塑料排水板联合堆载预压法处理软土路堤浅析

结合塑料排水板加固软土路堤的工程实例,对比分析了排水板间距、堆载预压时间及堆载预压荷载对软土固结度、残余沉降的影响。总结出在工期允许的情况下,适当增加排水板间距并延长堆载时间,可有效减少工程造价并达到与较小排水板间距时相近的处理效果。在工期紧张的情况下,可通过减小排水板间距并结合超载预压,加快施工期沉降速率,满足残余沉降要求。     

Competition and disruption in a dynamic urban supply chain

Rapid changes and complexities in business environments have stressed the importance of interactions between partners and competitors, leading supply chains to become the most important element of contemporary business environments. There is a concomitant need for foresight in describing supply chain performance in all operating environments, including those involving punctuated disruptions. Furthermore, the urban metropolis is now widely recognized to be an environment which is especially vulnerable to supply chain disruptions and for which integrated supply chain decisions can produce very substantial net benefits. Accordingly, this paper presents a dynamic supply chain network model formulated as a differential variational inequality; the model is fashioned to allow consideration of supply chain disruption threats to producers, freight carriers, and retail enterprises. The DVI is solved using a fixed-point algorithm, and a simple numerical example, introduced to illustrate how the impacts of supply chain disruptions may be quantified, is presented.     

Approximate network loading and dual-time-scale dynamic user equilibrium

In this paper we present a dual-time-scale formulation of dynamic user equilibrium (DUE) with demand evolution. Our formulation belongs to the problem class that Pang and Stewart (2008) refer to as differential variational inequalities. It combines the within-day time scale for which route and departure time choices fluctuate in continuous time with the day-to-day time scale for which demand evolves in discrete time steps. Our formulation is consistent with the often told story that drivers adjust their travel demands at the end of every day based on their congestion experience during one or more previous days. We show that analysis of the within-day assignment model is tremendously simplified by expressing dynamic user equilibrium as a differential variational inequality. We also show there is a class of day-to-day demand growth models that allow the dual-time-scale formulation to be decomposed by time-stepping to yield a sequence of continuous time, single-day, dynamic user equilibrium problems. To solve the single-day DUE problems arising during time-stepping, it is necessary to repeatedly solve a dynamic network loading problem. We observe that the network loading phase of DUE computation generally constitutes a differential algebraic equation (DAE) system, and we show that the DAE system for network loading based on the link delay model (LDM) of Friesz et al. (1993) may be approximated by a system of ordinary differential equations (ODEs). That system of ODEs, as we demonstrate, may be efficiently solved using traditional numerical methods for such problems. To compute an actual dynamic user equilibrium, we introduce a continuous time fixed-point algorithm and prove its convergence for effective path delay operators that allow a limited type of nonmonotone path delay. We show that our DUE algorithm is compatible with network loading based on the LDM and the cell transmission model (CTM) due to Daganzo (1995). We provide a numerical example based on the much studied Sioux Falls network.     

考虑融沉的冻土地区沥青路面结构设计

地基融沉是造成冻土地区路面病害的主要原因之一,在路面设计当中需要对此进行有效考虑。在对冻土地区路面破坏模式分析的基础之上,采用力学方法和数学方法对诱发常见路面病害的冻土融沉规律进行研究,对冻土温度场与环境温度变化的相关性规律以及不同融沉条件下路面结构内部的应力应变场进行研究,并通过大量的分析计算以及实地观测,提出了考虑融沉的路面设计方法和流程。该方法能够使路面设计时有效考虑未来融沉可能对基层、面层等不同层位产生的附加应力,从而使得在路面结构设计初期能够更加有效地考虑冻土融沉的影响。     

粉喷桩处理高速公路加宽工程新路软基的数值分析

通过合理的有限元数值模拟,分析了粉喷桩处理高速公路加宽工程新路地基时,桩体处治范围、桩体模量和桩间距等因素对地基沉降变形的影响,所得结论可以为今后的相关工程设计提供参考。     

冲击碾压在高填方路基中的应用研究

采用冲击碾压技术对高填方路基进行冲压补强,测试分析路基在冲击碾压作用下相关力学参数的变化,以确定更优化的相关施工参数:主要考虑了冲压遍数对路基沉降变形、路基不同深度处压实度、路基填料最大干密度及整体强度的影响.结果表明:随碾压遍数的增加,路基沉降量增加,其增量曲线趋于收敛;碾压20～25遍可以起到对路基较好补强的作用,...     

浅析善后河枢纽工程云善船闸主体沉降规律

通过对云善船闸的定期观测和分析,获得船闸工程各部位的沉降情况,监控船闸的施工及使用状况。同时,根据沉降观测资料来分析沉降规律,探讨船闸变形的原因,为船闸施工和运行安全提供保证。     

电分相设置对高速动车组运行速度及时分影响研究

高速铁路对列车运行安全及运输效率的要求越来越高,电分相对列车运行速度和时间的影响逐步受到重视。本文重点研究采用不带电过分相方式对列车运行速度及时分的影响,通过描述动车组不带电自动电分相的微观过程,建立了电分相对速度及时分影响的算法,模拟计算了不同运行条件、不同设置位置和纵断面情况下电分相对列车速度及时分的影响,提出高速...     

沂北船闸底板宽缝封缝条件分析

文章以连云港港疏港航道沂北船闸为例,讨论船闸底板预留施工宽缝的意义和宽缝封缝的条件,同时提出相关建议。     

基于高速铁路软土路基固结沉降有限元分析

利用大型有限元软件ABAQUS,结合工程实例分析了软土路基分步修筑固结沉降的变形特性。计算结果表明:在路基分步填筑过程中,填土加载引起内部孔隙急剧变化,水体流失产生附加应力导致路基沉降。因此,施工中通过控制填土的速度来减小路基沉降是提高路基修筑质量的一个重要手段。同时,该标段结合实际情况,采用旋喷桩和土工栅格的加固方法,通过路基施工后沉降观测数据来看,效果明显。