海底线缆在液化海床中的受力试验及防护固定桩最优间距计算

为解决海床液化以后埋置线缆被液化土体携带作近似椭圆的运动而导致其位于液化区域边缘处的部分发生弯折疲劳破坏的问题,本文利用波浪水槽试验,对模型线缆的竖向位移和端部受力进行了监测,结果显示土体液化后的波动造成此2项监测数据均有增大,表明了液化土可能对埋设其中的线缆有损毁作用。本文提出在海床内埋设桩基固定线缆的方案,从而基于悬链线方程,并根据埕岛海域海洋动力环境特征来计算该海域海底电缆的防护固定桩最优间距。计算结果表明,当土体液化后,埕岛海域电缆在无保护措施的情况下可能会发生断裂,当设置防护固定桩间距为300 m时,可起到保护作用。

水下沉积物流速度特征及对管状结构物拖曳力试验研究

沉积物流是海底沉积物运移的重要载体,高速的沉积物流会冲击海底结构物并导致其损坏,其中拖曳力通常被认为是结构物破坏的主要因素,因此研究结构物在不同沉积物流流速下的拖曳力具有重要意义。本文采用可调坡度平直水槽对结构物进行冲击试验并对所配粘土组分的沉积物流进行流变测试,分析结果表明,当坡度一定时,存在一个临界沉积物流浓度,使沉积物流速度和结构物所受拖曳力达到最大值,本次试验条件下在0°、3°、6°、9°坡下,所得临界沉积物流浓度为560 g/L。同时,给出了在试验浓度范围内(280~700 g/L),对于纯粘土组分沉积物流速度较低(0.2~0.6 m/s)时,结构物所受拖曳力与沉积物流速度、密度三者之间的关系表达式。

Horizontal Normal Force on Buried Rigid Pipelines in Fluctuant Liquefied Silty Soil

The submarine pipelines that are buried in the Yellow River subaqueous delta can be subject to fluctuant local-liquefied soil caused by storm wave action, possibly causing pipeline damage. An experimental investigation was carried out in a wave flume to study the horizontal normal force on buried rigid pipelines in fluctuant liquefied soil. In this experiment, the soil bed was made of silt from the Yellow River Delta, whereas a steel pipe served as pipeline. Under the experimental conditions, the normal force range on the pipeline in fluctuant liquefied soil was several times higher than that in stable soil, specifically on the side of the pipeline exposed to the wave direction. The resultant force of the horizontal normal forces on the buried pipeline grew by about one order of magnitude after soil liquefaction.

球状结构物在波动液化土中沉降过程研究

海底粉质土在波浪作用下发生液化,液化后的土体丧失原有承载能力,对海洋构筑物造成巨大危害。研究结构物在液化土中沉降规律的数学表达,对评估海洋构筑物的稳定性具有重要意义。本文结合有限水深小振幅波及斯托克斯波的水质点位移公式,提出波动液化土中球状结构物的位移公式,并设计波浪水槽试验进行验证。结果表明,用公式计算出的沉降位移曲线与实测沉降位移曲线在较浅深度内符合良好,在接近液化底界面处发生偏移。偏移的原因推测是由液化土的剪切稀化流体特性所致或由于粉质土的波动液化分选所致。

Sedimentary Changes of a Sand Layer in Liquefied Silts

A flume experiment was conducted to investigate the restratification of liquefied sediment strata under a wave load with the focus on the interbedded strata of coarse and fine sediments formed in estuarine and coastal areas.The aim of this research was to study the characteristics and processes of liquefied sediment strata in terms of wave-induced liquefaction.In the experiment,the bottom bed liquefied under the wave action and the liquefied soil moved in the same period with the overlying waves,and the track of the soil particles in the liquefied soil was an ellipse.The sand layer consisting of coarse particles in the upper part,settled into the lower silt layer.The sinking of coarse particles and upward migration of the fine particles of the lower layer induced by liquefied sediment fluctuations are the likely reasons for sedimentation of the sand layer in liquefied silt.

黏粒分离对淋洗法修复Pb污染土壤的影响研究

根据黏粒含量不同配制4种Pb污染土壤(砂土、砂质黏壤土、壤质黏土、黏土),分析4种污染土壤中不同颗粒组分中Pb分布情况,采用湿筛和虹吸法将土壤中部分黏粒进行分离,通过室内振荡淋洗试验,对比分析黏粒分离前后Pb污染土壤的淋洗效率,计算最优淋洗条件下的药剂成本。试验结果表明,污染土壤中黏粒含量越高,土壤中Pb形态越稳定,越不易被淋洗去除;污染土壤中Pb的分布情况与土壤类型密切相关;随着淋洗剂(乙二胺四乙酸二钠)浓度增加,Pb去除率整体呈现先快速增加后逐渐稳定的趋势,Pb去除率为砂土>砂质黏壤土>壤质黏土>黏土;分离部分黏粒可以降低最优淋洗剂浓度与液固比,使砂土、砂质黏壤土、壤质黏土、黏土淋洗所需药剂成本分别降低25%、52%、83%、87%。

土柱淋洗法修复铬污染土壤的水力梯度优化试验

针对重金属污染土壤的修复,淋洗法是一种比较成熟的方式,但目前研究主要聚焦于淋洗剂的选择,而关于水力停留时间对淋洗效果影响的研究相对较少.水力梯度是影响水力停留时间的重要因素,优化水力梯度能够缩短修复周期,降低淋洗成本,有效提高淋洗效率,为现场淋洗修复工程应用提供参考.本文针对人工制备的不同质地的铬污染土壤进行了土柱淋洗试验,探究了土柱淋洗过程中不同水力梯度条件下淋出液的pH值、淋洗液渗流速度和淋洗前后不同类型土壤中Cr(VI)及总Cr含量的变化情况,并根据土壤中Cr(VI)、总Cr去除情况对水力梯度进行了优化,研究结果表明淋洗铬污染土壤的最佳柠檬酸浓度为0.15 mol·L^(-1),淋洗铬污染壤土、砂质壤土和砂土的最佳水力梯度分别为7.2、3.6和1.2,总Cr去除率分别达到82.86%、77.27%和82.15%.