瞬变电磁法在煤矿采空区注浆效果检测方面的应用

通过对某煤矿采空区进行瞬变电磁法勘探及注浆效果评价实例分析,证实瞬变电磁法不仅能准确圈定采空区的分布范围,而且能有效检测采空区注浆后的工程质量。利用瞬变电磁法进行采空区注浆前后的检测评价,须采用相同的勘探网度及测点布设,相同的数据采集参数及处理方法、处理流程及处理参数等。实例表明采空区的电阻率异常值及分布范围在注浆前后有明显的差别,表现为电阻率等值线的起伏形态、梯度、展布方向等特征存在着较大差异。     

井下瞬变电磁法在巷道底板含水性探测的应用

某矿井目前主要开采山西组煤,为保证下部太原组煤的安全开拓,需查明其底板的水文地质条件。根据该矿井的地质条件,采用井下瞬变电磁法小线框的工作方式,在一采区-530m水平及其以上相关大巷及17煤首采工作面两顺槽内布置6条测线进行探测。在资料解释中,通过设定2级异常阀值对井下富水性进行评价,查明了巷道底板的含水性。经验证,资料处理解释结果与实际揭露地质构造对应良好。     

内蒙古额济纳旗道噶地区土壤地球化学特征及找矿方向

内蒙古额济纳旗道噶地区矿化类型为石英脉型,见含Au石英脉出露。通过对该地区进行土壤地球化学测量工作,在统计研究区各地层Cu、Ag、Au、Pb、Zn、Sb、Mo、Ni、Co、W、As、Sb等微量元素含量基础上,应用聚类分析方法分析元素间相关关系。在研究区圈定出61处单元素异常区,其中Au元素异常8处。根据地球化学异常分类规范,综合考虑地球化学异常的规模、形态、异常的强度、分带性、异常元素的组合及异常区成矿地质条件和地球化学条件,在单元素异常的基础上圈定出乙类综合异常区2个(Ⅰ号、Ⅱ号综合异常区),丙类综合异常区1个(Ⅲ号综合异常区)。在对研究区地质特征及土壤地球化学特征的基础上圈定出3个找矿靶区,并进行地表工程验证,为进一步找矿工作提供有利依据。     

Effect of velocity hiatuses in oscillatory flow on migration and geometry of ripples: wave‐flume experiments

A series of wave‐flume experiments was conducted to closely look at characteristics of geometry and migration of wave‐generated ripples, with particular reference to the effect of velocity ‘hiatuses’ during which the near‐bed flow velocity becomes much smaller than the threshold of sediment movement. Three types of wave patterns were generated: two types for simulating waves with intervening velocity hiatuses; and regular waves for comparison purposes. In the former two types, two different wavelengths of water waves were generated alternately in the course of a wave test: the wave with a longer wavelength was set large enough to mobilize the bottom sediment, whereas the wave with a shorter wavelength was set too small to mobilize the sediment. The former two types were designed to be different in sequence of convexity and concavity of wave patterns. The sequence with the convex–concave longer wave and successive convex–concave shorter wave was described as a ‘zero‐up‐crossing’ wave pattern, and the inverse sequence was described as a ‘zero‐down‐crossing’ wave pattern. The ripples developed under oscillatory flow with intervening hiatuses manifested the following characteristics in geometry and migration. (i) The morphological characteristics of ripples, namely wavelength, height and the ripple steepness, are unaffected by the intervening hiatuses of velocity. (ii) The directions of ripple migration under the zero‐up‐crossing and zero‐down‐crossing wave patterns corresponded well with the directions of the flow immediately before onset of the hiatuses. (iii) The observation of sand particle movement on the ripple surface indicated that, under the zero‐up‐crossing waves, the velocity hiatus prevents the entrained sediment cloud from being thrown onshore, and thus the sediment grains thrown onshore are fewer than those thrown offshore. As a result of the sediment movement over one wave‐cycle, the net sediment transport is directed offshore under the zero‐up‐crossing wave pattern. (iv) The velocity of ripple migration was highly correlated with acceleration skewness. Under most of the zero‐up‐crossing (zero‐down‐crossing) wave patterns, flow acceleration skewed negative (positive) and ripples migrated offshore (onshore).     

A Boussinesq-type wave driver for a morphodynamical model to predict short-term morphology

The prediction of near-shore morphology on the time scale of a storm event and the length scale of a few surf zone widths is an active area of research. Intense wave breaking drives offshore-directed currents (undertow) carrying sediment seawards, resulting in offshore bar migration. In contrast, higher order nonlinear properties, such as wave asymmetry (velocity skewness) and velocity asymmetry, are drivers for shoreward transport. These wave processes are included in phase-resolving models such as Boussinesq-type wave models (e.g., TRITON). Short-wave averaging in the wave model yields wave-induced forces (e.g., radiation stress gradients) and a wave asymmetry term. The wave-induced forces are used in a hydrostatic model (e.g., Delft3D flow module) to drive the current and undertow, resulting in a 3D velocity profile. The wave model and hydrostatic model are coupled online with a morphodynamic model (e.g., Delft3D morphology module). The latter computes, based on the 3D flow profile and the wave asymmetry term, the sediment transport and performs the bathymetry updates. The updates are transferred directly back to the hydrodynamic models. The coupling of the wave model TRITON and the Delft3D modules is validated by comparing against extensive laboratory data sets (LIP and Boers) and a field case (Duck94), and show a good performance for the hydrodynamics and a reasonable/fair performance for the bar movements.     

Evolution of wave shape over a low-crested structure

This paper investigates the evolution of wave shape over a low-crested structure (LCS) using a 2-D RANS-VOF model. The model predictions of surface elevation and wave skewness and asymmetry are in good agreement with the recent measurements collected in a small scale wave channel at the University of Cantabria (UCA). The empirical formulae relating wave skewness and asymmetry to local Ursell number by Peng et al. (2009) have been extended to include the effect of wave reflection and the ramp in front of LCS and a wider range of Ursell number in the present study. In the presence of LCS, wave skewness decreases slightly above the seaward slope, then increases rapidly up to a maximum value above the structure crest, and decreases drastically above the leeward slope. Wave asymmetry decreases sharply above the seaward slope to a negative minimum value at the structure crest, and then increases rapidly to a positive value above the leeward slope. Our bispectral analysis indicates that sum interactions increase skewness and decrease asymmetry while difference interactions have opposite effects and that the former dominate above the seaward slope and on the structure crest but the latter dominate above the leeward slope of LCS. The observed wave shape evolution over a LCS can be attributed to the changes in the interplay of sum and difference interactions. We found that incident wave height and wave period, relative structure freeboard, structure crest width and structure porosity are the controlling factors for wave shape evolution over LCS. This study provides new insights on the role of wave skewness and asymmetry in the breakwaters stability and sediment transport around the structure and on the beaches behind it.     

陕北高精度磁测找油探讨

在陕北进行高精度磁法找油是非地震方法在此区的一次尝试。通过地面及井中岩石磁化率测定,其地表黄土及侏罗系、三叠系岩石磁性都不强,在富油区40～110m埋深处,岩石磁化率值偏高。为磁法找油的机理研究和富油区上方磁异常模式的建立提供了依据。通过对次生成岩磁铁矿产状分析及已知区实测资料分析总结出陕北富油区上方三种磁异常模式。为了从实测资料中提取这些模式,我们采用了光滑、向上延拓、趋势分析及带通滤波等处理方法。依此对未知区进行了推断,结果与其它物探方法吻合较好。     

青藏高原水系沉积物地球化学衰减模式与区域地球化学勘查对策

文章主要涉及青藏高原干旱荒漠、半干旱草原、高寒草甸等三个景观区。风力搬运的影响遍及整个干旱荒漠和半干旱草原景观区,使其疏松覆盖层中的本域地球化学模式受到不同程度的干扰和变型。干旱荒漠区中水系沉积物的地球化学性质受到风成沙和黄土的双重稀释。高寒草甸区,化学风化作用加强,基本上无外域物质干扰。 考虑技术可能和经济合理两个因素,提出现有交通状况下的区域地球化学勘查对策。     

On the predictive skill of morphodynamic models for onshore sandbar migration

A simplified process-based approach for evaluating onshore sandbar migration is presented in this study. This approach takes wave-averaged parameters as input and computes sediment transport processes using a reconstructed intra-wave orbital velocity signal. The proposed method guarantees good predictive skills for multiple onshore sandbar migration cases without an ad hoc calibration for each scenario. The study differs from previous onshore sandbar migration models, where calibration and testing are performed on just one or few events, and model assessment for uncalibrated realizations is rarely carried out. The present version of the model only addresses onshore sandbar migrations. For the onshore migration cases analyzed, the model has better predictive skills than state-of-the-art morphodynamic models (XBeach and Unibest-TC).     

山西地区Ms〉4．0地震地倾斜资料异常变化特征

2009-2010年山西地区相继发生4次Ms〉4．0地震,着重对地震前地倾斜资料的异常变化进行分析,汲取地倾斜数字资料中的地震前兆信息,从而为准确利用临汾地震台地倾斜资料,分析预报地震提供依据。