The study of the transient electromagnetic detection device with small sized coil and easy installation underground will offer new insights into the real-time dynamic exploration and forecast water-bearing structure in excavation roadway.By drawing on the full-space transient electromagnetic theory, this paper adopted the three-dimensional time-domain finite element method for numerical simulation to explore the characteristics of the secondary field response obtained by small coil excitation and the transient electromagnetic response received by the magnetic core coil.This study constructed a geological-geophysical model of the water-bearing fault in front of the roadway excavation working face, studied the transient electromagnetic response characteristics of the small coil device for the water-bearing fault, and compared the effects of small coil and conventional coil in advance detection.The study shows that :（1）the decay law of the induced electric potential generated by the small coil source excitation is the same as that of the induced electric potential generated by the conventional transmitting coil with time,（2）the magnetic core coil can effectively improve the induced signal strength,（3）the application of both the small coil device and the conventional coil device can effectively explain the distribution range of the low resistance area,（4）the detection results match the verification results of the roadway excavation.Combined with the underground field test, this paper verified the applicability and effectiveness of the small coil device applied to mine transient electromagnetic method advance detection.

According to historical records, from 1128, when the Yellow River encroached the Huai river to flood the Sishui river, to 1855, when the Yellow River flowed through Xuzhou, the Yellow River flooded many times, causing several changes in the direction of the surface water system and the repeated scouring and burying of the paleochannel, which has contributed to the complexity of today's paleochannel in terms of its direction, burial depth and stratigraphic structure, over these seven hundred years.In this paper, the characteristics of changes, erosion, identification, depth and stratigraphic structure of the Xuzhou paleochannel are analyzed through data collection, field exploration, drilling, geophysical exploration and other geological methods, and the influence of alluvium formed by the paleochannel on karst collapse and engineering construction has been studied. It is concluded that since the late Pleistocene, a total of 5 rivers have flowed through Xuzhou. Among them, there are 2 paleochannels in late Pleistocene, both originating in Shandong and entering Xuzhou City from north, and 3 in the Holocene, namely, the ancient Sishui river, the ancient Bianshui river and the ancient Yellow River. Besides, the strata of the Xuzhou paleochannel were firstly formed by the flood of the Bianshui river and the Sishui river, and then by the alluviation of the Yellow River. Therefore, the strata are characterized by "new" (The age is young, mainly formed by the flooding of the Yellow River.), "soft" (Many strata present the large compressibility with high water content), "miscellaneous" (The strata contain bricks, tiles, stones and pottery of the underground ancient city.), "changing" (The large area of cover caused by the flooding of the Yellow River not only buried the ancient city, but also changed the landform). Furthermore, the paleochannel has created favorable geological structure for the formation of karst collapse because the formation of superimposed silt and silt deposits as well as the scouring to the old clay that is steadily distributed formed a replenishment skylight of underlying karst aquifer. This is also the main reason why the collapse points are densely distributed near the paleochannel. Finally, due to the strong water abundance near the paleochannel, the construction of the subway shield is subject to the sand inrush caused by silt and mealy sand. At the same time, the special stratigraphic structure and engineering geological characteristics of the paleochannel will have a great influence on the stability of foundation pit engineering and shallow foundation buildings, and hence corresponding engineering measures should be taken during the project construction.

Ultra-small coil is generally used by transient electromagnetic logging as the transmitting device. Due to the low intensity of excited transient electromagnetic field, only the rock layer near the borehole wall can be detected, but the remote radial detection of the outer borehole and the accurate location of geological anomalies cannot be realized. Based on the theory of transient electromagnetic field in whole space, the scanning detection method for borehole transient electromagnetic method（BTEM）is proposed. The magnetic core coil is used to excite the electromagnetic field, enhance the transmitting magnetic moment, and improve the radial detection distance of BTEM. At the same time, by flexibly adjusting the direction of the coils, the borehole wall can be scanned at 360° to realize all-round detection in the borehole radial direction, the spatial resolution and positioning accuracy of BTEM for the water-bearing geological body can be improved. Three-dimensional geological-geophysical model of borehole whole space is established, optimized mesh generation strategy is proposed, and special grid structure is used to encrypt and standardize the magnetic core coil in the borehole to improve the accuracy of numerical simulation. Using the finite element method, the electromagnetic field response of BTEM excited by magnetic core coil is calculated under the condition of uniform medium, and then the transient electromagnetic field response of different devices for the model of low resistivity geological anomaly is also calculated. The response characteristics of transient electromagnetic field with coplanar dipole device and coaxial dipole device and with different geometric parameters are analyzed. The whole space all-time apparent resistivity calculation and time to depth conversion algorithm are used to image the resistivity in whole space. The research shows that the electromagnetic field strength can be significantly enhanced by adding a magnetic core to the ultra-small coil of BTEM,and the amplitude of the enhancement is proportional to the diameter and length of the magnetic core. In comparison, the enhancement of the electromagnetic field response is more significant by increasing the length of the magnetic core. The detection result of BTEM with magnetic core coil in whole space can better reflect the transient electromagnetic field anomaly caused by low resistivity geological body in the surrounding rock layer of the borehole radial direction. Both the coplanar dipole device and the coaxial dipole device can obtain ideal detection effect, and the resolution of resistivity imaging in whole space is high, In comparison, the anomaly amplitude obtained by the coplanar dipole device is larger, and the positioning of the center of anomaly body is more accurate, while the description of the overall shape and boundary of the anomaly body by the coaxial dipole device is more accurate.

采用综合地球物理方法对徐州地区的覆盖型岩溶区进行调查,研究岩溶发育的地球物理场特征及平面分布规律.基于综合地球物理解释成果进行分类统计,实现研究区内岩溶发育规律的定量分析.研究表明,在覆盖型岩溶区调查中综合利用多种物探方法,能够相互补充和验证,可以有效地查明基岩埋深及起伏特征、覆盖层结构、断裂构造、岩溶破碎带及具有一定规模的溶洞.通过地球物理统计分析,徐州地区马家沟组和张夏组岩溶发育极强,岩溶破碎带占比在25％以上;三山子组和炒米店组岩溶发育强,岩溶破碎带占比在10％左右,废黄河断裂带对主要可溶岩地层的岩溶发育具有明显的控制和影响作用.徐州地区岩溶发育与埋藏深度呈反向相关关系,即岩溶发育总体上具有随深度增加而逐渐减弱的趋势,岩溶在30～40 m深度最为发育,岩溶破碎带占比可达11％以上,在80 m深度占比减少至约3％.综合地球物理探测与统计分析结果经钻探资料证实较为可靠,很好地说明了在覆盖型岩溶发育规律研究中基于综合地球物理方法的探测与统计分析的有效性.

封闭不良钻孔不同程度地连通含水层,形成隐蔽性较强的导水通道,对巷道掘进和工作面回采构成水害威胁.基于全空间瞬变电磁理论,构建掘进工作面前方封闭不良钻孔三维地质?地球物理模型,模拟研究封闭不良钻孔影响区模型的全空间瞬变电磁场响应特征,进而探讨矿井瞬变电磁法用于封闭不良钻孔超前探测的有效性.数值模拟结果表明,封闭不良钻孔附近含水体在感应电动势多测道图上表现为幅值增强,异常特征明显.结合宁夏双马煤矿I0104108工作面运输巷掘进工作面前方封闭不良钻孔超前探测工程开展应用研究,探测结果显示,在钻孔位置的煤层顶板出现局部低阻,表明该钻孔具有一定的导水性,引起顶板局部相对富水性增强.研究结果表明,封闭不良钻孔导致的局部富水性增强可以引起典型且易于识别的瞬变电磁场响应.采用矿井瞬变电磁法进行超前探测,并结合精细化处理解释可以有效查明钻孔附近岩层的相对富水特征,进而对封闭不良钻孔的导水性进行评价,为封闭不良钻孔的治理提供依据,保障矿井安全生产.

苏南地区中浅层构造裂隙型地热资源丰富,是一种潜力巨大的清洁能源.本文从区域地质及物性资料入手,综合运用重力、磁法、电法、测温、测氡多种地球物理方法,通过多元物探信息融合,从热源、通道、储层、盖层四个方面开展地热地质条件研究.区域重力与面积性电测深资料揭示研究区属于隆、凹相间构造,表明中生代以来上地幔热动力作用强烈,具备寻找地热资源的有利构造条件.区内磁法异常平静、单调,不存在隐伏岩体等附加热源,地热主要来自地球内部自然增温.可控源音频大地电磁法资料揭示区内北东向与北西向断裂发育,其中北西向断裂具有张扭性质,规模及切割深度大,伴生浅表地温及放射性氡异常,是导水、导热的重要通道和控热构造.面积性电测深资料显示区内三叠系青龙组灰岩广泛分布,成为良好的裂隙-岩溶含水热储层,第四系松散层及白垩系浦口组厚度大,导热率低,有利于热储层蓄热增温,为理想的地热盖层.在对研究区源、通、储、盖四个要素进行综合研究的基础上确定了地热井位置RSQ1.经钻探验证,RSQ1井钻遇地层及构造情况与物探推断结果基本吻合,水量及水温参数均满足设计要求,充分说明综合地球物理方法在苏南地区中浅层构造裂隙型地热资源勘查中的有效性.

徐州城区是岩溶塌陷地质灾害危害严重的区域,已发生的塌陷均展布在废黄河断裂带内,有明显的规律性,为断裂带地下水富集区过量抽水所造成.研究表明,废黄河断裂带内岩溶发育,发育有向上开口的溶洞和裂隙,断裂带沟通了不同时代的含水层,形成了地下水强径流带或富集带;地堑式断裂带构成的负地形形成了晚更新世和全新世古河道,古河道区域形成"单一透水型盖层"和"透-阻型盖层",使黄河泛滥沉积的砂性土直接覆盖在岩溶含水层上,为过量抽水发生岩溶塌陷提供了重要水动力条件.因此,废黄河断裂带及其伴生断裂控制了岩溶塌陷的形成条件,特别是岩溶发育强度、岩溶水文地质结构和地下水富集规律.

徐州是江苏省地质环境最脆弱的城市,岩溶塌陷、采空塌陷等地质灾害和区域稳定性问题已影响经济社会的可持续发展,解决城市地质问题已成为徐州城市地质调查的首要任务.物探属于无损探测技术,凭借高效、经济、施工灵活、信息丰富,探测效果好等优点在城市地质调查中应用广泛.徐州城市地质调查项目在实施过程中,采用了可控源音频大地电磁、高密度电阻率、瞬变电磁和地质雷达4种物探技术,结合钻孔验证和区域地质资料对比,查证了主要断裂带分布位置,判别了岩溶发育和上覆松散层古河道分布特征,识别采空区空间特征和边界条件,为区域稳定性、岩溶塌陷易发性及采空区稳定性评价提供依据.

Investigation of ancient channels is of great significance for earthquake disaster reduction,urban planning and reasonable de-velopment of ground water resources. Based on the significant electrical property difference of rock and soil in Xuzhou area, Holocene ancient channel was detected using high density resistivity method. Firstly, through numerical simulation of geoelectrical models and field test nearby boreholes, the effectiveness of high density resistivity method in detecting Holocene ancient channel and the device choice were discussed;Secondly,the result maps of section,plane and 3D were analyzed;Finally,the detecting result of high density resistivity method was verified by boreholes. Result of theoretical research and applied case indicates that Holocene ancient channels in Xuzhou area show representative electrical field response characteristics, information such as morphology and stratum structure of ancient channels can be obtained through the analysis of response characteristic; the dipole-dipole device of high density resistivity method is very sensitive to the structure variation of overburden,maximum anomalous intension,and it has certain advantages in the as-pect of stratum division,so dipole-dipole device is the preferred device for the investigation of ancient channels;through arranging mul-tiple survey lines in investigated area and with the help of 3D visual software platform,3D spatial interpretation of target can be real-ized,and interpreted results will intuitively reveal the 3D morphology and spatial distribution characteristics of Holocene ancient chan-nels.

Based on the projects of Xuzhou urban geological survey and Xuzhou karst collapse investigation,stuck to karst geological characteristics and urban construction demand for karst geological survey with full use of the previous data,the geological survey of bare karst area and covered karst area has been respectively carried out,which is aimed to find out the karst development characteristic in urban planning area.At the same time,the geophysical exploration,drilling and some other methods have been used for exploration and validation.Then the accuracy of karst geological survey in this area has been improved effectively.As well,the author has analyzed the karst formations,karst exposed conditions and development degree.The karst development in this area is mainly superficial karst since the Cenozoic and the degree is generally controlled by geological structure which is distributed with the type of "strong-weak" in the northeast direction.Along the Old Yellow River fault zone,the karst of O2m and ∈ 2z develops very well.

Xuzhou urban region has been seriously threatened by the geological hazards, such as karst collapse. Several collapses that had widely occurred were distributed in the ancient Yellow River Fault zone. Obviously, they were zonal and being controlled by the river fault zone. The karst was developing well in the fault zone and it connected the Cambrian and the Ordovician aquifer which made karst groundwater was very rich. The long-term pumping groundwater made the level up and down around the bedrock surface and the sandy soil covered directly on the karst aquifer which deposited with the form of paleochannels had changed. That is the main reason for the occurrence of karst collapse.

Radon transform is a kind of technical method widely used in seismic data processing,but there are problems of low reso?lution and low computational efficiency in practical application.On the basis of phase shift hyperbola,the authors deduced time?invari?ant hyperbolic integral path,proposed sparse hyperbolic Radon transform based on Bayes principle,provided parameter selection prin?ciple of discrete transform,and introduced dynamic time windows to ensure the condition that reflection waves of different layers have the best convergence.Sparse hyperbolic Radon transform in the frequency domain has higher resolution and it can be realized in the frequency domain,so the computational efficiency can be drastically improved.Model data test and actual application result show that sparse hyperbolic Radon transform in the frequency domain can effectively remove regular interference, suppress random noise and improve the signal?to?noise ratio;in addition,it also has better fidelity and amplitude preservation.

薄覆盖隐伏断层调查对城市规划建设和防震减灾工作具有重要意义,文中选择徐州废黄河断裂为例对薄覆盖隐伏断层电场响应特征进行研究.首先,对徐州废黄河断裂构造模式进行总结和概化,建立3种具有代表性的简化地电模型;其次,针对不同地电模型,采用有限差分和阻尼最小二乘法进行正、反演计算探讨其电场响应特征;然后,选择地震勘探和钻孔联合地质剖面已揭露断点上进行现场试验,检验和提升数值模拟成果;最后,将理论研究成果应用于指导野外调查工程实践.理论研究及工程实践结果表明,薄覆盖隐伏断层在电阻率断面上表现出典型且易于识别的电场响应特征,高密度电阻率法各装置均可有效地进行地质分层及断裂构造定性分析,但是相比较而言,偶极-偶极装置对隐伏断层响应特征最为显著,在地层成层性及基岩面起伏调查方面也最有优势,可作为薄覆盖隐伏断层探测的首选方法.

Based on analyzing the excitation distribution characteristics of the bipolar source in a homogeneous half?space electromag?netic field and discussing the correlation between the transmit?receive distance and the maximum depth of prospecting, the authors hold that CSAMT characterized by small transmit?receive distance, long bipolar source and short potential electrodes can be applied to geo?logical exploration in the shallow layer of a strong noisy?level environment, and has such merits as high signal?to?noise and uniform dis?tribution of electromagnetic field along the line direction. This paper briefly describes fieldwork and data?processing methods of CSAMT, and illustrates typical experimental curves under man?made interferences, controlled tests on the dipole?dipole resistivity sounding and applied cases in shallow geophysical exploration. The inversion results are similar in controlled tests, but CSAMT has higher resolution and stronger anti?interference capability. Interpretations of applied cases match the drilling verification, indicating that CSAMT with small and medium?sized transmit?receive distance array has practical value and application prospect in the shallow geo?physical exploration.

为研究均匀全空间介质中任意点(除发射框边)处矩形回线源瞬变电磁响应,从全空间磁偶极子的切向电场和水平圆形回线发射框中心磁场出发,采用互易原理和积分法推导了全空间任意点处的瞬变响应.通过对全空间瞬变场磁场Bx及其时间导数OBz/Ot的核函数Y(ω)和y'(ω)特征的研究,将全程瞬变响应分为早期、中期和晚期.Y(ω)的早期和晚期阶段,其内层误差函数采用渐近展开式,外层积分采用直接多项式积分;中期阶段,内层误差函数采用有理契比雪夫展开式,外层积分采用龙贝格积分.y'(ω)的晚期和非对角区域的早期采用误差函数渐近展开式;Y''(ω)的中期和对角区域的早期采用龙贝格积分.采用理论模型计算验证了公式的精度.结果表明,该算法求取的数值解,其Bz核函数Y(ω)的相对误差可以控制在1×10-6％以内;而OBz/Ot的核函数Y'(ω)的相对误差可以控制在1×10-4％以内.早期阶段,Bz和OBz/Ot在发射框内部的极值中心沿着与短边呈45 °夹角方向向发射框内部移动,并且短边处的2个极值中心先行合并,然后再沿长边方向合并;相同时刻,Bz过零点等值线比OBz/Ot过零点等值线传播的更远.

矿井瞬变电磁法得到了广泛应用,但其数据处理解释方法研究相对滞后,为提高勘探精度本文对全空间处理及三维解释方法进行研究.以均匀全空间磁偶极源瞬变响应为基础,探讨全空间磁感应强度垂向分量Bz及其时间变化率(e)Bz/(e)T的核函数曲线特征,并给出全区视电阻率数值计算方法.研究结果表明Bz的核函数Y(Z)存在一个转折点Z=1,以转折点为界可以划分为两个单调区间;(e)Bz/(e)T的核函数Y'(Z)存在两个转折点Z=0.707和Z=1.732,以转折点为界可以划分为三个单调区间,在单调区间内通过二分搜索算法可以计算区间内视电阻率值,各区间视电阻率曲线通过转折点可构成全区视电阻率曲线.采用Voxler软件平台实现矿井瞬变电磁三维立体解释,并给出数据三维可视化的具体步骤.应用实例表明本文提出的全空间处理及三维解释方法可以实现工作面内煤层及其附近岩层三维电阻率成像,直观展现富水异常体三维空间展布特征,方法实用性强、探测效果较好.

Detecting coal mined?out areas with effective measures has been major issue to be addressed in mining area environment management, mine safe production and major construction projects site selection. Based on the fundamental principle of frequency do?main electromagnetic method (FDEM), method characteristics of EH?4 and CSAMT was compared and analyzed, electrical character?istic of mined?out area filled with different materials was analyzed through numerical modeling, and practical detecting effect was dis?cussed by typical project cases of EH?4 and CSAMT. Numerical modeling result and engineering practice prove that compared with sur?rounding rock mined?out area has prominent electrical difference, and base on this physical property mined?out area detecting with FDEM can obtain ideal effect. FDEM is an effective method in detecting coal mined?out area and it has already been an effective tech?nological means in coal mine water prevention and control and geological disaster survey of mined?out area.

将优化二分搜索算法应用于全区视电阻率计算,以期提高计算精度和运算效率.以均匀全空间回线源中心的瞬变响应为基础,探讨全空间磁感应强度垂向分量Bz及其时间变化率(δ)Bz/ (δ)T核函数曲线特征,推导晚期视电阻率表达式.给出全空间条件下由(δ)Bz/(δ)T数值积分计算Bz的方法,并通过模拟计算对转换精度进行分析.对瞬变延时T一定时Bz和(δ)Bz/(δ)T相对于电阻率p的单调性进行研究,结果表明Bz为ρ的单值函数,满足对p二分搜索的条件,而(δ)Bz/(δ)T为p的双值函数,其二分搜索的前提是辅助参数Z在变量p的取值区间内恒满足Z≤1.225,并在此基础上对二分搜索的初始区间和具体流程进行了优化.模型算例和应用实例表明,该优化算法计算速度快、精度高,并可同时获得由Bz和(δ)Bz/(δ)T定义的全区视电阻率ρall和ρ'all.

In order to effectively predict and prevent each type water bearing body in a front of the heading face of the mine roadway,to eliminate the potential danger of the water inrush and to ensure the safety heading of the mine,base on the mine transient electromagnetic method and the mien DC method detection technology as examples,the data collection,data pretreatment and inverse calculation of the advance diction in the underground mine were applied to form a cross section of the resistivity to explain the water bearing conditions in the front of the heading face of the mine roadway.A set suitable technical method to predict water bearing body during the mine roadway heading process was established.The results showed that the combined application of the mine transient electromagnetic method and the mine DC method could make the detection of each type water bearing body more accurately.