共查询到20条相似文献，搜索用时 140 毫秒
1.
《浙江大学学报(A卷英文版)》2020,(5)
土拱效应是桩承式路堤的主要荷载传递机理。本文旨在探讨随着桩土差异沉降量的增加,平面土拱和空间土拱演化过程中的相似点和差异性,以深化对桩承式路堤作用机制的理解。创新点:1.基于离散元法对比分析平面土拱和空间土拱的作用发挥机制,包括细观角度的强弱力链分布特征和宏观角度的沉降变形模式;2.探讨路堤设计参数和土体参数对二维和三维路堤荷载传递和沉降变形(路堤顶面和路堤内部)的影响。方法:1.基于活动门室内模型试验建立桩承式路堤二维和三维离散元数值模型;依据接触力均值划分强弱力链,得到土拱结构的空间分布特征;采用颗粒位移分组获取土体变形模式。2.通过变化路堤高度、桩净间距、填料内摩擦角以及孔隙率来分析路堤荷载和变形响应。结论:1.平面土拱效应存在高估路堤荷载传递效率和低估路堤沉降变形的现象。2.当路堤高度高于等沉面,即土拱结构处于全拱状态时,路堤土体的空间滑裂面表现为穹顶状,且等沉面位置高于二维模型。3.增大路堤高度和填料内摩擦角以及减小桩净间距和孔隙率都能够提高平面土拱和空间土拱的荷载传递能力,进而减小路堤沉降量;其中,孔隙率对沉降变形的影响最为明显。4.当路堤高度低于等沉面,即土拱结构处于非全拱状态时,在三维模型中增加路堤高度主要减小四桩间上部土体沉降,而对两桩间上部土体沉降的影响较小。 相似文献
2.
在系统分析红砂岩工程特性以及与水的相互作用关系的基础上，结合红砂岩路基的施工处理方法以及三种典型红砂岩高路堤的沉降观测结果的分析研究，探讨了红砂岩作为高路堤填料的可行性、施工方法的合理性以及不同红砂岩路基的沉降稳定性. 相似文献
3.
《东南大学学报》2017,(2)
为了分析膨胀土地区路堤初始开裂行为,使用ABAQUS模拟了典型路基断面的路堤顶部张拉应力峰值和峰值位置的改变.模拟结果表明:基质吸力在膨胀土地基顶部呈凹形分布,并且引起了地基和路堤的不均匀变形.路堤顶部张拉应力峰值并非位于某一固定点,而是随着蒸发的持续逐渐朝路肩移动.蒸发强度越大,随着地表蒸发的进行,路堤顶面张拉应力峰值增大越快,其位置越靠近路肩;厚层膨胀土有助于路堤顶面张拉应力峰值快速到达其抗拉强度阈值,而膨胀土厚度小于1.5m时,地表蒸发30天,路堤不会开裂;路堤越高,路堤顶面张拉应力峰值越小,其位置越远离路肩.因此,薄层膨胀土土层上修筑较高路堤可以减少路堤裂缝的形成. 相似文献
4.
利用将图像处理软件photoshop和madab结合起来进行数据处理扫描电镜图像的新技术,给出了实现图像处理的程序代码和图像处理前后的可视化效果对比,提出了有关描述粘性土微观结构的定量信息．结果表明：这种方法能较为全面地分析粘性土劈裂注浆前后孔隙形态及组合特征,包括孔隙的面积、周长、数量等关系,为粘性土微观结构定量研究提供了参考． 相似文献
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6.
ZHOU Mei-lin 《怀化学院学报》2007,(3)
在系统分析红砂岩工程特性以及与水的相互作用关系的基础上,结合红砂岩路基的施工处理方法以及三种典型红砂岩高路堤的沉降观测结果的分析研究,探讨了红砂岩作为高路堤填料的可行性、施工方法的合理性以及不同红砂岩路基的沉降稳定性. 相似文献
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8.
吴进甫 《安阳师范学院学报》2000,(2):35-37
土的塑性，颗粒组成，比重是土定名和物理力学性质计算的基本指标，他们之间有着内在的联系，由于不同时代生成土的地质环境不同，他们之间又有差异。笔者用数理统计的方法，对安阳市范围内的一般粘性土和新近沉积粘性土进行了分析对比，探讨了其相关性，建立了相关方程。 相似文献
9.
《浙江大学学报(A卷英文版)》2016,(10)
目的:旨在从宏细观角度探究桩承式路堤中土拱结构的形态特征及其演化规律。创新点:1.基于接触力链网络的细观统计与分析并结合土拱结构的特点,对路堤中的接触力链进行划分;2.从宏细观角度,揭示路堤中土拱结构的形态特征,并研究土拱结构随桩土相对位移增加的演化规律。方法:1.采用傅里叶级数近似法对接触力链组构各向异性进行统计与划分;2.基于路堤填料位移、接触力分布以及组构各向异性主方向等的分布及变化规律,从宏细观角度对土拱结构的形态及其演化规律进行综合分析。结论:1.土拱结构是由路堤中大于1.5倍接触力均值的强力链构成,而弱力链则主要起支撑作用。2.土拱结构随桩土相对位移的增加而历经倾斜剪切面→半圆形拱→悬链线形拱的演化规律,土拱结构的最大高度约为0.8倍桩净间距。3.路堤填料内摩擦角对土拱结构的形态及演化规律几乎无影响;路堤填筑高度对土拱结构形态则有显著影响;桩净间距对土拱结构的演化有一定影响,但是对其最终形态特征则几乎无影响。 相似文献
10.
汉江遥堤为国家Ⅰ级堤防，遥堤王家营险工险段堤身填筑修筑时间跨度大，土体成分复杂。堤基地质结构为典型的“上砂下粘”双层结构，地表直接出露粉细砂。渗透变形试验表明，王家营粉细砂临界比降和破坏比降比其它长江重要堤防同类土小，渗径短，水力比降大，容易产生渗透破坏。建议对堤基和堤身进行垂直防渗处理，处理深度入粘性土2m为宜。 相似文献
11.
路堤下土体侧向变形性状研究 总被引：1，自引：0，他引：1
分析了路堤荷载作用下土中水平向附加应力随深度的变化特征,得出了侧向变形沿深度"弓"形分布的变化规律,大量实测结果也证明了这一点.在此基础上提出了符合该变形规律的预测模型,分析了模型曲线随其中3个参数a,b 和 c的变化规律,并且通过3个实测点的侧向变形数据(s0,0),(s1,h0) 和 (s2,2h0)就可以简单地定出模型中这3个参数.将该模型应用到2个工程实例当中,预测结果和实测数据比较吻合,取得了较好的效果. 相似文献
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张品 《石家庄铁路工程职业技术学院学报》2013,(4):1-7
基于现场测试手段,深入研究分析软弱黄土地基桥头引道路堤变形的时空特征,并从技术方面系统提出变形控制技术措施,确保桥头引道的工程质量。通过现场观测,分析各类技术手段对桥头引道路堤变形控制的有效性。 相似文献
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首先通过对安徽淮南地区煤矸石进行室内材料试验,重点完成了抗剪强度、压缩模量等力学性能试验,结果表明其满足公路路堤材料的力学性能要求。采用ABAQUS有限元法分析不同影响因素对煤矸石浸水路堤路堤顶面处不均匀沉降的影响,对不同条件下路堤模的竖向顶面不均匀沉降并进行了参数敏感性分析。最后量化分析了各要素的影响程度并对其变化规律进行了研究。 相似文献
14.
Wan-huan Zhou Ren-peng Chen Lin-shuang Zhao Zheng-zhong Xu Yun-min Chen 《浙江大学学报(A卷英文版)》2012,13(11):888-894
In this paper, a semi-analytical method for the analysis of pile-supported embankments is proposed. The mathematic model describes the cooperative behavior of pile, pile cap, foundation soil, and embankment fills. Based on Terzaghi??s 1D consolidation theory of saturated soil, the consolidation of foundation soil is calculated. The embankments with two different types of piles: floating piles and end-bearing piles are investigated and discussed. The results of axial force and skin friction distributions along the pile and the settlements of pile-supported embankments are presented. It is found that it takes a longer time for soil consolidation in the embankment with floating piles, compared with the case using end-bearing piles. The differential settlement between the pile and surrounding soil at the pile top is larger for the embankment with end-bearing piles, compared with the case of floating piles. 相似文献
15.
The seasonal-frozen layer may have an influence on embankment motion from train-induced vibrations. Based on the field monitoring in a seasonally-frozen region of northeastern China, the effects of the frozen layer on the embankment responses to train-induced vibration were investigated in winter and summer via acceleration time histories and acceleration frequency spectrums. The results show that： （1） Compared to unfrozen soil conditions, the amplitudes of longitudinal and vertical vibrations at the points near the rail were increased, different influences of freight versus high-speed trains are the most evident. （2） With greater distance from the rail, the dominant frequency ranges of embankment with both frozen and unfrozen layers narrowed and shifted to low frequency bands. （3） The predominant frequency of embankment vibration with frozen soil layers shifted to higher frequencies with the increased train speed, although there was little change with unfrozen condition. Layer condition （frozen versus unfrozen） and distance to rail both play important roles in investigating the embankment vibration characteristics and rail transit field monitoring to improve the criterion of the rail construction in seasonally-frozen regions. 相似文献
16.
Piled embankments are widely used in highway and railway engineering due to their economy and efficiency in overcoming several issues encountered in constructing embankments over weak soils. Soil arching, caused by the pile-subsoil relative displacement (Δs), plays an important role in reducing the embankment load falling on weak soil, however, the fundamental characteristics (e.g., formation and features) of soil arching remain poorly understood. In this study, a series of discrete element method (DEM) modellings are performed to study the formation and features of soil arching with the variation of Δs in piled embankments with or without geosynthetic reinforcement. Firstly, calibration for the modelling parameters is carried out by comparing the DEM results with the experimental data obtained from the existing literature. Secondly, the analysis of the macroand micro-behaviours is performed in detail. Finally, a parametric study is conducted in an effort to identify the influences of three key factors on soil arching: the friction coefficient of the embankment fill (f), the embankment height (h), and the pile clear spacing (s?a). Numerical results indicate that Δs is a key factor governing the formation and features of soil arching in embankments. To be specific, soil arching gradually evolves from two inclined shear planes at a small Δs to a hemispherical arch at a relatively large Δs. Then, with a continuous increase in Δs, the soil arching height gradually increases and finally approaches a constant value of 0.8(s?a) (i.e., the maximum soil arching height). For a given case, the higher the soil arching height, the greater the degree of soil arching effect. The parametric study shows that the friction coefficient of the embankment fill has a negligible influence on the formation and features of soil arching. However, embankment height is a key factor governing the formation and features of soil arching. In addition, pile clear spacing has a significant effect on the formation of soil arching, but not on its features. 相似文献
17.
公路拓宽会引起老路路堤的不均匀沉降、路面裂缝等病害。对于拓宽路堤的变形,国内外研究度还不够,针对研究中不足本文采用PLAXIS商用有限元软件对不同工况下拓宽路堤进行了非线性有限元分析,得出拓宽路堤的变形规律。分析结果表明:拓宽路堤的自重荷载会使老路堤产生较大的竖向位移和水平位移。 相似文献
18.
郑军锋 《福建工程学院学报》2019,(4):307-313
对新建兴泉铁路黄塘车站挤密螺纹桩复合地基的桩、土沉降及应力进行监测,分析了路堤荷载下桩、土沉降及差异沉降变化规律,桩土应力比与差异沉降关系。结果表明:桩、土沉降及差异沉降均随路堤填土高度的增加而呈线性增大;桩顶和桩间土应力随路堤填土高度的增加均不断增大,且桩顶应力大于桩间土应力;桩土应力比随着桩土差异沉降的增加先增加后减小,最终趋于稳定。结合修正的Terzaghi土拱理论提出了简化桩土应力比随桩土差异沉降变化曲线。现场试验分析结果有助于完善挤密螺纹桩复合地基设计理论,为工程实践提供一定的参考。 相似文献
19.
《海外英语》2012,(7):247-249
This research made comparisons of cohesive ties between the good and poor compositions of sixty senior three students in a senior high school in Shenzhen,Guangdong Province to examine cohesive features in L2 argumentative writing.The findings of the present study reveals that the composition scores were significantly co-varied with the number of conjunction ties and lexical ties,as well as the total number of cohesive ties used.Among the three main categories of cohesive ties,lexical ties(66.7%) used most frequently in the sampled L2 essays.Moreover,cohesive ties with the most frequently used,lexical ties,contribute to the quality of syntactical structure. 相似文献
20.
针对解决《土工试验方法标准》三轴试验中,黏性土抗剪强度指标出现的变异问题,提出一种黏性土试样组合方法,准确测定黏性土抗剪强度指标值在原有的一组相同物理性质(含水率,液塑限,级配)黏性土三轴试样的基础上,增加一组或两组相同物理性质试样,通过系统软件对试样进行完备组合,重新形成黏性土抗剪强度指标值样本基数,取其样本数的平均值为黏性土抗剪强度指标.通过试验验证了试样组合方法能有效避免三轴试验中出现的互不包容的莫尔圆,或黏聚力c出现负值试验结果,并在不增加试样数量的前提下,扩大了黏性土抗剪强度指标的样本基数,从而可准确测定抗剪强度指标值组合方法的提出为黏性土抗剪强度指标的测定提供一定的参考价值. 相似文献