Geophysical Approach in the Geological Characterization of Chebabta Dam, Northeast-Algeria (original) (raw)
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Journal of Applied Geophysics, 2020
In foundation research of engineering structures, application of geophysics methods before drilling work allows not only more economical studies but also a more detailed determination of underground sections. Especially in pre-feasibility studies on long tunnel routes, dam sites and lake areas, it has a vital importance in terms of structural safety to determine possible underground buried fault lines, lithology changes, anticlinal-synclinal structures and underground openings. By considering these effective factors, the alluvium/bedrock border and the positions of potential buried faults in the dam site and lake area in the Kırklartepe area of the province of Bayburt in northeastern Turkey were determined by comparison with geophysical and geotechnical methods. First of all, the resistivity of the dam axis location and the change of the V p wave velocity by depth were determined by comparing the results between geophysical methods of electrical resistivity tomography (ERT) and seismic refraction tomography (SRT), respectively. Afterwards, from the foundation boreholes opened in the dam axis location, joint frequency and the other parameters determined by observations were obtained. With these parameters, 2-dimensional zoning profiles of the dam axis location were formed, and the alluvium-bedrock border and the locations of the buried faults were determined. Two potential faults in the NW-SE direction relative to the location of the dam axis were clearly revealed in the zoning profiles obtained in the ERT and SRT measurements. Additionally, the presence of these faults was determined as a result of examining the separation and joint frequency parameters from the drilling core samples collected from the BH_3 and BH_5 boreholes opened in the investigated area based on changes in the vertical and horizontal directions. In addition to these, in the ERT study, two potential faults other than the determined two were also detected. It was seen in the zoning profiles that these faults corresponded to right under the BH_2 borehole and 60 m SW of the BH_6 drilling. Consequently, in the zoning studies conducted at the examined site, the change in the lithology at the dam axis by depth (alluvium-bedrock border), lateral correlations of boreholes and potential faults were determined. It was recommended for the selected dam axis location to be constructed at a more suitable place in the NW direction in terms of engineering. Furthermore, with this study, it was revealed once again that it is highly essential to use geophysical and geotechnical together in conceptualizing large engineering structure projects.
researchgate.com, 2023
Over the past few decades, climate change and population growth in semi-arid regions, especially in the Middle East, have caused water shortages. To mitigate this problem, an increasing number of dams have been constructed. The Kurdistan Regional Government (KRG) decided to build forty dams to control water shortages and drought problems and decrease the of effect climate change. The site selection for all these dams requires geological engineering, hydrology, metrology, and satellite image studies. The selected river basin in this study (Kanarwe) is considered the priority location for dam construction by the KRG in the future. The Kanarwe River Sub-Basin (KRB) is part of an enormous transboundary watershed called the Lesser Zab River Basin (LZRB) with 750 mm annual average rainfall. It covers about 1542 km2, of which 83% is located within the Iraqi border and 17% is located within the international border of Iran. This dissertation concludes the best site for dam construction on the Kanarwe River based on three aspects: hydrological conditions, geophysical, and engineering geology studies within the lesser Zab Basin. The first aspect is a hydrological perspective aimed at estimating the catchment area, the volume of water, the peak flood, and the peak time based on different unit hydrographs (UH). The HEC-1, HEC-HMS, Snyder model, TR55, Soil Conservation Service (SCS-CN), and Rational Unit Hydrographs are selected to calculate the peak flood and peak time in the KRB basin. The results of the peak discharge and the peak time of the HEC-1 and HEC-HMS models gave similar results: Qp=739.93m3/sec, Tp=20hrs; Qp=800 m3/sec, Tp=12hrs, respectively. The results from TR55 are Qp=181.1m3/sec; Tp=14hrs, while the Rational and Snyder's models are somewhat close to each other; they are Qp = 341.13 m3/sec, Tp=11.65hrs; Qp=443m3/sec, Tp=19.9hrs, respectively. Comparing these model results with observed data 263 m3/sec (Gumbel Approach) reveals that Snyder, rational and TR55 are more accurate because these three models work more with geographic location, climatic data, and geomorphic parameters. The second aspect is an electrical resistivity 2D tomography survey to detect cavities or faults. Different traverses were taken at the dam site (left side, right side, and foundation), and the data were processed with ProsysII and Res2Dinv. The results show three zones of resistivity, with the first low resistivity zone ranging from 15 to 45 Ohm. m that they are siltstone and marl of the Tanjero Formation. The second zone is a moderate resistivity zone ranging from 45 to 90 Ohm. m, that they are Sandstone and Siltstone of the Tanjero Formation. The third resistivity iv zone, ranging from 90 to 450 Ohm. m is the limestone of the Aqra Formation. The result of the profile inversion shows that there is no cavity or fault detection at the dam site. The third aspect is applying an accurate rock mass evaluation for the proposed dam site, composed of an interlayer of limestone rocks (Aqra Formation) and flysch rocks (Tanjero Formation). Three rock mass classification systems are used to evaluate rock masses at the site: geological strength (GSI), dam mass rating (DMR), and rock mass rating (RMR) geomechanical classification systems. The results of the GSI value for rock masses in twenty units at the dam site reveal that the values of the carbonate rocks of the Aqra Formation are between 74 and 77, while the flysch rocks of the Tanjero Formation give a lower value of 45 to 55. The strength properties of all rock mass units were determined by the Hoek-Brown failure criterion using the RocLab program. The DMRSTA, which indicates the stability of the rock foundation of the Aqra Formation, ranges from 70.4 to 83.4, and for flysch of the Tanjero Formation ranges from 43.7 to 60. These values indicate no stability problems except for some flysch rock masses. The foundation excavation desirability and consolidation grouting evaluation was done based on RMRDB. It indicates that limestone units are suitable for gravity, rock-fill, earth-fill, and Arch dams; meanwhile, the clastic rocks required systematic grouting for Arch dams and spotted grouting for gravity dams. The rock mass units were evaluated based on the ratio of the dam's deformation modulus and the deformation modulus of foundation rock mass (Ec/Em) to determine site suitability for dam types. This ratio for different limestone rock mass units ranges from 0.3 to 0.93, indicating that the site is suitable for different kinds of dams such as gravity, fill, and arch. While the (Ec/Em) for clastic rock ranges from 1 to 6.4, indicating that some units have a serious problem that needs treatment. The DMRDEF (RMR related to relative Deformability) values are 69.3–80.2 for limestone units. However, the DMRDEF value for clastic rock mass units ranges from 40-50, and these values generally show no deformability problems. A new procedure and classification were suggested for quantifying stress relaxation and damage level (disturbance factor D) in rock masses as a novelty for this dissertation work, where calculating the rock mass disturbance factor is based on the joint spacing and strength index (Is50) of the intact rock, and the new disturbance factor is used in Hoek et al. (2002) equation and RocLab software feature to evaluate the foundation rock masses. Based on the hydrological, engineering geological, and geophysical assessments for the Kanarwe River Basin and the proposed dam site, the site is very convenient for the construction of different types of dams with a height of 80 m from the valley floor of 817 m, and the water v level in the reservoir will reach an elevation of 897 m above mean sea level and the dam storage volume reach to 440 MCM. Finally, due to the near location of the proposed dam from Sulaymaniyah City, it will provide fresh drinking water and create a good space for tourism in the future.
Geophysical study of the Chame-Rezan Dam Site, Sulaimaniyah City, NE IRAQ
2013
A 1D and 2D resistivity surveys were carried out over the area of Chame Rezan dam site which is located about 33 km to the Northwest Sulaimaniyah City, NE Iraq. Schlumberger array were conducted in 34 locations with AB/2 spacing equal to 200m, as well as two representative Winner-Schlumberger profiles were laid out with electrode spacing equal to 5 m. The study concluded that the combination of 1D and 2D resistivity surveys is successful in identifying and producing a complete high-resolution image of the subsurface. The results were obtained show excellent correlation with the several bore holes were drilled on the recommendation of the surveys. The depths obtained by interpretation of 1D sounding points is slightly smaller than the actual depths recorded from the boreholes at the location of both dam abutments where the dip of the beds is ranging from 40 to 70 degrees. Consequently more reliable depths are obtained in the same locations from 2D resistivity profiles as well as the ...
Environmental Geology, 2001
Vertical electrical sounding and seismic refraction geophysical surveys were conducted on the northeast Badia of Jordan over the location of a proposed dam, as part of a national project to develop the Jordan Badia at the same national level. The objective of the study was twofold: (1) to evaluate the possibility of mapping of volcanic medium in areas where little is known about the subsurface geology and to infer a shallow geological structure from the geophysical data interpretation, (2) to identify formations that may be present, and subsequently estimate the relationship between groundwater resources and geological structures. Geoelectrical data collected at 12 locations and refraction data collected along two pro®les were interpreted utilizing both manual and automatic techniques. Vertical electrical sounding data were pieced together along the survey lines to make a geoelectrical cross section. From the surface down, the cross sections reveal a thin layer of alluvial and wadi sediments, alluvial fans, alluvial mud¯ats and soils of Holocene to Recent age with high resistivity values. A layer of dense basalts of medium resistivity values, 100±400 Wm, was recognized beneath the upper unit. Porous and fracture volcanic tuff bodies that have high resistivity value signatures were resolved at different depths along the eastern and western¯anks of Wadi Tahawi. The seismic refraction data reveal three different units. From the surface down, the upper unit was 20±35 m thick and the velocity was 3,710±3,800 m/s underlain by a 20-m-thick low velocity unit of~1,560±2,000 m/s and lower dense basalt unit with a velocity ranging from 4,400 to 4,580 m/s.
The Role of Geological Investigations for Dam Siting: Mosul Dam a Case Study
Geotechnical and Geological Engineering
Dams are engineering structures constructed for different purposes. They are of different sizes, shapes and types. In all cases, many essential studies should be carried out before deciding the location, type and size of the dam. Among those studies is the geological investigations which should be carried out to deduce the geological conditions in the most relevant site, depth of the foundations and their types, cut-off depth, type of the available construction materials, and type of the expected geological hazards. Without proper geological investigations, the siting of a dam will cause serious hazards during construction and during commissioning of the dam. In this study, Mosul Dam case is considered as the consequences of inadequate geological investigations which were carried out by the contractor and supervised by Swiss Consultant. The location of the dam site and its foundations are built over a highly karstified area, where gypsum and limestone beds are exposed and exist deep...
Geologic problems related to dam sites in Jordan and their solutions
Engineering Geology, 1995
The geologic structures associated with several selected dam sites in Jordan and the tectonic effects on dam foundations and reservoir margins are reviewed. Rock defects, especially discontinuities represented by faults and closely spaced, open joints are investigated. Related problems, such as loss of water from the reservoir by seepage and leakage within the dam foundation are evaluated. The regional seismicity is analyzed and a design earthquake is established for each dam site.
Al-Jawadi, A.S., Abdul Baqi, Y.T. & Sulaiman, A.M. (2020). Qualifying the geotechnical
Qualifying the geotechnical and hydrological characteristic of the Bandawaya stream valley – Northern Iraq, 2020
In northern Iraq, countless non-abuse stream valleys can be used to store water for a variety of purposes; domestic, supplementary irrigation, and recharging groundwater. Bandawaya is one of the stream valleys, which form the first perspective has excellent quality. The location of the suggested dam has been evaluated by hydrological and geotechnical studies. Geotechnical studies included measurement of all the parameters related to the rock mass classification for evaluation based on four classification systems, which are the Q-System, the Rock Mass Rating RMR, the Geological Strength Index GSI, and the Rock Mass Index RMi. The classification results indicated that the rocks of the valley are good for constructing a dam on them, with some weak zones that may affect the integrity of the dam, which the study recommended treating before starting the construction of the dam. According to preliminary studies on different dam’s heights the qualification demonstrates an excellent choice of the site. Four stream orders are recognized, dendritic pattern in the southern part of the watershed, and trellised in the northern part. Three heights assumed to the proposed dam 450, 460, 470 m.a.s.l. with 640764, 3429787, 8590763 m3 storage capacity respectively. According to Rock Mass Rating RMR and Geological Strength Index GSI, the rock mass of the study area is evaluated. The findings illustrate the excellent selection by geotechnical, hydrological, and engineering features of the dam place.
Investigation of the Geological and Geotechnical Characteristics of Daroongar Dam, Northeast Iran
Geotechnical and Geological Engineering, 2011
This paper discusses the results of the engineering geological and geotechnical investigations that have been carried out at the Daroongar dam site. According to the geomorphology and geological conditions and economic reason, the dam has been designed as an earth dam with a clay core. The dam foundation is composed of a sequence of sandy limestone and limy marl of the Upper Cretaceous period. This study is based on field and laboratory investigations, surface discontinuity surveying, drilled borehole data and permeability of dam foundation. The present studies include the evaluation of the dam foundation by water pressure tests. The water pressure tests indicate the necessity to provide a grout curtain below the dam foundation.The geology of the Daroongar dam foundation has a significant influence on the permeability and groutability characteristics. The permeability of jointed rock masses is strongly depended on joint characteristics; degree of jointing, opening, continuity and presence of filling materials. The laboratory tests included tests for unit weight, porosity, uniaxial, triaxial, tensile strength and deformation parameters. The strength and modulus of elasticity of rock masses were determined using the Hoek-Brown empirical strength criterion. The rock mass qualities and classifications of the dam site is assigned using the rock mass rating (RMR), the rock quality (Q) and the geological strength index (GSI) classification systems.
Geophysical Methods and their Applications in Dam Safety Monitoring
Journal of Earth Sciences and Geotechnical Engineering, 2020
The use of geophysical methods in dam sites investigations and safety monitory has proved their good value and versatility in many earthfill dam sites as early as the 1920s. In the following years great development has occurred in the methods, application procedures and tools used. They may be considered today as good ways for carrying out observation tasks on existing dams in non-intrusive and much faster and cheaper ways than the traditional geotechnical methods. It is possible using them to discover anomalies in the dam body or its foundation at an early stage and allowing quick intervention repair works. These methods seek to register and present variations in the basic geotechnical material properties in dams such as; bulk density, moisture content, elasticity, mechanical properties of rocks, electrical resistivity and mineralogy and magnetic properties and so forth. Such variations can indicate increasing seepage flow, progression in cracks’ sizes, formation of voids, caverns ...
Application of Combined Geophysical Methods for the Examination of a Water Dam Subsoil
Water
The paper presents the results of geophysical measurements that were carried out in the vicinity of the water dam/water reservoir supplying the city of Bielsko-Biala with drinking water. The measurements were performed in order to non-invasively detect faults, fractured zones and areas filled with breccia, which may be, at the same time, a preferential path of groundwater flow. The aforementioned factors influence the stability of the dam. The general identification of the examined media was realized by the electrical resistivity tomography method. The ERT surveys were supplemented by capacitively-coupled resistivity. The electrical methods allowed them to recognize geological settings, indicate possible fault locations, and point out the fault plane as a path of water flow. The ground penetrating radar method detected fractured and filled water areas and underground water paths in the dam’s forefield as a result of the method’s very high resolution. The high resolution seismic refl...