Local scour at a pile or pier in current or wave environments threats the safety of the upper structure all over the world.The application of a net-like matt as a scour protection cover at the pile or pier was propose...Local scour at a pile or pier in current or wave environments threats the safety of the upper structure all over the world.The application of a net-like matt as a scour protection cover at the pile or pier was proposed.The matt weakens and diffuses the flow in the local scour pit and thus reduces local scour while enhances sediment deposition.Numerical simulations were carried out to investigate the flow at the pile covered by the matt.The simulation results were used to optimize the thickness dt(2.6 d_(95)∼17.9 d_(95))and opening size dn(7.7 d_(95)∼28.2 d_(95))of the matt.It was found that the matt significantly reduced the local velocity and dissipated the vortex at the pile,substantially reduced the extent of local scour.The smaller the opening size of the matt,the more effective was the flow diffusion at the bed,and smaller bed shear stress was observed at the pile.For the flow conditions considered in this study,a matt with a relative thickness of T=7.7 and relative opening size of S=7.7 could be effective in scour protection.展开更多
网纹红土红色基质和白色网纹的成分和结构差异性影响并控制着工程特性。文章通过扫描电子显微镜(scanning electron microscope,SEM)实验和数字图像处理技术定量研究原状网纹红土的微孔隙特征,进而基于能量色散谱仪(energy dispersive s...网纹红土红色基质和白色网纹的成分和结构差异性影响并控制着工程特性。文章通过扫描电子显微镜(scanning electron microscope,SEM)实验和数字图像处理技术定量研究原状网纹红土的微孔隙特征,进而基于能量色散谱仪(energy dispersive spectrometer,EDS)和X射线衍射仪(X-ray diffractometer,XRD)分析了红色基质和白色网纹的化学成分和黏土矿物构成,以探讨网纹红土微结构和成分与其力学特征的内在联系。研究得出,网纹红土孔隙主要为小于0.5μm2面积的微孔隙,而面积超过50μm2的大孔隙则较少,但红色基质颗粒表面粗糙、棱角分明,主要由绿泥石/蒙脱石混层和伊利石以及少量的绿泥石和高岭石构成,而白色网纹颗粒则较为圆滑,由伊利石/蒙脱石混层和伊利石构成,且红色基质中Fe元素质量分数高于白色网纹,而两者中的Ti元素质量分数稳定。研究结果可为深入分析网纹红土工程特征提供依据。展开更多
网纹红土松弛特性具有非线性。基于分数阶微积分理论,探讨了能更准确描述网纹红土松弛非线性特性和全过程的FVMS(Fractional Voigt and Maxwell model in series)松弛模型和FVMP(Fractional Voigt and Maxwell model in parallel)松弛...网纹红土松弛特性具有非线性。基于分数阶微积分理论,探讨了能更准确描述网纹红土松弛非线性特性和全过程的FVMS(Fractional Voigt and Maxwell model in series)松弛模型和FVMP(Fractional Voigt and Maxwell model in parallel)松弛模型及其理论解,进而应用提出的模型对三轴松弛试验实测数据进行反演,讨论了分数阶阶数的敏感性,并与西原模型和Burgers模型进行对比分析。研究结果表明,建立的四元件分数阶松弛本构模型应用于网纹红土应力松弛特性分析是有效可行的,模型灵活且精度更高,参数确定简便,发现分数阶阶数对应力松弛量的影响较大,但其对FVMS模型和FVMP模型松弛速率的影响不同,为实际工程长期稳定性分析提供了参考。展开更多
水化作用后的网纹红土强度演变研究对其污染修复具有重要意义。文章基于不同质量分数HCl、CaO和NaCl水化作用后的网纹红土直剪试验和扫描电子显微镜(scanning electron microscope,SEM)试验,探讨了水化作用后的网纹红土强度和微结构演...水化作用后的网纹红土强度演变研究对其污染修复具有重要意义。文章基于不同质量分数HCl、CaO和NaCl水化作用后的网纹红土直剪试验和扫描电子显微镜(scanning electron microscope,SEM)试验,探讨了水化作用后的网纹红土强度和微结构演化规律。研究结果表明:HCl、CaO和NaCl水化作用后的网纹红土呈现不同的特征和累积效应,低质量分数HCl水化作用可使土体强度和黏聚力增大,但当质量分数大于5.7%后可引起强度和黏聚力骤降,内摩擦角则表现为始终增大;经CaO水化作用后的土体强度参数则随着CaO质量分数的增大而增大,但质量分数大于3%后的变化值相对明显;而经NaCl水化作用后的强度参数总体呈现下降趋势,但当质量分数超过8.4%后,呈现平稳趋势。同时发现经NaCl、CaO和HCl污染后的网纹红土微结构特点不同,表明水化作用引起的宏观力学特征与其微结构变化密切相关,研究结果为污染网纹红土的修复提供了依据。展开更多
基金supported by National Natural Science Foundation of China(No.52171268)CCCC Road&Bridge Special Engineering Co.,Ltd.
文摘Local scour at a pile or pier in current or wave environments threats the safety of the upper structure all over the world.The application of a net-like matt as a scour protection cover at the pile or pier was proposed.The matt weakens and diffuses the flow in the local scour pit and thus reduces local scour while enhances sediment deposition.Numerical simulations were carried out to investigate the flow at the pile covered by the matt.The simulation results were used to optimize the thickness dt(2.6 d_(95)∼17.9 d_(95))and opening size dn(7.7 d_(95)∼28.2 d_(95))of the matt.It was found that the matt significantly reduced the local velocity and dissipated the vortex at the pile,substantially reduced the extent of local scour.The smaller the opening size of the matt,the more effective was the flow diffusion at the bed,and smaller bed shear stress was observed at the pile.For the flow conditions considered in this study,a matt with a relative thickness of T=7.7 and relative opening size of S=7.7 could be effective in scour protection.
文摘网纹红土松弛特性具有非线性。基于分数阶微积分理论,探讨了能更准确描述网纹红土松弛非线性特性和全过程的FVMS(Fractional Voigt and Maxwell model in series)松弛模型和FVMP(Fractional Voigt and Maxwell model in parallel)松弛模型及其理论解,进而应用提出的模型对三轴松弛试验实测数据进行反演,讨论了分数阶阶数的敏感性,并与西原模型和Burgers模型进行对比分析。研究结果表明,建立的四元件分数阶松弛本构模型应用于网纹红土应力松弛特性分析是有效可行的,模型灵活且精度更高,参数确定简便,发现分数阶阶数对应力松弛量的影响较大,但其对FVMS模型和FVMP模型松弛速率的影响不同,为实际工程长期稳定性分析提供了参考。
文摘水化作用后的网纹红土强度演变研究对其污染修复具有重要意义。文章基于不同质量分数HCl、CaO和NaCl水化作用后的网纹红土直剪试验和扫描电子显微镜(scanning electron microscope,SEM)试验,探讨了水化作用后的网纹红土强度和微结构演化规律。研究结果表明:HCl、CaO和NaCl水化作用后的网纹红土呈现不同的特征和累积效应,低质量分数HCl水化作用可使土体强度和黏聚力增大,但当质量分数大于5.7%后可引起强度和黏聚力骤降,内摩擦角则表现为始终增大;经CaO水化作用后的土体强度参数则随着CaO质量分数的增大而增大,但质量分数大于3%后的变化值相对明显;而经NaCl水化作用后的强度参数总体呈现下降趋势,但当质量分数超过8.4%后,呈现平稳趋势。同时发现经NaCl、CaO和HCl污染后的网纹红土微结构特点不同,表明水化作用引起的宏观力学特征与其微结构变化密切相关,研究结果为污染网纹红土的修复提供了依据。
