A Comparison Study of the Climatological Air-Sea Heat Fluxes Estimated by Different Computational Schemes of Bulk Formula

In this paper the different results of estimated air-sea heat fluxes by different computational schemes of bulk formula are researched. The varying results may bring another source of the uncertainties of flux climatology.In addition to the classical scheme and the sampling scheme, a revised sampling scheme named semi-sampling scheme is proposed in this paper. In this revised version, the monthly means of and are cal?culated from each simultaneous measurement as that in the sampling method. But the transfer coefficients in this version are defined based on monthly means of and instead of those in each measurement in older to use the files of monthly mean variables and in COADS (Woodruff et al. 1987).The results of a comparison study show that the covariance between and and that between and are less than 2 W / m2 and 5 W / m2 respectively in most areas, which are about one order of magni?tude less than the standard deviation of the fluxes. Therefore the difference between two schemes is not statistically significant on average. However, in the regions off coast of Asian and North American continents, the contribution of covariance between and can be as large as 15 W / m2, which is about one third to a half of the standard deviation. Since there are files of monthly mean and for each year in the COADS, we pro?pose to use these files directly in calculation of climatology. It is not necessary to use every individual report.The flux climatology calculated directly from the long-term mean values of basic meteorological elements shows an significant difference from that calculated from the mean of each year’s flux, particularly for the latent heat flux which is on the order of 10 to 15 W / m2, about 3-4 times of the difference between semi-sampling and classical schemes and about one third of the standard deviation. Therefore it indicates that the time interval of months is per?haps a better one in the calculation of flux climatology. It is not recommended to use the long-term means of the me?teorological variables.     

Sediment variability and bed material sampling in gravel-bed rivers

In a 350 m wide reach of the braided, gravel-bed Ashley River, the surface layer of the bed material was sampled in 141 areas of homogeneous graded sediment along seven cross-sections, and 30 kg bulk samples were collected at 86 randomly selected locations along the cross-sections. At one location, a single 854 kg sample composed of 28 subsamples was also collected. Analysis of the single large sample indicate that accurate determination of mean grain size D at that site requires, desirably, a sample of ～ 100 kg, but that samples in which the weight of the largest stone is less than 5 per cent of the total weight have unbiased estimates of D. Spatial variability of bulk material is such that 228 and 50 samples are needed to estimate D to ± 10 and ± 20 per cent respectively of the true value; requirements for estimating inclusive graphic standard duration are only 11 and 3 respectively. The grain-size distribution of the surface layer is only weakly related to the bulk material beneath. The results of ‘Wolman sampling’ along 12 cross-sections at two pace intervals (average 120 stones per cross-section) indicate that estimation of overall surface D to ±10 and ±20 per cent would require sampling along 64 and 14 cross-sections respectively. It is concluded that accurate characterization of bed sediment in gravel-bed rivers is very demanding of labour and resources, and that careful planning is needed to ensure efficiency and meaningful results.     

A simple solution for drainage through a 2-dimensional hydraulic fill stope

Inadequate drainage has been attributed as the major cause of failure of several hydraulic fill stopes that have claimed lives. Therefore it is necessary to be able to predict the pore water pressure developments and flow rates throughout the filling operation. There are computer programmes that can simulate the hydraulic filling of a mine stope and enable computations of the pore water pressures, flow rates and hydraulic gradients at any time. This paper presents a simple analytical solution for estimating the maximum pore water pressure within the stope, flow rate and the hydraulic gradients at the entry and exit. The proposed solutions are verified against solutions derived from FLAC, a finite difference software, and the agreement is found to be excellent. A simple equation for the hydraulic gradient at the top of the stope, as a function of the height of water within the fill, is also presented.     

Study of Drainage Through Hydraulic Fill Stopes using Method of Fragments

A good understanding of the pore water pressure developments within the hydraulic fill stope and the discharge through the drain is essential for improving the designs of barricades and the safety in the mines. A finite difference software FLAC was used to study the drainage and pore water pressure developments within a two dimensional rectangular stope with a single drain at the bottom. Using the method of fragment, a simple solution was proposed for determining the discharge and the maximum pore water pressure within the stope, when the height of water is greater than the width of the stope. The predictions are within 1% of those obtained from FLAC.     

吹填砂土地基的不同加固方法效果评价

某港口堆场地基由砂土吹填而成,地基承载力约为65kPa,为使地基达到150kPa的承载要求,必须对该吹填砂土地基进行处理。根据场区不同的地层条件、使用功能和地基强度,设计分别采用插板振冲、插板强夯、不插板强夯三种加固方法进行试验。试验检测结果表明,三种加固方法处理后的地基承载力均能满足设计,插排强夯效果最佳。     

深圳某填土滑坡破坏机理研究

2002年9月18日13:40,在连降暴雨的影响下,深圳一填土边坡发生滑坡,约2.5×104m3的松散填土体在水平地面高速滑动了140m,造成5人死亡3、1人受伤。文章首先介绍了滑坡区的地质环境特点及滑坡特征;为了揭示该滑坡的发生机理,开展了松散击实填土的等压固结不排水剪(ICU)及常剪应力排水剪(CS)试验。ICU试验结果表明,土体具有明显的应变软化特性并伴随孔隙水压力的上升;CS试验结果表明,土体在低围压条件下破坏具有突然性,破坏过程中孔隙水压力急剧上升,表明土体出现突然性结构丧失。ICU及CS试验均表明松散填土具有静态液化特性。从现场孔隙比与稳态线(SSL)的关系来看,原位填土的状态参数位于稳态线上方,因此该填土边坡是由于地下水位上升造成土体出现静态液化、液化土体形成流滑所致。无限斜坡稳定分析表明造成该填土边坡破坏需要有较高的地下水位。     

岗曲河面板堆石坝数值模拟分析

采用非线性有限元方法,对岗曲河混凝土面板堆石坝在施工期和蓄水期的应力变形进行了深入研究.有限元计算结果表明:坝体应力变形规律合理,坝体设计方案可行.     

Analysis of Weak Wind Stable Conditions from the Observations of the Land Surface Processes Experiment at Anand in India

The observations in weak wind stable conditions are scarce. The present study examines the observations from the Land Surface Processes Experiment (LASPEX) conducted at Anand, (Gujarat, India) during the year 1997–1998 to study the characteristics of surface layer under weak wind stable conditions. The observed surface fluxes are compared with those computed using Monin-Obukhov (M-O) similarity theory. The upper air observations and regional climatology are used to justify the persistence of weak wind conditions at Anand. The frequency of occurrence of weak wind stable conditions is observed to be around 67%. In 86% of the cases under weak wind conditions, bulk Richardson number (R_iB) is found to be larger than 0.2. The magnitude of surface fluxes computed from M-O similarity theory is shown to be smaller in comparison to those based on the observations in weak wind stable conditions. Surface fluxes computed using the empirical relations for the eddy diffusivities and drag and heat exchange coefficients are found to be comparable with those based on M-O similarity theory however these fluxes are under-predicted in comparison to the observations. The traditional M-O similarity theory is not able to simulate the observed fluxes well in weak wind stable conditions at Anand.     

长白山地区杂填土地段嵌岩桩施工技术

杂填土地段填土成分复杂,土层松散,力学强度低,桩基施工难度较大,尤其是填土时间较短的地段。以长白山地区杂填土地段施工钻孔灌注桩为实例,分析了不同成孔方法的适用情况,最后选择冲击钻进成孔。介绍了施工工艺、施工难点和应对措施、泥浆处理等,阐述了在厚层杂填土地段嵌岩桩的施工技术。     

Optimization of the Rock Physical Model in Tight Sandstone Reservoir

Krief model, Nur model and Pride-Lee model are usually used to calculate dry rock modulus of sandstone reservoirs, but they are not effective for tight sandstone reservoirs. Based on Krief model and Nur model, and minimizing the difference between predicted P-wave or S-wave velocities and measured velocities, we acquireed lithologic index m in Krief model and critical porosity ?_c in Nur model by Gassmann relationship. The empirical parameters used in the models are expressed as the values changing with depth, so the accuracy of Krief and Nur models to estimate the P-wave and S-wave velocities was improved, and these two models are called as the variable parameter Krief model and the variable parameter Nur model. In addition, comparing with prediction accuracy of P-wave and S-wave velocities under different constraints, we can see that the shear modulus formulas in the three models are more accurate and more suitable in the tight sandstone reservoir. Han’s relationship about K_dry and u_dry is not affected by porosity, lithology and other factors, and the paper established dry rock model by Han’s relationship and any one of the above three models. The new dry rock model was applied in the Gassmann relationship to predict S-wave velocity of H8 tight sandstone reservoir in Sulige Gas Filed, Ordos Basin, which improved the accuracy of predicting S-wave velocity. At the same time, lithology index m in Krief model, critical porosity ?_c in Nur model and consolidation parameters c in Pride-Lee model which are corresponding to each sample can be obtained. The values of these parameters can reflect lithology difference, pore structure, compaction degree and other characteristics, which indicate the geological characteristics of the reservoir.