煤矿井下定向钻孔超长套管下放技术

针对煤矿井下定向钻孔超长套管下放成功率低、速度慢的问题,提出开孔段保直钻进、造斜段曲率控制、钻机驱动主动钻杆下放及套管导正等改进技术措施。在阳泉新景矿进行了现场试验,完成了3个满足煤矿井下水力压裂要求的定向钻孔超长套管下放,最大下深达到168 m,套管下放成功率达到100%,下套管平均工效由5.5 m/h最大提高至13.1 m/h,有效地解决了定向钻孔超长套管下放受限的难题。     

2016年"7.19"京津冀极端降水系统的动热力结构及不稳定条件分析

利用NCEP/NCAR 的GFS再分析资料,结合中国气象局气象信息中心提供的全国自动站观测降水量资料、CMORPH卫星反演降水资料、FY2反演降水资料和雷达定量估测降水产品融合的降水资料,对造成2016年7月19~21日北京—天津—河北（以下简称京津冀）地区的极端降水天气系统动热力结构演变以及不稳定条件进行了诊断分析,揭示了京津冀地区上空不同气压层上天气尺度系统的配置,水汽条件,降水发生的垂直运动条件及不稳定层结演变情况。结果表明:（1）500 hPa呈现东高西低的环流形势,与700 hPa低涡和高低空急流相配合,副高北抬阻挡华北地区低涡的东移,导致低涡在京津冀地区停滞是此次降水发生的环流背景;（2）低层的低涡东移发展与中高层正涡度叠加对暴雨发生有重要作用;（3）引用位势散度分析对流不稳定度变化的原因表明,降水区后部的京津冀西南地区,低层的位势不稳定主要由位势散度的水平风垂直切变部分决定,代表水平风垂直切变和大气湿斜压的共同作用,弱降水区以及降水区后方的低层位势散度为负值,有利于该区域位势不稳定加强,强降水区及降水区前方位势散度为正值,抑制了位势不稳定发展。位势散度变化可以通过影响大气稳定度变化进而影响降水落区,位势散度的高值区对应了降水大值区,尤其是700 hPa位势散度对降水落区有很好的指示作用,可以结合位势散度的变化对降水落区进行预估。     

Charney's Model—the Renowned Prototype of Baroclinic Instability—Is Barotropically Unstable As Well

The Charney model is reexamined using a new mathematical tool, the multiscale window transform(MWT), and the MWT-based localized multiscale energetics analysis developed by Liang and Robinson to deal with realistic geophysical fluid flow processes. Traditionally, though this model has been taken as a prototype of baroclinic instability, it actually undergoes a mixed one. While baroclinic instability explains the bottom-trapped feature of the perturbation, the second extreme center in the perturbation field can only be explained by a new barotropic instability when the Charney–Green number γ 1, which takes place throughout the fluid column, and is maximized at a height where its baroclinic counterpart stops functioning.The giving way of the baroclinic instability to a barotropic one at this height corresponds well to the rectification of the tilting found on the maps of perturbation velocity and pressure. Also established in this study is the relative importance of barotropic instability to baroclinic instability in terms of γ. When γ 1, barotropic instability is negligible and hence the system can be viewed as purely baroclinic; when γ 1, however, barotropic and baroclinic instabilities are of the same order;in fact, barotropic instability can be even stronger. The implication of these results has been discussed in linking them to real atmospheric processes.     

一次夏季冷锋后暴雨的形成机制探析

利用常规观测资料,卫星、雷达及NCEP再分析资料,对2013年7月9日山西太原至河北石家庄一带的暴雨成因分析表明:(1)山西太原附近的暴雨发生在持续性层云弱降水持续6 h之后,层云中镶嵌积云并伴有弱雷电活动,暴雨区位于地面冷锋北侧低层冷区中,距离地面锋面120 km以上,极易漏报;(2)850 hPa东北风显著增强,低层假相当位温小的干冷空气随东北风向西南方向伸展,低层稳定层持续增厚,不稳定区位于稳定的边界层之上,强降水由高架对流造成;低层东北风和高层西南风同时增强,锋区斜压性显著增强,锋面抬升加强,锋面抬升和与500 hPa西南气流相伴的干平流使得锋区上空大气层结由近中性的绝对稳定转化为位势不稳定,锋区抬升使得位势不稳定转化为条件性不稳定;(3)午后河北中西部大气层结绝对稳定,石家庄雷达监测到其附近数条平行于热成风方向的水平尺度几十千米的对流云带是由条件性对称不稳定导致的倾斜对流。     

空气跟管钻进在南苏丹供水井流沙层中的应用实践

在南苏丹供水井钻探施工过程中,遇特别松散的流沙层,常规的泥浆护壁钻进难以成孔。简要介绍了在南苏丹供水井施工现场制作简易同步回转拨杠实现空气跟管钻进的基本原理与工作程序,有效地解决了流沙层的钻进成孔问题。并针对这一技术应用过程中存在的问题,提出了改进建议。     

基于现场和卫星有效波高数据评估WAVEWATCH III的输入/耗散项

基于WAVEWATCH III,在输入相同的风场条件下,评估了三个输入耗散项WAM3,WAM4以及TC96在是否考虑大气稳定性时的模拟能力。通过5组实验,用南海的测波雷达数据以及研究区域内HY-2高度计的有效波高数据对不同源项的模拟结果进行了比较分析,研究区域为100-135°E,0-35°N。对TC96中的风速校正参数进行了敏感性分析。结果表明,这几种源项在涌浪占主导时的模拟效果都不太理想;考虑大气不稳定性的TC96源项模拟的效果最好;大气不稳定性的影响是以一种所谓的“高效风速”的策略来反映的,其中最重要的一个参数为风速转换参数,这个参数非常敏感,在对特定区域进行模拟之前,应先分析出这个参数的最优值。     

波致海床滑动稳定性计算方法及滑动失稳特征研究

波浪引起的海床不稳定性是海洋工程中需要考虑的重要问题。在对现有波致海床滑动稳定性计算方法进行分析的基础上,提出了一种波致海床滑动稳定性计算的全应力状态法,将其与现有计算方法进行了对比分析,并进一步研究了波致砂土海床和软土海床的滑动失稳特征。结果分析表明,全应力状态法在波致海床滑动稳定性分析中具有较好的适用性。对于砂土海床,其滑动稳定性受饱和度的影响较大,且当海床计算厚度约为0.2倍波长时对应的滑动深度最大。波浪作用下坡度不超过2°的均质软土海床,其最危险滑动面的位置仅与波长有关,其滑动深度约为0.21倍波长,滑动面半弦长约为0.33倍波长;海床表面的波压力数值只影响其安全系数的大小,而不影响其滑动深度。     

Late Holocene channel and floodplain development in a wandering gravel‐bed river: the River South Tyne at Lambley,northern England

Geomorphological analyses of the morphology, lithostratigraphy and chronology of Holocene alluvial fills in a 2·75 km long piedmont reach of the wandering gravel‐bed River South Tyne at Lambley in Northumberland, northern England, have identified spatial and temporal patterns of late Holocene channel and floodplain development and elucidated the relationship between reach‐ and subreach‐scale channel transformation and terrace formation. Five terraced alluvial fills have been dated to periods sometime between c. 1400 BC –AD 1100, AD 1100–1300, AD 1300–1700, AD 1700–1850 and from AD 1850 to the present. Palaeochannel morphology and lithofacies architecture of alluvial deposits indicate that the past 3000 years has been characterized by episodic channel and floodplain change associated with development and subsequent recovery of subreach‐scale zones of instability which have been fixed in neither time nor space. Cartographic and photographic evidence spanning the past 130 years suggests channel transformation can be accomplished in as little as 50 years. The localized and episodic nature of fluvial adjustment at Lambley points to the operation of subreach‐scale controls of coarse sediment transfers. These include downstream propagation of sediment waves, as well as internal controls imposed by differing valley floor morphology, gradient and boundary materials. However, the preservation of correlated terrace levels indicates that major phases of floodplain construction and entrenchment have been superimposed over locally complex patterns of sediment transfer. Reach‐scale lateral and vertical channel adjustments at Lambley appear to be closely related to climatically driven changes in flood frequency and magnitude, with clusters of extreme floods being particularly important for accomplishing entrenchment and reconfiguring the pattern of localized instability zones. Confinement of flood flows by valley entrenchment, and contamination of catchment river courses by metal‐rich fine sediments following recent historic mining operations, have combined to render the South Tyne at Lambley increasingly sensitive to changes in flood regimes over the past 1000 years. Copyright © 2000 John Wiley & Sons, Ltd.     

Stiffened steel box columns. Part 2: Ductility evaluation

The purpose of this study is to evaluate the ultimate strength and ductility capacity of stiffened steel box columns failed by local and overall interaction instability under a constant compressive axial force and cyclic lateral loading. In a companion paper, a finite element formulation accounting for both geometrical and material non‐linearity was developed to obtain cyclic hysteretic behaviour of such columns. In this paper, the effect of loading patterns on the cyclic inelastic behaviour is first studied; then, a parametric study is carried out to investigate the effects of flange plate width–thickness ratio parameter, column slenderness ratio parameter, stiffener's equivalent slenderness ratio parameter, magnitude of axial load, and material type of stiffeners on the strength and ductility of the columns. Last but not least, empirical formulae of both the ultimate strength and ductility capacities are proposed for stiffened steel box columns, and the limit values of various parameters for the required ductility demand are also discussed. Copyright © 2000 John Wiley & Sons, Ltd.     

A note for the mechanism of high-frequency oscillation instability resulted from absorbing boundary conditions

In this paper the explanation of the mechanism of high-frequency oscillation instability resulted from absorbing boundary conditions is further improved. And we analytically prove the proposition that for one dimensional discrete model of elastic wave motion, the module of reflection factor will be greater than 1 in high frequency band when artificial wave velocity is greater than 1.5 times the ratio of discrete space step to discrete time step. Based on the proof, the frequency band in which instability occurs is discussed in detail, showing such high-frequency waves are meaningless for the numerical simulation of wave motion.