Mostafa El Sawwaf

The effect of under/after high temperature conditions on the thermo-mechanical behaviour of different rocks is extremely important issue for several engineering applications. Changes in the properties of rock after undergoing high temperature may affect stability and even induce engineering disasters. In General, the scope of high temperature ranges from normal temperatures (10-50 ¡C) to high temperatures (1000- 1500 ¡C). Temperature is one of the key factors that influence the microstructure, the physical and mechanical properties for variety of rocks as Granite, Sandstone, Limestone, Mudstone, Marble and Diorite. A review study for vast majority of previous experimental investigations was carried out for some mechanical, physical and thermal properties of rocks, including deformation modulus, Poisson’s ratio, tensile strength and compressive strength all vary considerably with increasing temperatures. Therefore, the results of experimental studies indicated that, behavior of rocks that exposed to high temperatures is different from those under normal temperature conditions. It has been known that rock strength and deformation modulus generally declined with the elevated temperature, especially beyond a certain temperature. Moreover, new correlations for the uniaxial compressive strength (UCS) with Tensile strength (TS) and for Young’s modulus (Es) with uniaxial compressive strength (UCS) due to the elevated temperatures for different types of rocks were presented.

This paper presents an experimental study of the behavior of an eccentrically loaded model ring footing resting on a compacted replaced layer of sand that overlies an extended layer of loose sand. Particular emphasis is placed on the potential benefits of reinforcing the replaced sand layer with geogrid reinforcement. Load configuration was designed to simulate ring footings under vertical loads and overturning moment caused by lateral loads. Several configurations of geogrid layers, number, and stiffness were used to study ring footings with different inner-to-outer-diameter ratios and load eccentricities. The effect of the depth and the relative density of the replaced sand layer was also investigated. Test results indicate that the behavior of an eccentrically loaded ring footing significantly improves with an increase in the depth and the relative density of the replaced compacted sand layer. However, the inclusion of soil reinforcement not only leads to a significant reduction in the depth of the rep...

Piled raft foundations are often used when the supporting soil has adequate bearing capacity but the raft settlements exceed allowable values. In traditional practice, long piles with high load capacity are usually used that may lead to two structural problems: the structural collapse of the pile and large strains mobilized in the raft leading to an uneconomic design. This paper presents an experimental study of the effectiveness of using short piles either connected or unconnected to the raft (instead of long piles) on the behavior of an eccentrically loaded raft. The load configuration was designed to simulate rafts under vertical loads and overturning moment. Several arrangements of piles with different lengths and numbers along with the effect of the relative density of the soil and the load eccentricity were studied. Test results indicate that the inclusion of short piles adjacent to the raft edges not only significantly improves the raft bearing pressures but also leads to a reduction in raft settle...

An experimental and numerical study of the behavior of an eccentrically loaded strip footing resting on geosynthetic-reinforced sand is presented. Particular attention was given to simulate footings constructed on unsymmetrical geogrid layers with eccentricity either direction of the footing. Several configurations of geogrid layers with different number, length, layer eccentricity along with the effect of the sand relative density, and the load eccentricity were investigated. A numerical study on a plane strain prototype footing was performed using finite element analysis. Test results indicate that the footing performance could be appreciably improved by the inclusion of layers of geogrid leading to an economic design of the footing. However, the efficiency of the sand-geogrid system is dependent on the load eccentricity ratio and reinforcement parameters. A close agreement between the experimental and numerical trend lines is observed. Based on the numerical and experimental results, critical values of...

An experimental study of the lateral behavior of vertical pile groups embedded in reinforced and nonreinforced sandy earth slopes was carried out. The model tests include studies of group configurations, pile spacing, embedment length of pile, relative densities of sand, and location of pile groups relative to the slope crest. Several configurations of geogrid reinforcement with different lengths, widths, and number of layers were used to reinforce a sandy slope of 1 (V) : 1.5 (H) . Pile groups of 2×2 and 3×3 along with center-to-center pile spacing of 2D , 3D , and 4.5D and piles with embedment length to diameter ratios of L∕D=12 and 22 were considered. Based on test results, geogrid parameters that give the maximum lateral capacity improvement are presented and discussed.

An extensive program of laboratory tests was carried out to study the effect of reinforcing an earth slope on the lateral behavior of a single vertical pile located near the slope. Layers of geogrid were used to reinforce a sandy slope of 1 (V) :1.5 (H) made with sands of three different unit weights representing dense, medium dense, and loose relative densities. Several configurations of geogrid reinforcement with different numbers of layers, vertical spacing, and length were investigated. The experimental program also included studies of the location of pile relative to the slope crest, relative density of sand, and embedment length of pile. The results indicate that stabilizing a soil slope has a significant benefit of improving the lateral load resistance of a vertical pile. The improvement in pile lateral load was found to be strongly dependent on the number of geogrid layers, layer size, and relative density of the sand. It was also found that soil reinforcement is more effective for piles located c...

This paper presents the results of laboratory model tests on the behavior of a strip footing supported on a row of piles and sheet pile-stabilized sandy slope. A comparison between the bearing capacity improvements in the two cases was made to study the most efficient one. The parameters varied in the study include pile diameter, pile length, pile spacing and location of pile row, height of sheet pile, location of sheet pile, and location of the footing relative to the slope crest. Initially, the bearing capacity of the nonstabilized cases were determined and then compared with those of stabilized slopes. The results were then analyzed to study the effect of each parameter. The results indicate that stabilizing the earth slope using a row of piles or sheet pile has a significant effect in improving the bearing capacity of the strip footing. This improvement in bearing capacity increases when pile spacing decreases and pile length increases with a further improvement upon increasing the pile diameter. Howe...

This paper presents the results of laboratory model tests on the influence of soil confinement on the behavior of a model footing resting on granular soil. Confining cylinders with different heights and diameters were used to confine the sand. The ultimate bearing load of a circular footing supported on a three-dimensional confined sand bed was studied. The studied parameters include the cell height, cell diameter, the depth to the top of the cell, and the embedded depth of footing. Initially, the response of a nonconfined case was determined and then compared with that of confined soil. The results were then analyzed to study the effect of each parameter. The results indicate that the bearing load capacity of circular footing can be appreciably increased by soil confinement. It was concluded that such reinforcement resists lateral displacement of soil underneath the footing leading to a significant improvement in the response of the footing. For small cell diameters, the cell–soil footing behaves as one ...