青藏高原北麓河地区沥青路面辐射特征分析

沥青路面是寒区道路工程主要路面类型之一, 其对热量的吸收易诱发寒区道路病害. 在青藏高原北麓河试验场对沥青路面和天然地表的太阳辐射和地面辐射通量进行了观测, 对比分析了两种地面类型在能量辐射方面的差异. 结果表明: 天然地表的反照率是沥青路面的2~3倍. 沥青路面和天然地表的辐射通量总体呈夏季 >秋季 >春季 >冬季特点. 到达沥青路面的向下长、短波辐射量均大于天然地表, 沥青路面向上的长波辐射通量大于天然地表. 2009年9月-2010年8月沥青路面的净辐射量比天然地表多302.2 MJ·m^-2, 2010年9月-2011年8月向上的短波辐射相对增加, 使得沥青路面的净辐射量仅比天然地表多28.21 MJ·m^-2. 在5 cm深度, 沥青路面的温度比天然地表高约1.15~8.6 ℃. 对短波辐射的削减和对长波的吸收是其净辐射量增加的重要原因, 在能量辐射方面的差异是造成沥青路面吸热的重要原因之一.     

三种碎屑颗粒形态定量分析方法的比较及应用

沉积物颗粒的形态是沉积成因分析的主要标志之一。目估对比法是沉积物颗粒圆度分析中常用的方法。目估法直观、简捷,但主观因素影响较大。本文利用计算机图像分析软件Image Pro Plus 6.0获取鲍尔斯目估标准颗粒的轮廓,并用3种定量方法测量这些标准颗粒的IPP圆度、轮廓分维数和傅里叶不圆度,然后对比这些圆度的划分标准与目估标准之间的差别,最后用3种圆度测定方法同时测量广东马头山风化坑和河流壶穴中碎屑颗粒的圆度,通过测量结果的对比来评价这3种定量方法的应用效果,检验这些方法能否在实际应用中代替目估方法以区分不同成因的碎屑颗粒。分析表明：目估法的磨圆度标准不是简单地表达颗粒的圆形与否,其中包括了颗粒表面结构的差异;3种定量方法的圆度划分标准很难与目估划分标准完全一致;3种方法所表征的圆度均能区分风化作用和流水侵蚀作用形成的颗粒,因此3种定量方法均可以代替目估方法测量颗粒的圆度;在不强调颗粒表面特征的前提下,IPP圆度的测量方法比其他两种方法更加有效;颗粒形态的分析结果证明河谷壶穴中的颗粒由流水侵蚀作用而成,山顶风化坑中的颗粒由风化作用而成     

Co‐development of alluvial fan surfaces and arid botanical communities,Stonewall Flat,Nevada, USA

Arid alluvial fan and fluvial dry wash surfaces in Stonewall Flat, Nevada, USA, are characterized using surface geomorphic surveys, soil pits, botanical line surveys, and varnish microlamination dating techniques. Active and abandoned washes, and active fan surfaces are dominated by primary geomorphic processes of high‐energy sedimentation from flash floods. These surfaces are characterized by bar and swale topography, a lack of stone pavements, soil horizons, and rock varnish. Younger terraces and slightly older intermediate fan surfaces are in transition from primary sedimentation processes to lower energy secondary surface‐modifying processes of sheet wash and eolian transport and deposition. These surfaces are characterized by faint to no bar and swale topography, incipient to moderately well‐developed pavements and soil horizons, and abundant coppices. Old and stable fan surfaces are dominated by lower energy secondary processes and manifest well‐developed pavements, soils, and sparse coppices around widely distributed shrubs. Varnish microlamination dating yields ages of 13·15 ka for intermediate fan surfaces and 25·55 to 86·75 ka for stable fan surfaces. Plant communities co‐developing with these surfaces affect and are affected by both primary and secondary geomorphic fan processes. Relatively active surfaces contain few woody species. Co‐dominance of shrubs and annuals with abundant annuals between the shrubs is characteristic of surfaces transitional from primary processes to secondary processes. Stable surfaces dominated by secondary processes are characterized by woody perennials, with long‐lived woody species inhabiting the oldest surfaces. Feedback mechanisms between early botanical communities and eolian deposition affect coppice and pavement development. In turn, these surface features control both the composition and distribution of botanical communities on older, more stable surfaces. Published 2012. This article is a U.S. Government work and is in the public domain in the USA.     

Land-use comparison of depression-focussed groundwater recharge in the Canadian prairies

In the cold semiarid Canadian prairies, groundwater recharge is focussed under numerous topographic depressions, in which snowmelt runoff converges. Agricultural land uses on the uplands surrounding the depressions affect snow accumulation, snowmelt infiltration, evapotranspiration (ET) and soil moisture dynamics, thereby influencing snowmelt runoff and depression-focussed recharge. The objective of this study is to compare the differences in hydrological processes under two common land uses in the Canadian prairies, namely grazed grass and annual crop, and examine how they affect groundwater recharge. A short-term (3 years) paired catchment study was used for detailed observation of hydrological processes in two depressions, supplemented by a longer-term (17 years) data set covering a larger scale to quantify the differences in snowmelt runoff between the two land uses. Compared to the grazed grassland, the cropland had a shorter and more intense period of ET, and root water uptake restricted to the shallower (top 0–80 cm) soil zone. The amount of snowmelt runoff was greater in the grazed grassland primarily due to a higher amount of snow accumulation, which was dictated by differences in topography. This finding was contrary to previous studies in the Canadian prairies that indicated substantially smaller snowmelt runoff in ungrazed grassland, but was consistent with the larger-scale remote sensing results, which showed only a marginal difference between grazed grasslands and croplands. Groundwater recharge rates were estimated using the chloride mass balance method for the present condition using “modern” pore water containing tritium. The rates were similar between the grazed grassland and croplands, implying similarity in snowmelt runoff characteristics. These results suggest that groundwater recharge will continue to be focussed under depressions in the future, though the amount and seasonality of recharge may be influenced by warmer winters.     

Support vector regression to predict the performance of stabilized aggregate bases subject to wet–dry cycles

Durability is a notion that is integrated with the performance of stabilized pavement materials. Also, because it can be quantified and measured, it carries significant influence on the design of pavements. This study focuses on using support vector machine, a machine learning algorithm, in assessing the performance of stabilized aggregate bases subject to wet–dry cycles. Support Vector Regression (SVR) is a statistical learning algorithm that is applied to regression problems and is gaining popularity in pavement and geotechnical engineering. In our study, SVR was shown to be superior to the least‐squares (LS) method. Results of this study show that SVR significantly reduces the mean‐squared error (MSE) and improves the coefficient of determination (R²) compared to the widely used LS method. Copyright © 2011 John Wiley & Sons, Ltd.     

214国道不同路面形式下碎石护坡工程效果实测分析

沥青路面和水泥路面是214国道江河源段采用的两种基本路面形式,由于该路段地处高温不连续多年冻土区,碎石护坡等多种工程措施被尝试用来稳定冻土路基.对两种路面形式下碎石护坡路段的地温监测资料进行综合分析发现,碎石护坡能显著降低路基边坡坡面的年平均温度,减小路基边坡坡面温度的年较差,并对坡脚、路肩和路基中心具有从大到小的冷却...     

Finite element modeling of slab–foundation interaction on rigid pavement applications

Bending stresses produced in pavement concrete slabs are influenced by the contact condition along the slab–foundation interface. A finite element model for the analysis of frictional contact between unbonded pavement layers is presented. A 2D plate element is proposed for the idealization of composite slabs. Interface elements are used to connect the unbonded layers within the composite slab and to model the interface between the bottom slab layer and the foundation layer. Interface elements have the ability to capture the separation and sliding between pavement layers, due to thermal loads, and to calculate the frictional traction at their interface.     

广东大峡谷河床壶穴形态的形成与发育

The goal of this study is to provide information on the process of pothole growth on a gorge streambed. Pothole geometries were measured in a reach of the Dabu river bed at the head of a gorge more than 200 m deeply incising into a 650–750 m high planation surface formed in the middle Miocene in northern Guangdong, China. Geometric and derivative data of the potholes obtained from fieldwork were interpreted using standard statistical methodologies. Our study shows that the formation and development of a stream pothole were only related to local conditions of a stream reach where the pothole occurs; the weaknesses, which are usually intersect fractures, typically interconnected vertical joints, or triangular pits generated by hitting of rock fragments during floods, initiate the pothole development on a streambed; the geometrical dimensions of the potholes are controlled by tectonic joints developed in bedrock of the stream reach; the radius and the depth of potholes are strongly (log) positive correlated; the pothole shapes and the flow patterns are inconstant during pothole growth; a pothole can be formed within a short period, but cannot be fully developed and maintained for a long time in a strong incision streambed. The finding in our study can improve the understanding of Quaternary environment in Guangdong. Foundation: National Natural Science Foundation of China, No.40871020; Guangdong Natural Science Foundation, No.7005836 Author: Wang Wei (1956–), Ph.D and Professor, specialized in Quaternary geology and geomorphology.     

Topographic analysis for the prairie pothole region of Western Canada

The unique topography of the pothole region of the North American prairies creates challenges for properly determining basin contributing area. Numerous depressions or potholes within the landscape impound runoff. However, potholes can ‘fill‐spill’ resulting in surface water connections between the potholes. Surface water connectivity between potholes ultimately influences basin contributing area. Currently, automated methods, such as landscape analysis tools, treat depressions in the landscape as artifacts and simply fill the depressions to delineate a drainage basin. Using this method to calculate contributing area assumes that all surface storage has been satisfied (threshold) and the drainage basin will contribute 100% of its area for all runoff events. However, most runoff events in the prairie pothole region are pre‐threshold events that contribute only a portion of surface runoff to the outlet. These pre‐threshold events have surface storage that varies because of antecedent water levels and have a variable or dynamic potential to store further runoff in the basin. Government agencies have developed methodologies for determining pre‐threshold contributing areas, but these methodologies do not incorporate current technologies and, as a result, have limitations. We propose an automated method for determining contributing area that incorporates the fill‐spill of prairie potholes. The algorithm, which uses the D‐8 drainage direction method, automates a methodology for identifying and quantifying runoff contributing area. Any algorithm that determines pre‐threshold contributing area, must allow the DEM to be filled in an incremental manner. This will simulate increasing pond levels, and the resulting decrease in available storage in the basin, in response to runoff events. The SPILL algorithm is an iterative solution that increases the magnitude of input runoff events and records the decreasing change in available surface storage and the increase in contributing area until the storage threshold is reached and the contributing area reaches 100%. Through application of the algorithm on prairie pothole region basins, we test proposed conceptual curves that describe a hypothesized non‐linear relationship between decreasing potential storage in the landscape and contributing area. Results indicate that the proposed conceptual curves represent the relationship between potential surface storage and contributing area in the test basins very well. Copyright © 2012 John Wiley & Sons, Ltd.     

水泥混凝土路面施工探讨

结合宁连一级公路连云港段10km水泥混凝土路面和连云港市新牛线及连云港市玉凤路水泥混凝土路面施工经验,对水泥路面常见病害进行了分析,以期找到一套完整可行的水泥混凝土路面的施工方法。