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1.
Wind erosion is a dominant geomorphological process in arid and semi-arid regions with major impacts on regional climate and desertification. The erosion process occurs when the wind speed exceeds a certain threshold value, which depends on a number of factors including surface soil moisture. The understanding and modelling of aeolian erosion requires a better understanding of the soil erodibility associated with different moisture conditions. In arid regions during the dry season, the atmospheric humidity plays an important role in determining the surface moisture content and the threshold shear velocity. By a series of wind tunnel tests and theoretical analyses, this dependence of threshold velocity on near surface air humidity is shown for three soils of different textures: sand, sandy loam, and clay loam. The results show that the threshold shear velocity decreases with increasing values of relative humidity for values of relative humidity between about 40% and 65%, while above and below this range the threshold shear velocity increases with air humidity. A theoretical framework is developed to explain these dependencies assuming an equilibrium between the surface soil moisture and the humidity of the overlying atmosphere. The conditions under which soil-atmosphere equilibrium occurs were tested experimentally in the laboratory for different soils in order to determine the effect of grain surface area and texture on the time required to reach equilibrium starting from different initial conditions.  相似文献   

2.
荆江段河岸粘性土体抗冲特性试验   总被引：2，自引：0，他引：2       下载免费PDF全文
粘性土体具有较强的抗冲能力,其抗冲性强弱决定了河岸的侵蚀速率。为了估算河岸的侵蚀速率,确定粘性土体的起动条件、侵蚀系数及两者之间的数量关系非常重要,为此开展了荆江段河岸粘性土体起动条件与冲刷特性的水槽试验研究。根据试验结果获得了粘性土体的起动流速与土体液限/自然含水率之间关系以及起动切应力与干密度、起动切应力与液性指数之间的定量表达式,综合反映了粘性土起动条件与其物理性质指标之间的关系;结合冲刷特性试验结果,还获得了土体侵蚀系数随起动切应力的变化规律,并与已有其他试验结果进行了比较。结果表明:荆江河岸粘性土侵蚀系数均比相同条件下其他公式计算值偏大,这与该试验土体中粘粒含量相对较低、土体结构受到扰动等因素有关;根据试验结果,拟合得到了荆江河岸粘性土侵蚀系数与起动切应力之间定量关系式,其相关系数R2=0.90,故该关系式能为荆江段崩岸过程的计算提供参考依据。  相似文献   

3.
冻土前期固结压力的试验研究   总被引：2，自引：0，他引：2  
胡伟  齐吉琳  马巍 《岩土力学》2009,30(5):1313-1316
前期固结压力 在土力学中占有重要的地位。对于融土, 是土受力历史的重要指标,与土的力学性质有着密切关系;对于冻土,由于冰和土颗粒骨架的联结使其具有一定的结构性,也应当具有类似前期固结压力的指标存在。以冻结青藏黏土为研究对象,对不同初始干重度和不同温度下的冻土试样进行 压缩试验,采用双对数法得到冻土的前期固结压力 。研究表明,这个指标尽管不同于融土前期固结压力的概念,但其对于冻土的力学性质同样具有重要意义。试验研究还发现,冻土前期固结压力与干重度和温度具有一定的关系。  相似文献   

4.
Interface erosion is one of the main phenomena in dams, dikes and their foundations which may increase their failure risk. In laboratories, the jet erosion test (JET) and the hole erosion test (HET) are commonly used for the evaluation of the sensibility of interface erosion of fine soils. The results are interpreted by two distinct methods that are valid for one test only. A new energy analysis of the tests is developed, relating the total eroded mass to the dissipated fluid energy, and a new erosion resistance index is proposed. Seven naturally occurring fine-grained soils, covering a large range of erodibility, are compacted with the Proctor protocol, and they are tested with the two devices. It was shown that by using the commonly used methods, the values of the erosion coefficient are systematically higher with the JET than with the HET and the HET critical shear stress is about fifty times higher than the JET critical shear stress. Thus, the relative soil classifications yielded by the two erodimeters are not exactly the same. Based on energy analysis, values of erosion resistance index are roughly the same for each tested soil with the two apparatuses and a single classification of soil erodibility is obtained.  相似文献   

5.
A laboratory investigation was conducted to determine properties of five samples of ‘oolitic ironstone’ lateritic gravel aggregates which are relevant to their use as road construction materials. Measured values of physico-chemical, physico-mechanical as well as index properties and compaction characteristics are similar to those of other lateritic, gravels occurring in West Africa which are used in road pavement applications. These lateritic clayey gravels have good workability as engineering construction materials and are rated fair to good as road aggregates in terms of probable in-situ behaviour based on water absorption values. Relationships between maximum dry unit weight and optimum moisture content as well as those between California bearing ratio and some derived soil parameters such as grading modulus, plasticity product or plasticity modulus can be described using a third-order polynomial function. The maximum dry unit weight has a bimodal frequency distribution and can be predicted from logarithm to base 10 of compaction energy with fairly good accuracy.  相似文献   

6.
The present study aims to investigate the relationships between several soil parameters (texture, organic matter and CaCO3 content) and the threshold wind velocity and erodibility of different soil types. Our aim was to determine the role of these soil parameters play in soil loss due to wind erosion and also to statistically evaluate these correlations. The erodibility studies were carried out in wind tunnel experiments, and the resulting data were analysed with multiple regression analysis and the Kruskal-Wallis test. We found that both the threshold wind speed and the erodibility of soils were mostly determined by silt fraction (0.05–0.02 mm), while sand fractions had a lesser effect on it. Our experiences with organic matter and CaCO3 similar, i.e. in spite of their correlation with the erosion, their contribution was not significant in the multivariate regression model. Consequently, based on mechanical composition of soils, one can predict threshold wind velocity and erodibility of soils.  相似文献   

7.
Grass cover is considered as a sustainable means of controlling soil erosion and enhancing durability of soil slopes. A number of grass species are commonly available for soil bioengineering in Hong Kong, but their capacities to control soil erosion have not been characterized quantitatively. The main objectives of this paper are to study the influence of soil density on characteristics of grass roots, to measure the erodibility parameters of the root-permeated soils at two growth stages, and to select the proper Hong Kong grass species that effectively control soil erosion. Three types of Hong Kong turf grass including Cynodon Dactylon, Paspalum Notatum, and Zoysia Matrella were planted on three soil grounds with degrees of compaction of 80, 90, and 100 %, respectively. The featural parameters of grass roots on each compacted ground, including root mass density, root volume density, and root depth, were measured in two growth stages. A jet index apparatus was applied to measure two erodibility properties (i.e., coefficient of erodibility and critical shear stress) of these vegetated soils in the two test stages. Cynodon Dactylon and Zoysia Matrella have higher root mass density values than Paspalum Notatum does, and reduce the susceptibility of soil erosion more effectively. Therefore, the two grass species are suggested for soil bioengineering in Hong Kong.  相似文献   

8.
Soil suction is the most relevant soil parameter for characterization of the swell behavior. An attempt was made to predict swell pressures from soil suction measurements. In this study, Na-bentonite was mixed with kaolinite in the ratios of 5, 10, 15, 20 and 25% of dry kaolinite weight to obtain soils in a wide range of plasticity indices (i.e. 30, 50, 68, 84 and 97%). Suction measurements using thermocouple psychrometer technique were made on statically compacted specimens. The dependence of soil suction on water content, dry density and bentonite content was examined. Soil suction was correlated to the soil properties, namely, water content, plasticity index, dry density, cation exchange capacity and specific surface area using multiple regression analyses. The correlations revealed a simple regression equation for a quick prediction of soil suctions from easily determined soil properties. In order to investigate soil suction versus swell pressure behavior, the results of standard constant volume swell tests (ASTM, 1990) performed on statically compacted samples of these clay mixtures were used. A linear relationship was established between the logarithm soil suction and the swell pressure. It was also found that an experimental relationship which would directly relate the initial soil suction to the swell pressure can be established.  相似文献   

9.
Improvement in engineering properties of expansive soils by mixing ground granulated blast furnace slag (GGBFS) is the main focus of this research. For this purpose two expansive soil samples were collected from DG Khan and Sialkot areas (Pakistan). Classification tests revealed that DG Khan sample belonged to fat clay (CH) while Sialkot soil was lean clay (CL) as classified by Unified Soil Classification System. GGBFS has been added in varying proportions between 0 and 55% in these soil samples to study its role in stabilizing these expansive soils. Based on the laboratory test performed on composite soil samples, it was observed that maximum dry unit weight increased up to 10 % by adding 50% GGBFS in both samples. California bearing ratio (CBR) value showed an increase from 3.2 % to 11.5% for DG Khan soil while CBR values varied from 2.4% to 10.7% for Sialkot soil by mixing 50% GGBFS. Addition of 30 % GGBFS to DG Khan soil reduced swell potential from 8 % to 2 % while in Sialkot soil, 20 % addition of GGBFS reduced swell potential from 5 % to 2 %. Unconfined compressive strength of remoulded sample cured for 28 days increased by about 35% with the addition of 30%GGBFS. The results indicated that mixing of GGBFS in the expansive soil samples have a marked increase in their engineering properties. Also, it is an affective and environmental friendly means to dispose waste of steel industry.  相似文献   

10.
ＩＮＴＲＯＤＵＣＴＩＯＮＬａｒｇｅａｒｅａｓｏｆａｒｉｄａｎｄｓｅｍｉａｒｉｄｒｅｇｉｏｎｓｏｆｔｈｅｗｏｒｌｄａｒｅａｆ ｆｅｃｔｅｄｂｙｗｉｎｄｅｒｏｓｉｏｎ .Ａｐｐｒｏｘｉｍａｔｅｌｙ 2 8.4%ｏｆｔｈｉｓａｒｅａａｒｅａｆｆｅｃｔｅｄｂｙｓｅｖｅｒｅａｎｄｖｅｒｙｓｅｖｅｒｅｗｉｎｄｅｒｏｓｉｏｎ (Ｋａｔｅｓｅｔａｌ.,1977) .ＩｎＩｒａｑ ,ｔｈｅａｒｉｄａｎｄｓｅｍｉａｒｉｄｒｅｇｉｏｎｓｒｅｐｒｅｓｅｎｔｎｅａｒｌｙ 75%ｏｆｔｈｅｔｏｔａｌｌａｎｄ .5 0 %ｏｆｔｈｉｓｌａｎｄｉｓｓｕｂｊｅｃ…  相似文献   

11.
Arid regions worldwide are plagued by collapsible soils. Collapsible soil is characterised by the sudden decrease in volume that occurs when it is subjected to inundation under constant stress. This volume change manifest itself as drastic and unpredicted foundation settlement, which may lead to further catastrophic failure of the supported structures. Collapse settlement is the term applied to the additional settlement of a foundation due to wetting of the underlying soils. The results of an experimental investigation of the effects of the saturation of soil with water, kerosene, and crude oil, and of the effects of the fluid head on the magnitude, degree, and rate of collapse of the underlying soil are presented in this paper. Soil erodibility is presented in terms of the applied hydraulic shear stress and the rate of erosion. The relationship between soil erosion and the magnitude and rate of collapse is examined. Empirical methods for the prediction of the magnitude and rate of collapse of a soil saturated with the test fluids and subjected to a hydraulic constant head are proposed.  相似文献   

12.
Conducting research about the relationships between soil chemical properties and vegetation coverage at different slope aspects is especially important in reconstructed ecosystems of vulnerable ecological regions. This study was conducted in the first reclaimed dump within the Pingshuo mining area of Shanxi Province, China, to analyze patterns of soil chemical properties (soil organic matter (SOM), soil total nitrogen (STN), soil available phosphorus (SAP) and soil available potassium (SAp) and vegetation coverage (NDVI) and their correlations at different slope aspects. In the reclaimed dump, 26 quadrats were established along four slope aspects (i.e., shady, semi-shady, sunny and semi-sunny slopes). There was no significant difference in SOM or STN among different slope aspects, while SAP differed between shady slopes compared to semi-shady, sunny and semi-sunny slopes; SAP differed significantly between semi-shady and semi-sunny slopes. The NDVI of semi-sunny slopes differed significantly from that of the other three aspects. There was variation in the relationships between NDVI and soil chemical properties, depending on the slope aspects. The logarithm of SOM and NDVI was related linearly on shady and semi-shady slopes, while NDVI was inversely related to the natural logarithm of the logarithm of SOM on sunny and semi-sunny slopes. STN and NDVI had a first-order function relationship on shady and semi-shady slopes, yet a quadratic function relationship on sunny and semi-sunny slopes. The relationships between SAP and NDVI were inverse on all types of slopes. On shady and semi-shady slopes, NDVI had a quadratic relationship with the logarithm of SAp, but it was well fitted by using a cubic function on sunny and semi-sunny slopes. The sensitivity coefficients of soil chemical properties and NDVI were different, and soil chemical properties changed differently depending on changes in NDVI at different slope aspects.  相似文献   

13.
A strong earthquake of magnitude 8 in Richter scale, occurred in Sichuan Province, China on 12 May 2008, triggered about 257 landslide dams. The erodibility of fresh landslide deposits plays an important role in evaluating the initiation and development of breaching of such landslide dams. In this research, field jet index tests were conducted shortly after the earthquake at 27 locations on the Hongshihe landslide dam and the Libaisi landslide dam. The purpose of these tests was to investigate the erodibility of freshly deposited landslide soils. The landslide deposits are broadly graded. The bulk density increases and the coefficient of erodibility decreases with the depth of deposition. The erodibility of the fresh landslide deposits falls into a moderately resistant category and the fresh deposits are much more erodible than the native geomaterials before the earthquake. The main factors that control soil erodibility are found to be grain-size distribution, void ratio, fines content, and plasticity index. Particularly, the coefficient of erodibility decreases exponentially with the degree of compaction. Two empirical equations are developed for estimating the coefficient of erodibility and critical erosive shear stress of the freshly deposited landslide soils based on their basic soil properties.  相似文献   

14.
含盐土渗透系数变化特征的试验研究   总被引：4，自引：0，他引：4  
对含盐土的渗透系数进行了室内试验研究.结果表明:在干容重相同的情况下,渗透系数随着含盐量的增加而减小;对同一类型土,随着含盐量的增加,硫酸盐土的渗透系数要比氯盐土渗透系数减小显著;在干容重和盐类相同的情况下,细颗粒含盐土的渗透系数要比粗颗粒含盐土的渗透系数减小显著.在含盐量相同的情况下,同一种土的渗透系数随着干容重的增大而减小.当干容重在一定的范围内时,渗透系数与干容重呈线性关系,但当干容重超过该范围时,渗透系数与干容重呈幂函数关系.  相似文献   

15.
Environmental degradations caused by erosion and landslide within an area in the South-eastern part of Nigeria were assessed, and also an attempt to characterize the underlying soils based on their degree of susceptibility to erosion and landslide. Factors affecting soil erodibility such as physical and chemical properties of soil, as well as vegetation density and slope gradient was determined in 20 different areas. Simple linear regression and principal component analysis were employed to relate the factors controlling erosion and landslide to the erosion and slide densities, and to determine the pattern that exists in the data and as well express the data in such a way as to highlight their similarities and differences. Four vertical horizons and two horizontal zones of soil were distinguished based on their degree of weathering as well as their chemical and mineralogical composition; hence the soils were classified into six different types based on their degree of susceptibility to erosion and landslide. Variations in their degree of susceptibility to erosion and landslide were majorly controlled by its chemical and mineralogical composition rather than its particle size distribution.  相似文献   

16.
文章对近年来基于生物固土技术的防风固沙研究进行了回顾和分析。常用于防风固沙的生物过程包括基于微生物或酶诱导碳酸钙沉积（MICP或EICP）的矿化固土技术,加入黄原胶等生物高聚物作为辅助剂,可获得更好的固土效果。土壤风蚀过程中,除了风力本身,风携带的跃移颗粒对土的撞击,也是侵蚀破坏的重要因素,这在生物固化土风蚀试验中体现明显。生物固化防风固沙的处理过程简单易行,以尿素和钙盐作为处理材料,用细菌或脲酶作为催化诱导媒介,对土体进行单遍喷洒处理即可获得很好的抗风效果。室内抗风试验中,将风蚀速率与临界起动风速两个指标结合是较为合理的评估方法。在室内和现场条件下,表面贯入强度测试可用来快速测定处理效果和抗风性能。目前的现场试验研究表明,生物固化土中植物可以生长,但是极端条件下生长受限。为了将该方法推向实用,需要从多重侵蚀因子作用下的抗风力侵蚀能力、生态恢复能力和现场施工技术等方面进一步研究探索。  相似文献   

17.
At present, nearly 100 million tonnes of fly ash is being generated annually in India posing serious health and environmental problems. To control these problems, the most commonly used method is addition of fly ash as a stabilizing agent usually used in combination with soils. In the present study, high-calcium (ASTM Class C—Neyveli fly) and low-calcium (ASTM Class F—Badarpur fly ash) fly ashes in different proportions by weight (10, 20, 40, 60 and 80 %) were added to a highly expansive soil [known as black cotton (BC) soil] from India. Laboratory tests involved determination of physical properties, compaction characteristics and swell potential. The test results show that the consistency limits, compaction characteristics and swelling potential of expansive soil–fly ash mixtures are significantly modified and improved. It is seen that 40 % fly ash content is the optimum quantity to improve the plasticity characteristics of BC soil. The fly ashes exhibit low dry unit weight compared to BC soil. With the addition of fly ash to BC soil the maximum dry unit weight (γdmax) of the soil–fly ash mixtures decreases with increase in optimum moisture content (OMC), which can be mainly attributed to the improvement in gradation of the fly ash. It is also observed that 10 % of Neyveli fly ash is the optimum amount required to minimize the swell potential compared to 40 % of Badarpur fly ash. Therefore, the main objective of the study was to study the effect of fly ashes on the physical, compaction, and swelling potential of BC soils, and bulk utilization of industrial waste by-product without adversely affecting the environment.  相似文献   

18.
融雪侵蚀研究进展   总被引：6，自引：0，他引：6       下载免费PDF全文
融雪侵蚀在中国及世界上许多地区都有发生,其对表层土壤的破坏作用越来越为人们所认识,已成为土壤侵蚀研究中的重要问题之一。在总结相关研究成果的基础上,分析了影响积雪和融雪的气候、海拔、地形地貌及土地利用等因素。在融雪侵蚀影响因素方面,认为融雪径流、表层土壤解冻深度、解冻期表层土壤可蚀性是影响融雪侵蚀发生的特殊因素。同时指出,融雪侵蚀预报模型中冻融作用对土壤水分迁移的影响、未完全解冻层对表层土壤水分的影响以及坡面融雪过程研究是未来融雪侵蚀研究中应重点解决的问题。  相似文献   

19.
This paper studied the use of burned sludge ash as a soil stabilizing agent. The sludge ash was obtained from a public wastewater treatment plant, and it was burned at 550 °C. Different percentages of burned sludge ash were mixed with three different types of clayey soil. A laboratory study consisting of Atterberg’s limits test, unconfined compressive strength test, standard proctor density test, and swelling pressure test were carried out on samples treated with burned sludge at different percentages by dry weight of the clayey soils. The results show that the addition of 7.5 % of the burned sludge ash by the dry weight of the soil will increase the unconfined compressive strength and maximum dry density and also decrease the swelling pressure and the swell potential of the soil. The addition of percentage higher than 7.5 % by dry weight of the soil decreases both the maximum dry density and the unconfined compressive strength; as a result it showed less effectiveness in stabilizing the soil. The conclusion of this research revealed that the burned sludge ash can be used as a promising material for soil stabilization.  相似文献   

20.
Municipalities and recycling and environmental authorities are concerned about the growing amount of carpet waste produced by household, commercial and industrial sectors. It is reported that 500,000 tonnes of carpet waste fibre are plunged into landfills annually in the UK. In the United States of America, around 10 million tonnes of textile waste was generated in 2003. In geotechnical engineering, expansive clay soils are categorised as problematic soils due to their swelling behaviour upon increase in the moisture content. The problematic nature of such soils is intensified with the increase in the plasticity index. This paper presents results of a comprehensive investigation into utilisation of carpet waste fibres in order to improve the swelling characteristics of compacted cohesive soils. Therefore, two different clay soils with markedly different plasticity indices (i.e. 17.0 and 31.5 %) were treated with two different types of carpet waste fibre. Waste fibres were added to prepare specimens with fibre content of 1, 3 and 5 % by dry weight of soil. Soil specimens with different dry unit weights and moisture contents were prepared so as to the swelling behaviour of fibre reinforced compacted clays is completely attained under various scenarios. The results indicated that the behaviour of the fibre reinforced soils seems highly dependent on the initial compaction state and secondary on the moisture content. It was found that the swelling pressure drops rapidly as the percentage of fibre increases in samples prepared at the maximum dry unit weight and optimum moisture content. Reducing the dry unit weight, while maintaining constant moisture content or increasing the moisture content at constant dry unit weight was found to reduce the swelling pressure.  相似文献   

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