煤层中的河道泥石流相沉积及相关采煤生产措施

在陆相含煤断陷盆地，煤层中的河道泥石流相沉积通常比较发育，并成为影响采煤生产的重要地质因素。以铁法盆地大兴井田为例，文章论述了煤层中的河道泥石流相沉积发育的地质背景，指出冲积扇前泥炭沼泽是这类河道泥石流的多发地段，冲积扇源洪水是形成煤层中河道泥石流相沉积的主要因素；从岩石学、几何形体等方面阐述了煤层中河道泥石流相沉积特征；并根据煤层中河道泥石流的平面分布规律，提出相关采煤生产方案以减小或避免这类泥石流相沉积对采煤生产的负面影响。     

在煤田地震勘探中与速度无关的DMO技术探讨

由于煤田地质条件的局限性,与速度无关DMO的技术,在实际应用中只能用均方根速度来近似地震反射波的速度,而在速度分析中,较好的办法是在DMO后得的道集上作DMO速度分析,同时注意数据处理参数的合理选择,与速度无关的技术才能在煤田地震勘探中取得很好的应用效果。     

基于DEM的沟谷系统提取算法综述

该文对近20多a来基于栅格数字高程模型(DEM)提取沟谷系统的方法与技术进行了综述。将沟谷系统提取方法归纳为三类：局部方法、全局方法、局部与全局相结合的方法，比较了各类方法的优缺点。分别综述与比较了提取沟谷系统的三个主要问题——水流路径的确定、洼地的处理以及累计汇流阈值的确定的解决算法以及存在的不足。笔者认为要使这方面的研究走向真正的实用化，必须借助其它的信息，利用人工智能和模式识别等多种手段来实现自动提取。     

GMS卫星资料估算地表旬太阳辐射

GMS－5静止气象卫星较宽的可见光波段，为估算到达地表的太阳辐射提供了极好的信息源。利用GMS－5可见光通道资料，分析估计太阳辐射的可行性，并给出了相应的卫星资料处理方法。利用逐时观测资料和济南日射观测站太阳总辐射小时辐照总量实测资料，建立了可见光反照率与小时辐照总量的统计关系，探讨了旬太阳辐射的估算模型。估算结果与日射站实测结果比较，旬辐射估计量的均方误差为7．7MJ.m^-1，平均相对误差为3．4％。     

预防锤击预制桩挤土效应的措施与效果

对沉桩施工过程中所产生的问题及其对周围建筑物等设施造成影响做了初步分析。以上海海怡花园预制桩工程为例，介绍几种预防和减少预制桩施工挤土效应的方法，并对几种方法的实践成果作了论述。     

河道复杂采砂坑附近流场的数值模拟

数值模拟研究紊流问题的关键是充分考虑雷诺应力的差异,应用各向异性三维代数应力紊流数学模型(ASM)模拟研究了天然河道的次生流问题。以方形管道为算例与试验的比较表明,所应用的ASM模型精度较高;将ASM与非结构网格有机结合模拟分析河道复杂采砂坑,计算成果与前人结果类比,令人满意。ASM模型为研究河床稳定与变形提供了有力工具。分析表明,采砂坑使原稳定的水流形态发生变化,沿主流方向形成纵向涡旋导致采砂坑上游缘口冲刷,坑内的横向次生流则造成横向侵蚀;紊动特性研究表明采砂坑严重影响河床稳定。     

黄河下游游荡河段河床演变对河道整治的响应

为预测黄河下游游荡性河道大规模整治后对河床演变的作用,基于河流动力学理论,通过物理模型试验的方法,以黄河下游游荡性河道典型河段为对象,研究了河床过程对河道整治的复杂响应关系。研究结果表明,河槽横断面形态的调整与人工边界约束程度、流量变差及含沙量变差有关;只要整治工程体系平面布设合理,整治工程量达到一定规模后,通过河道整治,可使河槽横断面形态趋于窄深方向发展,促使游荡型河道向限制性弯曲型河道转化,同时,河道泄洪输沙能力有所提高;河道整治后,不同河段的比降调整不会平行进行。     

Managing urban river channel adjustments

In managing river channels, awareness is increasing to acknowledge spatial patterns of channel adjustments, to adopt a holistic catchment perspective, to progress from hard to softer engineering methods, and to utilize a geomorphological approach. However, specific methods for analyzing urban channels have not been related to a management framework. Using Fountain Hills, AZ, as an example of an urbanizing area, this paper develops a dynamic approach for urban river channels that analyzes variations in channel adjustments in a spatial context. The approach requires methods for delineating the drainage network, for dividing the network into channel segments in the area investigated according to road crossings, and for categorizing and characterizing channel segments. Using stream channel hazards as a basis for characterizing channel segments, together with consideration of community views, this approach provides a potential framework for management as illustrated provisionally by indicating the most significant hazards that require management and then suggesting possible management options.     

The influence of pool length on local turbulence production and energy slope: a flume experiment

The in?uence of pool length on the strength of turbulence generated by vortex shedding was investigated in a 6 m long recirculating ?ume. The experiment utilized a 38% constriction of ?ow and an average channel‐bed slope of 0·007. The base geometry for the intermediate‐length pool experiment originated from a highly simpli?ed, 0·10 scale model of a forced pool from North Saint Vrain Creek, Colorado. Discharge in the ?ume was 31·6 l/s, which corresponds to a discharge in the prototype channel of 10 m³/s. Three shorter and four longer pool lengths also were created with a ?xed bed to determine changes in turbulence intensities and energy slope with pool elongation. Three‐dimensional velocities were measured with an acoustic Doppler velocimeter at 31–40 different 0·6‐depth and near‐bed locations downstream of the rectangular constriction. The average velocity and root mean square (RMS) of the absolute magnitude of velocity at both depths are signi?cantly related to the distance from the constriction in most pool locations downstream of the constriction. In many locations, pool elongation results in a non‐linear change in turbulence intensities and average velocity. Based on the overall ?ow pattern, the strongest turbulence occurs in the center of the pool along the shear zone between the jet and recirculating eddy. The lateral location of this shear zone is sensitive to changes in pool length. Energy slope also was sensitive to pool length due to a combination of greater length of the pool and greater head loss with shorter pools. The results indicate some form of hydraulic optimization is possible with pools adjusting their length to adjust the location and strength of turbulent intensities in the center of pools, and lower their rate of energy dissipation. Copyright © 2004 John Wiley & Sons, Ltd.     

Impact of hydroelectric power releases on the morphology and sedimentology of the bed of the Warche River (Belgium)

The Butgenbach dam on the Warche River was built in 1932 in order to maintain a suf?cient supply of water to the Robertville reservoir situated 7 km downstream, for the production of hydroelectricity. During winter months, releases are made almost every day from the Butgenbach dam. From a hydrological point of view, this has resulted in signi?cantly reducing the number of discharges that are higher than bankfull. Despite the reduction in peak discharge, there is a signi?cant increase in the number of ef?cient discharges (0·6 bankfull). The impacts of these hydrological modi?cations on the bed morphology and sedimentology below the Butgenbach dam have been studied and the following geomorphological modi?cations have been identi?ed: a doubling of the width of the channel in 45 years, a reduction in the number of rif?es and pools, an increase in the number of gravel bars and islets and an increase in bedrock outcrops in the channel. Moreover, the ?nest bed particles are mobilized by the almost daily releases, inducing a signi?cant increase in bed‐material size sorting. The reduction of sinuosity and the disappearance of bed differentiation and rif?e/pool sequences have produced a diminution of bed roughness and an increase of the competence of the river. Thus relatively small ?oods can remove the armoured layer. Copyright © 2003 John Wiley & Sons, Ltd.