波浪和潮波作用下黄河口快速沉积海床土非均匀固结试验研究

黄河高含沙量水体在弱潮陆相河口入海，80 %的泥沙在河口附近快速堆积。过去研究发现，黄河三角洲潮滩表层沉积物呈现非均匀固结状态。为了揭示该现象产生的机制，在黄河刁口流路三角洲叶瓣潮坪上，现场取土配置黄河口快速沉积形成的流体状堆积物，研究快速沉积的粉质海床土在波浪和潮波作用下的孔压响应及非均匀固结过程。利用静力触探、十字板剪切试验、孔隙水压力监测等原位测试手段，实时测定快速沉积的海床土强度和孔压变化过程。研究发现，快速沉积的粉质土在自重作用下的固结速度很快，正常固结完成后，强度随时间的发展依然不断增加，沿深度方向出现类似原状土体的固结非均匀现象和似超固结状态；在波浪和潮波作用下快速沉积粉质土孔压沿深度出现非均匀变化，在波浪作用下出现了超静孔压的积累。分析发现，该固结状态和强度沿深度方向非均匀变化是由于土体在潮波及潮波和波浪的联合作用下形成的；潮滩表层土体在波浪荷载长期作用下形成硬壳层。

An experimental study of nonuniform consolidation of rapid sediment seabed soils at Yellow River mouth subjected to wave and tide wave loading

80 % of silts abundantly contained in the Yellow River water rapidly deposit at the River estuary. From previous investigation, it was found that the topsoils on the tide flat of Yellow River delta have been in a nonuniform consolidation state. In order to reveal the mechanism of aforementioned phenomena, a series of experiments were conducted on the tide flat of Diaokou delta-lobe which lies in the north of Yellow River delta. The fluid sediments imitating the rapidly deposited seabed silts were made in situ, and the fluid sediments were promptly filled into a one-meter deep pit excavated at the tide flat. By field-testing methods, such as static cone penetration test, field vane shear test and pore water piezometer test, the variation of strength and pore water pressure are measured at real time. It is shown from the testing data that the consolidation speed of the rapidly deposited seabed silts measured by water piezometer in situ is much quicker than the speed calculated through the Terzaghi’s one-dimensional consolidation theory. It is also shown that after consolidation compression had completed, the strength of such silts increased unequally along the depth continuously. Thus the rapidly deposited silts present a nonuniform consolidation state and a quasi-overconsolidated state, which is similar to undisturbed soils of the Yellow River estuary. Analyses show that the formation of such quasi-overconsolidated state and nonuniformity changes of strength along depth are attributable to the coupling effects of wave and tide loading and that long-term effect of wave loading which can cause the accumulation of excess pore water pressure within certain depth is the fully convincing evidence to form the crust layer of tide flat topsoil at the Yellow River estuary.