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581.
582.
G. A. Athanasopoulos 《Geotechnical and Geological Engineering》1994,12(2):122-132
Summary A review is presented of conceptual approaches that are currently in use for interpreting the operation of reinforced soil.
The concepts of enhanced confining pressure and of reduced normal tensile strains are found to be closely related to current
experimental and theoretical investigations as well as to the design methodologies available at present for reinforced soil
applications. Focusing on the enhanced confining pressure concept, analytical expressions are developed that allow the estimation
of the value of equivalent confining stress increase when the properties of soil and reinforcement and the state of stresses
acting on a cylindrical reinforced soil element are known. The derived expressions can also be utilized for estimating the
soil-reinforcement friction angle from the results of triaxial tests on cylindrical samples reinforced with horizontal layers
of reinforcement. 相似文献
583.
通过实验,对饱和粘性土的渗透规律进行研究,得到几点新认识。利用此认识建立了饱和粘性土越流补给量的计算公式,并在实际应用中得到验证。 相似文献
584.
A new experimental method is introduced for determining the relative magnitudes of liquid and vapor diffusion by using a small amount of soluble chemical as a tracer. The theoretical justification of the method is presented for the case where ice is absent. The feasibility of the method is demonstrated by an experiment using marine-deposited clay. 相似文献
585.
Field measurements of NO and NO2 emissions from soils have been performed in Finthen near Mainz (F.R.G.) and in Utrera near Seville (Spain). The applied method employed a flow box coupled with a chemiluminescent NO
x
detector allowing the determination of minimum flux rates of 2 g N m-2 h-1 for NO and 3 g m-2 h-1 for NO2.The NO and NO2 flux rates were found to be strongly dependent on soil surface temperatures and showed strong daily variations with maximum values during the early afternoon and minimum values during the early morning. Between the daily variation patterns of NO and NO2, there was a time lag of about 2 h which seem to be due to the different physico-chemical properties of NO and NO2. The apparent activation energy of NO emission calculated from the Arrhenius equation ranged between 44 and 103 kJ per mole. The NO and NO2 emission rates were positively correlated with soil moisture in the upper soil layer.The measurements carried out in August in Finthen clearly indicate the establishment of NO and NO2 equilibrium mixing ratios which appeared to be on the order of 20 ppbv for NO and 10 ppbv for NO2. The soil acted as a net sink for ambient air NO and NO2 mixing ratios higher than the equilibrium values and a net source for NO and NO2 mixing ratios lower than the equilibrium values. This behaviour as well as the observation of equilibrium mixing ratios clearly indicate that NO and NO2 are formed and destroyed concurrently in the soil.Average flux rates measured on bare unfertilized soils were about 10 g N m-2 h-1 for NO2 and 8 g N m-2 h-1 for NO. The NO and NO2 flux rates were significantly reduced on plant covered soil plots. In some cases, the flux rates of both gases became negative indicating that the vegetation may act as a sink for atmospheric NO and NO2.Application of mineral fertilizers increased the NO and NO2 emission rates. Highest emission rates were observed for urea followed by NH4Cl, NH4NO3 and NaNO3. The fertilizer loss rates ranged from 0.1% for NaNO3 to 5.4% for urea. Vegetation cover substantially reduced the fertilizer loss rate.The total NO
x
emission from soil is estimated to be 11 Tg N yr-1. This figure is an upper limit and includes the emission of 7 Tg N yr-1 from natural unfertilized soils, 2 Tg N yr-1 from fertilized soils as well as 2 Tg N yr-1 from animal excreta. Despite its speculative character, this estimation indicates that NO
x
emission by soil is important for tropospheric chemistry especially in remote areas where the NO
x
production by other sources is comparatively small. 相似文献
586.
In the first part of this project, the extent to which moisture content of alluvial soils could be predicted from imagery derived from an airborne thematic mapper (ATM) was investigated. From sampling done on the same day as the flight, it was found that digital numbers derived from the thermal channel (waveband 11) were strongly correlated with gravimetric moisture content. From sampling three fields of contrasting land cover, the relationship between waveband 11 values and moisture content was found to be independent of land cover type. Spatial variation in waveband 11 values and thus moisture content were related to palaeochannel patterns on the alluvial land. This was investigated by deriving variograms for long transects from each of the three investigated fields. The range and sills of the variograms are shown to express the nature and pattern of palaeochannels. By the application of such geostatistical techniques, high resolution imagery can thus be used to quantify palaeochannel characteristics on alluvial land. 相似文献
587.
本文根据安太堡露天煤矿排土场基底黄土的粘土矿物组成的微结构及其在分级荷载下微结构变化的研究,论述了排土场基底黄土内弱层的形成机理,提出弱层是在上覆排土压力下由于黄土的微结构变化而形成的演化弱层。并指出弱层的形成是导致排土场失稳滑坡的主要控制因素,这种弱层在新排土场设计时期并不存在,极具隐蔽性,但在设计时必须考虑在排土增至一定高度后,弱层的形成对排土场稳定性的影响,否则必将会存在重大滑坡隐患。 相似文献
588.
膨胀土判别与分类的人工神经网络方法 总被引:18,自引:0,他引:18
提出了运用神经网络理论对膨胀土进行判别与分类的方法。通过对安康膨胀土的实测数据分析,建立了研究膨胀土判别与分类的计算机智能专家系统。结果表明,用人工神经网络方法对膨胀土进行判别与分类的准确率很高,它无需在判别因子与预测目标之间建立基于某种理论的经验统计关系,该方法具有重要的实用价值。 相似文献
589.
本文是我们在内蒙中部所发现的一种新型膨胀土即玄武岩残积粘土的宏观微观综合研究结果。本文揭示了在内蒙中部异常发育的残积粘土的特殊的形成环境,并从物质成分、物理化学性质、微结构等方面探讨了不良工程特性形成的机理,并进行了膨胀土的工程评价。这类膨胀土在我国北方的发现,改变了对我国北方膨胀土形成发育规律的认识。 相似文献
590.
F. Amini 《Soil Dynamics and Earthquake Engineering》1995,14(6):439-443
Two types of clayey soils, a kaolinite and a bentonite, were tested using a resonant column apparatus under random excitation conditions. The concept of root mean square (rms) strain was utilized for the purpose of strain calculations during random loading. The conventional estimator of the transfer function was used for random vibration analysis. The effect of confinement duration (at a constant pressure) on dynamic soil properties, namely damping and shear modulus, was evaluated. The results indicate that for both cohesive soils, the effect of time was less pronounced during random vibration than sinusoidal loading at the same rms strain. This effect is however more pronounced when the peak shearing strain of sinusoidal loading is considered. Furthermore, time effects were more pronounced at low strain levels than at high strain levels. 相似文献