水闸闸基隐患探测雷达图像特征分析

水闸闸基隐患严重威胁水闸安全，闸基淘空是水闸较常见的隐患之一。闸底地基垫层在水闸上下游水位差的作用下，经一段时间的运行后，往往会形成强渗流层和淘空区，洪水到来时便产生管涌，危及水闸的安全运行和人民的生命财产安全。利用探地雷达技术可探测出闸基冲刷剥蚀程度、淘空区的位置、范围、发育程度及规模，便于及早采取防范措施，进行加固处理。探地雷达技术是水闸闸基隐患探测的有效手段，雷达图像的特征分析是雷达资料解释的关键，通过雷达图像的特征分析，可判译出闸基隐患的具体部位和类型。     

宽带探地雷达系统研究及在工程检测的应用

宽带探地雷达系统以其高分辨率而受到重视。我们系统地分析、模拟和实验测试了宽带天线，在同络分析仪的基础上研究和开发了宽带的探地雷达系统。对不同模型进行探测，结果表明系统具有很高的分辨率。更重要的是该系统可以在与被探测介质不接触的情况下对介质内部进行探测，具有很高的工作效率。在工程质量检测中将具有巨大应用前景。     

探地雷达在隧道衬砌混凝土质量检测中的应用

简要介绍了应用探地雷达对隧道衬砌混凝土质量进行检测的方法、原理及其实际应用效果。测试结果表明,探地雷达能及时、快速地发现衬砌混凝土的质量问题,为工程质检和评价提供依据,是一种能很好地对衬砌混凝土的质量进行检测的无损检测方法。     

偏移技术在GPR资料处理中的研究

针对GPR剖面中存在的绕射波影响资料处理和解释问题,根据雷达波波动方程和声波波动方程在形式上的一致性,合理地将地震勘探中成熟的相位移波动方程偏移法、克希霍夫积分偏移法和有限差分波动方程偏移法引入到GPR资料处理中。理论模型的试验和实测资料的处理分析表明,该方法有较好的效果。     

Aquifer architecture analysis using ground-penetrating radar: Triassic and Quaternary examples (S. Germany)

 Applying the concept of "analogue studies" long used in reservoir characterization, outcrop analogues in two aquifer units of Southern Germany have been investigated: Upper Triassic (Keuper) alluvial sandstones (Stubensandstein) and Quaternary glaciofluvial gravels. Architectural element analysis of the outcrops is combined with ground-penetrating radar profiles derived a few meters behind the outcrop walls. Such calibration is used to better understand the three-dimensional sedimentary architecture. Many sedimentary units at the same time represent hydraulic flow units and are characterized by specific radar signatures. This approach leads to promising results, not only in unconsolidated aquifers but also in fully consolidated sedimentary rocks. Our studies will lead to a database with which more realistic predictions of the hydraulic behaviour of sedimentary aquifers systems, needed for numerical hydrogeological simulations, will be possible. Received: 17 June 1996 · Accepted: 12 August 1996     

Potentialities of ultrawideband GPR in low-resistivity geoenvironments

We assess the potentia4lities of ultrawideband (UWB) electromagnetic pulse sounding of low-resistivity geoenvironments using the ground-penetrating radar (GPR) system developed by us and compare the obtained results with 2D electrical resistivity tomography and standard GPR data. The research was performed in an area of Quaternary clay deposits with a resistivity of 20-50 Ohmm. For an OKO-2 GPR antenna with a center frequency of 150 MHz, the sounding depth is 2-4 m, whereas UWB sounding provides penetration of the GPR pulse to a depth of 30-40 m. Deep UWB sounding of low-resistivity environments is possible under the following conditions: use of generators based on drift step recovery diodes (DSRDs), high matching of the UWB receiving and transmitting antennas to the environment, and an increase in the noise immunity of the recording system, in particular, due to a decrease in the intensity of air waves.     

青海玛多MS7.4地震安西站VP宽频带倾斜仪数据特征分析

青海玛多M_S7.4地震前甘肃省安西县地震监测站VP宽频带倾斜仪出现明显异常变化且记录到该地震的同震波形。结合CTS-1地震计进行融合分析可知,2套仪器同震波形的震相到时基本同步,表明2套仪器具有可靠性和一致性,但震相记录特征存在差异。2021-04-17 VP宽频带倾斜仪数据打破原有倾斜趋势,年变向西北方向倾斜,05-13恢复为向西南方向倾斜,震前记录到倾角急剧增大的方位与震中至台站的方位一致,倾斜旋转变化方向与区域构造应力方向一致。在同时段时均值数据时频谱中,异常时段存在（1.085~4.340）×10^-6 Hz(周期为64~128 h)的低频信号。此次地震中2套仪器的优势频率和时频变化特征存在显著差异,这种差异可能与2套仪器不同的机械结构、频段宽度、采样频率有关。     

Broadband Plasma Waves In The MagnetopauseAnd Polar Cap Boundary Layers

Boundary layers occurring in the magnetosphere can support a wide spectrumof plasma waves spanning a frequency range of a few mHz to tens of kHz andbeyond. This review describes the main characteristics of the broadband plasma waves observed in the Earth's low-latitude magnetopause boundary layer (LLBL), in the polar cap boundary layer (PCBL), and the possible generation mechanisms. The broadband waves at the low-latitude boundary layer are sufficiently intense to cause the diffusion of the magnetosheath plasma across the closed magnetospheric field lines at a rate rapid enough to populate and maintain the boundary layer itself. The rapid pitch angle scattering of energetic particles via cyclotron resonant interactionswith the waves can provide sufficient precipitation energy flux to the ionosphere to create the dayside aurora. In general, the broadband plasma waves may play an important part in the processes of local heating/acceleration of the boundary layer plasma.     

Photographing layer thicknesses and discontinuities in a marble quarry with 3D GPR visualisation

An important problem of marble-quarry management is assessing the quality and the homogeneity of quarry blocks before excavation. In this study, we decided to image the limestone, which we studied in a marble quarry, in terms of layer thickness, discontinuities and cavities using the ground-penetrating-radar (GPR) method. The method was successfully applied to detect and map the fractures with the cavities in a marble layer according to depth in the Ankara City Polatli Town (Turkey) region, which represents upper Miocene–Pliocene lacustrine carbonate rocks.This paper is based on interactive transparent 3D visualisation of the 2D GPR profiles to determine changes in layer thickness and discontinuities. In addition, this paper indicates the importance of the appropriate opacity-function construction to obtain transparent 3D visualisation. Firstly we acquired and processed parallel 2D GPR profile data, then we assigned two different amplitude–colour ranges using a limited number of colours to determine the layer thickness and its discontinuities separately. We obtained a 3D volume using parallel 2D GPR data and displayed a limited amplitude range by arranging an opacity function. Therefore, we obtained transparent 3D blocks for thickness and discontinuities, and we formulated an interactive 3D display to image the horizontal, vertical and inclined discontinuities and their directions in the x–y plane versus depth. The GPR results were compared with the petrographical investigation on the basis of textural and mineralogical compositions. The vesicular textures within carbonate platform were supported by the GPR results.     

基于GPR图像的河北昌黎海岸横向沙脊北段沉积构造及其成因

运用探地雷达对河北昌黎海岸带横向沙脊的沉积构造进行探测,通过对探地雷达探测影像进行处理与解译,获得海岸沙丘约20 m深度范围内的海岸横向沙脊沉积构造图像,包括沉积层理的倾向、倾角与平面展布信息等。研究发现,昌黎海岸横向沙脊北段的沉积构造主要由高角度交错层理和波状交错层理组成,两者之间界面应为古海滩沿岸沙坝的顶面。界面以上发育稳定的向SWW倾斜的高角度交错层理,倾角约为30°~32°,为向岸风作用形成的前积层理;横向沙脊的丘顶可见槽状交错层理,可能是沙丘脊顶部沉积作用对风向季节性变化的响应。界面以下波状交错层理发育,为波浪作用形成的海滩沉积构造。结合前人对探测区地层调查以及全新世晚期以来海岸线变迁研究成果综合分析,认为海岸横向沙脊是大约2000 aBP以来,以澙湖海滩沿岸沙坝为基础经长期风力吹扬作用持续增长而发育的风成沙丘。