复合地基不同参数对地面动力特性的影响分析

复合地基在我国的应用极为广泛,但应用水平参差不齐,工程质量需要提高,更需要理论指导。由于复合地基的复杂性,复合地基参数对地震作用下地面运动特性的影响,学者研究的结论和意见也不一致。因此,进一步研究其理论及工程应用问题既是客观要求又是现实需要。为了更深入地探讨有关问题,笔者采用有限元法,引入粘弹性人工边界,同时把地震波转化为等效荷载输入到模型中,认为比较符合实际。最后,通过系统分析,得出了一些有益的结论,有一定的工程价值,同时也为进一步研究提供了科学依据。     

WATER LOSS EQUATIONS AND COEFFICIENTS TO ESTIMATE RUNOFF FROM RAINFALL1

Infiltration models are based on physical characteristics of the soil and initial soil moisture. For a given soil it is based on the initial soil moisture distribution. A computer simulation model for flood runoff systems (FH-Model) was used to analyze 39 sets of rainfall-runoff data on four small watersheds ranging in size from 17 to 342 square kilometers located in the Yamaska River basin in Quebec. From these analyses, parameters and coefficients have been determined for a water loss (infiltration) equation. A method for determining the loss parameters, using a nonlinear least square curve fitting technique, is presented. Expressions were made to relate the loss parameters to antecedent precipitation. The equations were tested on 11 storm rainfall and runoff events on a watershed located in the same region and close agreements were found.     

THE UNIT HYDROGRAPH: A SATISFACTORY MODEL OF WATERSHED RESPONSE?1

ABSTRACT: Some 96 flood events larger than the mean annual flood from 16 watersheds in the Commonwealth of Pennsylvania were used to derive unit hydrographs by the least-squares method. Analyses of the unit hydrographs were conducted to ascertain their response to watershed parameters, climatic and storm variables and locations within different hydrologic regions. Significant differences both within and among watersheds led to the formulation and testing of hypotheses stating that differences among watersheds are caused by physiographic differences while differences within watersheds result from climatic and storm differences. The analysis showed, that while many watersheds parameters strongly influence the shape of the unit hydrograph, only the storm variables duration and volume of precipitation excess produce significant differences. Seasonal differences were apparent but not proven statistically significant.     

OBSERVATION WELL NETWORK DESIGN FOR PUMPING TESTS IN UNCONFINED AQUIFERS1

ABSTRACT: This paper presents a method for determining locations of observation wells to be used in conducting pumping tests in unconfined aquifers. Sensitivity coefficients, the distribution of relative errors, and the correlation coefficients between four aquifer parameters (horizontal and vertical hydraulic conductivities K_r and K_z, storage coefficient S, and specific yield S_y) are used as the criteria for the design of observation well networks and the interpretation of pumping tests. The contours of the relative errors over a vertical profile are very useful in selecting the “best” location of an observation well. Results from theoretical analyses suggest that a wide range of locations is suitable for the determination of K_r and that good locations for the determination of K_z and S may be poorly suited for the determination of S_y. Consideration must be given to the position and lengths of the pumping well screen in the selection of observation well locations. For a given location, the quality of test data can be improved by using high pumping rates and frequent sampling of drawdowns. We found that a minimum of two and preferably three observation locations are needed along a given transect. Results of the four parameters from a single well analysis may contain higher uncertainties. However, composite analyses of multiple observation wells can reduce the correlation between the four aquifer parameters, particularly between K_r and S_y, thus, improving the quality of parameter estimation. Results from two pumping tests conducted at sites located in Nebraska were examined with regard to the proposed methodology.     

座舱减压时间对应急供氧参数的影响

通过实验和理论计算的方法对座舱爆炸减压过程中压力变化进行了研究 ,推导了座舱减压时间的计算公式 ;并就座舱减压时间的变化对应急供氧参数进行了分析。结果表明 :减压时间与座舱的容积成正比 ,与爆炸孔的有效面积成反比 ;减压时间的不同 ,对爆炸减压峰值有影响 ,而对剩余压力、稳定值影响不大。研究结果为今后进行供氧系统的爆炸减压实验提供了依据     

新庄煤矿井下出现不明雾气原因分析

根据新庄煤矿 1110 1进风巷出现不明雾气 ,笔者认为 ,研究和分析该雾气的成因及是否有毒 ,对煤矿安全生产和矿工的生命安全与健康至关重要。通过现场气象测定和实验室模拟试验 ,确定了雾气成因 ,经雾气发生地点采样分析 ,空气中未发现有毒气体。经实测分析和研究表明 ,进风巷雾气成因是 :当突然打开 1110 1工作面回风巷道中的调节风门时 ,巷道气压突然降低 ,空气膨胀 ,温度有所下降 ,使得空气中的水分凝结 ,从而形成雾气。通过实验室模拟实验再现了这一过程 ,表明对雾气现象的分析和研究的结果是正确的     

PROJECTION OF URBANIZATION EFFECTS ON RUNOFF USING CLARK INSTANTANEOUS UNIT HYDROGRAPH PARAMETERS1

ABSTRACT: To alleviate serious flooding problems brought upon by rapid urbanization in the Beargrass Creek watershed, located in Louisville, Kentucky, the U.S. Army Corps of Engineers undertook a major flood study in 1973. In order to predict flood conditions in 1990, the year when the watershed was expected to undergo complete urbanization, trends in the Clark Instantaneous Unit Hydrograph (Clark IUH) parameters were utilized to determine the 1990 unit hydrograph and flood conditions. Based on the results from this flood study, this paper demonstrates the applicability of using projected Clark IUH parameters for modeling future runoff conditions in an urbanizing watershed. Values of these parameters, as estimated from maximum annual historical flood data, are used to develop regression models for predicting future Clark IUH parameters. Using the projected parameters, selected annual flood events since 1973 are simulated in order to verify the accuracy of these projections. Results show a close correspondence between the simulated and observed flood characteristics. Hence, the use of projected Clark IUH parameters is an appropriate procedure for modeling future runoff conditions in an urbanizing watershed.     

标贯试验N值与土体物理力学参数的相关性分析

以武汉某地铁工程为例,通过标贯试验和室内土工试验,对地基土标贯试验指标N值与土体部分物理力学参数的相关关系进行了研究,并给出了线性拟合关系式及其相关系数。结果表明:一般性黏土和老黏土的压缩模量、内聚力及内摩擦角,砂土的变形模量、承载力、内摩擦角、剪切波速及动弹模量都与标贯击数N值成正比关系;对于不同的地层类型,其拟合精度也有所区别,而对于该工程地基土,砂土的预测精度普遍高于黏土的预测精度。     

大鹏湾中表层沉积物的有害要素及其环境质量

依据20多个航次的调查资料,简要描述和分析了大鹏湾表层沉积物中8项有害要素多年的平均分布变化及其环境质量变化.结果表明:绝大多数表层沉积物中的有害要素含量在本湾的西部和北部沿岸区域明显偏高,这说明香港和深圳某些渠道的排放对沿岸区域造成了污染.9a调查期间,香港海区表层沉积物中Pb、Cu、Cr、A8和Hg含量的年际变化趋...