综合多频率地质雷达天线探测活断层浅层结构——以玉树活动断裂为例

地质雷达技术具有操作性强、分辨率高、探测深度深、对地表环境无破坏和可重复探测等特点,在活断层探测中具有很大的优势。为验证综合多中心频率地质雷达天线探测活断层地下浅层结构效果,以民主村处发育的玉树活动断裂为研究对象,采用25 MHz、100 MHz、250 MHz和500 MHz中心频率的地质雷达天线对活断层浅层结构进行探测,并与探槽剖面进行效果对比。研究结果表明:低中心频率的地质雷达天线（25 MHz和100 MHz）可获取大范围内深度较深（约32 m）的活断层地下浅层结构的整体形态,从雷达图像上可识别出主断层分布范围、断层倾向及地下浅层结构等;而中高中心频率的地质雷达天线（250 MHz和500 MHz）则可获取局部范围内深度较浅（约3 m）的地下浅层结构,尤其是500 MHz天线。探测结果与地表构造地貌形态和探槽剖面地质构造一致,表明综合多中心频率地质雷达天线探测玉树活动断裂浅层结构的有效性和适用性,为活断层研究提供多尺度数据及方法支持。      

综合物探方法在采空塌陷区调查中的应用

在山东某金矿区浅层采空塌陷地质灾害调查中,为准确圈定采空区的空间分布,根据对探测场地地质条件和外界环境因素的综合分析,采用探地雷达法和瞬变电磁法开展了野外探测工作.通过对典型断面图上采空区异常特征的分析,推测了采空区的规模和埋深,并结合钻孔进行了验证.研究结果表明,综合物探方法应用于浅层金矿采空区调查是快速、有效的.     

煤矿采空区四维地震特征分析及识别方法:以淮南煤田张集矿区为例

煤矿采空区塌陷是一个重要的地质问题,由于采空塌陷区地震、地质条件的复杂性,传统三维地震勘探探测方法难以准确查明采空区边界.本研究提出一种基于四维地震特征的煤矿采空区识别方法,并以淮南煤田张集煤矿为靶区开展采空区探测.该方法从模型驱动入手,通过建立煤层开采前、后地质模型及进行正演模拟,利用模型地震叠前时间偏移剖面回溯分析...     

探地雷达技术在煤矿采空区探测中的应用

不明采空区对煤矿的安全生产构成潜在危害,而人工地震勘探对埋深较浅的采空区存在盲区。采用RAMAC/GPR探地雷达仪配备的超强地面耦合天线(RTA50MHz)探测采空区。由于煤层及采空区相对雷达探测的有效范围较深,综合考虑探地雷达的分辨率与探测深度的关系,选用合适的雷达参数和探测模式进行数据采集,并采用了VC++开发了三维系统进行了补充解释,实现了探测目标体的准确定位,取得较好的探测效果。      

探地雷达在探测地下采空区范围中的应用

由放心弃的地下采空区引起的地面沉陷,已成为一种典型的地质灾害,严重影响工程建设的顺利进行。为了采取相应的治理措施,查明地下采空区的埋深及分布范围显得十分重要通过实例,简述探地雷达在探测地下采空区范围中的应用,探测目的在于确定地下采空区的深度,查明地下采空区的范围,为公路建设选线提供可靠依据。     

老采空区勘查技术方法研究

老采空区往往无矿产勘查资料和历史矿产开采资料,圈定采空区范围,分析采空塌陷灾害发育程度,只能通过多方面的地质勘查技术手段确定。本文通过实例浅部采空区勘查工作总结研究,采用地质调查、地球物理探测、钻探等多种勘查技术方法,综合研究分析如何准确圈定采空区平面范围,并通过岩石力学实验与计算的方法确定采空塌陷影响范围,为老窑采空区边界和深度的准确判定,提供实际经验和理论上的支持。     

浅部采空区电磁场特征分析研究

目前采空区探测的技术手段主要有地质调查,地球物理探测和钻探。对于老采空区,往往无矿产勘查资料和历史矿产开采资料,地质调查远不能准确固定采空区范围,只能依靠地球物理探测工作来确定采空区范围.深度和边界,之后用钻探验证。对于浅部小窑采空区,目前常用电磁类方法有高密度电阻率法和地质雷达。本文通过分析高密度电阻率法和地质雷达探测采空区的成果案例,总结了浅采空区电磁异常特征。通过对比分析自然条件下地层和采空区地层的电磁场特征,研究判定采空区边界和深度的方法。     

三维地质雷达探测技术在城市道路空洞病害普查中的应用研究

由城市道路地下空洞、路面脱空、土体疏松等病害引起的道路塌陷事故是目前国内许多城市面临的重大安全隐患。城市道路空洞病害具有隐伏性、突发性,造成的灾难性后果长期以来困扰着城市安全运营。以国内多地的项目实测及验证成果为基础,对三维地质雷达探测技术方法和工作流程进行了梳理,通过分析三维地质雷达剖面数据中病害体的顶界面反射、多次波反射、边界绕射波等异常特征和三维地质雷达切片数据中病害体周边地下管、井分布特征,总结了三维地质雷达技术在城市道路地下脱空、空洞病害探测中病害体的数据异常特征。实践研究证明,三维地质雷达探测技术以其作业高效、定位精准、抗干扰能力强、数据丰富全面等优点可有效地探测出道路下方存在的空洞等安全隐患,为城市道路病害的防患和治理提供准确、可靠的依据。     

综合物探在金属矿采空区中的应用—以焦家金矿望儿山采空区为例

矿山开采范围和深度的不断加大形成了越来越多的金属矿采空区。采空区塌陷等地质灾害给矿山安全开采和居民生活带来了极大的不便,因此对金属矿采空区的准确定位显得尤为重要。本文以山东焦家金矿望儿山采空区为例,开展了以高密度电阻率法、地震映像和探地雷达探测为主的综合探测试验,通过综合探测发现异常16处,结合地质资料和钻孔验证,证实了其中12处异常为采空区(准确率达到75%),并结合电-震综合异常特征建立了采空区3D空间形态。试验结果表明,以电-震为主的综合地球物理勘探技术可以有效的定位采空区位置及空间分布,为焦家金矿及其它金属矿区采空区探测提供了借鉴。     

选频法在南阳宏发煤矿老窑水勘探中的应用

探讨选频法在煤矿老窑水勘探中的应用,以南阳宏发煤矿部分采空区及采空充水区为例,运用选频法,探测地下煤矿采空区及采空充水区位置。通过瞬变电磁法验证,选频法解释成果准确可靠。该资料可以说明选频法在寻找、确定煤矿采空充水区具有良好的效果。     

基于GPRMax2D的地下管线精细化探测方法

探地雷达是探测地下结构及其分布规律的一种重要的浅层地球物理探测方法,具有分辨率高、无损、抗干扰能力强、结果直观等优点,在工程物探领域被广泛应用。为提高对地下管线雷达图像特征的认识,确定管线异常体的位置,提高地质雷达的解释精度,利用时域有限差分法(FDTD)对地下管线进行精细化探测,包括对管线埋深、材质、管线内充填物、管线病害等影响因素的数值模拟,以此建立地下管线正演模拟合成图库,进而指导探地雷达实际探测图像的解释工作。现场管线探测结果表明:探地雷达可准确探测出地下管线的埋设位置及运行状态,为今后的维修养护提供了依据。     

Detection of underground cavities by combining gravity,magnetic and ground penetrating radar surveys: a case study from the Zaragoza area,NE Spain

A geophysical survey routine is proposed to detect underground cavities and dolines; it is based on the sequential application of magnetic, low-frequency ground penetrating radar (GPR) and microgravity techniques. A case study near Zaragoza (Ebro valley, Spain) demonstrates the applicability of these methods. The strong contrast of magnetic and electromagnetic properties (and to a lesser scale, of density) between the doline filling and the surrounding stratified Tertiary and Quaternary rocks allows the shape of filled cavities to be clearly outlined by these methods.     

Collapse hazard assessment in evaporitic materials from ground penetrating radar: a case study

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.     

探地雷达在管线探测与工程勘察中的应用

简要地介绍了探地雷达的勘探原理,工作方法、技术,及其在工程勘察中的应用,并在前人的基础上,利用ＳＩＲ－２型探地雷达,寻找地下管线和确定工程地质界面,进行了一系列的实测工作,获得了高质、清晰、直观的ＧＰＲ图像。     

Ground penetrating radar-based experimental simulation and signal interpretation on roadway roof separation detection

Roof separation is one of the major indications for coal mine roadway roof accidents. Therefore, it is important that efforts be made to detect roadway roof separation. Currently, the instrument used for detecting roadway roof separation is the roof-off-the-strata indicator, but its installation and use is complicated and the need is greater than can be managed. This thesis takes ground penetrating radar (GPR) as a means for roof separation detection and analyzes its feasibility for use in detecting roof separation both theoretically and experimentally. First, numerical simulation experiments on roof separation detection are carried out using GprMax2D software. The results show that it is feasible to detect roof separation by using GPR electromagnetic waves. Next, physical simulation experiment on roof separation detection is carried out using MALA GPR (RAMAC/GPR). Lastly,  the traditional image segmentation algorithm of 2D maximum between a cluster variance is improved to interpret the GPR signal. Good results were achieved using the improved algorithm to interpret detection signals of roof separation by GPR in a physical simulation experiment.     

抚顺西露天矿北帮变形有限元分析

本文应用有限单元法对抚顺西露天矿北帮边坡及地表变形进行分析.确定了在地下开采当时、露天开采当时及不同充填类型地下采场当构造地应力降低时边坡及地表的变形特征.给出了不同情况下的位移场、应力场及塑性区的分布.并对不同情况下的变形、应力分布及塑性区特征进行了对比研究.     

Requirements for the performance of a ground-penetrating radar system in searching for cavities

The requirements for the performance of a ground-penetrating radar (GPR) system for detecting subsurface cavities are analyzed by numerical modeling of the GPR problem. The algorithm used to solve the forward GPR problem is approximated to a real experiment with regard to the design of the GPR system, the parameters of the source and receiver, and their position relative to the medium under study and its inhomogeneity. We calculated the spatiotemporal distribution of the field of the detected signal from a pulse source located at the interface between the medium and a cavity anomaly of a given geometry. The results were used to estimate the dynamic range of the GPR system necessary for determining the anomaly. We also performed GPR surveys of low-contrast inhomogeneities (cavities in mines) using GROT 12 GPR systems and analyzed the survey results by numerical modeling. It is shown that the GPR performance required to detect and locate inhomogeneities of interest at a certain sounding depth can be estimated in the experiment design phase.     

Exploration of subsurface strata conditions for a limestone mining area in India with ground-penetrating radar

. A study has been conducted for the exploration of underground voids and strata conditions at shallow depth in a limestone mine of Manikgarh Cement at Maharashtra in India. The Manikgarh Cement is surrounded with high-quality limestone having platy formations with excessive fractures and fissures. A perennial river, the Amal Nala, is flowing across the middle of limestone mining lease of the Manikgarh Cement Captive Mine. The impact of this water body on the mining is the central theme of this study. Excavation of limestone is in progress in different blocks on both sides of the Amal Nala. For the purpose of planning it was necessary to know the ground conditions of the area surrounding the Amal Nala so that seepage of the water can be checked. If there is no adverse impact due to deepening of mining activity, the minerals lying at depth can be safely exploited. A ground-penetrating radar (GPR) survey was carried out in the mining lease area to investigate the condition of the strata (status of fractures, cracks, cavities, etc., through which seepage or water percolation takes place). The results of this survey reveal that solid compact layers exist from the surface to depths varying from 2 to 5 m only along the three sections G1G1, G2G2 and G3G3 (lying in the mining area of the Manikgarh limestone along both sides of the Amal Nala). Fractured/weathered rocks and solution cavities exist from the surface to depths varying from 4 to 16.5 m. Therefore, extraction of limestone is possible only to depths of 2 to 5 m from the surface in this mining area. If extraction continues below this depth, the seepage of water from the Amal Nala will start due to the presence of enormous fractures and cavities (solution holes) in the underlying limestone strata. In addition, the water of the Amal Nala will be disturbed, which is the main water reservoir of this area.     

Ground-penetrating radar as a tool to detect rock heterogeneities (channels, cemented layers and fractures) in the Luxembourg Sandstone Formation (Grand-Duchy of Luxembourg)

A combined study of radar profiles and thin section analysis supported by modelling of synthetic radar traces reveals that ground-penetrating radar (GPR) reflections generated in diagenetically altered sandstones cannot always be interpreted unequivocally. This is illustrated in the Luxembourg Sandstone Formation, which has been altered diagenetically by selective carbonate cementation and fracturing. Cemented lenses and concretions developed along the bedding planes, especially at places with high primary carbonate content. Cementation resulted in the alternation of cemented carbonate-rich sandy layers (thickness 30–50 cm and variable length) and uncemented carbonate-poor sandstone layers. The ability of GPR to detect the geometry of these lenses and vertical fractures with centimetre apertures has been tested at several antenna frequencies (100, 200, 250 and 500 MHz). Relative dielectric permittivity calculations were carried out to assess variations of this electric property within the cemented and uncemented layers as a function of porosity, calcite and water content in the pores. Two-dimensional full waveform modelling was also carried out to study the effect of conductivity in the sandstones and the effect of interlayer clay seams. At the penetration depth of the radar (7 m with 250 MHz), cemented lenses and concretions could only be detected with GPR when the porosity contrast was sufficiently high, which is not always the case. This conclusion is supported by the modelling. The data also proved the ability of radar to detect large open vertical fractures along which sandstones are weathered. The study has implications for investigations which will use GPR to detect three-dimensional distribution of diagenetic pore filling precipitates as well as secondary porosity development along fractures.