الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
part of Greater Cairo, the eastern part of the Nile Delta, Egypt. It is located between X-coordinates 350940 and 352171 meter easting and Y-coordinates 3349671 and 3350543 meter northing at Zone 36 UTM-coordinate system. The study area is mainly covered by Tertiary and Quaternary sediments. The exposed section is varied in thickness and increase toward the Nile Delta recording more than 1000 m.
The main objective of this study is to delineate groundwater occurrences depending on identification of the geological formations, geological structures and groundwater aquifers in the study area. The second objective is the use of modern geophysical method (seismoelectric method) which sensitive to the presence of fluids. The third objective is the integration between the different geophysical methods that are shallow seismic refraction tomography, geo-electric and seismoelectric to identify how successful to use seismoelectric method, where it has not been used before in Egypt, by comparing the results of these geophysical methods in the study area. Finally calculation of the near surface soil geotechnical parameters and dynamic characteristics.
The present work is divided into six chapters: Chapter 1 discuss the general geology of the east Nile Delta structure and stratigraphy. The surface geological units represented at the area of study belong to the Quaternary and Middle Miocene ages. Quaternary deposits are represented by sand sheet cover the western part of the study area. The Tertiary deposits are represented by Hommath Formation, which consists of sandy limestone, sandstone and sandy marl of Middle Miocene deposits. The Oligocene deposits are represented by Gabal Ahmar Formation, which is composed of sand and sandstone.The exposed section is varied in thickness and increase toward the Nile Delta recording more than 1000 m. The top portion of this section is mainly sand and clay facies, whereas the lower portion is dominant by carbonate facies.
The study area was affected by the regional structural characteristics of the eastern Nile Delta region. Major unconformities existed between the Mesozoic and Tertiary; between the Tertiary and Quaternary sections. Faults detected in the study area are of normal type that striking mainly in two directions, i.e. the E-W and NW-SE.
The folding has a relatively minor importance and is only recorded at few localities on the surface. East Nile delta region was divided into three different structural zones. These zones are the metastable belts, to the south, the hinge belt in the middle and the mobile belt to the north.
Chapter 2 discuss the using of seismic refraction tomography method to delineate near-surface structures and stratigraphic features that suitable for groundwater aquifers occurrences. Five survey lines of seismic refraction tomography consist of 16 Seismic Refraction tomography profiles are performed at the study area. The collected data are used to estimate the P-wave velocity and surface wave velocity to delineate the near surface ground model beneath the study area. The seismic refraction data were acquired by using 24-channel seismograph as a recording system with 14-Hz vertical geophones and sledgehammer source. The data set comprise 2,688 traces. Seismic refraction tomography survey designed at the study area were consists of five seismic lines with line to line spacing of about 200 meter. Three lines (Line-1, Line-2 and Line-3) lies at the (ENE-WSW) direction while the other two lines (Line-4 and Line-5) lies at the (NNW-SSE) direction. The first line (Line-1) consists of 4 seismic profiles with a length of 800 m and the other lines (Line-2, Line-3, Line-4 and Line-5) consist of 3 seismic refraction tomography profiles with a length of 670 m. each seismic refraction profile has 24 receivers with interval of 7.5m and seven shot points located through each profile with sample rate 500 µsec and total recording time of one second.
The collected shot records were subjected to some processes that are sorting, editing and filtering to increase the signal to noise ratio by using the Geogiga Seismic Pro.8.0, 2015 software. Filtered refraction tomography data (shot records) were analyzed and interpreted using the software program Zond2DST, version 4.0, zond geophysical software.
The velocity-depth models that are constructed by using the smoothed and layered inversion methods indicate a presence of five distinct seismic layers:
Layer 1: The surface layer (Quaternary surficial deposits); its average P-wave velocity is 478 m/sec with average thickness of about 4.93 meter.
Layer 2: The second layer (Miocene Sand); its average P-wave velocity is 614 m/sec with average thickness of about 13.04 meter.
Layer 3: The third layer (Miocene dry deposits (upper part)); its average P-wave velocity is 848 m/sec with average thickness of about 22.26 meter.
Layer 4: The fourth layer (Miocene dry deposits (lower part)); its average P-wave velocity is 1162 m/sec with average thickness of about 35 meter.
Layer 5: The last layer (Miocene aquifer); its average P-wave velocity is 1638 m/sec. Its thickness is not determined where the maximum depth of the seismic refraction survey along the study area reaches its upper surface only but its lower surface obtained by the vertical electrical sounding data.
Two major normal faults named as F1 and F2 trending in the NE-SW direction forming graben between the two faults. The others minor faults named as F3, F4, F5, F6, F8, F9, F10 and F11 trending in the NW-SE direction while another minor normal fault F7 trending in NE-SW direction. All the determined faults affected on the geologic units presented at the study area to reach the Miocene sand layer.
Chapter 3 discuss the identification of the groundwater aquifers and investigation their vertical and lateral extent at the study area, three Vertical Electrical Sounding (VES) using Schlumberger field array carried out through the study area with AB/2 500, 500 and 600 meter are the data acquired using Abem Terrameter SAS 300 resistivity meter. The three VES’s are located along the trends of the seismic refraction tomography lines. That is to integrate and correlate between the results interpreted from each method for enhancing the interpretation accuracy, determine more information about the near-surface layers, get the best real subsurface geological model and determine the groundwater aquifers and their extensions through study area.
Measured data were analysed and interpreted using Moscow State University IPI2win V3.1.2 resistivity sounding interpretation software and Golden Surfer 12 software. The apparent resistivities values ranged from 20 to 300 ohm.m. The highest apparent resistivity values (150-300 ohm.m) found at the upper near-surface horizon. Then, the zone with AB/2 (250-350 m) which represents the dry zone, while the lower part of the section has low apparent resistivity values (20-150 ohm.m) represents the water bearing zone.
Seven geological layers were found, the first geological layer (Quaternary surficial deposites) with an average thikness (3.71 m). The second layer (Miocene sand) with an average thickness (6.44 m) where its thickness increased at the location of VES 1 to reach about (14.1 m). The third layer (Miocene dry deposits (upper part)) with an average thickness (18.77 m). The forth layer (Miocene dry deposits (Lower part)) with an average thickness (44.87 m). The fifth layer (Miocene aquifer) composed of sand and sandstone saturated with fresh water with average thickness (39.40 m). The sixth layer (fractured saturated basalt layers) with average thickness (63.1m). The last layer (Oligocene aquifer) compoed of sand and sandstone saturated with saline water.
Chapter 4 discuss the using of the seismoelectric method to delineate the groundwater aquifers located in the study area. Then making a comparison between the results of the three geophysical methods that are used in this study to accurate determination of the groundwater aquifers in the study area and show at what extend the seismoelectric method has successful application for groundwater exploration since it has not been used before in Egypt.
The seismoelectric survey designed at the study area were consists of ten seismoelectric profiles. These profiles were acquired at the same locations of the seismic refraction tomography lines. Each seismoelectric profile composed of three shot locations (Normal, Middle and Reverse) with a sample interval of 200 µsec and a record length of 400 ms.
The processed seismoelectric records exhibited that there are seven events (A to G) based on the polarity reversal around the shot points location at the shallow part. The averaged layers boundaries (A to G) expected at depths 17.97m, 25.00m, 33.00m, 40.19m, 54.19m, 75.19m and 114.59m, respectively corresponding to averaged one way travel times expected at 31.16ms, 38.34ms, 47.18ms, 55.31ms, 64.58ms, 80.90ms and 97.69ms respectively.
By comparing between the results obtained from seismoelectric data interpretation and that obtained from the interpretation of seismic refraction tomography data and the D.C electrical resistivity vertical electrical soundings data, it is found that the seismoelectric events are identical to the interfaces separated between the layers interpreted from the final models that are deduced from seismic refraction tomography and D.C electrical resistivity models especially in the shallow part of the section. But the seismoelectric events at the deeper part of the seismoelectric records aren’t identified in the model of other two methods because the max depth of the deduced models is lower than the depth of these events.
Finally Chapter 5 discuss the using of MASW method to determine the shear wave velocity. Then using shear velocity and cop velocity to calculate near-surface soil geotechnical parameters that suitable for identification the soil properties. So, the suitable selection for surface casing and well designation of the groundwater wells in the study area is available.
Soil presented in the area of study consists of three layers based on the compressional wave (Vp) and shear wave (Vs) velocities models. Based on the values of compressional and shear wave velocities of the generated velocity models for each seismic line, the geotechnical parameters and dynamic characteristics of the soil layers presented in the study area can be calculated. The generated compressional wave (V_p) and shear wave (V_s) velocity models showed that the soil presented in the study area can be differentiated into three layers according to the change in velocities as follow:
Layer 1: The top layer has an average compressional wave velocity of about 478 m/sec and an average shear wave velocity of about 288.2 m/sec with an average thickness of about 4.93 m where it is composed of sand and gravel which belongs to the Quaternary surficial deposits. Based on the values of V_p and V_s, this layer has an average density of about 1.45g/cm^3 , Poisson’s Ratio ≈ 0.21, Young’s Modulus ≈ 3.42E+09 Dyn/cm^2, Rigidity Modulus ≈ 1.20E+09 Dyn/cm^2, Bulk Modulus ≈ 2.02E+09 Dyn/cm^2, Material Index ≈ 0.16, Concentration Index ≈ 5.89, Stress Ratio ≈ 0.27 and Ultimate Bearing Capacity ≈ 0.91 Kg/cm^2.
Layer 2: The second layer which underlies the Quaternary surficial deposits has compressional wave velocity of about 614 m/sec and shear wave velocity of about 339.60m/sec with an average thickness of about 13.04 m. It is composed of sand that belongs to the middle Miocene Hommath Formation. Based on the values of V_p and V_s it has an average density ≈ 1.54 g/cm^3, Poisson’s Ratio ≈ 0.24, Young’s Modulus ≈ 5.88E+09Dyn/cm^2, Rigidity Modulus ≈ 2.00E+09Dyn/cm^2, Bulk Modulus ≈ 3.79E+09 Dyn/cm^2, Material Index ≈ 0.06, Concentration Index ≈ 5.38, Stress Ratio ≈ 0.31 and Ultimate Bearing Capacity ≈ 1.75 Kg/cm^2.
Layer 3: The third layer which underlies layer 2 has compressional wave velocity of about 848 m/sec and shear wave velocity of about 517 m/sec with an average thickness (22.22 m) it is composed of sand that belongs to the middle Miocene Hommath Formation. Based on the values of V_p and V_p it has an average density of about 1.67g/cm^3 , Poisson’s Ratio ≈ 0.20, Young’s Modulus ≈ 1.25E+10 Dyn/cm^2, Rigidity Modulus ≈ 4.50E+09 Dyn/cm^2, Bulk Modulus ≈ 7.08E+09 Dyn/cm^2, Material Index ≈ 0.19, Concentration Index ≈ 6.27, Stress Ratio ≈ 0.26 and Ultimate Bearing Capacity ≈ 5.13 Kg/cm^2).
It is found that the relationship between the compressional wave (V_p) and shear wave (V_s) velocity models is almost linear represented by straight line equation where (V_s) is direct proportional to the (V_p) multiplied by a constant (0.6014) according to the following equation:
V_S=0.6014 V_P
Finally by comparing between the seismic refraction tomography and geo-electric results with the seismoelectric method we find good matching between the results.