Journal of …, 2006

An integrated geophysical survey was carried out in a new dwelling area at 15-May town, southeast Cairo, Egypt. The buildings in this area are intensively affected by dangerous cracks that cause structural instability. The survey aimed to image the shallow subsurface structures, including karstic features, and evaluate their extent, as they may cause rock instability and lead to cracking of the residential buildings. Resistivity profiling (2-D), using a dipole-dipole array and ground penetrating radar (GPR) surveys were carried out along seven parallel traverses extending about 150 meters between the buildings blocks. Additional measurements using a Schlumbereger array and very low frequency electromagnetic (VLF-EM) methods were conducted. The acquired data were processed and interpreted integrally to elucidate the shallow structural setting of the site. Integrated interpretation led to the delineation of hazard zones rich with karstic features in the area. Most of these karstic features are associated with vertical and sub-vertical linear features such as faults, fracture zones, and geologic contacts. These features are the main reason of the rock instability that resulted in potentially dangerous cracking of residential buildings.

Environmental Earth Sciences, 2014

Geophysical techniques such as gravity, magnetic and seismology are perfect tools for detecting subsurface structures of local, regional as well as of global scales. The study of the earthquake records can be used for differentiating the active and non-active fault elements. In the current study, more than 2,200 land magnetic stations have been measured using two proton magnetometers. The data are corrected for diurnal variations and then reduced by the International Geomagnetic Reference Field. The corrected data have been interpreted by different techniques after filtering the data to separate shallow sources (basaltic sheet) from the deep sources (basement complex). Both Euler deconvolution and 3-D magnetic modeling were carried out. The results of interpretation indicate that the depth to the upper surface of basaltic sheet ranges from \10 to 600 m, depth to the lower surface ranges from 60 to 750 m, while the thickness of the basaltic sheet varies from \10 to 450 m. Moreover, gravity measurements are conducted at 2,250 stations using a CG-3 gravimeter. The measured values are corrected to construct a Bouger anomaly map. The least squares technique is then applied for regional-residual separation. The third order of least squares is found to be the most suitable to separate the residual anomalies from the regional one. The resultant third-order residual gravity map is used to delineate the structural fault systems of different characteristic trends. The trends show an NW-SE trend parallel to that of Gulf of Suez, an NE-SW trend parallel to the Gulf of Aqaba and an E-W trend parallel to that of the Mediterranean Sea. Taking seismological records into consideration, it is found that most of the 24 earthquake events recorded in the study area are located on fault elements. This gives an indication that the delineated fault elements are active.

International Journal of Geosciences, 2017

New Sohag City has an area of approximately 1300 acres (546 hectares) and is located within Sohag Governorate limits, about 18 km away from old Sohag City. It is established to reduce the population within the old Sohag city and to create better economic conditions in a new appropriate living environment. The main target of this study is to apply the relevant surface geophysical methods to image the shallow subsurface setting, to define the shallow lithological layers and to locate any geological structures that may be cause cracks in buildings, and any unstable materials, which may decrease the bearing capacity or human activities, hence increasing hazards in the study area. This study embraces, Electrical Resistivity Tomography (ERT), Shallow Seismic Refraction (SSR), and Ground Penetrating Radar surveys (GPR). The integrated interpretation of all techniques classified the subsurface layers into two layers. A strong reflector separating the upper gravel and calcareous sandy layer from the lower clayey layer. They gave also interesting information about the geotechnical competent of the ground and some structural features in the study area.

Arabian Journal of Geosciences, 2013

The flood plain of the Nile River has been a safe dwelling throughout history. Recently with a growing population and vast growing urbanization some buildings have started to experience structural damages, which are not related to their construction design, but rather to the ground conditions around the buildings' foundations. Variations in properties of the soil supporting the buildings' foundations such as soil bearing capacity, moisture content and scouring may eventually lead to the failure of these buildings. This study is attempting to characterize the variations in the soil properties around the City Star shopping mall, in eastern Cairo, where a large building has tilted over the past few years. This tilting may lead to the collapse of the whole building if it continues at the same rate. An integrated geophysical investigation including multi-channel analysis of surface wave (MASW), ground penetrating radar (GPR) and 2-D electrical resistivity tomography (ERT) was used around the affected building to help detect possible causes of deterioration. The GPR data showed a soil-fill layer overlaying a thick bottom layer of higher moisture content. The MASW data revealed a middle layer of relatively low shear wave velocity sandwiched between two relatively high shear wave velocity layers. The ERT data showed an upper low resistivity layer overlying a high resistivity layer. Integrating the interpretations of the three geophysical methods provide a combined model that reflects lateral and vertical variation in the soil properties. This variation becomes dramatic near the tilted corner of the building.

Natural Hazards and Earth System Sciences, 2005

An integrated geophysical survey using both the electrical resistivity tomography (ERT) and ground-penetrating radar (GPR) methods was undertaken over a cave of great archaeological interest in southern Italy. The survey was performed to assess the stability of the carbonate rock roof of the cave. A geophysical survey was preferred to boreholes and geotechnical tests, in order to avoid the risk of mass movements. The interpretation of integrated data from ERT and GPR resulted in an evaluation of some of the electromagnetic (EM) characteristics (such as the EM wave velocity) and the detection of discontinuities (fractures) in the carbonate rock. It is well known that rock fractures constitute a serious problem in cave maintenance, and progressive cracking within the bed rock is considered to be one of the main causes of collapse. An analysis of the back-scattered energy was also required for the GPR data interpretation. Cracks within the bedrock were detected to a depth of about 2 m by using GPR, which allowed for the identification of the loosened zone around the cave.

GeoScience Engineering

Building collapse has been a recurrent environmental hazard in Nigeria in the last two decades. This is a corollary of inadequate foundation investigation prior to construction, poor government policies, and general lack of awareness on the importance of geophysical and geotechnical investigations. In this study, geological mapping and detailed geophysical investigation using Electrical Resistivity Imaging (ERI) and Vertical Electrical Sounding (VES) were carried out to understand the suitability of proposed building sites at the main campus of the Olabisi Onabanjo University (OOU), Ago-Iwoye, Nigeria for construction. Both Wenner array and dipole-dipole were used for profiling and Schlumberger for sounding. Four transverses and VES were used in each of the three areas investigated. Our results show that the subsurface of the study areas is underlain by Precambrian basement rock of Nigeria. Rocks in the study area include banded gneiss, porphyroblastic gneiss, biotite-hornblende gra...

International Journal of Geosciences, 2013

A geophysical survey involving the electrical resistivity method utilizing the Vertical Electrical Sounding (VES) and Electrical Imaging Techniques was conducted around the premises of an area within southwestern Nigeria with the aim of studying structural defects which may be responsible for future problems and characterizing the soil conditions of the site. A total of 15 VES stations were occupied using Schlumberger Configuration with AB/2 varying from 1 to 65 m. In the electrical imaging, dipole-dipole array was adopted and the two traverses were occupied in the S-N and E-W directions close to where wall cracks and subsurface problems were manifested. Five main geoelectric sequences were delineated within the study area; these include the topsoil (clay and sandy clay), lateritic clay, weathered bedrock (clay, sandy clay and clayey sand), fractured bedrock and fresh basement. A major discontinuity (fracture zone) was discovered along the S-N direction, while a weak zone was also discovered along E-W direction. The result of this research has shown that the causes of the cracks and distress on the walls within the site may have been influenced by the differential settlement resulting from the incompetent subsoil materials and the fractured bedrock on which the foundation of the building was laid.

SUMMARY Geoelectrical measurements were used in association with soil engineering tests in environmental engineering investigations at Tenth of Ramadan city, east Nile Delta, Egypt. The genetic algorithm (GA) approach with structure-based (SB) model is applied towards an optimal interpretation of DC resistivity measurements. The inverted models together with borehole data and soil classification exhibit two soil types, gravelly sand and clayey sand with free lime. The survey demonstrates that the combined use of the GA with SB model provides valuable information to constraint the number of interfaces. The reliable resistivity inversion results are considered as a key role in studying the geotechnical parameters such as Atterberg limits unconfined compressive strength and swelling tests. The clay sediments are described by medium plasticity and sensitivity for swelling. Further, the free lime with water makes gill action with decreasing the compressive strength. Therefore, such soil, in turn, may cause soil water appearance on the ground surface and geotechnical problems during or after the process of any construction. In this respect, the integration of the geoelectrical survey with soil engineering properties is efficient and less time consuming for characterizing the engineering-geologic zone.

Geoelectrical measurements were used in association with soil engineering tests in environmental engineering investigations at Tenth of Ramadan city, east Nile Delta, Egypt. The genetic algorithm (GA) approach with structure-based (SB) model is applied towards an optimal interpretation of DC resistivity measurements. The inverted models together with borehole data and soil classification exhibit two soil types, gravelly sand and clayey sand with free lime. The survey demonstrates that the combined use of the GA with SB model provides valuable information to constraint the number of interfaces. The reliable resistivity inversion results are considered as a key role in studying the geotechnical parameters such as Atterberg limits unconfined compressive strength and swelling tests. The clay sediments are described by medium plasticity and sensitivity for swelling. Further, the free lime with water makes gill action with decreasing the compressive strength. Therefore, such soil, in turn, may cause soil water appearance on the ground surface and geotechnical problems during or after the process of any construction. In this respect, the integration of the geoelectrical survey with soil engineering properties is efficient and less time consuming for characterizing the engineering-geologic zone.

Due to a rapid increase in the population during the last few decades, the banks of the Nile River and its delta have reached maximum capacity. As a consequence of this increase, the Egyptian Government has constructed a number of new urban areas and industrial cities outside the Nile Delta. New Borg El-Arab City is one of these new industrial cities. This city is located around 60 km southwest of Alexandria City. This industrial city is proposed to include an airport, a number of factories, worker settlements and heavy truck roads. Therefore, a detailed study of site characterization should be performed before construction being in order to. The main target of this study is to determine the dynamic characteristics and geotechnical parameters at the proposed site using seismic refraction and electrical resistively techniques. Analysis and interpretation of the obtained results reveal that the subsurface consists of three layers with a gentle general slope toward the Mediterranean Sea. The classification of rock material for engineering purposes reveals that the study area is divided into three zones. A. A. Basheer et al. 21 km 2 . This new industrial city is an urbanization project that is relatively large-scale regional development project and it will be good if the determination the dynamic characteristics and geotechnical parameters being incorporates in the planning stage. So, the main target of the present study is investigating the shallow subsurface structure conditions, the dynamic characteristics and geotechnical parameters of subsurface rocks using shallow seismic refraction profiling and electrical resistivity tomography surveys. The output of this study is very important for solving problems, which associated with the construction of various civil engineering purposes, land use-planning and earthquakes resistant structure design. The integrated interpretation of these techniques classifies the subsurface succession into three layers.