早期裂隙内充填物类型的影响。上述两种地层裂隙内充填物沉积特征均与后期充注期次相对应,表现出很好的韵律性。裂隙纵剖面中生物发育层的出现,对裂隙内充填物的物理、化学性质将产生重要影响。

Based on field measurements and experimental analyses of underwater shrinkage cracks, we discuss formation processes of the cracks, sedimentary models of their filling, factors that influence them. and propose theoretical models. There are four steps that lead to the formation of cracks： （1） the primary muddy state of underwater sediments in low-lying areas ; （2） sedimentary compacting processes; （3） the forming of shrinkage cracks after falling water levels and increasing salinity; （4） the filling of cracks. Abnormal pressure plays an important role in the initial step of crack formation, discharging water from sedimentary pores, and developing a primary flow-channel matrix. An homogeneous layer is different from a sand-mud interbedded layer in many aspects, such as the lubricating action of sandy layers and the initial type of filling in shrinkage cracks. The sedimentary models of filling in two types of cracks Correspond to the input frequency of mud-water mixtures, showing a clear rhythmicity. In the vertical section of cracks, there is a biological layer, where seed plant can germinate and grow in suitable conditions, which has a vital function on changing the physical and chemical properties of crack filler.