Groundwater Potential Mapping in Lapan Gwari Community Using Integrated Remote Sensing and Electrical Resistivity Soundings

This research aims to address the pressing issue of failed and abandoned wells, causing water scarcity in Lapan Gwari Community, through an improved groundwater exploration approach integrating remote sensing and electrical resistivity soundings. The study area, located within the Zungeru Sheet 163 SE, spans Latitudes 9°30'00"N to 9°32'00"N and Longitudes 6°28'00" to 6°30'00". The surface geologic, structural, and hydrogeological mapping provided essential insights into the hydrogeological framework. Leveraging SRTM DEM data, thematic maps were created for geomorphology, slope, land use, lineament density, and drainage density. These datasets were then integrated using ArcGIS to develop a preliminary groundwater potential zones map. Further investigations were conducted using Vertical Electrical Sounding (VES) and Electrical Resistivity Imaging (2D VES) surveys at targeted locations identified by the preliminary map. Results show that the study area predominantly consists of crystalline rocks of the Nigerian Basement Complex, primarily comprising schist and granite with minor occurrences of quartz vein intrusions. Surface joint directions indicated a dominant NE-SW trend. The VES data revealed three to four geoelectric layers, encompassing the topsoil (1 to 5 m depth, resistivity: 100 Ωm to 300 Ωm), the weathered layer (in the 3-layer system) or fractured layer (in the 4-layer system), and the fresh basement rock characterized by infinite resistivity. The shallow weathered layers (3 to 30 m thickness) are believed to hold aquiferous potential. Hydrogeological interpretation, facilitated by 2D resistivity models, delineated water horizons trapped within clayey sand and weathered/fractured formations. Notably, the aquifer resistivity range was found to be between 3 - 35 m and 100 - 300 Ωm, signifying a promising aquifer positioned at depths of 40 to 88 m. This aligns with corroborative static water level measurements. Given this, we recommend drilling depths of a minimum of 80 m to ensure the acquisition of sufficient and sustainable water supplies. The final groundwater potential zones map derived from this study is expected to serve as an invaluable guide for prospective groundwater developers and relevant authorities in formulating effective water resource management plans. By effectively tackling water scarcity challenges in Lapan Gwari Community, this integrated approach demonstrates its potential for application in similar regions facing comparable hydrogeological concerns.

Characterization of Aquifers in Crystalline and Crystallophyll Basement Zones Using the Electrical Resistivity Method (Trails and Electrical Soundings) in the Gagnoa Region, (Central-Western Côte d’Ivoire)

Introduction: Located in the central-western part of Côte d’Ivoire, the subsoil of the Gagnoa region is made up of sedimentary volcano formations and granitoids with developed fracturing. This complex Precambrian basement contains most of the region’s water resources. This is at the origin of the high failure rate during the various hydrogeological prospecting campaigns. Methodology: The database consists of resistivities from 42 holes and 51 trails drilled as part of the implementation of high-throughput drilling in the study area. The objective of this study is to deepen the knowledge of the fissured basement by interpreting profile curves and electrical soundings. It will be a question of classifying the different types of anomalies obtained on the profiles and their shapes. The orientation of the lineaments observed on the profiles was determined. Results: The interpretation of the geophysical data revealed various anomalies, the main ones being of the CC (Conductor Compartment) and CEDP (Contact between two bearings) types. These types of anomalies are mainly expressed in various forms: the “V”, “W” and “U” shapes. From these anomalies and the appearance of the electrical profiles, lineaments and their orientations were identified with N90-100, N130-140, N170-180 as major orientations. Conclusion: These results could contribute to a better understanding of the fractured environment of the Gagnoa region.

Electrical Resistivity Sounding for Groundwater Investigation around Enugu Metropolis and the Environs, Southeast Nigeria

This report evaluates the use of electrical method and borehole data to investigate the subsurface to delineate the groundwater potential in Enugu metropolis and the environs, south-eastern Nigeria other than rely only on resistivity method which could lead to interpretation error. Integrating these 2 data sets is key in this study. The study area is located in the Anambra Basin and is underlain by Nkporo/Enugu Shale which is overlain by the Mamu Formation. It is bounded by Latitudes 6°2 0'00"N to 6°30'00"N and Longitudes 7°25'00"E to 7°35'00"E and covers surface area of about 342 m2. Thirty-one vertical electrical soundings (VES) were carried out across the area using the Schlumberger electrode array with current electrode separation from 2 to 500 m to identify the depths and resistivity values of the identified geo-electric layers. Through data analysis using WinResist software, the apparent resistivity, thicknesses and depths and the thicknesses of the aquifers were generated. The resistivity and depths were modelled to generate resistivity map and depth map. The resistivity of the aquiferous zone within the study area varied from 20.55 - 427.8 ohm-m at depths of between 10.7 - 40.05 m. Depth to the water table appears to be shallow at the south western part of the map. The interpreted geo-electric layers show a sequence of lateritic top soil, shale, sand and shale. The frequency distribution of the VES curves generated shows the presence of 3 to 5 layers with HK type as the highest. Also, a 2D model was generated using the correlation of VES to VES data and borehole data to VES data to show the underlying stratigraphy beneath the study area as well as the direction of ground water flow. Result of the VES curve analysis reveals that the sub-surface is underlain by three lithological layers namely: lateritic top soil, shale, sand and shales with NW direction of groundwater flow from the 2D model. Groundwater prospective zones can be seen along NW, SW and central parts of the study area which have low resistivity values.

Geophysical Study by Electrical Soundings of the Tartar Aquifer Unit, Boujdour Region, Morocco

The Tartar aquifer unit, is located at the SSO of the city of Boujdour, at a distance of nearly 86 km, and crossed (in its western part) by the National Road N1 connecting the towns of Boujdour and Lagouira passing through the vicinity of the city of Dakhla (PK40). It is exploited by rural settlements for domestic use (especially the inhabitants of fishing villages) and livestock watering, only through wells named Khtout Hobia (IRE 126/124) and Hassi Tartar known as Khtout Trayh (IRE 104/124). These wells have been tracked by a piezometric groundwater table and from 2011 to the present day. The interpretation of the electrical soundings in AB ≤ 2000 m allowed to differentiate the presence of two families of electrical soundings A and B, to establish the resistivity maps in AB = 200, 300 and 400 ihm&#8901m with qualitative aspects, to draw up the map of the isohypses of the roof of the intermediate Dt1 representing the impermeable floor of the aquifer and to highlight two types of discontinuities;electrical discontinuities corresponding to lateral facies changes (limit of erosion surfaces) separating the families A and B of electrical soundings and those corresponding to syn-sedimentary faults which structured the formations into horsts and grabens. The lithological sections of the existing water points and that of oil well 43-1 allowed the geological identification of the geoelectric layers highlighted by the electrical soundings diagrams. As a result, the sandstone and lumachelic formations constituting the aquifer are of Moghrebian-Pleistocene age represented by the resistant R (Family A), sometimes grouping, in its basal part, sandstone levels of the Miocene roof (Family B). These formations lie directly on the Miocene sandy marls represented by the intermediate Dt1. For the present work, we will focus only on the transverse geoelectric cross-section TA, with an SW-NE orientation, which characterizes all the longitudinal sections established following the correlation between the different electric sounding diagrams. It highlights the presence of the gravels G1 and G3 separated by the horst H1 where the resistant R is admitted as aquiferous at the level of the gravels G1 (Khtout Trayh well 104/124) and G3 (well 126/124) and sterile at the level of the horst H1.

Vertical Electrical Sounding of Water-Bearing Sub-Surface of Issele-Azagba in Southern Nigeria

An electrical resistivity survey involving vertical electrical sounding (VES) technique was carried out in Issele-Azagba, Aniocha North Local Government Area of Delta State, Nigeria. This was aimed at investigating the lithologic boundaries and classification of the various subsurface formations. The data obtained were subjected to a twofold interpretative procedure involving initial partial curve matching and computer iteration. Results showed that a maximum of five subsurface layers was delineated from the geoelectric sections. This is made up of loamy topsoil underlain by relatively continuous sandy units composed of different compaction, wetness and clay content. The result also showed that the fifth substratum of the geoelectric section was the aquiferous sand relevant in groundwater development within the study area. Analysis of the result had shown that the aquifers identified in this study were vulnerable contamination percolating from the surface due to the absence of a protective aquitards.

Gravireception in <i>Phycomyces</i>: Threshold Determination on the Sounding Rocket TEXUS 50

Under parabolic flight conditions microgravity is not lower than 3 to 5 times 10-2 g. In contrast to parabolic flights, sounding rocket flights are virtually vibrational-free allowing microgravity as low as 10-5 g. Thus, a rotating platform serving as centrifuge allows the precise generation of gravitational forces ranging from 5 to 100 mg (not possible during parabolic flights). On this basis we determined the threshold1 for optical reflection/absorption changes in Phycomyces to be lower than 25 × 10-3 g. This compares well with the threshold determination of gravitropism in Phycomyces on a clinostat centrifuge. Kinetics of gravity-induced absorption changes and gravity as generated by the on-board centrifuge do not coincide but show a distinctive hysteresis with a latency of 4 s (75 mg-ramp, pull-up).

Delineation of Shallow Aquifers of Umuahia and Environs, Imo River Basin, Nigeria, Using Geo-Sounding Data

This work was undertaken to study the hydrogeophysical characteristics of Umuahia and environs,ImoRiver Basinusing geophysical data. Thirty (30) vertical electrical sounding data with a maximum electrode spacing of (AB/2) of 500 meters were acquired using the Schlumberger electrode configuration. The VES data were interpreted using the conventional partial curve matching technique to obtain initial model parameters, which were used as input for computer iterative modelling using the OFFIX software. The study revealed three (3) to six (6) geo-electric layers with underlying shale beds. Aquifer apparent resistivity in the study area ranges from about 50 to 850 Ωm with the aquifer depth varying between 0.53 - 82.67 m. Similarly, the aquifer thickness in the study area ranges from 0.8 - 110 m, with very low thicknesses around Ajata Ibeku. These shallow aquifers with very small thicknesses in the western areas around Ajata Ibeku are believed to be perched or fractured shale units with very low or no yield. Finally, transverse resistances in the study area range from 200 - 3400 Ωm2 with low values in the western part. Information extracted from iso-resistivity models, geoelectric cross sections, litho logs and electric logs revealed a sandy clay lithology at very shallow depths with a thick layer of shale/clay extending to over 300 m within the western part. These shallow aquiferous units are however perched, partially saturated and may not have sufficient yield. Finally, this study has helped to delineate the aquifers of the study into two distinct zones, thus revealing a groundwater divide.

Frequency-domain electromagnetic sounding with combination wave in near-field zone

By analysing the propagation law of electromagnetic wave,the distribution pattern of the field and the theory of frequency electromagnetic sounding,the physical mechanisms that make the frequency electromagnetic sounding in near-field zone difficult are discussed.Based on the theory of near source field,a new method of dual-frequency electromagnetic sounding of combination wave in near-field zone is advanced.Meanwhile,the method of measurement of fields,the definition of apparent resistivity and the numerical algorithm are approached.

Application of 2-D and 3-D Geo-electrical Resistivity Tomography and Geotechnical Soil Evaluation for Engineering Site Investigation:A Case Study of Okerenkoko Primary School,Warri-Southwest,Delta State,Nigeria

In the design of building structures,joint efforts must be decided to resolve the depth of competent layers across the intended site to safeguard the durability of civil engineering structures and to avert the disastrous consequences of structural failure and collapse.In this study,an integrated methodology that employed DC resistivity tomography involving 2-D and 3-D techniques and geotechnical-soil analysis was used to evaluate subsoil conditions for engineering site investigation at Okerenkoko primary school,in the Warri-southwest area of Delta State,to adduce the phenomena responsible for the visible cracks/structural failure observed in the buildings.The results obtained brought to light the geological structure beneath the subsurface,which consists of four geoelectric layers identified as topsoil,dry/lithified upper sandy layer,wet sand(water-saturated)and peat/clay/sandy clayey soil(highly water-saturated).The deeply-seated peat/clay materials(ρ≤20Ωm)were delineated in the study area to the depths of 17.1 m and 19.8 m from 2-D and 3-D tomography respectively.3-D images presented as horizontal depth slices revealed the dominance of very low resistivity materials i.e.peat/clay/sandy clay within the fourth,fifth and sixth layers at depths ranging from 8.68-12.5 m,12.5-16.9 m and 16.9-21.9 m respectively.The dominance of mechanically unstable peat/clay/sandy clay layers beneath the subsurface,which are highly mobile in response to volumetric changes,is responsible for the noticeable cracks/failure detected on structures within the study site.These observations were validated by a geotechnical test of soil samples in the study area.Atterberg’s limits of the samples revealed plasticity indices of zero.Thus,the soil samples within the depth analyzed were representatives of sandy soil that does not possess any plasticity.The methods justifiably provided relevant information on the subsurface geology beneath the study site and should be appropriated as major tools for engineering site assessment/geotechnical projects.

综合物探方法在碎屑岩地区找水中的应用——以云南宣威大路边村为例

为探索地球物理方法在碎屑地区找水应用的有效性,文章以云南宣威大路边村为研究对象,选取高密度电阻率法、联合剖面法、音频大地电磁法对碎屑岩层进行找水研究。结果表明:三叠系上统飞仙关组(T1f)碎屑岩富水性中等,含水性较均匀;受地面场地狭窄限制,高密度电法及联合剖面法测线长度有限,探测深度较浅,受碎屑岩电阻率小的影响,其找水应用效果不佳,在可探测的深度范围内较难识别基岩裂隙等找水有效异常,需结合其他物探方法甄别异常;音频大地电磁法找水应用效果相对较好,具有较高的横向分辨率,可有效识别碎屑岩中的断裂破碎带及构造裂隙带,表现为相对低阻异常特征;视电阻率单支测深曲线能有效分辨不同深度的岩土层结构,具有较高的纵向分辨率,对裂隙破碎带有较好指示意义。在地面场地较为狭窄的碎屑岩地区开展找水工作,音频大地电磁法结合视电阻单支测深曲线能取得较好效果,以音频大地电磁法确定碎屑岩地区中的裂隙发育带位置,以视电阻单支测深曲线确定裂隙发育带的深度。

基于等值反磁通装置频率域电磁法研究

人工源近区频率域电磁法具有轻便、分辨率高及抗干扰能力强等优点,但提取地质体二次场响应难题困扰了该方法推广应用。基于等值反磁通原理提取二次场响应,首先,推导出了基于等值反磁通原理的频率域近场垂直磁场响应的表达式;然后,采用层状介质与均匀半空间介质的垂向磁场同相分量的比值定义视电阻率,并计算了典型层状介质垂直磁场的频率响应;最后,通过试验对比时间域与频率域方法对浅埋藏铝板的异常响应。研究结果表明:基于等值反磁通原理能够有效提取近场频率域二次场信号,近场垂向磁场的同相分量与大地电导率的二次方成正比;垂向磁场同相分量的比值定义视电阻率能够清晰反映A型、Q型、H型及K型地电断面的特征。

青藏高原东构造结林芝地热田浅部典型电性结构及热储关系

约40 Ma以来,受控于印度板块的俯冲及后期演化,青藏高原喜马拉雅山系东构造结成为了板块活动最强烈的地区之一;由于深部动力学过程中的浅表响应,该地区地热资源极为丰富。笔者等通过对两条音频大地电磁(AMT)测线进行数据处理与分析,查明了测点覆盖区域范围内二维电性结构及主要存在的深大断裂。依据电性结构推测研究区地下1 km深度范围内可分为4层,浅部低阻层为松散砂泥卵石层,下伏的中阻为砾卵石层,其下的低阻为砂岩、板岩、页岩强风化层,最底部的中高阻层推测为古元古界林芝岩群真巴岩组以片岩、花岗岩为主的地层。结合以往大地电磁测深及地震研究发现的地下10~20 km存在大规模近东西向展布且向上延伸熔融流变导致的低速高导体,推测可能是该地区深部热源所在。进一步通过对深部及浅部电阻率模型的综合对比研究,基于地热地质背景、电性结构特征,探讨了该地区的深部热源及热储关系。

粉煤灰陶粒轻质混凝土声屏障性能试验研究

混凝土是一种应用广泛、可使用多种固废制备的建筑材料。本研究将粉煤灰陶粒作为轻骨料,水泥-粉煤灰-硅灰-煤系偏高岭土作为复合胶凝材料,制备用作声屏障的粉煤灰陶粒轻质混凝土,并对其力学性能、吸声性能和抗碳化性能进行试验研究。结果表明:当粉煤灰-硅灰-煤系偏高岭土总掺量为胶凝材料总质量的10%时,试样的力学性能、抗碳化性能有所提高,吸声性能有所降低;随着粉煤灰-硅灰-煤系偏高岭土掺量进一步增加,试样的力学性能、抗碳化性能有所降低,吸声性能有所提高。1500 Hz及以下频率吸声系数变化幅度较小,2000 Hz时吸声效果最好,试样的平均吸声系数在0.44~0.58,降噪系数在0.74~0.89。

超高密度电阻率法与音频大地电磁测深法对贵州普安某萤石矿区断层的探测效果

本文以贵州省普安县莲花山某调查区萤石成矿断层为研究重点,采用超高密度电阻率法和音频大地电磁测深法对同一断层进行了测量,查明了断层的平面分布情况和深部延伸情况,揭露出剖面峨眉山玄武岩组至茅口组“低阻-中阻-高阻”的三元分层电性结构。以峨眉山玄武岩组与茅口组接触带(蚀变体)的中阻特征为识别标志,结合断层延伸情况,推断出萤石矿体埋深范围,得到了钻孔验证。两种方法均对断层探测有较好的效果,也存在优劣势,超高密度电阻率法探测深度浅,测量精度高,但容易出现多种非目标体异常;音频大地电磁测深法探测深度深,但浅部分辨率较差,测量精度较低。实际工作中,应根据勘探目标的埋深情况选择合适的工作方法或综合两种方法,以达到更加可靠的物探解译成果。

大地电磁测深法在冀中坳陷深部碳酸盐岩热储调查评价中的应用

地热资源作为一种清洁能源,在“双碳”背景下,其开发和利用越来越受到重视。为了探查渤海湾盆地的冀中坳陷深部碳酸盐岩的热储条件,笔者等利用3条大地电磁测深剖面,进行了数据处理、分析和反演,获得可靠的二维电阻率模型和电阻率等深度平面图。分析研究区深部电性结构特征及主要断裂构造特征,同时根据基底隆起形成的高阻异常对深部碳酸盐岩分布和埋深进行了推断,并对冀中坳陷深部碳酸盐岩热储进行评价,以圈定地热异常远景区。分析认为:①研究区电性结构可以被划分为5层,其中第5电性层为高阻标志层,对应深部碳酸盐岩基底;②据此圈定了3类深部地热远景区:基岩埋深小于4000 m,如高阳低凸起地热远景区、黑龙口低凸起地热远景区(徐水凹陷)和河间潜山地热远景区(饶阳凹陷),基岩埋深4000~5000 m,如雁翎潜山地热远景区(霸县凹陷),基岩埋深5000~5500 m,如肃宁潜山地热远景区和留路潜山地热远景区;③大地电磁测深方法适用于冀中坳陷深部碳酸盐岩热储远景区的探查。深部热储远景区的圈定,可为后期的地热资源评价和开发利用建立基础。

船用空调阻性消声器消声量计算方法优化的实验研究

在船用空调系统中,由于已有的阻性消声器消声量的经验公式忽视了高频失效效应的影响,使得原有的消声量计算方法在高频段不再适用,为了探究出一个符合船用空调阻性消声器消声量的计算公式,通过分析实验数据,选择一个与模型相适应的经验公式,最终在此基础上结合实际工况对经验公式进行修正与检验。结果表明:当频率处于中低频时,罗杰斯公式的消声量计算值与插入损失值的变化趋势十分接近,误差在4dB左右,但在高频段,由于高频失效效应,经验公式不再适用;其次拟合出来的经验公式修正式,在倍频程下的消声量值与实际工况相互一致,误差低于3dB,满足实验预期要求。

电测深联合剖面法在高铁路基岩溶探测中的应用

采用电测深联合剖面法,对新建莱荣高铁路基岩溶进行综合勘探。该方法结合电测深与联合剖面法的特点,通过测量地下岩层的电性分布,从而准确反映岩溶的位置和形态,且具有横向分辨率高和纵向探测深度可计算等显著优点。将电测深低阻凹陷及联合剖面双线交叉点重叠的位置推测为岩溶发育区,适用于类似地质条件下的路基岩溶探测。探测结果显示,DK11+352~DK11+750段电阻率介于240~560Ω·m,电测深联合剖面法岩溶探测准确率为86.7%;DK11+750~DK12+025段电阻率介于320~1000Ω·m,电测深联合剖面法岩溶探测准确率为50%;路基岩溶综合探测结果准确率为75%。研究结果表明,电测深联合剖面法在路基岩溶探测方面具有较高的精度,为高铁路基岩溶探测提供一种较好的解决方案。

Electrical Resistivity Survey for Predicting Aquifer at Onicha-Ugbo, Delta State, Nigeria

A geoelectric survey employing the vertical electrical sounding (VES) was carried out in parts of Onicha-Ugbo in Aniocha North Local Government Area of Delta State using Abem Terrameter SAS 300C together with SAS 2000 booster. The study was carried out with the aim of delineating the subsurface geologic sequence present in the study area, determining their geoelectrical parameters (layer thicknesses and resistivities), and delineating the structural and geomorphological features present beneath the subsurface. The results of the survey suggest that the subsurface comprises of 5 - ?6 layers and that clay and silt content varies vertically and horizontally, thus influencing the apparent resistivity of the area. The geoelectric section developed shows that the subsurface units are dominantly sandy underlying loamy sandy topsoil which is relatively dry. The depth to water table from the sites is above 150 m and suggests that groundwater exploration is encouraging.

电阻率测深法在咸淡水界面探测中的应用

通过电阻率测深法探测沧州献县的地下咸淡水界面,首先结合水文地质条件的综合研究,通过小四极测试法对工作区内不同岩性地层做了物性测试;根据地下咸淡水界面两侧存在着明显的电阻率差异这一地球物理前提条件,布置了7条测线,并进行反演和解释,查明了研究区地下0~250 m深度咸淡水分布情况。结果表明,区域内咸淡水分界线近NE走向,其西北区面积约1/3范围为淡水区,分界线东南大片面积略超2/3范围为咸水区;咸水区内有3个面积较小的淡水区,咸水与淡水分界面深度总体呈现西浅、逐渐向东变深的趋势,并存在4个下凹幅度不等、影响面积及特征不同的漏斗区。研究证明电测深方法在地下水勘查、咸淡水界面勘查中具有良好的有效性。

激电中梯与激电测深法在多金属矿勘探中的物探响应特征研究与矿化异常圈定——以青海省都兰县沟里乡南多金属矿为例

查明青海省都兰县沟里乡南多金属矿(化)体激电特征,可以为钻探布置提供依据。该研究首先采用激电中梯法对勘探区进行扫面工作,圈定5处(M1、M2、M3、M4、M5)低阻高极化异常,并在现有电物性特征和探槽揭露矿体地质资料的基础上,采用短极距激电测深进一步精细查明矿化异常区的空间展布和埋深情况等。研究发现,激电异常与探槽揭露具有良好的对应性,表明激电中梯和激电测深在多金属矿勘查中有较好的找矿效果。