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探地雷达在水利设施现状及隐患探测中的应用 总被引：13，自引：0，他引：13
简述探地雷达的一些基本原理,介绍探地雷达用于水利工程设施现状及隐患探测的3个实例,包括拦洪闸底板现状探测;海滨防浪堤隐患探测以及江堤滑塌成因调查。 相似文献
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探地雷达在淡水区浅水域的探测试验 总被引：1，自引：0，他引：1
通过堤防护岸水域抛石探测、水下砼格及碎石层探测、江边堆场滑坡水域探测三个案例,说明探地雷达在淡水区浅水域探测效果。重点分析了探测对象所处环境的电导率、介电常数和探测所采用天线频率对探测效果的影响。探地雷达填补了浅水域工程勘察空白,研究成果对非水域探地雷达探测与检测具有借鉴意义。 相似文献
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《物探与化探》2017,(6)
通过对低频探地雷达在青藏高原冻土带环境下的探测深度、分辨率及反射特征分析的正演模拟来研究其在冻土带天然气水合物勘探中的可行性和关键参数。首先通过雷达测距方程计算确定了理论上探地雷达的最大探测深度与发射频率、地下介质电阻率、介电常数之间的关系,并根据电磁波反射理论计算满足冻土带天然气水合物探测深度所需的系统增益;随后通过低频探地雷达分辨率计算和仿真模拟来确定低频探地雷达在大尺度(200 m)范围的广义分辨率;最后参考已经发现天然气水合物的木里地区基本情况设计冻土及天然气水合物模型,利用时间域有限差分(FDTD)方法进行二维正演,获得了探地雷达信号在冻土带底界以及天然气水合物顶、底界的反射特征,为野外实测数据的处理及解释提供有用信息。研究结果表明,采用中心频率小于等于15 MHz且系统增益大于165 dB的低频探地雷达在地表电阻率较高的冻土区能够满足天然气水合物储层的探测深度要求;分辨率计算及仿真模拟表明低频探地雷达在满足一定条件下在200 m深度可以达到探测深度1%的广义分辨率;探地雷达信号在冻土底界、天然气水合物顶、底界均存在明显的强振幅和频率突变特征;理论计算结果认为应用低频探地雷达直接探测冻土带天然气水合物是可行的。 相似文献
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古城墙由于长年雨、雪水的侵蚀,容易造成城墙内部砖层、土体疏松等病害区域的发生,然而如何确定这些病害的位置、深度、规模等,是非常棘手的问题。探地雷达作为一种无损探测手段,具有探测效率高、分辨率高、结果直观等特点,对探测目标体不会造成任何损伤。结合工程实例,采用探地雷达技术对古城墙顶面进行探测。根据对探地雷达图谱进行处理分析,并选取5处有代表性的雷达图谱进行轻型动力触探验证。结合轻型动力触探验证资料,综合解释分析,提高了查找病害区域的准确性,同时说明探地雷达在古城墙探测中的适用性。 相似文献
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探地雷达在探测玉树走滑断裂带活动性中的初步应用 总被引：4，自引：1，他引：3
探地雷达具有快速、检测范围广、探测深度深、分辨率高及对地表环境无破坏等特点,在活动断层探测应用中具有很大的优势。在简要介绍玉树走滑断裂带活动性的基础上,选择高分辨率的探地雷达对隆宝、昔日达和盘琼沟处断裂带附近的活动断层进行探测。采用时间域有限差分法建立活动断层的数值模型对其雷达波响应特征进行模拟,分析断层在探地雷达剖面上的反射波特征。根据断层的反射波特征解译探地雷达图像,判断断层的位置、走向及空间展布。结合探槽开挖对比,探地雷达图像的解译结果与探槽开挖后的断裂带剖面展示的断层活动性质基本一致。根据隆宝、昔日达和盘琼沟处的探地雷达图像与探槽剖面上断层反射波特征的对比研究,解译了玉树地震震中位置探地雷达剖面上的断层展布。研究表明,探地雷达是一种快速探测活动断层的有效方法,尤其是在地表破裂不明显的区域,不仅可以准确地判断断层的位置、走向及空间展布,还可以将断裂带附近地下岩层的层位信息及探槽断面之外的地表下图像清晰地呈现出来,为以后运用探地雷达探测活动断层提供参考。 相似文献
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为了分析与雷达探测方向相反方向的障碍物对雷达采集数据的影响,以探地雷达理论为基础,运用时域有限差分法（FDTD）,建立相应的地质模型,进行探地雷达二维正演模拟。结合工程实例,对福建某隧道的雷达探测数据进行分析研究。研究结果表明,在使用探地雷达进行目标体探测时电磁波并非仅向探测方向发射和传播,在天线的四周都会有电磁波发射出来,而非探测方向上的电磁波将会对雷达采集的数据产生一定的影响,干扰数据解释人员解译的准确性。因此在使用探地雷达和解译雷达数据时,要了解现场环境和剔除干扰波,做到对探测目标体的正确判断。 相似文献
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The geological characterization of the shallow subsurface in the unconsolidated sediments of the Atlantic Coastal Plain, and other unconsolidated sediment regimes, may involve jointing, faulting, and channeling not readily detectable by conventional drilling and mapping. A knowledge of these features is required in environmental, geotechnical, and geomorphological studies. Ground-penetrating radar (GPR) may be used to routinely map these structures. Three principal shallow subsurface features are readily detectable using GPR: paleochannels, joints or fractures, and faults. The detection of paleochannels is dependent on the scale of the GPR survey and the attitude of the channel within the survey area. Channel morphological features such as scour surfaces, point bars, and thalwegs are observable. Joints and fractures are more difficult to detect depending upon size, patterns, orientation, and fill material. Vertical joints may not be visible to radar unless they are wider than the sampling interval or are filled with radar-opaque materials such as limonite. Angled joints or fractures may be distinguished by an apparent continuous reflector on the radar profile. Faulting on radar profiles may be observed by the offset of reflectors, the image of the fault plane, or the coherent interpretation of a fault system. 相似文献
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Luis Rees-Hughes Natasha L. M. Barlow Adam D. Booth Landis J. West George Tuckwell Tim Grossey 《第四纪科学杂志》2021,36(3):377-390
Across the UK, sandy beaches and dunes protect coastal infrastructure from waves and extreme water levels during large-scale storms, while providing important habitats and recreational opportunities. Understanding their long-term evolution is vital in managing their condition in a changing climate. Recently, ground-penetrating radar (GPR) methods have grown in popularity in geomorphological applications, yielding centimetre-scale resolution images of near-surface stratigraphy and structure, thus allowing landscape evolution to be reconstructed. Additionally, abrupt changes in palaeo-environments can be visualized in three dimensions. Although often complemented by core data, GPR allows interpretations to be extended into areas with minimal ground-truth control. Nonetheless, GPR data interpretation can be non-intuitive and ambiguous, and radargrams may not initially resemble the expected subsurface geometry. Interpretation can be made yet more onerous when handling the large 3D data volumes that are facilitated with modern GPR technology. Here we describe the development of novel semi-automated GPR feature-extraction tools, based on ‘edge detection’ and ‘thresholding’ methods, which detect regions of increased GPR reflectivity which can be applied to aid in the reconstruction of a range Quaternary landscapes. Since reflectivity can be related to lithological and/or pore fluid changes, the 3D architecture of the palaeo-landscape can be reconstructed from the features extracted from a geophysical dataset. We present 500 MHz GPR data collected over a buried Holocene coastal dune system in North Wales, UK, now reclaimed for use as an airfield. Core data from the site, reaching a maximum depth 2 m, suggest rapid vertical changes from sand to silty-organic units, and GPR profiles suggest similar lateral complexity. By applying thresholding methods to GPR depth slices, these lateral complexities are effectively and automatically mapped. Furthermore, automatic extraction of the local reflection power yields a strong correlation with the depth variation of organic content, suggesting it is a cause of reflectivity contrast. GPR-interpolated analyses away from core control thus offer a powerful proxy for parameters derived from invasive core logging. The GPR data collected at Llanbedr airfield highlight a complex dune system to a depth of 2.8 m, probably deposited in several phases over ~700 years, similar to elsewhere in North Wales. 相似文献
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Sytze Van Heteren Duncan M. Fitzgerald Paul A. Mckinlay & Ilya V. Buynevich 《Sedimentology》1998,45(1):181-200
Analysis of a large data base of ground-penetrating-radar (GPR) profiles from both natural and developed paraglacial barriers along the coast of New England has allowed identification of eight reflection configurations that characterize this type of mid- to high-latitude coastal environment. Bedrock anchor points yield primarily hyperbolic configurations, whereas glacial anchor points and sediment-source areas are characterized by chaotic, parallel, and tangential-oblique configurations. Beaches and dunes produce predominantly sigmoidal oblique, hummocky, reflection-free, and bounding-surface configurations. Back-barrier sediments may yield basin-fill configurations, but generally include abundant signal-attenuating units.
The GPR data, calibrated with information from cores, were collected across swash-aligned and drift-aligned barriers in a variety of wave- and tidal-energy settings. Application of a 120-MHz antenna, as used in this study, enables portrayal of a range of sedimentary units, from individual bedforms (on single records) to entire barrier elements (using large numbers of intersecting GPR sections), at maximum vertical resolutions that vary between 0·2 m and 0·7 m.
The most important drawback of GPR in the coastal environment is attenuation of the electromagnetic (EM) signal by layers of salt-marsh peat or by brackish or salty groundwater, primarily along barrier edges. This disadvantage is offset by many benefits. Data can be collected at rates of several km per day, making GPR an excellent reconnaissance tool. A core that is used in the calibration of GPR data can be matched with great accuracy to its position on the complementary GPR record, allowing detailed correlation between lithostratigraphy and reflection configuration. 相似文献
The GPR data, calibrated with information from cores, were collected across swash-aligned and drift-aligned barriers in a variety of wave- and tidal-energy settings. Application of a 120-MHz antenna, as used in this study, enables portrayal of a range of sedimentary units, from individual bedforms (on single records) to entire barrier elements (using large numbers of intersecting GPR sections), at maximum vertical resolutions that vary between 0·2 m and 0·7 m.
The most important drawback of GPR in the coastal environment is attenuation of the electromagnetic (EM) signal by layers of salt-marsh peat or by brackish or salty groundwater, primarily along barrier edges. This disadvantage is offset by many benefits. Data can be collected at rates of several km per day, making GPR an excellent reconnaissance tool. A core that is used in the calibration of GPR data can be matched with great accuracy to its position on the complementary GPR record, allowing detailed correlation between lithostratigraphy and reflection configuration. 相似文献
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Identifying causes of ground-penetrating radar reflections using time-domain reflectometry and sedimentological analyses 总被引：5，自引：0，他引：5
Ground-penetrating radar (GPR) is a geophysical technique widely used to study the shallow subsurface and identify various sediment features that reflect electromagnetic waves. However, little is known about the exact cause of GPR reflections because few studies have coupled wave theory to petrophysical data. In this study, a 100- and 200-MHz GPR survey was conducted on aeolian deposits in a quarry. Time-domain reflectometry (TDR) was used to obtain detailed information on the product of relative permittivity (ɛr ) and relative magnetic permeability (μr ), which mainly controls the GPR contrast parameter in the subsurface. Combining TDR data and lacquer peels from the quarry wall allowed the identification of various relationships between sediment characteristics and ɛr μr . Synthetic radar traces, constructed using the TDR logs and sedimentological data from the lacquer peels, were compared with the actual GPR sections. Numerous peaks in ɛr μr , which are superimposed on a baseline value of 4 for dry sand, are caused by potential GPR reflectors. These increases in ɛr μr coincide with the presence of either organic material, having a higher water content and relative permittivity than the surrounding sediment, or iron oxide bands, enhancing relative magnetic permeability and causing water to stagnate on top of them. Sedimentary structures, as reflected in textural change, only result in possible GPR reflections when the volumetric water content exceeds 0·055. The synthetic radar traces provide an improved insight into the behaviour of radar waves and show that GPR results may be ambiguous because of multiples and interference. 相似文献
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Cape Henlopen, Delaware is a coastal spit complex located at the confluence of Delaware Bay and the Atlantic Ocean. This region was occupied by prehistoric peoples throughout the evolution of ancestral Cape Henlopen. A ground‐penetrating radar (GPR) survey was conducted at one of the prehistoric archaeological sites (7S‐D‐30B) located within the Cape Henlopen Archaeological District. The site was in a remote location in the center of a tide dominated back‐barrier marsh. Ground‐penetrating radar waves penetrated to depths of 7 m, and four major sets of reflections were observed. Three sets were interpreted to be GPR images of geomorphic units associated with the spit complex, and the fourth was identified as the GPR image of a shell midden deposit. The GPR survey was used to determine the approximate dimensions of the shell midden, including its depth below ground surface (up to 2.1 m) and horzontal extent (∼250 m2), and to establish the paleoenvironmental setting and antecedent topography of the site prior to occupation. The GPR data suggests that the shell midden was initially deposited upon an aeolian dune surface and the antecedent topography at the site included an up to 1 m deep trough located 5 m to the north of, and trending parallel to, the axis of a present‐day topographic high. This survey illustrates that GPR is a useful, noninvasive, tool that may be implemented at archaeological sites in coastal areas. It provides constraints on the environmental setting and topography of the terrain which prehistoric peoples inhabited, and it can be used in planning excavations at sites in coastal geomorphic settings. © 2000 John Wiley & Sons, Inc. 相似文献
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Evaporitic materials have been studied by means of ground penetrating radar (GPR) in order to evaluate the collapse hazard.
The obtained 200 MHz GPR profiles show a low signal-noise ratio over the first 3 m depth, where well-defined and continuous
reflectors can be observed. Between 3 and 4.5 m depth, the signal to noise ratio decreases due to attenuation of the electromagnetic
(EM) waves. As a result, reflectors located deeper than 3 m become more discontinuous and poorly defined. GPR profiles show
trails of continuous and subhorizontal reflectors, with a slightly undulated and irregular geometry. Although some of these
reflectors laterally vanish or seem to disappear, sudden interruptions or hyperbolic reflections that could be originated
by the occurrence of cavities have not been detected. These reflectors have been interpreted as corresponding to several evaporitic
layers (gypsum) that constitute the main lithology in the area. Clear interruptions of reflectors have only been observed
in some GPR profiles, and they could be attributed to small (1–2 m long) subvertical faults, with only a few centimetres offset.
These faults may be generated by the accommodation of the evaporitic layers to local collapses affecting deeper materials. 相似文献
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Internal structure and trend of glacier change assessed by geophysical investigations 总被引：1，自引：1，他引：0
Ground-penetrating radar (GPR) is a useful tool for mapping the thickness, morphology and structure of alpine glaciers. Englacial information obtained during a field survey of the Koxkar Glacier in Tian Shan, China, in June 2008 was retrieved from GPR profile data. At least four specific types of structures can be identified from the GPR reflection image: (1) hyperbolae from point sources, (2) irregular linear distributed features, (3) a dense chaotic return zone above a clearly defined bed reflection and (4) linear reflection within the ice body. The interpretation of a typical GPR image was validated using waveform analysis and a finite-difference time-domain numerical model. Through a series of data analyses, these types of reflection characteristics were strongly related to englacial melting. Considering also the GPR result of the debris thickness distribution at the terminus, it is concluded that strong glacial ablation does not occur at the terminus but at a position higher than the terminus where there is a thin layer of debris and relatively high temperatures. Meanwhile, there are many lakes receiving mostly englacial discharge that greatly erode the ice body through melt-water discharge in some regions, and a thick layer of debris insulating the ice body at the terminus; these features may differentiate the retreat of the Koxkar Glacier from the general retreat of glaciers. In the future, with the ablation of glaciers, the central positions of intense ablation may be disconnected and there may be a dead zone at the terminus. 相似文献
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文章叙述了探地雷达对桩基探测的一系列实验工作，通过探地雷达三个参数的匹配对比，研究适合在上海地区应用探地雷达探测桩的一些技术措施和方法。 相似文献