Coupled Model of Two-phase Debris Flow, Sediment Transport and Morphological Evolution

The volume fraction of the solid and liquid phase of debris flows,which evolves simultaneously across terrains,largely determines the dynamic property of debris flows. The entrainment process significantly influences the amplitude of the volume fraction. In this paper,we present a depth-averaged two-phase debris-flow model describing the simultaneous evolution of the phase velocity and depth,the solid and fluid volume fractions and the bed morphological evolution. The model employs the Mohr–Coulomb plasticity for the solid stress,and the fluid stress is modeled as a Newtonian viscous stress. The interfacial momentum transfer includes viscous drag and buoyancy. A new extended entrainment rate formula that satisfies the boundary momentum jump condition(Iverson and Ouyang,2015) is presented. In this formula,the basal traction stress is a function of the solid volume fraction and can take advantage of both the Coulomb and velocity-dependent friction models. A finite volume method using Roe's Riemann approximation is suggested to solve the equations. Three computational cases are conducted and compared with experiments or previous results. The results show that the current computational model and framework are robust and suitable for capturing the characteristics of debris flows.     

小浪底水库溯源冲刷效率评估试验

水库溯源冲刷试验是评估在水库速降水位过程中,结合工程控制条件、水沙条件、冲刷时机和初始水库蓄水条件等因素,研究支流拦门沙坎破坏程度对干流溯源冲刷的影响。采用按照水库高含沙模型相似律建立的小浪底水库实体模型开展了4个组次的水库降水库区发生溯源冲刷的试验,第1~4组次库容恢复率依次为11.6%、6.8%、12.2%和6.6%。拦门沙坎破坏越严重,水量越大,库区溯源冲刷量越大,库容恢复率大;侵蚀基准面越低,库区溯源冲刷量大,库容恢复率大;库区淤积量42.00亿m3时采用降低水位引起库区发生溯源冲刷优于库区淤积量32.00亿m3。对原有的陕西水利科学研究所与清华大学的逐日溯源冲刷公式在考虑支流促因的基础上进行了改进,说明支流蓄水量进入干流越多,引起支流口以下的干流河段冲刷量越大,其计算结果与实测值满足生产实践精度,可作为多沙河流水库调水调沙方案制定参考。     

Time-domain simulation of berthing problem between FPSO and shuttle tanker in waves

A time-domain simulation method based on potential flow model has been developed to investigate the berthing problem between two floating bodies in wave. The boundary value problem is formulated with respect to an earth-fixed coordinate system because the relative positions of the two vessels continuously change during the berthing operation. The classical finite element method is used to solve the Laplace equation in the fluid domain with moving boundary. The linearized free-surface boundary conditions are integrated in time by applying 4th-order Adams–Bashforth–Moulton method. A simple re-mesh algorithm with local and global mesh systems is introduced to update mesh by considering large horizontal movement of the berthing vessel. The developed numerical method is used to investigate the berthing problem between a FPSO and shuttle tanker in waves. The focus is on the wave-induced motion response during the berthing process. The characteristics of the motion responses in berthing operation are examined with various wave frequencies, berthing speeds and wave headings.     

Incremental elastoplastic FEM for simulating the deformation process of suction caissons subjected to cyclic loads in soft clays

This paper presents an incremental elastoplastic finite element method (FEM) to simulate the undrained deformation process of suction caisson foundations subjected to cyclic loads in soft clays. The method is developed by encoding the total-stress-based bounding surface model proposed by the authors in the ABAQUS software package. According to the model characteristics, elastoplastic stress states associated with the incremental strains of each iteration are determined using the sub-incremental explicit Euler algorithm, and the state parameters describing the cyclic accumulative rates of strains are updated by setting state variables during the calculations. The radial fallback method is also proposed to modify the stress states outside the bounding surface to the surface during determination of the elastoplastic stress states. The stress reversals of soil elements are judged by the angle between the incremental deviatoric stress and the exterior normal vector at the image stress point on the bounding surface to update the mapping centre and state variables during cyclic loading. To assess the general validity of the method, the reduced scale model tests and centrifuge tests of suction caissons subjected to cyclic loads are simulated using the method. Predictions are in relative good agreement with test results. Compared with the limit equilibrium and quasi-static methods, the method can not only determine the cyclic bearing capacity, but can also analyse the deformation process and the failure mechanisms of suction caisson under cyclic loads in soft clays.     

近60年来长江河口河势变化及其对水动力和盐水入侵的影响I.河势变化

河势是影响河口水动力和盐水入侵基本因子。本文利用20世纪50和70年代长江河口海图,数值化岸线和水深,结合2012年长江河口实测水深资料,分析长江河口自50年代以来的河势变化。长江河口为分汊河口,50年代仅为二级分汊,至70年代才形成三级分汊,四口入海的河势格局。70年代相比于50年代,北支淤浅严重,其上、中、下段容积变化分别为-64.13×106、-306.60×106和-639.27×106 m3,对应的变化率分别为-16.30%、-22.74%和-25.69%,均显著减小;南支的上、中、下段容积变化分别为-28.61×106、-35.69×106和126.43×106 m3,相应的变化率分别为-1.30%、-2.12%和4.36%;北港由于崇明浅滩和横沙浅滩的淤浅,下段容积明显减小,其上段和下段容积变化分别为109.21×106和-797.14×106 m3,对应的变化率分别为5.01%和-15.25%;南港上段由于河道淤浅容积减小,下段北由于铜沙浅滩被冲开形成北槽,导致水深变深、容积增加,其上段、下段北和下段南容积变化分别为-238.95×106、203.58×106和153.34×106 m3,对应的变化率分别为-8.96%、6.85%和3.26%。2012年相比于70年代,北支由于大量淤浅和围垦容积大幅减小,其上、中、下段容积变化分别为-199.06×106、-504.61×106和-654.12×106 m3,对应的变化率分别为-60.45%、-48.44%和-35.38%;南支的上、中、下段容积变化分别为92.34×106、193.01×106和-163.62×106 m3,相应的变化率分别为4.24%、11.73%和-5.40%;北港上段青草沙水库的围垦和下段横沙东滩的围垦造成面积和容积减小,其上段和下段容积变化分别为-154.64×106和-511.79×106 m3,对应的变化率分别为-6.75%和-11.55%;南港由于上段河道刷深而下段九段沙以及南汇边滩淤浅、围垦,导致其容积上段增加,下段减小,上段、下段北和下段南容积变化分别为136.39×106、-658.28×106和-1266.11×106 m3,对应的变化率分别为5.62%、-20.73%和-26.06%。     

水射流破碎南海含水合物沉积物数值模拟研究

为研究高压水射流切割、破碎南海天然气水合物储层的过程,采用著名的LS—DYNA显示动力分析有限元程序,对淹没状态下,水射流破碎海底含水合物沉积物过程进行数值模拟研究,研究了不同射流速度对高压水射流作用下含水合物沉积物破碎效果的影响规律。随着射流速度的增大,冲蚀深度逐渐增大,两者呈线性递增关系。含水合物沉积物冲蚀体积是轴向冲蚀与径向冲蚀共同作用的结果,射流速度越大,对含水合物沉积物的轴向与径向冲蚀作用增强,加大了含水合物沉积物冲蚀体积递增速率。     

塔里木溢流玄武岩火山通道的三维结构及其热成因气体释放

塔里木上奥陶统-志留系沉积地层中广泛发育早二叠世溢流玄武岩的火山通道相岩床-岩墙网络。三维地震数据解释结果显示,这些火山通道以平行围岩地层的岩床和斜切围岩地层的"碟状岩床"为主要特征。在玄武岩喷发过程中,火山通道岩浆的热量可以导致沉积围岩发生热接触变质并将沉积围岩中的有机质转化为"热成因气体"。在塔北英买2井区火山通道烘烤沉积围岩模型基础上,利用有限元热模拟方法确定了该区早二叠世玄武岩喷发时火山通道热烘烤影响范围随时间的变化。基于沉积围岩有机质丰度估算,该区热烘烤成因甲烷释放量可达11.3Gt(即113亿吨)。如果整个塔里木溢流玄武岩省具有与英买2地区相同的释放强度,则塔里木溢流玄武岩省活动期间释放的甲烷总量可达7062.5Gt,必然导致非常显著的环境效应。同时,玄武岩火山通道岩浆引起的热接触变质作用对已存在的油藏具有明显的破坏作用,塔里木盆地古生界总量约8~10Gt的油藏破坏和大量沥青的形成可能与此有关。     

准噶尔盆地吉木萨尔凹陷梧桐沟组层序地层划分

准噶尔盆地吉木萨尔凹陷二叠系梧桐沟组作为一套重要的储集岩,具有良好的油气成藏前景,但对其层序划分及地层沉积样式的认识一直存在争议。在构造背景分析的基础上,结合岩芯、测井及地震资料,对研究区梧桐沟组层序地层划分及地层沉积样式研究表明,梧桐沟组沉积时期构造强度较弱,地形较为平缓,地层在全区稳定分布;中晚二叠世盆地发生造山运动,吉木萨尔凹陷东南边缘区域经过构造抬升,上部地层遭受不同程度的剥蚀,形成了现今"底平顶削"的地层样式。以凹陷中部少数地层保存较全的井的地层叠加样式分析为基础,通过井-震结合识别不同类型界面,特别是最大湖泛面,建立了区域层序地层格架,即梧桐沟组为一个完整的长期基准面旋回(三级层序),并在其内部识别出5个中期旋回。梧桐沟组地层在不同的层序发育时期表现出不同的旋回叠加样式:下段沉积时期,即最大湖泛面以下,随着可容纳空间的增大,地层表现为明显的退积叠加样式;上段沉积时期,即最大湖泛面以上,随着可容纳空间的减小,地层表现为明显的进积叠加样式,符合沉积物体积分配原理。     

岩溶坝基帷幕灌浆高注浆量控制措施与效果分析

帷幕灌浆是坝基防渗处理的一种常用技术手段,而岩溶地区因其岩溶发育致使岩溶裂隙和通道纵横交错,且难以获取其规律性,灌浆过程中往往会出现注浆量偏高的现象。为了能够既有效控制帷幕灌浆成本,又确保帷幕灌浆施工质量,就需要采用科学、合理、可靠的施工技术措施和手段,对高注浆量的情况进行重点控制和改进。本文结合某水电站岩溶坝基帷幕灌浆中突出的高注浆量现象,通过有针对性地从技术措施和控制手段等方面的综合探索与应用,最终达到了坝基防渗的目的,并最大限度地节约了帷幕灌浆的时间,有效控制了高材料消耗所带来的高成本问题,为类似项目的帷幕灌浆积累了一定的经验。     

基于SEED波形文件的运行率统计

介绍了基于SEED波形文件运行率计算的技术和实现方法,介绍了SEED文件中标识时间的特殊掩码、时间片的具体格式和程序的实现,并给出了与其相关的部分源代码.