大断面管幕箱涵顶进引起地表变形的解析解答

研究大断面管幕箱涵顶进全过程对土体变形和周围环境的影响,对于事前预测变形并控制施工扰动影响具有重要意义。基于Mindlin解答、修正Sagaseta公式等经典理论解答,分别考虑由正面推进力、摩擦力和土体损失等因素引起的地表变形,提出考虑三者共同作用下的大断面管幕箱涵顶进引起的地表变形计算方法。建立管幕箱涵顶进作用下土体受力模型,采用Mindlin解答分别给出正面推进力和摩擦力引起的土体变形计算公式;基于当层法原理提出由土体损失引起的横向地表沉降计算公式。根据各影响因素的相对独立性,将各因素引起的土体变形量叠加,从而得到一种适用于大断面管幕箱涵顶进施工,可综合考虑多种施工因素和土体三维变形的理论解答公式。通过工程实例验证公式的合理性,研究成果可为实际施工变形预测提供参考。

浅埋超大矩形顶管小净距下穿既有箱涵的变形特性分析

大断面顶管施工不可避免地会引起临近既有结构物的变形,准确分析与预测其变形规律是采取针对性保护措施的前提。本研究基于三维数值模拟,分析浅埋超大矩形顶管左右密贴顶进小净距下穿既有箱涵变形特性的影响规律。结果表明:(1)箱涵变形随着顶管的顶进呈现出先隆起后沉降的变化趋势;顶管顶进对箱涵造成3次明显扰动,分别对应顶管头部位于箱涵前部、箱涵中部、箱涵后部三个位置。(2)左线顶管穿越后,箱涵整体沉降呈V字型的分布规律;右线顶管施工会造成箱涵二次沉降,最大沉降变形由9.33 mm增至11.18 mm。(3)箱涵水平位移整体呈中间大、两头小的倒V字型分布,最大水平位移为15.7 mm;且既有箱涵水平位移大于竖向沉降变形。(4)顶管顶进过程中,箱涵迎土面土压力呈现先增加后减少,再趋于稳定的变化趋势。(5)参数敏感性分析表明,与管土摩擦系数相比,掌子面支护比对箱涵变形的影响效应更显著。

缩窄淮安枢纽分流岛宽度的研究与实践

淮河入海水道为季节性明显的分洪河道,在非汛期,有利于控制工程的检修和加固,分流岛宽度因此不受限制。淮安枢纽扩建的分流岛宽度对泄洪、施工、环境和投资等方面有直接影响。为了获得科学合理的分流岛宽度,本文分析了工程地质条件、运河通航条件、设备布置、施工布置以及邻近建筑物影响等因素与分流岛宽度之间的关系。研究结果表明,缩窄分流岛宽度能减少施工围封面积,节约工程占地和工程量,并且节省工程投资,经济效益明显。

河道防洪治理的工程措施探析

针对诸多河道治理工程措施尚无系统比较分析,易造成经费浪费或治理效果不达标的情况发生,本文简要介绍了河道防洪治理各工程措施的特点,并以徒骇河防洪治理工程为例,详细介绍了一种“防洪墙护岸+河道清理+排水涵闸”的综合治理措施,其思路和经验可供类似工程治理项目参考借鉴。

跨天然气管道施工防护工程设计分析与应用

本文以贵州省安顺至盘州高速公路项目为例,以项目百石荞特大桥跨中缅天然气管道施工工点为背景,论述了采用“盖板防护”+“贝雷梁钢便桥”两种主动与被动相结合的跨天然气管道施工防护工程的设计与应用,并采用有限元分析软件分析了钢便桥的强度、刚度,满足设计规范要求,可为类似跨管涵等工程施工提供借鉴经验。

泵站方涵施工质量控制的关键因素与优化策略研究

泵站方涵施工过程中受到多方面因素的影响,导致质量管控的精度和效率不足。为此,本研究提出了泵站方涵施工质量控制的关键因素分析方法。以中新天津生态城丽水道雨水泵站工程施工为研究对象,根据其工程特点总结影响施工质量的因素指标。为了得到关键影响指标及其重要性程度,引入随机森林计算方法。以各类影响因素指标作为输入要素、施工偏差作为输出要素,得到要素的重要性程度。在此基础上,面向实际项目的施工过程,给出关键指标对应的控制措施。工程实践表明,所提理论方法可以有效获取关键指标。另外,建立的控制措施有效地保证了施工精度。施工偏差整体低于容许偏差的21.84%,节省了18.9%的时间成本。

大跨径钢波纹板拱涵设计方法研究

针对大跨径钢波纹板拱涵设计方法不完善的问题,结合工程设计实例,总结钢波纹板结构的特点,分析钢波纹板拱涵与钢筋混凝土拱涵的受力区别,对比规范计算方法和有限元模型计算方法,提出对于跨径为8 m的高填土钢波纹板拱涵,采用规范计算方法计算应力偏小,应采用考虑土拱相互作用的有限元分析方法。

满水暗涵续建工程临时封堵技术研究

为解决满水暗涵续建工程封堵难度大的问题,研究了一种适用三级封堵、以疏代堵临时混凝土封堵技术。文章重点分析了该技术关键控制要点及质量保证措施,并对该技术现场实施效果、社会环保效益、经济效益方面进行了分析。研究结果发现,满水暗涵临时封堵技术操作简单、成本较低、表现出了良好的经济和社会效益,值得同类型工程推广应用。

施工顺序对中小型涵洞变形的影响分析

涵洞变形受多种因素影响,其中施工技术和施工顺序起到关键作用。为减少中小型涵洞变形,提升工程质量和安全性,基于某泵站工程基础资料,构建了三维数值模型,模拟逐步施工和同时施工2套施工方案,分析施工顺序对建筑物及地基变形的影响。研究发现,当地基土层存在较厚软弱夹层时,涵洞与其紧邻的建筑物同时施工,对地基整体变形控制较好,所产生的不均匀沉降小于分步施工产生的不均匀沉降。

The effects of water flow and temperature on thermal regime around a culvert built on permafrost

Temperature and water flow through a culvert beneath the Alaska Highway near Beaver Creek,Yukon,were measured at hourly intervals between June and October 2013.These data were used to simulate the effect of the culvert on the thermal regime of the road embankment and subjacent permafrost.A 2-D thermal model of the embankment and permafrost was developed with TEMP/W and calibrated using field observations.Empirical relations were obtained between water temperatures at the entrance to the culvert,flow into the culvert,and water temperatures inside the structure.Water temperatures at the entrance and inside the culvert had a linear relation,while water temperatures inside the culvert and water flow were associated by a logarithmic relation.A multiple linear regression was used to summarize these relations.From this relationship,changes in the flow rate and water temperatures at the entrance of the culvert were simulated to obtain predicted water temperatures in the culvert.The temperatures in the culvert were used in the thermal model to determine their effects on the ground thermal regime near the culvert.Variation of ±10% in water flow rate had no impact on the thermal regime underneath the culvert.Variation of water temperature at the entrance of the culvert had a noticeable influence on the thermal regime.A final simulation was conducted without insulation beneath the culvert.The thaw depth was 30 cm with insulation,and 120 cm without insulation,illustrating the importance of insulation to the ground thermal regime.

Study on dynamic response of embedded long span corrugated steel culverts using scaled model shaking table tests and numerical analyses

A series of scaled-model shaking table tests and its simulation analyses using dynamic finite element method were performed to clarify the dynamic behaviors and the seismic stability of embedded corrugated steel culverts due to strong earth-quakes like the 1995 Hyogoken-nanbu earthquake. The dynamic strains of the embedded culvert models and the seismic soil pressure acting on the models due to sinusoidal and random strong motions were investigated. This study verified that the cor-rugated culvert model was subjected to dynamic horizontal forces (lateral seismic soil pressure) from the surrounding ground, which caused the large bending strains on the structure; and that the structures do not exceed the allowable plastic deformation and do not collapse completely during strong earthquake like Hyogoken-nanbu earthquake. The results obtained are useful for design and construction of embedded long span corrugated steel culverts in seismic regions.

Centrifugal model test and numerical simulation of vertical earth pressure on soft foundation box culvert

To obtain the vertical earth pressure on a soft foundation box culvert and investigate the interaction of the soil-culvert-foundation system, both a centrifugal model test and a numerical simulation were conducted and the comparisons with the current methods to determine the load on a culvert were completed. The results of the model test and numerical analysis are in satisfactory agreement, which shows that the direction of the shear stress between the culvert and the adjacent embankment depends on the differential settlement between them. A vertical earth pressure concentration appears on the culvert with a rigid piles foundation because of a downward shear stress. The ratio of the load on a soft foundation culvert and the overburden pressure above the culvert raises first and then decreases as the backfill height increases. In order to reduce the load on a culvert, it is suggested to limit the stiffness difference of the foundations under the culvert and embankment and to use a light backfill over the culvert.

The Collapse of Culverts-Arch in Several Cities around the World, Technical Arguments for Their Maintenance and a Legal Proposal for Prohibiting Their Construction in Mexico

Construction underground pipes and underground culvertsarch (UCA) in order to transport the flow natural rivers and city’s sewage at the same time, is a practice that should be prohibited by the Mexico National Water Law (NWL). When UCA collapse, it causes severe damage to surrounding infrastructure, public and private property, and puts citizens’ lives at risk. This work presents some examples of UCA collapse incidents in several cities around the world, emphasizes how important preventive maintenance of these structures is, highlights the need to classify risk areas, and stresses the need to formulate norms and civil defense plans as article 83 of the NWL suggests. We also propose an addition to Fraction I, article 100 of the National Water Law, to protect the animal and plant life of its banks and safety of their natural runoff.

Frost heave analysis of ballasted track above box culvert and its influence on train vibration

The uneven frost heave of frost-susceptible subgrade soil causes track irregularity,which highly enhances train vibration and affects the comfort and safety of railway transportation.This paper presents a coupled thermo-hydro-mechanical(THM)analysis for the freezing behavior of railway located above a box culvert.The vertical acceleration of the vehicle,an indicator of riding comfort,is predicted through a vehicle dynamic model.The results reveal that the existence of a box culvert changes the subgrade thermal pattern,leading to a deeper frost penetration depth.The frost heave amount above the box culvert is larger than the adjacent section,resulting in uneven track structure upheave and track irregularity.This frostinduced track irregularity highly affects train vibration.

Relative Depth Effects on Corrugated Culvert Roughness

Fish passage is important to the overall health of an ecosystem. Therefore, it is important to be able to accurately predict flow conditions within a stream crossing for high and low flow periods. This paper evaluates the effect of relative water depth on the hydraulic roughness of culverts at low discharge. A 21 m long, 0.8 m diameter corrugated steel pipe with 0.068 × 0.013 m annular corrugations was used. For relative depths below 0.5, Manning’s n was found to increase with decreasing relative depth. An equation was developed to predict relative depths below 0.5 within a corrugated steel pipe based on the corrugation height, slope and culvert diameter. While Manning’s equation does perform reasonably well, the percent difference from the measured to predicted water levels warrants the use of an additional prediction method at low flows.

Origin of Erosion and Hydraulic Problems of the San Roque Underground Arched Culvert Channel and Its Relationship with the Maximum Flow Rate and the Maximum Permissible Velocity

This work presents the hydrologic estimations of the hydraulic underground arched culvert channel (UACC) in Sabinal Basin, Chiapas, México and the hydrological problems associated with it, such as the erosion phenomenon and abrasion cavity formation in it. On the other hand, the maximum flows that the UACC could transport were analyzed, concluding that it no longer has the hydraulic capacity to transport the flow rate associated to return periods equal to or greater than five years and that maximum permissible velocity UACC’s bottom is 3 m/s.

Finite Element Analysis Study of Box Culvert Jacking-Out Construction under Existing Railway Line

To shorten the existing box culvert demolition construction period and ensure the normal operation of the railway, the jacking-out construction method was adopted. The ABAQUS finite element software was used to establish a three-dimensional model of the box culvert and soil body of the relying project, and three excavation thickness (0m, 1 m, 2 m) were used as the main variation parameters for numerical analysis and research, and the change law of the box culvert itself and soil body stress during the culvert jacking out process was obtained. The results show that the jacking force-displacement curves of the three working conditions can be divided into two stages, and the jacking force reaches the maximum value at the moment when the static friction turns into sliding friction at the end of the first stage. The stress distribution at the bottom slab of the box culvert in the jacking process is approximately normal, and the stress decreases with the increase of the roadbed excavation thickness. The increase of the roadbed excavation thickness can reduce the soil pressure on the side of the box culvert and effectively reduce the deformation of the roadbed in the jacking-out process. The deformation of the roadbed during the jacking process can be reduced by increasing the thickness of the roadbed excavation.

Seismic Performance Assessment of Reinforced Concrete Box Culverts under Near and Far Fault Seismic Ground Motion Records

Studying the critical response characteristics of reinforced concrete box culverts with diverse geometrical configurations under seismic excitations is a necessary step to develop a reasonable design method. In this work, numerical analysis and assessment of reinforced concrete box culverts for seismic loading in addition to standard static loading from dead and live loads is conducted, aiming to highlight the critical difference in the seismic performances between two and three cell box culverts under near and far-fault ground motion. The results show how and where the seismic loading alters the responses of seismic loading of the models including the effect on safety and failure. The geometrical configurations of the culvert combined with the loading scenarios also significantly influence the magnitude and distribution of the seismic responses. The findings of this work shed light on the critical role of the geometrical configurations and shaking event in the seismic responses of reinforced concrete box culverts and this procedure can be applied as seismic assessment method to any culvert shape, size, and material.

波纹板加固技术在铁路病害涵洞中的应用研究

涵洞是铁路的重要组成部分,也是日常管养中最容易忽略的铁路设备,涵洞结构的劣化状况和受力性能直接影响线路的安全与稳定。针对提速改造条件下重载铁路涵洞出现的承载能力不足、沉降过大、错位和耐久性降低等诸多问题,基于有限元分析、试验检测和工程应用等方法,开展拼装波纹板加固涵洞机理分析、波纹板关键参数加固涵洞性能与敏感性分析,以及波纹板加固涵洞实际工程应用技术研究。研究结果表明:既有涵洞采用波纹板加固技术后,涵洞结构整体刚度显著提高,涵洞顶板受力和变形明显降低,加固效果较好;同样尺寸条件下,相对于矩形和三角形波纹板结构,采用圆弧形波纹板加固涵洞后,其顶板跨中最大竖向位移和最大应力值均能减小20%及以上,圆弧形波纹板具有更好的加固效果;主力组合荷载作用下,随波纹板波高和波距增加,波纹板Mises应力表现为逐渐减小趋势,且Mises应力与涵洞跨度基本成反比关系。16座涵洞现场实测结果表明,采用波纹板加固后,不同跨径盖板涵和框构涵受力和变形显著降低,跨中挠度及动应变较加固前降低幅度均超过40%,波纹板技术在重载铁路病害涵洞中具有较好的加固效果。

Research on 3D visualization design system of hydraulic culvert

The conventional 2D design method of culverts separated from 3D model cannot directly visualize the process of creating and renewal process. This paper explores graphics application framework of Open GL based on MFC, developing the 3D visualization system of hydraulic culvert. This system effectively integrats with building design, structural design and parametric design and image processing technology. The results can be shown by 3D visualization design.