黄河三角洲潮滩表层沉积物在潮波和波浪作用下的孔压响应及固结机理现场试验研究

In-situ tests on pore-water pressure response and consolidation mechanism of surface sediments in tidal flat of Yellow River Delta under tide and wave loading

为了研究黄河三角洲潮滩表层粉质土在波浪和潮波作用下的孔压响应及对沉积物固结状态影响,在黄河三角洲潮滩上现场取土在试坑内配置了模拟黄河口快速沉积形成的流体状堆积物,利用静力触探试验、孔隙水压力测试手段,对比研究了试坑扰动恢复土体和潮滩原状土体在波浪和潮波作用下的孔压响应,并探讨了黄河三角洲潮滩表层粉质土非均匀固结机理。研究发现:在潮波作用下,潮滩和试坑土体产生了不同的孔压响应,在涨退潮过程中试坑土体超静孔隙水压力经历了负-零-正的变化,相当于经历了一次加卸荷过程,而潮滩土体仅产生了负值超静孔隙水压力。在潮波与波浪相互耦合作用下,潮滩浅部土体产生了明显的孔隙水压力积累,在深度0.3 m附近出现超静孔隙水压力最大值。潮滩表层土体强度沿深度从上到下呈现高-低-次高不均匀固结现象,产生这一现象的机理与潮滩土体在潮波、波浪和潮波相互耦合作用下孔压响应特点有关,特别是潮滩0.3 m深度附近土体受波浪影响显著,长期作用下形成硬壳层。

s:In order to study the pore pressure response and consolidation mechanism of the surface sediments in the tidal flat of the Yellow River Delta under the action of wave and tide loading,the fluid sediments imitating the rapidly deposited seabed silty soils are made in situ,and they are promptly filled into a one-meter deep pit excavated at the tidal flat.By using the static cone penetration tests and the pore water piezometer tests,a comparative study is conducted about the pore-water pressure responses of pit soils and the tidal flat soils under the action of tide and wave loading,meanwhile the non-uniform consolidation mechanism of the tidal flat soils is discussed.It is shown that the pore-water pressure responses between the the tidal flat soils and the pit soils are different under the tide loading,in the process of rising and falling tide,the excess pore-water pressure of the pit soils undergoes negative-zero-positive changes,and it is equivalent to a process of loading and unloading,however,the tidal flat soils only produce negative excess pore-water pressure.Under the coupling action of tide and wave loading,the accumulation of pore water pressure is obvious in the surface soils of tidal flat,and the maximum excess pore water pressure is generated near a depth of 0.3 m.The strength of the tidal flat soils in the Yellow River Delta presents the phenomenon of high-low-subhigh non-uniform consolidation along the depth,and the mechanism of this phenomenon is related to the characteristics of pore pressure responses of tidal flat soils under the tide loading and coupling action of tide and wave loading,especially near the surface of 0.3 m of soils,which is significantly affected by long-term wave loading and a hard shell layer is formed.