机车动荷载作用下多年冻土区铁路路基动力响应的试验研究

青藏铁路穿越多年冻土区因地温和含冰量的不同而采取了不同的路基结构形式,以减小或避免气温和工程扰动对其下部多年冻土的影响。为了把握多年列车振动荷载作用下多年冻土区不同结构路基的动力响应特征,对青藏铁路北麓河段典型结构路基进行了实时强震动测试,得到了多年冻土区铁路路基的振动加速度衰减规律,对于研究机车动荷载对青藏铁路多年冻土区路基变形的定量影响规律,保障青藏铁路安全运营具有重要的科学意义。     

青藏铁路清水河地区路基下伏多年冻土地温变化特征研究

基于埋设在青藏铁路清水河地区路基中两个断面内的共8个地温测试孔3年来的地温观测资料,研究了该地区铁路路基下伏高原多年冻土融化特征,分析了多年冻土上限的变化规律以及填筑铁路路基施工对下伏多年冻土赋存条件的影响。研究表明,由于受到填筑路基时赋存在路基填料内的热量的影响,铁路路基下伏多年冻土近地表的地温变化特征与天然地面下的多年冻土的地温变化特征有明显的不同,且向阳面与被阴面差别较大。多年冻土的上限在施工初期会有一个明显的下移沉降,随着时间的推移,虽然残存在路基中的热量逐渐消散,多年冻土上限下降会逐渐稳定。由于受到太阳辐射和路基边坡形状及融化夹层的影响,多年冻土上限会逐渐稳定,但不会在短时期内上升到天然地面下多年冻土的上限水平。     

植物消浪护岸模型实验研究

对于在堤岸上种树消浪这一新的护岸工程,根据实际波浪要素和现有实验设备条件确定出几何比尺,选取桧柏树枝作为防浪树的模型,筛选主要影响因素进行量纲分析,确定实验组次,对实验现象和数据作定性和定量的分析,得出防浪林应有相当的宽度,才能起到预期的防浪护岸效果,防浪林过窄,可能会引起“共振”现象,并且斜坡的消浪效果好于平坡,对实际工程可起参考作用。     

Role of piles in mitigating the movement of pipes in soft grounds during embankment loading

Abstract

Pipes buried in soft ground can be damaged due to the vertical and lateral movement of the ground during the construction of the embankment. To investigate such a movement of the soft ground, full-scale tests using embankment piles and stabilizing piles were conducted for 70?days. A pile-supported embankment has been used to reduce the deformation of soft ground by transferring the embankment load through piles to the firm layer below the soft ground, whereas stabilizing piles have been employed to resist the lateral earth pressure that is induced in soft ground by embankment loads. The Coupling Area (CA), which was defined as the quantitative index to determine the resistance effect of both settlement and lateral flow of the soft ground when the embankment was reinforced, is adapted. The analysis results of the CA indicate that the piled embankment was more effective for preventing the damage to buried pipe installed near the embankment, while the stabilizing piles had almost the same effect as the piled embankment when the pipe was buried far away from the embankment.     

Analytical modeling on consolidation of stiffened deep mixed column-reinforced soft soil under embankment

Stiffened deep mixed (SDM) column is a new ground improvement technique to improve soft soil, which can be used to increase bearing capacity, reduce deformation, and enhance stability of soft soil. This technique has been successfully adopted to support the highway and railway embankments over soft soils in China and other countries. However, there have been limited investigations on its consolidation under embankment loading. This paper developed an analytical solution for the consolidation of embankment over soft soil with SDM column in which core pile is equal to or shorter than outer DM column. The consolidation problem was simplified as a consolidation of composite soil considering the load shear effect of core pile. The developed solution was verified by a comparison with the results computed by three-dimensional (3-D) finite element analysis. A parametric study based on the derived solution was conducted to investigate influence factors—length of core pile, diameter of core pile, diameter of SDM column, modulus of DM column, and permeability coefficient of DM column—on the consolidation behavior of SDM column-supported embankment over soft soil. The developed solution was applied to a case history of SDM column-supported embankment, and a good agreement was found between the predictions and the field measurements.     

考虑时效的高填石路堤工后沉降有限元及反馈分析研究

把填石体作为粘弹性介质,提出采用三参数本构模型来描述填石体的蠕变特性,在此基础上引入遗传算法与有限元分析,建立了填石体三参数本构模型参数确定的优化反演方法,结合某高填石路堤得实测工后沉降数据进行参数反演,并利用反演参数对类似断面进行工后沉降分析,结果表明,本文建立的填石路堤工后沉降计算方法能准确的预测工后沉降,参数便于求取,为寻求合理的路面铺筑时间和制定施工控制条件提供依据。     

Some engineering characteristics of a compacted lateritic residual soil

Summary In many parts of the world, particularly in humid tropical regions, residual soils are abundant. In this paper the suitability of a residual lateritic soil as a construction material is investigated, with respect to its strength and compaction characteristics. In comparison with other typical construction fills available in Southeast Asia, compacted lateritic soils produce excellent shear strengths and CBR values. However, the brittleness and tensile cracking of this compacted material become enhanced on the dry side of the optimum moisture content, or if excessive compaction is imparted. Nevertheless, at a moisture content of 2% wetter than the optimum, the tensile mode of failure is suppressed and the lateritic fills become ideally suited for the construction of high embankments and impervious dam cores.     

Wharf embankment and strengthening program at the Port of Oakland

The wharf and embankment strengthening program (WESP) is a structural modification project involving approximately 12,000 linear feet of pile-supported, marginal wharf structures. WESP is necessary because the Port of Oakland plans to deepen its berths from −42′ mean lower low water (MLLW) to −52′ MLLW, in conjunction with a Federal Government-sponsored channel dredging project. Unless they are structurally reinforced prior to the dredging, the waterfront components (i.e. wharves and embankments) will be weakened by the berth deepening project. WESP is a three-phase program that establishes the existing structural and seismic capacities of waterfront components, develops designs for improvements necessary to maintain these capacities after the berth deepening, and constructs the improvements. WESP also includes consideration of seismic upgrade improvements. The Port is currently completing the first phase of the WESP program. This paper will describe the design criteria, project phasing, construction type of waterfront components, project organization, and results to date for WESP.     

青藏公路普通填土路基长期变形特征与路基病害调查分析

基于长期监测系统2004－2011年现场监测数据,系统分析青藏公路近年来冻土路基变形特征及路基病害原因。结果表明,目前青藏公路普通填土路基变形主要以融沉变形为主,且沉降变形仍将继续发展。根据路基各部位变形速率的差异性,可以将路基变形划分为均匀与不均匀变形两大类。路基平均沉降速率在2～55 mm/a之间,河流沟谷地带路基变形速率最大,山区路基变形速率次之,其他地貌区路基变形速率最小。路基纵向变形对路面影响较大,主要形成波浪等病害,对道路行车舒适性与安全性有较大隐患。路基横向变形主要产生路基纵向裂隙病害,导致路基向变形较严重一侧坍塌,对路基整体稳定性有较大影响。通过2012年对青藏公路路基病害的调查研究发现,青藏公路多年冻土区路基优、良、中、次、差的比例分别为57.39% 、28.12%、9.71%、4.60%、0.17%。通过对青藏公路普通填土路基长期变形特征的分析,期望为青藏公路的整治维修提供参考,同时为未来青藏高速公路的设计和维护提供依据。     

郑州黄河岸边开采地下水对大堤稳定性影响

通过对郑州市黄河大堤一线土体的沉降，压密固结，饱水砂土的地震液化研究，认为黄河大堤附近浅层地下水开采后所诱发的地面沉降，固结过程，不会对大堤造成危害，而饱水砂土的水位降低，还会减轻或消除地震时液化砂土现象，对大堤的稳定性有利。