介绍一个用于流动液化变形分析的临界状态砂土模型.该模型的参量与应力和材料状态无关,模型能自动处理材料因过程发展而产生的各种状态变化.对于一种或几种类似的土,参量一经率定,不论材料初始处在松的可液化状态还是紧的剪胀状态,模型...介绍一个用于流动液化变形分析的临界状态砂土模型.该模型的参量与应力和材料状态无关,模型能自动处理材料因过程发展而产生的各种状态变化.对于一种或几种类似的土,参量一经率定,不论材料初始处在松的可液化状态还是紧的剪胀状态,模型以统一方式模拟材料从起始阶段近似弹性的响应直到趋于临界状态破坏,包括流动液化在内的全程响应,无需在分析过程中人为干预调整模型参量.作者利用完全耦合有限元分析程序SUMDES2D,以Upper San Fernando土坝在1971年地震中的分析为例,示范该模型在流动液化变形分析中的应用.展开更多
天然状态下水合物生成后往往填充于沉积物土骨架孔隙中或黏结于相邻土颗粒之间,对沉积物具有填充和黏结作用,改变了沉积物原有孔隙比和密度,影响了沉积物的物理力学特性,因此在描述含水合物沉积物的力学和变形特性时需考虑水合物填充和...天然状态下水合物生成后往往填充于沉积物土骨架孔隙中或黏结于相邻土颗粒之间,对沉积物具有填充和黏结作用,改变了沉积物原有孔隙比和密度,影响了沉积物的物理力学特性,因此在描述含水合物沉积物的力学和变形特性时需考虑水合物填充和黏结作用的影响。基于黏土和砂土的统一临界状态本构模型(clay and sand model,简称CASM),结合水合物侵入孔隙的致密化特性,通过提出等效孔隙比来反映水合物的填充作用;同时引入黏聚强度来反映水合物对沉积物的黏结作用;并利用状态参数来反映土体的应力状态和剪胀性,采用非相关联流动法则,进而建立能够描述水合物填充和黏结作用的含水合物沉积物弹塑性本构模型。通过与室内试验结果和已有本构模型对比,表明所提模型能较好地模拟含水合物沉积物的应力-应变关系,可有效地描述水合物含量、有效围压对沉积物的强度、刚度、剪胀性等力学特性的影响规律。展开更多
GSTARS (Generalized Sediment Transport model for Alluvial River Simulation) is a series of computer models developed by the U.S. Bureau of Reclamation while the author was employed by that agency. The stream tube conc...GSTARS (Generalized Sediment Transport model for Alluvial River Simulation) is a series of computer models developed by the U.S. Bureau of Reclamation while the author was employed by that agency. The stream tube concept is used in all GSTARS models which allow us to solve one-dimensional equations for each stream tube independently and obtain semi-two-dimensional variation of the hydraulic conditions along and across stream tubes for rivers and reservoirs. Sedi-ment transport, scour, and deposition processes are simulated along each stream tube independently to give us a semi-three-dimensional variation of the bed geometry. Most sediment transport computer models assume that channel width is given and cannot change during the simulation process. GSTARS models apply the theory of minimum stream power to the determination of optimum channel width and channel geometry. The concepts of channel side stability, and active, inactive, and armoring layers are used in all GSTARS models for realistic long-term simulation and prediction of the scour and deposition processes in rivers and reservoirs.GSTARS models have been applied in many countries for solving a wide range of river and reservoir sedimentation problems. Case studies will be used to illustrate the applications of GSTARS computer models.展开更多
River morphology has been a subject of great challenge to scientists and engineers who recognize that any effort with regard to river engineering must be based on a proper understanding of the morphological features i...River morphology has been a subject of great challenge to scientists and engineers who recognize that any effort with regard to river engineering must be based on a proper understanding of the morphological features involved and the responses to the imposed changes. In this paper, an overview of river morphology is presented from the geomorphic viewpoint. Included in the scope are the regime concept, river channel classification, thresholds in river morphology, and geomorphic analysis of river responses. Analytical approach to river morphology based on the physical principles for the hydraulics of flow and sediment transport processes is also presented. The application of analytical river morphology is demonstrated by an example. Modeling is the modern technique to determine both short-term and long-term river channel responses to any change in the environment. The physical foundation of fluvial process-response must be applied in formatting a mathematical model. A brief introduction of the mathematical model FLUVIAL-12 is described.展开更多
To optimize the distance between the bells in pile design,this paper reports a series of small scale tests on the uplift capacity of double belled piles embedded in dry dense sand considering different bell space rati...To optimize the distance between the bells in pile design,this paper reports a series of small scale tests on the uplift capacity of double belled piles embedded in dry dense sand considering different bell space ratios.Finite element modelling is also performed to evaluate the range of soil failure around the piles during pile uplift displacement.Test results show that when bell space ratio is 6 or 8,the uplift capacity reaches the peak value.The upper bell bears more load than the lower one for the piles with bell space ratio less than 6,while the lower bell bears more load than the upper one for the piles with bell space ratio larger than 8.展开更多
文摘介绍一个用于流动液化变形分析的临界状态砂土模型.该模型的参量与应力和材料状态无关,模型能自动处理材料因过程发展而产生的各种状态变化.对于一种或几种类似的土,参量一经率定,不论材料初始处在松的可液化状态还是紧的剪胀状态,模型以统一方式模拟材料从起始阶段近似弹性的响应直到趋于临界状态破坏,包括流动液化在内的全程响应,无需在分析过程中人为干预调整模型参量.作者利用完全耦合有限元分析程序SUMDES2D,以Upper San Fernando土坝在1971年地震中的分析为例,示范该模型在流动液化变形分析中的应用.
文摘天然状态下水合物生成后往往填充于沉积物土骨架孔隙中或黏结于相邻土颗粒之间,对沉积物具有填充和黏结作用,改变了沉积物原有孔隙比和密度,影响了沉积物的物理力学特性,因此在描述含水合物沉积物的力学和变形特性时需考虑水合物填充和黏结作用的影响。基于黏土和砂土的统一临界状态本构模型(clay and sand model,简称CASM),结合水合物侵入孔隙的致密化特性,通过提出等效孔隙比来反映水合物的填充作用;同时引入黏聚强度来反映水合物对沉积物的黏结作用;并利用状态参数来反映土体的应力状态和剪胀性,采用非相关联流动法则,进而建立能够描述水合物填充和黏结作用的含水合物沉积物弹塑性本构模型。通过与室内试验结果和已有本构模型对比,表明所提模型能较好地模拟含水合物沉积物的应力-应变关系,可有效地描述水合物含量、有效围压对沉积物的强度、刚度、剪胀性等力学特性的影响规律。
文摘GSTARS (Generalized Sediment Transport model for Alluvial River Simulation) is a series of computer models developed by the U.S. Bureau of Reclamation while the author was employed by that agency. The stream tube concept is used in all GSTARS models which allow us to solve one-dimensional equations for each stream tube independently and obtain semi-two-dimensional variation of the hydraulic conditions along and across stream tubes for rivers and reservoirs. Sedi-ment transport, scour, and deposition processes are simulated along each stream tube independently to give us a semi-three-dimensional variation of the bed geometry. Most sediment transport computer models assume that channel width is given and cannot change during the simulation process. GSTARS models apply the theory of minimum stream power to the determination of optimum channel width and channel geometry. The concepts of channel side stability, and active, inactive, and armoring layers are used in all GSTARS models for realistic long-term simulation and prediction of the scour and deposition processes in rivers and reservoirs.GSTARS models have been applied in many countries for solving a wide range of river and reservoir sedimentation problems. Case studies will be used to illustrate the applications of GSTARS computer models.
文摘River morphology has been a subject of great challenge to scientists and engineers who recognize that any effort with regard to river engineering must be based on a proper understanding of the morphological features involved and the responses to the imposed changes. In this paper, an overview of river morphology is presented from the geomorphic viewpoint. Included in the scope are the regime concept, river channel classification, thresholds in river morphology, and geomorphic analysis of river responses. Analytical approach to river morphology based on the physical principles for the hydraulics of flow and sediment transport processes is also presented. The application of analytical river morphology is demonstrated by an example. Modeling is the modern technique to determine both short-term and long-term river channel responses to any change in the environment. The physical foundation of fluvial process-response must be applied in formatting a mathematical model. A brief introduction of the mathematical model FLUVIAL-12 is described.
基金Project(51778346) supported by the National Natural Science Foundation of ChinaProject(2019GSF111007) supported by the Key Research and Development Project of Shandong Province of China+1 种基金Project(ZR201808040034) supported by the Natural Science Foundation of Shandong Province of ChinaProject(2015RCJJ010) supported by the Talent Introduction Research Start-up Fund Project of Shandong University of Science and Technology,China。
文摘To optimize the distance between the bells in pile design,this paper reports a series of small scale tests on the uplift capacity of double belled piles embedded in dry dense sand considering different bell space ratios.Finite element modelling is also performed to evaluate the range of soil failure around the piles during pile uplift displacement.Test results show that when bell space ratio is 6 or 8,the uplift capacity reaches the peak value.The upper bell bears more load than the lower one for the piles with bell space ratio less than 6,while the lower bell bears more load than the upper one for the piles with bell space ratio larger than 8.
