Three dimensional physical laboratory models were examined to investigate the influence of soil confinement on circular footing behavior resting on granular soil. A total of 23 model footing tests were performed. Nine hollow cylinders with various heights and diameters were installed around the footing model for soil confinement purpose. Square geogrid layers were placed at different depths beneath the bottom edge of the cylinder. Different parameters such as height, diameter, and depth of the cylinder were studied. Moreover, number, width, and position of the geogrid layers were, also, investigated. The response of a non-confined footing model was set as reference for comparison purpose. The results showed enhancement in the bearing capacity of the soil as well as a reduction in its settlement in all used configurations compared with the reference case. It is, however, observed that on increasing the number of geogrid layers more than one layer had a small significant effect on the footing behavior. Moreover, placing geogrid layers underneath the cylinders improves the bearing capacity up to 7.5 times that of the non-confined case. Footing with cylinder of a diameter nearly equal to the footing diameter behaves as one unit like a deep foundation. This behavior pattern was no longer observed with large cylinder diameter and small height. Finally, the study ends up with recommendations for selection of cylinder dimensions to maximize the bearing capacity. The benefits of using geogrid layers were also highlighted.
Abstract-Red Sea is one of the most important repositories of the marine biodiversity in the world. Red Sea oil and gas reserves are estimated to be around 100 billion barrel of oil equivalent necistate the use of offshore structure to extract it. Most of offshore drilling rigs and production platforms are found on group of large diameter piles which are driving into sea bed producing high amount of underwater noise. Underwater noise emitted during pile construction can mask biologically relevant signals for marine mammals. This noise might lead to behavioral reactions, harassment, and at very high levels can injure or even kill the mammal. Range-dependent Acoustic Model, Rogers Model, was used to assess underwater noise propagation of offshore pile driving taking into account seabed bathymetry, temperature, and salinity. It was found that an offshore pile driven with 235 kJ rated energy diesel hammer can cause behavioral disturbance to the marine mammal within a distance of 1000 m from the pile location; temporary threshold shift within a distance of 30 m; permanent threshold shift within a distance of 50 m; and injury, or even death, within a distance of 20 m. I. INTRODUCTIONRed Sea is one of the most important repositories of the marine biodiversity in the world, it support populations for many species of marine mammals (about 15 species of dolphins and whales, and one dugong species). Red Sea Governorate tourism industry, which depends mainly on marinewildlife and recreation tourism, contributed significantly to the Egyptian economy in 2003 to reach about 10% of GDP and 4% of total employment [1]. At the same time, Red Sea oil and gas reserves are estimated to be around 100 billion barrel of oil equivalent. Kingdom of Saudi Arabia is planning to employ 200 drilling rigs in 2014 most of it will be in the Red Sea [2] which, in the absence of proper environmental studies, will affect significantly the Red-Sea eco-system. Most of offshore drilling rigs and production platforms are found on group of large diameter piles which are driving into sea bed. During pile driving; extremely high sound levels are produced in both the surrounding air and underwater environment. In terms of the underwater environment, field observations show peak acoustic pressures of 1.0 kPa measured at a range of 3000 m [3], around 10 kPa measured at a range of 60 m [4], and around 100 kPa measured at a range of 10 m [5] from the pile driving operation. Such pressures are known to produce deleterious effects on both fish and marine mammals [6].Underwater noise effects on marine mammals are of particular interest because marine mammals has a wide distribution area in the coastal waters of the Red Sea, acute hearing, and functional hearing over a very wide frequency range [7]-[10]. Marine mammals are relatively easily deterred by anthropogenic underwater noises [11]. Avoidance threshold levels of harbor porpoises have been determined for noise bands and tonal signals around 12 kHz, a continuous 50 kHz tone, and continuous and pulsed 70 and 1...
The effect of using stone columns on settlement rate of soft clay soils is considered a subject with little studies. This paper presents implementation of 2D and 3D numerical model to predict settlement rate of soft clay soils. The numerical models were compared with observations of large-scale field project. The project consisted of implementation of 0.90m end-bearing stone columns with spacing of 2.90m and average the field behavior especially for settlement values, settlement rates, and pore water pressure. The 2D model is considered conservative at the early stage of loading and accurately predict the field observations for long-term behavior. The final results show that 3D model is more realistic than the 2D model, but it requires more time and computational efforts.
Stone column is one of the most effective techniques used in soil enhancement. Inserting stone columns under strip footing in the active zone of a retaining wall embedded in soft soils enhances the allover behavior of the retaining wall. Stone columns improve the bearing capacity under the footing, decreases the settlement of the footing, and decreases the lateral movement of the retaining wall. Increasing area replacement ratio of stone columns improves the bearing capacity under the footing, reduces settlement, and decrease the lateral movement of retaining wall.In this resaerch an experimental study was carried out on changing the area of replacement ratio of stone columns inserted in very soft clay in the active zone of embedded retaining wall with strip footing load at the top of backfill.Increasing stone columns area replacement ratio improves the bearing capacity under the footing, reduces settlement, and decrease the lateral movement of retaining wall.
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