In order to understand the effect of (length of pile / diameter of pile) ratio on the load carrying capacity and settlement reduction behavior of piled raft resting on loose sand, laboratory model tests were conducted on small-scale models. The parameters studied were the effect of pile length and the number of piles. The load settlement behavior obtained from the tests has been validated by using 3-D finite element in ABAQUS program, was adopted to understand the load carrying response of piled raft and settlement reduction. The results of experimental work show that the increase in (Lp/dp) ratio led to increase in load carrying capacity by piled raft from (19.75 to 29.35%), (14.18 to 28.87%) and (0 to 16.49%) , the maximum load carried by piles decrease from(9.1 to 22.72%), (15.79 to 47.37%) and (44 to 81.05%) and the response of settlement piled raftdecrease from (16.67 to 23.33%), (9.09 to 39.39%) and (30%) with increase the number of piles from 4 to (6 and 9) and (length of pile / diameter of pile) ratio increase to (14.14 and 21.2), respectively. The numerical and model test results are found to be in a good agreement.
Due to wind wave actions, ships impacts, high-speed vehicles and others resources of loading, structures such as high buildings rise bridge and electric transmission towers undergo significant coupled moment loads. In this study, the effect of increasing the value of coupled moment and increasing the rigidity of raft footing on the horizontal deflection by using 3-D finite element using ABAQUS program. The results showed that the increasing the coupled moment value leads to an increase in lateral deflection and increase in the rotational angle (α◦). The rotational angle increases from (0.014, 0.15 to 0.19) at coupled moment (120 kN.m), (0.29, 0.31 and 0.49) at coupled moment (240 kN.m) and (0.57, 0.63 and 1.03) at coupled moment (480 kN.m) with decreasing the raft thickness from (1.5, 1.0 to 0.5m), respectively. The computed maximum lateral deflection decreases with increasing the rigidity of raft. The maximum deflection decreases from (40 to 3mm) at coupled moment 120 kN.m, (150 to 60mm) at coupled moment 240 kN.m and (210 to 118mm) at coupled moment 480 kN.m with increase raft thickness from (t = 0.5 to 1.5m) and the maximum reduction in maximum stress value and lateral deflection mobilized due to applied coupled moment is noticed when width to thickness of footing ratio is less than (w/t<12). The failure of the footing is noticed when the rotational angle is more than 4◦ (α > 4◦)
Background: The skirt foundation is one of the powerful types of foundations to resist the lateral loads produced from natural forces, such as earthquakes and wind action, or from the type of structures, such as oil platforms and offshore wind turbines. Objective and Methodology: This research experimentally investigated the response of skirted footing resting on sandy soil of different states to lateral applications of loads on a small-scale physical model manufactured for this purpose. The parameters studied are the distance between the footing and the skirt and its depth. Results and Conclusion: The results show that the presence of the skirt behind the footing loads to an increase in bearing load and a reduction in the lateral movement whereas the skirt near or adjacent to the footing edge causes maximum increases in bearing load and reduction in lateral movement, for skirted footing. The ratio between the wall distance and the width of the footing has no effect when it is greater than one. On the other hand, the state of the soil influences the bearing load and lateral movement with different ratio of wall distance and wall depth to the width of the footing, especially when the wall distance to the footing width is less than one and the state of the soil has no effect on the bearing load and lateral movement when the ratio is more than one.
In this research, the geotechnical properties of the soil profile in Hilla city within Babylon Governorate in the middle parts of Iraq are described. The geotechnical data at the specific sites were collected from some geotechnical investigation reports performed at some selected locations. This article is devoted to studying the distribution of soil properties (the physical and mechanical) in the horizontal and vertical directions. Moreover, a correlation between different physical and mechanical properties is performed. The correlation is executed using statistical analysis by Microsoft Excel Software (2016). From the regression results, it was found that the nature of the soil is cohesive up to 15 m under the natural ground level, and the soil will change to noncohesive. The new line in the plasticity chart has been drawn parallel to A-line especially for the investigated region, the shear strength parameters depend on the consistency of the soil and the depth, and finally, there is a direct correlation between mechanical and physical parameters. Using these correlations with some available information help to predict the value of shear strength and consolidation parameters.
Ring footing represents a significant structural member in different applications such as fuel or water storage tanks in addition to other structures. The advantage of this type of footing is related to the ability to reduce the weakness of some soils that may affect the safety of structures. An experimental testing program was conducted by using a small-scale model in the laboratory of the college of engineering at the university of Al-Mustansiriyah which consists of twelve ring footing models resting on loose sand reinforced by geogrid layers. The parameters that studied in this research are the diameter of ring footing, thickness of ring, the position placed of one reinforced layer and vertical spacing between two reinforced layers. The findings of this research shown that the optimum percentage of diameter ratio of ring footing is (0.25) and when the depth-ratio increases, the bearing-capacity of ring footing begin decreases. In general, the increase in ring thickness causes the bearing-capacity and the rigidity of ring foundation to increase. The optimum of the depth-ratio of the first reinforced layer is (0.25) and the optimum value of vertical-spacing bounded by layers is around (0.25) which produces a maximum value of the bearing-capacity. Its noticed that when these percentages exceeded value 0.25, the bearing-capacity of the ring foundation drops eventually.
The risk of liquefaction phenomena increases during dynamic loading and can cause the shear failure of soil under foundations. Model tests for a small-scale model under vertical vibration loads are presented. The operating frequency was changed from 1000, 2500 to 3500 revolutions per minute and the amplitude of loading with time was applied as a sine wave. Several parameters were considered, such as the force-time history of the machine foundation, the final settlement of the foundation, the vertical stress inside the soil media, the excess pore water pressure and observed liquefaction phenomena. These observations were compared to the effect of the sub-base layer thickness under the footing and its ability to reduce the liquefaction phenomena. The results showed that the shape of the load-time history coincides with a sine wave and the increase in the operating frequency led to an increase in the measured vibration load. The settlement was observed to increase with increases in the operating frequency. The settlement depended on the state of the soil and the operating frequency applied. Increases in operating frequency of about 3 times led to an increase in the time interval of excess pore pressure and reached a maximum value. The phenomenon of liquefaction appeared clearly when sandy soil was in a loose state. When the soil changes to a medium state, the phenomena of liquefaction respond to the operating frequency more than the operating frequency in a loose state. No liquefaction occurs in a dense state. The use of a subbase layer more than 1.5 times the depth of the footing led to eliminating the liquefaction phenomena.
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