摘要
海底塌陷凹坑是黄河三角洲地区常见的一种地貌现象,广泛分布于近代沉积海床中。虽然目前海底塌陷凹坑形成机理尚未明确,但普遍认为其成因与波浪引起的海床渗流有关。为此,设计模拟波压力的实验装置,对粉土施加40kPa循环水压荷载,研究正常固结粉土在液化渗流条件下的侵蚀过程。试验过程中,粉土液化时产生2种不同的裂隙,即倾斜状的"干裂隙"和水平状的"水夹层";孔隙水从"水夹层"中渗出,把从土样侧壁冲刷下的物质运移至土样表面堆积,形成"泥火山"。试验表明,土体内气泡溢出对表层土的侵蚀具有强化作用;循环荷载产生的孔隙水压力梯度是粉土液化渗流动力,而渗流过程对土的粒径成分具有粗化作用;分析结果表明,波压力引起的海床渗流是长效的作用机制,不同于地震荷载引起的渗流侵蚀。这种侵蚀模式是海底塌陷凹坑形成的主要原因。
Submarine collapse pits are a kind of topographic feature universally observed in the Yellow River Delta,widely distributing in modern sedimentary seabed.Currently,their development mechanism is still ambiguous;however,it＇s commonly accepted that their cause is related with seepage in seabed due to wave actions.In order to further explore the mechanism,an experimental apparatus,which could exert cyclic water pressure loads of 40 kPa on silty soil,was designed to simulate the corrosion process in consolidated silty soil under liquefaction seepage conditions.During the course of the experiments,two typical kinds of crannies were observed when the silty soil liquefied,i.e.,one kind were slantwise＂dry crannies＂and the other horizontal＂water crannies＂.When pore water seeped from the＂water crannies＂,substance scoured from the side of soil body was simultaneously transported to soil surface,and gradually accumulated into＂mud volcanos＂.The experimental results showed that spillover of bubbles in soil body enhanced the corrosion of surface soil;pore water pressure gradient induced by cyclic loads was the impetus for seepage in silty soil,and the seepage process,in turn,resulted in coarsening of soil particles.Analyses of the experimental results also indicated that the seepage in seabed induced by wave loads was a long-term functional mechanism,which was different from the seepage corrosion induced by earthquake loads.This wave-induced corrosion mode was the main cause of collapse pits.
出处
《中国海洋大学学报（自然科学版）》
CAS
CSCD
北大核心
2014年第9期82-88,共7页
Periodical of Ocean University of China
基金
国家自然科学基金项目(41072216
41272316)
教育部博士点基金项目(20100132110001)资助
关键词
循环荷载
液化渗流
孔隙水压力
塌陷凹坑
cyclic load
liquefaction seepage
pore water pressure
collapse pit
