蓄能式真空预压排水系统及其节能效率

针对真空预压系统的高能耗问题,提出一种蓄能式真空预压排水系统,并通过室内单板真空预压排水试验,探究该系统的排水固结与节能效率。研究发现:真空室容积对该系统的排水固结效率存在一定影响,且对表层的影响大于深部,但与常规真空预压固结效率相差不大。该系统的节能效率与真空室容积密切相关,在试验条件下,对于功率1.5 kW、抽气速率7.2 m^(3)/h的真空泵,当真空室容积大于排水固结土体的孔隙体积约3‰时,该系统耗能比常规真空预压系统减少50%;真空室容积越大,节能效率越高。该研究可为解决真空预压系统的高能耗问题提供理论支撑。

垂直淹没射流对黏性底床冲刷挖掘体积的试验研究

射流冲刷作为一种高效挖掘手段被广泛应用于深海工程领域。针对黏性底床条件下垂直淹没射流冲刷挖掘体积进行研究,利用注浆成型法制备冲刷坑的胚体并利用3 d扫描技术获取冲刷挖掘体积。通过开展室内试验探索了射流流速、射流靶距、冲刷时间以及泥样含水率与冲刷挖掘体积的关系:1)冲击射流挖掘体积随着射流靶距的增加而减小;2)冲击射流挖掘体积随着射流流速的增加而增加;3)冲击射流挖掘体积随着冲刷时间的增加而增加,但逐渐趋于平衡;4)随着泥样含水率的增加,冲击射流挖掘体积也显著增加。最后,利用54组试验数据和无量纲分析得到了冲击射流挖掘体积的经验公式,可为射流挖沟以及射流沉桩等海洋工程实践提供参考。

Penetration Depth of Torpedo Anchor in Two-Layered Cohesive Soil Bed by Free Fall

The penetration depth of torpedo anchor in two-layered soil bed was experimentally investigated. A total of 177 experimental data were obtained in laboratory by varying the undrained shear strength of the two-layered soil and the thickness of the top soil layer. The geometric parameters of the anchor and the soil properties(the liquid limit, plastic limit, specific gravity, undrained shear strength, density, and water content) were measured. Based on the energy analysis and present test data, an empirical formula to predict the penetration depth of torpedo anchor in two-layered soil bed was proposed. The proposed formula was extensively validated by laboratory and field data of previous researchers. The results were in good agreement with those obtained for two-layered and single-layered soil bed.Finally, a sensitivity analysis on the parameters in the formula was performed.

Experimental Study on the Viscosity of Soft Cohesive Sediments Around A Vibrating Pillar

Offshore structures are subject to environmental loads such as waves,currents,or wind,which may induce cyclic lateral vibration at the foundations.These cyclic vibration loadings may affect the rheological property of the sediments adjacent to the foundation and the stability of the structures.This is especially true when the structures are founded on cohesive sedimentary bed.In this study,the viscosity of soft cohesive sediments adjacent to a vibrating pillar was considered,and as a primary index of the rheological characteristics of the sediments.The investigation was performed using the sinking ball method.The experimental findings indicated that the viscosity of cohesive sediments decrease with increase of the liquidity index and vibration intensity.A simple semi-empirical formula was proposed.The structures of the cohesive sediments were destroyed due to the mechanical vibration,and the sediments were fluidized during vibration loads.The shear strength of the cohesive sediments decreased with increased vibration intensity,not only because of the increased pore water pressure but also the decreased viscosity of cohesive sediments following sediment fluidization.

振动流变对泥浆管道输送的减阻效果研究

泥浆在管道输送中阻力大导致能耗高,严重制约疏浚生产效益。本文将泥沙流变学的振动加载流化技术应用到泥浆管道输送减阻研究中,在管道系统中开展振动流变减阻效果研究。结果表明,减阻效果随着振动频率的增大先显著提升后趋于平缓;随着体积浓度的增加而增强,但其增强的速度逐渐减小;随着输送流速的增加而不断减弱直至趋于平稳。且对于试验泥样,存在一个最优振动频率为40 Hz,此时系统达到了最佳减阻效益状态;在内径为100 mm管道中,当泥浆体积浓度为29.94%、管道输送流速为0.9 m/s、微幅机械振动频率为100 Hz时,对于中值粒径为31μm的奉贤海滩泥沙能减小20%以上的阻力损失;最后,提出了泥浆管道输送振动流变减阻的计算模型。

长直管道输砂的沿程临界流速

近年来,河湖水库的环保疏浚、港口航道建设与维护性疏浚工程越来越多,管道输送是疏浚泥沙搬运的主要方式,输送距离也越来越长。管道输送中流速沿程的再分布情况和临界流速尚待进一步研究。基于古雷镇填沙工程清水工况及输沙工况分层取样浓度实测数据对模型进行率定。在此基础上对长直管道输送砂类泥沙颗粒进行三维水动力及砂的运动模拟,分析了直管道沿程的剖面流速再分布特征和泥沙淤积临界流速规律,提出长管中不同断面位置发生泥沙淤积的临界流速公式,为疏浚工程设计提供参考依据。

Correlation Between Yield Stress of Silty Mud Sediments and Continuous Oscillatory Shearing Properties

Analyzing the rheological properties of silty beds subjected to continuous oscillatory shear loading is crucial for understanding the morphological deformation of the seabed and ensuring safety in geological and marine engineering applications.In this study,the effects of oscillatory shearing properties on the yield stress(S_(u))of silty sediments were quantitatively investigated.The effects of oscillatory shear strength(0-3),water content(26.6%-70.84%),and particle diameter(8.79-50μm)were examined extensively through a series of laboratory tests.The results indicated that the three aforementioned parameters were the major factors that affected the rheological characteristics of silty sediments.Furthermore,their effects could be elucidated using the yield stress of cohesive sediments as the indicator parameter.The ratio of yield stress(S_(u)/S_(u0))varied as the oscillatory shear strength increased up to a critical value,Λ_(cr).S_(u)bsequently,the ratio remained at a constant value.It was deduced that the yield stress decreased with increasing oscillatory shear strength forΛ<Λ_(cr),when the sediments were in a non-equilibrium fluidization stage.WhenΛ>Λ_(cr),the sediments entered an equilibrium fluidization stage,and the yield stress remained almost constant,irrespective of the oscillatory shear strength.Furthermore,during the equilibrium fluidization stage,it was observed that the ratio S_(u)/S_(u0)did not vary with water content but decreased as the particle diameter increased.Finally,based on regression analysis of the experimental data for non-equilibrium and equilibrium fluidization stages,a correlation between yield stress of silty sediments and continuous oscillatory shearing properties was proposed.This correlation can aid in understanding the changes in solid resistance and assessing safety in piling engineering.Furthermore,it can provide a theoretical guidance for reducing soil resistance in marine structures using mechanical vibrations.

霍尔锚落锚贯入力峰值及相应深度的分析

针对霍尔锚在静水中的垂直落锚情况,通过理论分析和物理试验,分析锚质量、触地速度、海床土体强度,以及土体粒径等对霍尔锚贯入力峰值及相应贯入深度的影响。结果表明,贯入力峰值及其对应的贯入深度与锚质量和触地速度呈二次函数关系,与土体粒径呈指数函数关系,以此分别提出霍尔锚贯入力峰值及相应贯入深度的计算公式,为海底结构物强度的设计与防护提供技术支撑。