基于物理模拟的三角洲前缘横向砂坝发育过程及形成机理

Development Process and Formation Mechanism of Transverse Sand Bar in Delta Front Based on Physical Simulation

为探究波浪作用对三角洲前缘砂体的控制作用,并研究横向砂坝形成过程,利用物理模拟实验再现波浪作用下三角洲前缘砂体的发育过程。研究发现:波浪作用除了对三角洲河口沉积物影响外,还对已形成的三角洲前缘砂体有着侵蚀、改造的作用;受波浪、波生沿岸流及局部离岸流的影响,三角洲前缘砂体表面发育多期次平行于湖岸线展布的横向砂坝,其后部发育冲沟。沿岸流将波浪和河流带来的沉积物向砂坝两侧搬运沉积,使砂坝横向延伸;同时,波浪的强度、入射角度也决定了横向砂坝的规模及发育位置。经与鄂尔多斯盆地西南部长82三角洲沉积对比,反映出较好的耦合关系,表明该实验认识对波浪作用下三角洲前缘砂体发育样式研究有一定的指导意义。

To explore the controlling influence of wave action on a delta front sand body and study the formation process of transverse sand bars,physical simulation experiments are conducted to reproduce the development of a delta front sand body subjected to wave action.The study found that wave action not only affected the delta estuarine sediments,but also eroded and transformed the delta front sand bodies that were formed.Under the influence of waves,of wave-generated coastal current and of local offshore current,transverse sand bars were developed parallel to the lake shoreline many times on the sand body surface of the delta front,and gullies were developed behind the sand bars.The coastal current transports and deposits the sediments carried by waves and rivers to both sides of the sand bar,extending the sand bar laterally.The strength and angle of incidence of the waves also determines the scale and location of any transverse sand bar developed.This observation reflects the deposition of the Chang 82 delta in the southwest of the Ordos Basin,which demonstrates that the experimental understanding has certain guiding significance for the study of the development style of delta front sand bodies due to the action of waves.