Roadbed, embankment, tower support and culvert stability problems on permafrost

The history of railway and highway construction in permafrost zones in Russia, the United States, Canada, and China spans more than 110 years. Nonetheless, no railway track or highway has yet been built in such area that is impervious to deformation caused by subsidence resulting from the thawing of ice-rich subgrade soils. This paper presents data on the roadbed states of the Transbaikalian and the Baikal-Amur Railways as well as the Russian "AMUR" Chita-Khabarovsk Highway. It also discusses the feasibility of roadbed stability maintenance using methods based on the reduction of the mean annual ground temperature and roadbed preservation in a permafrost state by means of the natural cooling and heating factors ratio regulation resulting in a reduction of the heat generation in the roadbed and the adjoining area accompanied by an increase of heat consumption with help of the sun-precipitation protective sheds (awnings), rock covers, dolomite powder (reflective paint), cooling tube and thermosyphons as well as tower supports and corrugated pipe culverts stability.     

Mountain permafrost distribution modeling using Multivariate Adaptive Regression Spline (MARS) in the Wenquan area over the Qinghai-Tibet Plateau

In high mountainous areas, the development and distribution of alpine permafrost is greatly affected by macro- and micro-topographic factors. The effects of latitude, altitude, slope, and aspect on the distribution of permafrost were studied to understand the distribution patterns of permafrost in Wenquan on the Qinghai-Tibet Plateau. Cluster and correlation analysis were performed based on 30 m Global Digital Elevation Model (GDEM) data and field data obtained using geophysical exploration and borehole drilling methods. A Multivariate Adaptive Regression Spline model (MARS) was developed to simulate permafrost spatial distribution over the studied area. A validation was followed by comparing to 201 geophysical exploration sites, as well as by comparing to two other models, i.e., a binary logistic regression model and the Mean Annual Ground Temperature model (MAGT). The MARS model provides a better simulation than the other two models. Besides the control effect of elevation on permafrost distribution, the MARS model also takes into account the impact of direct solar radiation on permafrost distribution.     

青藏高原西部区域多年冻土分布模拟及其下限估算

准确评估青藏高原西部多年冻土的空间分布及多年冻土下限深度情况对该区地下水资源利用、生态环境保护有重要意义.本文依托科技基础性工作专项“青藏高原多年冻土本底调查”在该区及周边取得的冻土调查资料,利用遥感数据和扩展地面冻结数模型模拟了该区多年冻土的空间分布,调查区的模拟验证表明该方法有较高的精度.在此基础上,根据有限的地温实测资料建立了地温与位置、高程、坡向和太阳辐射的关系,并根据地温-下限关系估算了该区多年冻土下限深度的分布情况.研究表明,该区有多年冻土约占36.9%,季节冻土占57.5%,多年冻土主要分布在34°N~36.5°N范围的喀喇昆仑、西昆仑一带,季节冻土主要分布在塔里木盆地和34°N以南地区.阿里高原及以南是岛状多年冻土分布区域,其多年冻土分布面积少于此前出版的冻土图所绘制的.青藏高原西部区域的多年冻土下限深度整体表现为由东南-西北逐渐加深.     

黄河源区冻土分布制图及其热稳定性特征模拟

以黄河源区多年冻土分布现状和热力特征为研究目标,通过野外调查及实测数据,分析了黄河源区不同地形地貌、不同地表覆盖条件下的冻土形成、分布特征和以地温为基础的热学特征,探讨了不同尺度因素对多年冻土分布的影响。结果表明,在高程低于4 300 m的平原区,多年冻土多不发育;在高于4 350 m的山区,局地地形对多年冻土的形成与分布作用显著。除阳坡地形外,多年冻土均比较发育;介于4 300~4 350 m的低山丘陵和平原区,局地地形、地表植被、土壤湿度等因素共同决定着多年冻土的形成和分布格局。以年均地温指标为基础,构建了以纬度、经度和高程为自变量的回归模型,并对阳坡地形进行微调和校正。结果表明,以0oC作为划分季节冻土和多年冻土的标准和界限,多年冻土面积2.5×10⁴km²,约占整个源区面积的85.1%;季节冻土面积0.3×10⁴km²,约占整个源区面积的9.7%。进一步以0.5oC或1.0oC为分类间隔绘制了黄河源区多年冻土热稳定性空间分布图。     

2000—2015年中蒙俄经济走廊东段冻土时空变化及植被响应

中蒙俄经济走廊东段位于欧亚大陆多年冻土区东南缘及森林线南界接近区,冻土及生态环境脆弱。本文基于MERRA-Land陆面模式离线运行产品分析了中蒙俄经济走廊东段2000—2015年间冻土冻融的时空变化模式,以及冻土变化对返青期和全年不同阶段植被生长状态的影响。研究表明：2000—2015年间研究区多年冻土及季节冻土均持续退化,时间上主要表现为冻土提前解冻、延迟冻结;空间上主要表现为多年冻土南界的多年冻土退化和季节冻土下限抬升,及连续多年冻土南界的活动层加厚。解冻始日是森林地区植被返青的主控要素,林下冻土解冻对土壤含水量的增加及沼泽湿地的隔热蓄水功能影响了森林地区植被的生长。但随着多年冻土南界森林及林下泥炭地演替为草甸和农田,多年冻土退化,进一步促进林下沼泽湿地的消失。探讨冻土退化与生态环境之间的协同关系,有助于识别气候变暖和人类活动叠加影响下的冻土退化脆弱区以及生态环境敏感区。     

黄河源区多年冻土空间分布变化特征数值模拟

基于IPCC第五次评估报告预估的气温变化情景,采用数值模拟的方法对黄河源区典型冻土类型开展模拟,推算过去及预测未来黄河源区冻土分布空间变化过程和发展趋势。结果表明：1972-2012年源区多年冻土只有少部分发生退化,退化的冻土面积为833 km²,季节冻土主要集中在源区东南部的热曲谷地、小野马岭以及两湖流域南部的汤岔玛地带;RCP 2.6、RCP 6.0、RCP 8.5情景下,2050年多年冻土退化为季节冻土的面积差别不大,分别为2224 km²、2347 km²、2559 km²,占源区面积的7.5%、7.9%、8.6%;勒那曲、多曲、白马曲零星出现季节冻土,野牛沟、野马滩以及鄂陵湖东部的玛多四湖所在黄河低谷大片为季节冻土;2100年多年冻土退化为季节冻土的面积分别为5636 km²、9769 km²、15548 km²,占源区面积的19%、32.9%、52.3%;星宿海、尕玛勒滩、多格茸的多年冻土发生退化,低温冻土变为高温冻土,各类年平均地温出现了不同程度的升高。到2100年,RCP 2.6情景下源区多年冻土全部退化为季节冻土主要发生在目前年平均地温高于-0.15 oC的区域,而-0.15~-0.44 oC的区域部分发生退化;RCP 6.0、RCP 8.5情景下目前年平均地温分别为高于-0.21 oC以及-0.38o C的区域多年冻土全部发生退化,而-0.21~-0.69 oC以及-0.38~-0.88 oC的区域部分发生退化。     

Artificially frozen ground and related engineering technology in Japan

Since the 1970's, frozen ground has been developing near the Tokyo Bay area around liquefied natural gas(LNG) inground storage tanks. For disaster prevention purposes, the tanks are constructed below the ground surface. Since the temperature of the liquid stored in the tanks is -162℃ the soil surrounding the tanks freezes. Since this frozen ground has existed for almost half a century, we have permafrost near Tokyo. The development of artificial frozen ground may cause frost heaving, resulting in frost heave forces that may cause structural damage of adjacent LNG in-ground storage tanks.Therefore, the demand for frozen ground engineering increased and consequently we now have advanced technology in this area. Fortunately, we use this engineering technology and artificial ground freezing for civil engineering, especially in big and crowded cities like Tokyo. This paper provides a summary of the testing apparatus, test methods, and assessment methods for frost heaving.     

Railroad bed bearing strength in the period of thawing and methods of its enhancement

The practice of building and operating of railroad beds shows that the greatest at enuation of soils occurs in the spring, during their transition from the frozen to thawed state. The greatest influenc...     

青藏高原沙漠化与冻土相互作用的研究

利用青藏高原地表热量平衡和长期地温观测的资料探讨高原沙漠化与冻土的相互作用,发现沙丘下或厚沙层覆盖地段下的地温较邻近天然无沙地表有所升高,而薄沙层覆盖地段下的地温反而比天然无沙地表有降低的趋势。分析造成高原冻土区沙漠化的因素有些与其它沙漠化区相似,但有些因素与高原冻土有关并具有特殊性。高原冻土层与土地沙漠化二者之间相辅相成、相互制约、相互作用、协调演化,构成了目前高原冻土区生态平衡系统。     

试论青藏高原多年冻土类型的划分

本文采用综合分析与主导因素相结合的原则，以干燥度作为主要指标并参考年降水量，年平均相对湿度及气温较差等，结合地形因素将青藏庙的多年冻土划分为：湿润，亚湿润，半干旱，干旱和极干旱５种类型，并对各类型代表性和冻土地区进行分别论述。     

Freeze-thaw processes of active-layer soils in the Nanweng'he River National Natural Reserve in the Da Xing'anling Mountains,northern Northeast China

The active-layer soils overlying the permafrost are the most thermodynamically active zone of rock or soil and play important roles in the earth-atmosphere energy system. The processes of thawing and freezing and their associated complex hydrothermal coupling can significantly affect variation in mean annual temperatures and the formation of ground ice in permafrost regions. Using soil-temperature and-moisture data obtained from the active layer between September 2011 and October 2014 in the permafrost region of the Nanweng'he River in the Da Xing'anling Mountains, the freeze-thaw characteristics of the permafrost were studied. Based on analysis of ground-temperature variation and hydrothermal transport characteristics, the thawing and freezing processes of the active layer were divided into three stages:(1) autumn-winter freezing,(2) winter freeze-up, and(3) spring-summer thawing. Variations in the soil temperature and moisture were analyzed during each stage of the freeze-thaw process, and the effects of the soil moisture and ground vegetation on the freeze-thaw are discussed in this paper. The study's results show that thawing in the active layer was unidirectional, while the ground freezing was bidirectional(upward from the bottom of the active layer and downward from the ground surface).During the annual freeze-thaw cycle, the migration of soil moisture had different characteristics at different stages. In general, during a freezing-thawing cycle, the soil-water molecules migrate downward, i.e., soil moisture transports from the entire active layer to the upper limit of the permafrost. In the meantime, freeze-thaw in the active layer can be significantly affected by the soil-moisture content and vegetation.     

THERMALLY DRIVEN SORPTION,DESORPTION, AND MOISTURE MIGRATION IN THE ACTIVE LAYER IN CENTRAL ALASKA

Combined observations of hourly soil temperature and electric potential, the latter converted to a relative index of soil-water solute concentration, yield information on the physical chemistry of near-surface frost effects. Solute concentration near the descending 0° C isotherm in the refreezing active layer above permafrost is divided into three distinct zones: (1) an ion-enriched zone in the unfrozen active layer that precedes the penetrating freezing front; (2) an ion-purified desorbed zone at the freezing front that is the source region of the downward-expelled ions and water; and (3) a hydrologically isolated subfreezing zone of enhanced solute concentration located above the freezing isotherm. High-frequency fluctuations superimposed on these general patterns are traceable to vapor migration driven by surface thermal fluctuations. These effects diminish at temperatures below about -0.4° C, as permeability decreases with soil-ice formation. The combined temperature-solute concentration time series is used to develop sorption curves for the frozen organic and mineral soils, and indicates that approximately half of the pore water present in the mineral soil at -0.4° C had not been converted to ice at -6° C. Gradual soil desiccation over winter appears to result from outward vapor diffusion, possibly through soil cracks. [Key words: Alaska, active layer, frozen ground, soil temperature, soil water, permafrost.]     

广州市荔湾区大坦沙岩溶地面塌陷成因及其稳定性评价

广州市荔湾区大坦沙是广州地区岩溶地面塌陷主要发生地区之一,2007-11-07-2008-01-29共发生7起岩溶地面塌陷,造成多间房屋倒塌和开裂,经济损失巨大.通过参与现场地质调查,之后收集、整理该地区地下水的动态监测资料,结合地面塌陷发育的基本特征,从区域地质环境条件分析其地面塌陷的形成原因,采用定性、半定量的评价方法,构建岩溶地面塌陷稳定性判别因子的量化指标体系,对其地面塌陷的稳定性进行综合预测.结果认为:(1)大坦沙地区岩溶地面塌陷具有一因多效现象,地下水位下降是引发该时段系列塌陷的主导因素,次要     

Research on the Suitability Evaluation of the Development and Utilization of Regional Selenium-rich Soil Resources and Spatial Zoning based on Niche Theory

Relying on the advantages of selenium-rich soil resources, the development of special selenium-rich agricultural industry is an effective measure to implement the rural revitalization strategy. This paper took Yuanzhou district as the research area, based on ecological niche theory, creatively determines the dominant and limiting factors of selenium-rich soil resources development and utilization from three aspects of natural resources endowment, land use conditions and ecological protection, constructed the evaluation index system of selenium-rich soil resources development and utilization and ecological niche suitability index measurement model, and explored the suitability of regional selenium-rich soil resources development and utilization and zoning. The research results show that: (1) The area suitable for exploitation of selenium-rich soil resources in the study area is 174658.4 ha, accounting for 68.83% of the total area, mainly distributed around Yuan River and in the central, northern, northwestern and northeastern areas of the study area. (2) Based on the evaluation results of the suitability of selenium-rich soil resources development and utilization and the development of related agricultural industries, the study area was divided into four functional zones of selenium-rich industrial development: core zone, key zone, development zone and radiation zone. The core zone and key zone are suitable for building selenium-rich agricultural industry demonstration area and selenium-rich products breeding production base, and the development zone and radiation zone can vigorously develop selenium-rich modern agriculture and selenium-rich recreation tourism, which will accelerate the development trend of multi-level and diversified selenium-rich industry in study area.This study can provide scientific, reasonable and feasible ideas and methods for the development and utilization of selenium-rich soil resources and the planning and development of selenium-rich industries in similar areas.     

Past and present permafrost as an indicator of climate change

The permafrost history of the high northern latitudes over the last two million years indicates that perennially frozen ground formed and thawed repeatedly, probably in close synchronicity with the climate changes that led to the expansion and subsequent shrinkage of continental ice sheets. The early stages of the Pleistocene are the least known and the changes that occurred in the Late Pleistocene and early Holocene are the best known.
Evidence that permafrost is degrading in response to the current global warming trend is difficult to ascertain. The clearest signals are probably provided by changes in permafrost distribution in the sub-Arctic regions. at the extreme southern fringes of the discontinuous permafrost zone.     

Geographical patterns of the summer thermal regime of soils in Transbaikalia

Long-term temperature data on a soil layer 3.2 m in thickness have been used in the differentiation of a topographically highly complicated permafrost on the territory of Transbaikalia. It was found that the geographical ranges are most clearly identified from mean annual temperature values. The schematic map displays the areas with the temperatures –4 to–1°C,–1 to 1°C and 1 to 4°C which are in good agreement with the permafrost distribution pattern (continuous and discontinuous permafrost, and permafrost islands). A classification of the thermal conditions of soils is carried out according to the highest mean monthly temperature at all depths. We identified four types which are characterized by the qualitative assessment as warm, moderately warm, cold and very cold. A relevant cartographic model shows the distribution of the thermal regime of soils for a warm season. The dot method was used to provide a clear display of available information on soil temperature, and it was possible to show the existence of small areas of the types of thermal regime and their fragmentation. Current changes in soil temperature were determined for August, which are in good agreement with regional changes in ground air temperature. In either case, we observed positive linear trends. Assessments of thermal resources of the soil layer and their geographical patterns belonging to the widespread depression-valley and valley natural systems as well as to the relatively planate surfaces of Transbaikalia can be used for scientific and practical purposes.     

Summary of research on frost heave for subgrade in seasonal frozen ground

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.     

近30年来青藏高原西大滩多年冻土变化

结合1975年已有勘探资料,对青藏高原多年冻土北界西大滩进行了雷达勘探。勘探发现,近30年来青藏高原多年冻土北界发生较大规模的多年冻土退化,多年冻土面积从1975年的160.5 km²退化成现在的141.0 km²,缩小约12%;开始出现多年冻土的最低高程为4 385 m,比1975年升高了25 m。近30年来研究区的气候变化是造成北界多年冻土退化的主要原因。相同气候背景下,多年冻土腹部地温有升高,但在30年尺度上不会发生明显的退化。本次冻土区域调查的结果可为检验冻土－气候关系模型的可靠与否提供依据。     

Geophysical Exploration of Shallow Groundwater Aquifers in Arid Regions: A Case Study of Siwa Oasis,Egypt

Geophysical and geological studies play a fundamental role in the strategic and sustainable utilization of natural resources, especially that of fossil groundwater, in arid regions. The geophysical exploration of shallow groundwater aquifers is common in arid regions. In this work, a feasibility study of future development plans in the Siwa Oasis, Egypt, was carried out. A land electric resistivity survey was conducted, and approximately 14 vertical electric soundings were measured covering the Siwa Oasis, northwestern desert, Egypt. A detailed surface geology study was also conducted to study the underground water aquifer. Digital filters were applied to the reduced to pole-available magnetic data covering the area. The normalized source strength transformation and tilt depth were calculated and applied to delineate the possible structures that may control the shallow and deep aquifers in the area. The integrated interpretation showed the presence of four main geoelectric layers forming the shallow section of the Siwa Oasis down to 220 m. These layers varied in their resistivity and rock constituents from very low (0.2 Ω m) to very high (6200 Ω m) values. The calculated hydraulic parameters showed that the uppermost central area and the eastern area were the most promising areas for the required water development. Finally, based on the integrated interpretation and the estimated shallow aquifer potentiality, a land use map for the Siwa Oasis was produced to assist future strategic development of the region.