共查询到20条相似文献，搜索用时 31 毫秒
1.
The temperature distributions of different parts of a subgrade were analyzed based on the results of three years of monitoring data from the Harbin-Qiqihaer Passenger Dedicated Line, a high-speed railway, including the slope toes, shoulders, and natural ground. The temperature variation with time and the maximum frozen depths showed that an obvious sunny-shady effect exists in the railway subgrade, which spans a seasonal frozen region. Development of frost heave is affected by the asymmetric temperature distribution. The temperature field and the maximum frozen depths 50 years after the subgrade was built were simulated with a mathematical model of the unsteady phase transition of the geothermal field. 相似文献
2.
The developed vertical coupling model of Vehicle-Track-Subgrade which considered subgrade layer vibration is present-ed. The equations of motion for the ballast, top and bottom subgrade layers are pres... 相似文献
3.
In order to study the shear behavior of coarse-grained fillings taken from the subgrade bottom layer of a cold region high-speed railway, large scale direct shear tests were conducted with different normal pressures, water contents and temperatures. The results indicate that the relationship between shear displacement and shear stress changed from strain-softening at lower normal pressures to strain-hardening at higher normal pressures, in both unfrozen and frozen states. This phenomenon was mainly due to the shear dilatation deformation effect. The shear displacement-shear stress curves show similar stages. Besides, the shear stress rapidly increased and there was not an increment in the shear displacement during the initial stage of the shear process in the frozen state. In both the unfrozen or frozen states at the same water contents, the shear strength increased with increasing normal pressure. 相似文献
4.
Dynamic characteristics of heavy-haul railway subgrade under vibratory loading in cold regions are investigated via low-temperature dynamic triaxial tests with multi-stage cyclic loading process. The relationship between dynamic shear stress and dynamic shear strain of frozen soil of subgrade under train loading and the influence of freezing temperatures on dynamic constitutive relation, dynamic shear modulus and damping ratio are observed in this study. Test results show that the dynamic constitutive relations of the frozen soils with different freezing temperatures comply with the hyperbolic model, in which model parameters a and b decrease with increasing freezing temperature. The dynamic shear modulus of the frozen soils decreases with increasing dynamic shear strains initially, followed by a relatively smooth attenuation tendency, whereas increases with decreasing freezing temperatures. The damping ratios decrease with decreasing freezing temperatures. Two linear functions are defined to express the linear relationships between dynamic shear modulus (damping ratio) and freezing temperature, respectively, in which corresponding linear coefficients are obtained through multiple regression analysis of test data. 相似文献
5.
利用1960-2015 年新疆塔什库尔干河谷季节性冻土的冻结始日、冻结终日、年冻结日数、年累积冻土厚度、最大冻土深度等特征指标资料,采用气候倾向率、气候突变、气候变化趋势的持续性等方法,分析近56 a该地区季节性冻土的年际、年代际变化特征。研究发现：（1）在全球变暖的背景下,1960-2015 年新疆塔什库尔干河谷气温变化亦呈上升趋势,升温趋势的持续性较强,升温幅度0.03 ℃·a-1、0.29 ℃·（10 a）-1、0.74 ℃·（30 a）-1。（2）在1960-2015年期间,该地区季节性冻土呈退化趋势,具体表现为;冻结始日推迟,冻结终日提前,年冻结日数减少,年累积冻土厚度减小,最大冻土深度减小。（3）在1960-2015年期间,该地区季节性冻土持续退化趋势持续性强。（4）1960-2015 年新疆塔什库尔干河谷季节性冻土对气温变暖的具体响应呈现为退化状态。（5）按气候升温率Gt;0.034~0.046 ℃·a-1 计算,在气候变暖背景下,该地区季节性冻土到2050 年（较2000 年）的冻结始日将推迟12~15 d、年冻结日数将减少21~27 d、年累积冻土厚度将减少36.3%~46.7%。 相似文献
6.
In this paper, a variation series of snow cover and seasonal freeze-thaw layer from 1965 to 2004 on the Tibetan Plateau has been established by using the observation data from meteorological stations. The sliding T-test, M-K test and B-G algorithm are used to verify abrupt changes of snow cover and seasonal freeze-thaw layer in the Tibetan plateau. The results show that the snow cover has not undergone an abrupt change, but the seasonal freeze-thaw layer obviously witnessed a rapid degradation in 1987, with the frozen soil depth being reduced by about 15 cm. It is also found that when there is less snow in the plateau region, precipitation in South China and Southwest China increases. But when the frozen soil is deep, precipitation in most of China apparently decreases. Both snow cover and seasonal freeze-thaw layer on the plateau can be used to predict the summer precipitation in China. However, if the impacts of snow cover and seasonal freeze-thaw layer are used at the same time, the predictability of summer precipitation can be significantly improved. The significant correlation zone of snow is located in middle reaches of the Yangtze River covering the Hexi Corridor and northeastern Inner Mongolia, and the seasonal freeze-thaw layer exists in Mt. Nanling, northern Shannxi and northwestern part of North China. The significant correlation zone of simultaneous impacts of snow cover and seasonal freeze-thaw layer is larger than that of either snow cover or seasonal freeze-thaw layer. There are three significant correlation zones extending from north to south: the north zone spreads from Mt. Daxinganling to the Hexi Corridor, crossing northern Mt. Taihang and northern Shannxi; the central zone covers middle and lower reaches of the Yangtze River; and the south zone extends from Mt. Wuyi to Yunnan and Guizhou Plateau through Mt. Nanling. 相似文献
7.
Frost heave is an upward swelling of soil during cryogenic conditions in cold regions. It is caused by the accumulation of ice crystals in subgrade soil, which grow upwards when freezing temperatures penetrate into the subgrade. This study establishes the allowable soil subgrade frost heave based on the roughness standard of asphalt pavement in China, and aims to balance the pavement design and frost heave resistance of subgrades in cold regions. We formulated a mechanical model of pavement supported by the boundary conditions of differential frost heave, based on the elastic layered system theory. The differential soil subgrade frost heave was modeled as a sinusoidal function, and the allowable frost heave and the roughness index were modeled as the displacement boundaries for the top and bottom of the pavement structure. Then the allowable frost heave was back-calculated according to the roughness standard. Numerical results show that the allowable frost heave depends on the pavement structure, material properties, the highway grade, and other factors. In order to ensure that the actual soil subgrade frost heave is lower than the allowable frost heave, pavement structures and materials need to be selected and designed carefully. The numerical method proposed here can be applied to establish the frost heave resistance of subgrade when the pavement structure and materials are determined. 相似文献
8.
Frozen ground is significantly stiffer than unfrozen ground. For bridges supported on deep foundations, bridge stiffness is also
measurably higher in winter months. Significant changes due to seasonal freezing in bridge pier boundary conditions require additional
detailing in order to ensure a ductile performance of the bridge during a design earthquake event. This paper reports the latest
results obtained from a project that systematically investigated the effects of seasonally frozen soil on the seismic behavior of
highway bridges in cold regions. A bridge was chosen and was monitored to study its seismic performance and assess the impact
of seasonally frozen soil on its dynamic properties. A Finite Element (FE) model was created for this bridge to analyze the impact
of seasonal frost. It was found that when frost depth reaches 1.2 m, the first transverse modal frequency increases about 200%
when compared with the no-frost case. The results show that seasonal frost has a significant impact on the overall dynamic behavior
of bridges supported by pile foundations in cold regions, and that these effects should be accounted for in seismic design. 相似文献
9.
京沪高铁对区域中心城市陆路可达性影响 总被引：31，自引：9，他引：22
针对目前可达性研究技术的局限,设计网络分析与成本栅格加权集成法,并应用该方法生成高铁通车后城市等时圈图。利用日常可达性、潜力值与加权平均时间,比较有无京沪高铁两种情景下京沪地区中心城市可达性空间格局变化,探讨高铁对中心城市可达性的影响,并采用场强模型计算高铁通车前后中心城市腹地范围。结果显示：高铁将扩展等时圈范围,实现城市日常可达性整体大幅优化,形成非均衡的时间收敛空间。高铁站点沿线成为时间收敛的最大受益者,它们的加权平均时间与潜力值变率高。在不同地理尺度下,高铁降低加权平均时间均衡性,对潜力值均衡性影响不一致。高铁扩大北京与上海的腹地,增强其区域辐射力。针对区域可达性变化,可达性变率高的城市可适时调整产业类型,变率低的城市可通过加强快速交通网络与高铁的衔接来提高可达性。 相似文献
10.
On the basis of on-site measured data of the newly constructed Gonghe-Yushu Highway in a permafrost region, this paper analyzed thermal conditions of the subgrade with XPS insulated board according to different selected monitoring sections in various locations. We also summarized the geothermal distribution and change rules of subgrade with XPS insulation board under the asphalt pavement in summarized a high temperature frozen soil region. It is suggested that the shoulder of subgrade with XPS insulation board be widen to a reasonable width so as to keep the subgrade stable. 相似文献
11.
According to the technical characteristics of short fixed wheelbase of a high-speed carriage, a subgrade-track integrated space mechanical response analysis model is proposed for trains under the action of biaxial load after the comparison of the stress distribution characteristics of the ballast track subgrade bed structures for high-speed railway under the action of uniaxial load and biaxial load. The loading threshold value (high-cycle long-term dynamic strength) under the circumstance where the cumulative deformation of subgrade structure gradually develops and finally reaches the convergent state, and its relationship with the foundation coefficient K30 were deduced, based on the characteristics of cumulative deformation evolution obtained from the unit structure filling model test under the action of cyclic loading. In view of structure stability and frost resistance requirements of the railway subgrade in cold regions, technical conditions to maintain good service performance of subgrade structure of high-speed railway ballasted track are discussed and analyzed. Study results show that the additive effect manifests itself obviously for railway train bogies under the action of biaxial load than uniaxial load, which has a significant dynamic effect on the subgrade bed bottom and a slight effect on the surface layer. Thus, the adoption of a biaxial load model in the design of a high-speed railway subgrade accurately reflects the vehicle load. Pursuant to the structure design principle, the design method of the subgrade structure of high-speed railway ballasted track is proposed to meet the technical requirements such as structural strength, bearing stiffness and high-cyclic and long-term stability. Technical indicators are obtained for the variation of thickness of the surface layer of reinforced subgrade bed in the double-layer subgrade mode along with the change of K30 at the subgrade bed bottom. The double-layer structure mode of "closure on the upper layer and drainage on the lower layer" was proposed in order to meet the waterproofing and drainage requirements of the upper layer of the subgrade bed in cold regions. A dense-framework graded gravel filler with weak water permeability at a coefficient of 10-4 cm/s is used on the upper layer and the void-framework graded gravel filler at the water permeability coefficient of 10-2 cm/s is adopted on the lower layer. 相似文献
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14.
《寒旱区科学》2021,13(3)
The building of railways on seasonally frozen ground is inevitable as China pursues economic development and the improvement of its citizens' living standards. However, railway construction in seasonally frozen soil areas is often faced with frost heave, leading to uneven subgrades which seriously threaten traffic safety. This article summarizes extant research results on frost heave mechanism, frost heave factors, and anti-frost measures of railway subgrades in seasonally frozen soil areas. 相似文献
15.
揭示高铁对中国航空客运市场影响的空间分异特征,对于针对性协调2种交通方式的发展具有重要参考价值。运用标准差椭圆和交通综合效用分析方法,对中国中心城市高铁、航空客运市场实际发展现状及空间竞合分异特征进行分析。结果发现：① 高铁、航空客运市场均形成以武汉为重心点的空间发展格局;与高铁客运市场相比,航空客运市场区域发展更加均衡;与东西部中心城市相比,中部中心城市旅客出行选乘高铁的概率更高。② 人均时间价值与高铁优势距呈反比,优势距的不同使各中心城市高铁、航空客运市场范围存在明显的空间分异特征;基于交通出行综合效用视角,中国大多数中心城市间的交往,航空出行依旧是最好的选择。③ 高铁对航空客运市场的影响存在明显的空间分异特征。中部大部分中心城市受影响最大,是协调高铁、航空发展的关键区域;西部地区受交通区位条件及高铁发展滞后的影响,中心城市间交往时飞机仍是旅客主要的出行方式,在航空主导优势区依旧存在一定的市场空白。 相似文献
16.
In seasonally frozen regions, the frost-heave properties of soil play a significant role in its upper-structure performance and durability. To investigate the frost-heave behaviors of saturated, compacted silty clay soil widely used as subgrade material, a series of one-side freezing tests was carried out; and the freezing depth and frozen front effected by the compactness, temperature, overburden pressure, and water-supply condition were analyzed and discussed. The results show that the moving speed of the frozen front and growth rate of the frozen depth are positively correlated. The frost heave is maximum in the frost-heave stability condition. The frost ratio of saturated soil is proportional to the water supply and cooling temperature under a one-side freezing condition. The frost ratio of saturated soil is inversely proportional to the initial compactness of the soil specimen and the overburden pressure. 相似文献
17.
An evaluation of the economic,social, and ecological risks of China-Mongolia-Russia high-speed railway construction and policy suggestions 总被引：2，自引：0，他引：2
Suocheng Dong Yang Yang Fujia Li Hao Cheng Jingnan Li Alexey Bilgaev Zehong Li Yu Li 《地理学报(英文版)》2018,28(7):900-918
The construction of China-Mongolia-Russia high-speed railways is a strategic move to promote transportation infrastructure inter-connectivity between these countries, which will accelerate the implementation of the China-Mongolia-Russia Economic Corridor. However, well-planned China-Mongolia-Russia high-speed railways demand accurately identifying construction risks, scientifically evaluating risk levels, and mapping the spatial distribution of these risks. Therefore, this study established the integrated risk evaluation model (IREM) to scientifically evaluate the economic, social, and ecological risks of China-Mongolia-Russia high-speed railway construction and determine their magnitude and spatial distribution pattern. Based on this analysis, we propose designs for the east and west China-Mongolia-Russia high-speed railways and policy suggestions to mitigate construction risks. Suggestions include developing innovative cooperation of the "high-speed railway for resources and market", strengthening communication and technology dissemination, and applying innovative engineering techniques and setting buffers; establishing collaborative prevention and control systems to mitigate the three major ecological risks in the China, Mongolia, and Russia trans-border areas; and promoting economic integration by improving strategic coordination. In summary, this study provides scientific support for designing the China-Mongolia-Russia high-speed railways minimizing construction risks. 相似文献
18.
To investigate the vibration characteristics of a railway subgrade in different seasons, three field experiments were carried out in
the seasonally frozen Daqing area of China during spring, summer, and winter. The vibration characteristics and attenuation rates
of the subgrade induced by passing trains were investigated, and the influences of the season, train speed, train type, train load, and
number of train compartments are described in this paper. The results show that: (1) near the rail track the vibration in the vertical
direction was more significant than in the lateral and longitudinal directions, and as the distance from the railway track increased,
the acceleration amplitudes and the attenuation rates all decreased in all three directions; (2) the acceleration amplitudes and attenuation
rates decreased in the three different study seasons as the distance from the railway track increased, and the attenuation
rates in the freezing period were the largest; and (3) the acceleration amplitude induced by a freight train was greater than that by a
passenger train, and the subgrade vibration increased with increasing passenger train speeds when the number of train compartments
was similar. These results have great significance for enhanced understanding of the characteristics of train-induced vibration
embankment response in seasonally frozen regions, and provide essential field monitoring data on train-induced vibrations in
order to improve the performance criteria of railroading in seasonally frozen regions. 相似文献
19.
The construction of China-Mongolia-Russia high-speed railways is a strategic move to promote transportation infrastructure inter-connectivity between these countries, which will accelerate the implementation of the China-Mongolia-Russia Economic Corridor. However, well-planned China-Mongolia-Russia high-speed railways demand accurately identifying construction risks, scientifically evaluating risk levels, and mapping the spatial distribution of these risks. Therefore, this study established the integrated risk evaluation model(IREM) to scientifically evaluate the economic, social, and ecological risks of China-Mongolia-Russia high-speed railway construction and determine their magnitude and spatial distribution pattern. Based on this analysis, we propose designs for the east and west China-Mongolia-Russia high-speed railways and policy suggestions to mitigate construction risks. Suggestions include developing innovative cooperation of the "high-speed railway for resources and market", strengthening communication and technology dissemination, and applying innovative engineering techniques and setting buffers; establishing collaborative prevention and control systems to mitigate the three major ecological risks in the China, Mongolia, and Russia trans-border areas; and promoting economic integration by improving strategic coordination. In summary, this study provides scientific support for designing the China-Mongolia-Russia high-speed railways minimizing construction risks. 相似文献
20.
This paper presents an analysis of the mechanisms and impacts of snow cover and frozen soil in the Tibetan Plateau on the summer
precipitation in China, using RegCM3 version 3.1 model simulations. Comparisons of simulations vs. observations show that
RegCM3 well captures these impacts. Results indicate that in a more-snow year with deep frozen soil there will be more precipitation
in the Yangtze River Basin and central Northwest China, western Inner Mongolia, and Xinjiang, but less precipitation in
Northeast China, North China, South China, and most of Southwest China. In a less-snow year with deep frozen soil, however,
there will be more precipitation in Northeast China, North China, and southern South China, but less precipitation in the Yangtze
River Basin and in northern South China. Such differences may be attributed to different combination patterns of melting snow
and thawing frozen soil on the Plateau, which may change soil moisture as well as cause differences in energy absorption in the
phase change processes of snow cover and frozen soil. These factors may produce more surface sensible heat in more-snow years
when the frozen soil is deep than when the frozen soil is shallow. The higher surface sensible heat may lead to a stronger updraft
over the Plateau, eventually contributing to a stronger South Asia High and West Pacific Subtropical High. Due to different values
of the wind fields at 850 hPa, a convergence zone will form over the Yangtze River Basin, which may produce more summer precipitation
in the basin area but less precipitation in North China and South China. However, because soil moisture depends on ice
content, in less-snow years with deep frozen soil, the soil moisture will be higher. The combination of higher frozen soil moisture
with latent heat absorption in the phase change process may generate less surface sensible heat and consequently a weaker updraft
motion over the Plateau. As a result, both the South Asia High and the West Pacific Subtropical High will be weaker, hence causing
more summer precipitation in northern China but less in southern China. 相似文献