الفهرس 
INTRODUCTION AND GEOLOGICAL OVERVIEWOnly 14 pages are availabe for public view
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Abstract
The present work comprises geological and engineering geological studies carried out at the Ain Sukhna area which lies in the eastern side of the Northern Galala Plateau. The coastal strip of this area is currently subjected to intense constructions representing the most promising new urbanized area. The studies comprise the delineation of geomorphological, lithostratigraphical, structural, and geotechnical characteristics of the study area as well as the stability of the existing rock cut slopes. Moreover, several samples of different lithologies were collected from the foundation bed in the northeastern part of the study area that belongs to the Paleozoic age. These samples were subjected to laboratory testing to determine the geotechnical characteristics.
Geomorphologically, the high-land of the study area is represented by the Northern Galala Plateau, while the low-land area comprises the coastal plain along the Gulf of Suez including alluvial fans. The intermediate area between high- and low-lands is a slope area represented by the eastern scarp of the Northern Galala Plateau. The slopes range from steep to gentle with several slope breaks along the slope profile.
Stratigraphically, the exposed stratigraphic rock units throughout the study area are dominated by Upper Paleozoic, Mesozoic and Cenozoic outcrops. The Upper Paleozoic rock units are represented by the Aheimer Formation and the lower part of Qiseib Formation while the upper part of Qiseib Formation represents the Triassic rock units. The Mesozoic rock units are of Cretaceous age and are referred to as Malha and Galala formations as well as the Wata Formation from oldest to youngest, respectively.
The Paleozoic (Permo-Carboniferous Aheimer Formation) strata are made up mainly of varicolored marine sandstone, siltstone, shales, claystone beds and minor carbonate bands of dolomitic composition. The Aheimer Formation (Upper Pennsylvanian-Lower Permian) underlies the red beds of Qiseib Formation (Permo-Triassic). The upper part of the Qiseib Formation is possibly of Triassic age. The Qiseib Formation is made up of brown, reddish brown and purple, fine to coarse-grained sandstones intercalated with varicolored alternating beds of claystone, siltstone and shale.
The Upper Jurassic strata are not exposed in the study area. On the other hand, the Cretaceous successions are represented by Malha, Galala and Wata formations. The Lower Cretaceous rock units are recognized by the non-fossiliferous bright varicolored sandstone sequence of the Malha Formation (Aptian-Albian) which unconformably overlies the Qiseib Formation. The Upper Cretaceous rocks of Galala Formation (Cenomanian) comprises alternating green shale and yellow marl beds. The Galala Formation beds are conformably overlain by the Turonian lithofacies represented in the
area by the marine dolomite and limestones alternating sequence of the
Wata Formation that unconformably underlies the Eocene rock units.
The Lower Eocene succession is represented by Thebes and Minia Formations from the oldest to youngest, respectively. The Thebes Formation is composed mainly of white limestone with some nodules and bands of chert. The Minia formation is made up of hard, massive, fossiliferous, white to light grey argillaceous limestone and dolomitic limestone with dolomite and thin beds of laminated chalky limestone at intervals. The rock units of Minia Formation conformably overly the Lower Eocene rocks of Thebes Formation. Oligo-Miocene basaltic dykes were found intruding older rocks in the study area.
The Quaternary sediments are the most recent deposits in the study area. These sediments are represented by wadi deposits and alluvium which are composed of mixtures of sand, silt and clay sediments with different sizes of gravels.
Field studies on the Ain Sukhna area, Northern Galala Plateau, included the construction of a geological map and engineering geological map. The structural elements affecting the rock units of the study area are represented by normal faults and associated joints. The dominating joint sets in the study area are oriented northwest to north- northwest, north-south, west-northwest, northeast to east-northeast, and east-west according to the degree of predominance. The dip amounts of joints range from 10° to 90°.
A total of twelve faults affecting the Paleozoic, Permo- Triassic, Cretaceous, Eocene and Oligo-Miocene rocks throughout the
study area were mapped with a scale of 1:25,000. The mapped faults have a normal dip-slip displacement including one listric normal fault. The fault systems are arranged according to the degree of predominance into three main sets oriented northwest, northeast, and north-south. The northwest striking fault set is oriented from N118° to N169° and range in length from 1 to 10 km. The dip angles of these faults range between 60° and 70°. One of these major faults is a listric normal fault that form a tilted fault block and half graben on the hanging wall. The northeast fault set are oriented between N040° and N046° and range from 1 to 1.6 km in length. The dip angles of these faults range from 60° to 72°. The north-south fault set are oriented between N178° and N180°. These faults range in length from 1.4 to 4.3 km with dip amounts ranging from 54° to 75°.
Furthermore, a major fault block (Abu Darag block) is observed along the coastal strip, in the northeastern part of the study area. The northern part of this block is composed of Cretaceous rocks of the Wata Formation at the upper part and Galala and Malha formations at the lower part. The southern part is made up of the Paleozoic rock units of the Aheimer Formation. The southern margin of the fault block is bounded by the east-west, north dipping fault zone. The northern margin of the fault block is controlled by the north-south, east dipping fault zone.
The geotechnical parameters of the collected samples from the Paleozoic units (Aheirmer Formation) at the foundation bed were studied. The studied Paleozoic section is subdivided into five units from base to top into the shale and sandstone unit (SC), white soft sandstone unit (WS), varied colored clay and claystone unit (C), yellow
massive sandstone unit (MS), clays and white sandstone unit (SO). These units are intercalated with some quartzite layers or lenses at different intervals particularly at the upper unit (SC) and lower unit (SO) of the studied section. The lab testing results reveal that their initial moisture content is variable and ranges between 2.08% and
2.42% for clay and claystone samples, and the values decrease for the sandstone samples from 0.2% to 0.9%. Moreover, the values of specific gravity and bulk density of these samples show minor variations with an average of 2.45 and 2.14 gm/cm3, respectively. The Atterberg limits show that the mudstone and claystone have relatively low liquid limits (average 28.28%) as compared with low plastic limits (average 19.5%) of these samples. The plasticity of the studied samples is supported by their low average plasticity index (8.77%). It is concluded that the clayey samples are low to medium swelling potential which may be also confirmed by the low values of shrinkage limit (average 16.85%). In contrast, the swelling behaviors of the mudstone and claystone were examined using free swell test as indirect methods to assess their swelling characteristics. Also, the test results show that the samples have medium to low free swelling properties (average 33.11%). On the other hand, the Schmidt hammer (L-type) was used in the field to estimate the uniaxial compressive strength (UCS) for the Paleozoic rock samples. The higher value of UCS is recorded for quartzite samples of the unit (SC and SO) ranging from 68 MPa to 90 MPa. Whereas, the lowest strength value of 12.5 MPa is recorded for the white sandstone samples collected from the unit (WS). The measured strength values of different sandstone samples of the unit (SC) range between 33.3 MPa and 60 MPa. The massive sandstone samples of the
unit (MS) show strength values range from 45 MPa to 61.5 MPa. Moreover, the recorded strength of claystone samples of the unit (SO) is 20.5, and the strength of sandstone samples ranges between 30 MPa and 49.5 MPa of the same unit. Based on this geotechnical study, the sandstone of the unit (SC) and massive sandstone layers in (MS) unit represent good rock layers for the foundation bed. Other rock units including white sandstone, shale and claystone rocks constitute a poor rock and cannot be used as foundation bedrock.
The different rock units of the study area are categorized using some rock mass classifications such as Rock Mass Rating (RMR), Geological Strength Index (GSI) and Tunnel Quality Index (Q-system) based on the numerical ratings. Based on RMR classification and considering the general conditions of the groundwater that are almost dry on the surface, the rock mass quality of the sandstone, dolomitic limestone and dolomite rocks are good rocks (class II). The shales and claystone of different rock units are considered poor rocks (class IV). Moreover, the marl and siltstone are fair rocks (III) which are occasionally present. The GSI values are estimated from the RMR classification and confirmed by the proposed chart of the GIS classification. A GSI range evaluated for different rocks mass corresponding to 60-64 for sandstone and 27-30 for shales and claystone, high value up to 40 and 43 for marl and siltstone rocks. However, the GSI value for the dolomites and dolomitic limestone reaches 72 and 69 for limestone.
In the study area, a cut and cover tunnel at Wadi Abu Darag area is selected to study the RMR-ratings, Q-system and stand-up concept for its rock units and suggest the required support. The tunnel is
excavated through two different rock units; the black shale in the lower part (invert level) and sandstone in the upper part of the tunnel wall. So, the rock quality of the sandstone of Aheirmer Formation is classified as a good rock (class II) while the shale, claystone and black shale are a very poor rock (class V). Hence, the recommended wall support of the sandstone is (class I) which represents sport bolting for unstable blocks at the upper part of the tunnel wall. Whereas, the suggested support for the black shale at the invert level is (class V) of fiber reinforced shotcrete of thickness ranging from 9cm to 12cm with bolting. These recommended supporting measures are necessary to ensure tunnel stability during and after excavation. The stand-up time concept is studied for the same tunnel to assess tunnel stability during construction. Based on this concept, the black shale (on the lower part) of the tunnel could be a long surviving rock for 1 day with a span distance ranging from 1.5m to 2m. While, for sandstone (at the upper part) of the tunnel could be long surviving rock during one year with a span distance ranging from 5m to 6m. It is recommended that, the unsupported span during excavation works shall be less than 5m as the sandstone at the upper part of the studied tunnel.
The slope stability analyses are carried out on the eastern side of the Northern Galala Plateau, particularly along a part of the Ain Sukhna-Zafarana highway. Slope failures were studied and each type was analyzed through predicting the failure type and its kinematic and deterministic analysis, and then a suggestion of mitigation and supporting measures for the unstable parts is documented. The slope rock mass consists of the Paleozoic sandstone and claystone interbedded rock units at the base and the Cretaceous-Eocene carbonate
rock units at the top. The rock masses of the study area produce a different style of slope failure due to the presence of unfavorable discontinuities with respect to the existing cut slope orientation. The planes of discontinuities and the cut slope orientation are plotted using stereographic projection to identify the possible pattern of slope failures. The deterministic analysis is carried out for the expected slope failures in order to calculate the factor of safety (FS) for planar and wedge failures using available software.
Assessment and analyses of the studied rock masses reveale that the planar, wedge, and toppling failures are dominant and controlled mainly by discontinuities that affect these rock masses. Kinematic analysis of the studied discontinuities with the slope angles and orientations identify slope failures that occur through the steeper parts of each slope profile. The Deterministic analysis and calculated FS show that the most expected rock slope failures are stable in dry conditions, and stability is significantly reduced in fully wet conditions (mostly become unstable) where the calculated FS is frequently less than unity in most studied slopes. This slope instability is mostly due to the reduction of shear strength and cohesion properties of rock units forming the slopes, which in turn leads to decreasing their friction angles. Therefore, the planar, wedge and toppling failures are mostly rare in dry conditions with potential occurrence, while by increasing the urban development and human activities these failure types lead to predominant geohazard problems along the study slope profiles.
Rockfall analysis and simulation are carried out at some selected profiles along the existing road to assess the rockfall hazards related to the falling rock blocks and debris. These sections are located
along the mountainous road that connects the Galala resort at the coastal area and the Galala city at the plateau surface. In this analysis, the seed area is selected at the back slope and mid-slope areas where both areas are characterized by the presence of rock fragments, debris and hanging blocks, respectively. Based on the trajectory analysis, the kinetic energy, impact velocity, the run out distance and bounce heights of the rockfall trajectory are significant factors when designing rockfall barriers and mitigation measures. For back slope seed area (upper part), the run out distance (coverage distance) for rockfalls of the studied profiles is ranging from 25m to 43m which is considered as moderate to high travel distance. The roll movement is observed at the upper segment of the natural slope (seed area) while, the fall and bounce movements are dominant along the cut slopes within the propagation area. The bounce heights of falling blocks range between 40m to 90m. The maximum total kinetic energy for the proposed profiles of fallen rocks along the cut slopes reach up to 2375 KJ as calculated at different studied sections. These outcomes can be taken as a preliminary value for design consideration of rockfall protection barriers (retaining walls). Based on the above, the rockfall barriers or fences are suggested to be constructed at the upper part of the cut slope with a height of about
3.5m to 10m which are effective and more economic than constructing the rockfall barriers at foot slopes.
For mid-slope seed area (middle part), the run out distance for rockfalls of the studied profiles ranges between 12m to 30m which is considered as moderately low to moderately high travel distance. The fall and bounce movements are prevailing along the cut slopes within the seed and propagation areas. The bounce heights of falling blocks
range from 14m to 35m. The maximum total kinetic energy for the studied profiles of fallen rocks along the cut slopes reach up to 65 KJ as calculated at different sections. These findings can be taken as a preliminary value for design consideration of rockfall protection barriers. Accordingly, the rockfall fences or gabions are recommended to be constructed at the middle part of the cut slope with a height of about 2m to 3m which are more reliable and economic than constructing rockfall barriers at slope toes.
Based on carried out slope stability interpretation of the kinematic, deterministic and rockfall analyses, the studied roads are clearly classified into several risk zones. The road segments are classified into three categories low, moderate and high risk zone of rockfalls and rock slope failures. On the map, low risk zones are colored in green which indicates a low rockfalls potential on road. Moderate risk zones are marked in yellow which indicates moderate slope failures and rockfalls impact along the highway. The red colored segments represent a highly dangerous segment of the road which is highly expected to be subjected to rockfall or landslide events.
7.2 Recommendations
Based on the result of the previous geological and engineering geological studies integrated with site inspections, the following recommendations should be taken into consideration during design and implementation stages in the study area.
7.2.1 Recommendations for rock foundation
The studied Paleozoic section in the study area for foundation purposes is dominated by many lithologies such as the yellow massive
sandstone, white friable sandstone, varicolored claystone, siltstone and shale. Hence, the estimated values of uniaxial compressive strength (UCS) for the massive sandstone layers range from 45 MPa to 61.5
MPa. Furthermore, the estimated rock mass rating classification (RMR) of these sandstone beds show that they are good rocks (class II) for the foundation. Using these sandstone rocks as foundation beds may need some appropriate geotechnical treatment at some intervals based on their engineering properties. Furthermore, the massive sandstone layers in the study area are highly recommended to be a foundation layer for engineering structures. It is highly recommended that a setback with considerable distance should be maintained between the foundation of any structures and the eastern scarp edge of the Northern Galala Plateau or cut slopes areas.
The Paleozoic claystone and shale have swelling potential properties that must be removed and replaced with suitable foundation materials or treated using the proper geotechnical method before construction. These recommendations should help avoid structural subsidence or damage. It is also recommended to manage and reduce the usage of surface water for irrigation. Treatment of water leakage particularly from the sewage lines and periodic maintenance for leakage control are also recommended.
7.2.2 Recommendations for cut slopes
The study area is dominated by several rock masses of the Aheimer (sandstone, clay, shale and claystone intercalated by quartzite lenses), Qiseib (sandstone, siltstone and claystone), Malha (sandstone),
Galala (clays and marl), Wata (dolomite and dolomitic limestone), Thebes (limestone with chert), and Minia (limestone) Formations.
The cut slope recommendations are discussed here after as many roads within this area are planned to be excavated along these rock units. The exiting cut slopes along the Ain Sukhna-Zafarana highway is excavated through several rock units of different lithologies. The northwestern segment is dominated by sandstone of the Malha formation as well as the shales and marl succession of the Galala Formation. The cut slopes of the southwestern part are made up mainly of the sandstone and shales, yellow massive sandstone, black shale of the Aheimer Formation. Likewise, the other road that connects Galala resort and new Galala city is routed from the coastal area up to the surface of the Galala Plateau. The existing cut slopes of this road are excavated through different rock masses of the Aheimer, Qiseib, Malha, Galala, Wata and Minia Formations.
The cut slope recommendations are optimized based on the engineering geological parameters and site inspection of different rock masses. It is highly recommended that cut slopes in competent lithologies (competent rocks) such as dolomites and dolomitic limestone, slightly weathered and fractured, should be cut at a steep angle of 75° (1H: 4V). Cut slopes in the less competent lithologies such as sandstone, moderately weathered and fractured, should be cut at an angle of 71° (1H: 3V). The incompetent (weak rocks) such as claystone and shale, highly fractured, moderately to highly weathered rocks should be cut at an inclination of 63° (1H: 2V). The uppermost highly to completely weathered rocks should be cut at slope ratio (1H: 1V) or (2H: 1V). A series of slope benches should be maintained with a width ranges from 3m to 4m based on the cut slope height for slope stability
and construction issues. For distinct cases of very high cut, the ramps
(wide bench) of 10m wide may be required for stability considerations.
The supporting and protection measures are recommended based on the carried out slope stability analyses, site inspection and encountered engineering geological conditions of different rock masses. It is highly recommended that the removal works including scaling and terming should be carried out at the upper part of the slopes to remove the hanging blocks and debris. Rock bolts are proposed to support the unstable planar and wedge failures to increase the resisting force and the safety factor. Rockfall barriers or fences are suggested to be constructed at the upper and middle parts of the studied cut slopes. Side ditches at slope toe are highly required to prevent the falling blocks to reach the existing roads or adjacent urban area. Wire mesh and shotcrete are recommended at highly weathered and fractured rock cut slope faces as protection layers to resist the erosion and degradation processes. Also, water drainage is a very essential system to prevent infiltration through slope discontinuities that can enhance the stability of final rock cuts.