瞬变电磁法在巨厚覆盖层地区勘查地下水源的应用

河南新郑市区东部覆盖层厚度达400m左右，其电阻率很低，对直流电法及瞬变电磁法勘探起着屏蔽作用，根据该区的地质条件在水源地勘察中，使用瞬变电磁法绘制TEM多测道剖面图，ρτ延时拟断面图，利用该区已知钻孔，求取得深度校正系数为1．8，得到深度拟断面成果图，最终查清巨厚覆盖层下的断层位置，圈定含水岩溶带，确定井位。     

Estimation of Earthquake Damage to Buried Pipelines Caused by Ground Shaking

One of the most critical lessons of the recent earthquakes is the need for seismic planning for lifelines, with appropriate supplies and back up systems for emergency repair and restoration. Seismic planning, however requires physical loss estimations before the earthquakes occur. Buried pipeline damage correlations are critical part of loss estimation procedures applied to lifelines for future earthquakes. We review the existing pipeline damage relationships only for ground shaking (transient ground deformations) in the light of recent developments and evaluate them with Denizli City, Turkey water supply system. Eight scenario earthquakes with four different earthquake magnitudes between M6 and M7 caused by two different fault ruptures (Pamukkale and Karakova-Akhan Faults) were used. Analyses were performed by using Geographical Information Systems (GIS). This high number of different scenario earthquakes made it possible to compare the pipeline damage relationships at different ground shaking levels. Pipeline damage estimations for Denizli City were calculated for each damage relationship and earthquake scenario. Relative effects of damage relationships and scenario earthquakes on the results were compared and discussed. The results were presented separately for brittle, ductile, and all pipelines. It was shown that the variation in ductile pipeline damage estimations by various relationships was higher than the variation in brittle pipeline damage estimations for a particular scenario earthquake.     

瞬变电磁法在探测小窑采空区、陷落柱中的应用

通过矿区勘探的三个典型实例,介绍了使用CUGTEM-2002型瞬变电磁系统在探测小窑采空区积水和陷落柱方面的应用。根据瞬变电磁法对低阻地质体的灵敏性,采用在已知地质异常位置布设测线获取地质异常资料特征,然后推断整个测区资料成果的勘探方法,可取得较好的地质效果。实践证明,瞬变电磁法是探测金属矿体、小窑采空区等地质异常体的一种有效手段。     

瞬变电磁法中的斜阶跃波效应及常规的几种校正方法分析

关断时间校正是瞬变电磁资料处理中的一个重要方面,针对常用的中心回线法,详细分析了瞬变场的斜阶跃波效应。斜阶跃波相对阶跃波高频迅速振荡衰减,斜阶跃波效应主要影响瞬变场的早期,表现为幅值较低,关断时间越长,影响越大。同时对常规的几种关断时间校正方法进行对比分析,结果表明:对于“全期”段数据校正宜选Eaton法,对“晚期”段数据可选Eaton法,也可选坐标移动法。在选用Fitterman法时要注意是否满足使用条件,坐标移动法的“晚期”条件,可根据实际地电参数,通过模拟实验来确定。     

矿井瞬变电磁法多匝小回线装置电感效应的理论研究

由于线圈的自感耦合作用,使瞬变电磁早期时间道信号严重失真。为研究瞬变电磁早期信号的特性,讨论多匝线圈与单匝线圈的自感系数的关系,得出线圈自感信号振幅的理论表达式,并推导出单匝和多匝回线的电感公式。分析瞬变电磁发射回线等效回路的暂态过程及感应电动势的产生和衰减规律。影响早期信号的因素为线圈自感信号,它的衰减不仅与时间有关,而且与等效回路的材料有关。该项研究对进一步研究瞬变电磁早期场的附加效应打下了基础,同时为提取早期数据的研究提供参考。     

高密度电阻率法和瞬变电磁法在场地溶洞勘查中的综合应用

文章介绍了高密度电阻率法和瞬变电磁法(TEM)工作原理、特点及工作方法,并举例示范两种物探方法查找场地内溶洞及岩溶发育带的工作程序.高密度电阻率法对圈定岩溶分布、断层破碎带的追索、管线调查、物探找水、采空区、岩溶、滑坡等问题非常有效,而且成果直观、易于判读;瞬变电磁法对探测低电阻目标物敏感,主要用于探测含水层、溶洞、陷落柱、含水断层等地质构造情况.两者综合应用,可以更好地解决工程地质问题.     

瞬态瑞雷面波勘探技术在工程勘察评价中的应用

文章介绍了瞬态瑞雷面波勘探技术的理论基础和勘探原理、工作方法、资料的整理与解释,并结合工程实例说明瞬态面波勘探技术的应用效果.     

瞬变电磁法在浑江盆地松树煤矿外围的应用

浑江煤田松树煤矿外围找煤项目主要是扩大煤炭储量,该区山高林密,地表条件差,地质构造复杂,侵入体多,形成高阻电性层。通过地面地质工作了解岩性变化规律,应用瞬变电磁法,工作便捷、观测精度高、不受高阻屏蔽。用其基础理论,进行数据处理。利用钻井电性地质资料对比,从已知到未知进行连续剖面解释,从定性、定量解释,确定火山岩的分布范围,划分煤系地层区段,提供建议孔位,从而完成地质任务,为后期工作提供物理信息。     

The transition of flow patterns through critical stagnation points in two-dimensional groundwater flow

A flow pattern is characterized by aquifer features and the number, type, and distribution of stagnation points (locations where the discharge is zero). This article identifies a condition for transition of flow patterns in two-dimensional groundwater flow obeying Darcy’s law by examining changes in stagnation points, using the Taylor series expansion of the discharge vector. It is found that the three standard types of stagnation points (minimums, maximums, and saddle points) are completely characterized by the first-order term containing the discharge gradient tensor. However, when the determinant of the tensor becomes zero, stagnation points of other types characterized by higher-order terms come into existence. In this article, we call these zero-determinant stagnation points as critical stagnation points; they may emerge suddenly, split to a set of new stagnation points, or disappear from the flow, resulting in transitions of flow patterns. Examples of both transient and steady flows are used to illustrate the usefulness and significance of critical stagnation points.     

瞬变电磁法多匝小回线装置实验对比

采用实验方法对多匝同一小回线和重叠小回线两种瞬变电磁法工作装置进行了对比研究,探讨了两种装置参数随线圈匝数的变化关系,从而为野外实际勘探提供数据参考。首先在地下一定深度埋置一低阻体,在该低阻体正上方布置一条测线,然后先分析单点数据的发射磁矩、关断时间、感应信号强度随线圈匝数的变化关系,在此基础上对比不同装置随线圈匝数变化的多测道剖面图,分析两种装置的异同点。实验表明两种装置的发射磁矩、关断时间、信号强度及对异常体的分辨能力都随发射线圈匝数的增加而增加;在相同匝数情况下,同一回线的发射磁矩和关断时间稍大,但有效信号部分能量衰减快,信号强度相对较弱,探测深度较浅,然而在有效探测深度下,同一小回线装置对低阻异常体的分辨能力更强。