Keywords : Sand density
Engineering and Technology Journal,
2021, Volume 39, Issue 7, Pages 1080-1091
This paper introduces an experimental research on the behavior of the piled raft foundation (PRF) in sand of two states (loose and medium sand). A small model has been tested in a soil container and the vertical load was applied to the foundation through a pneumatic jack. The settlement of the foundation was measured using a displacement transducer; three sensors were attached to the pile heads to measure the axial load borne in a group by each pile by the Arduino data logger. The laboratory experiments were carried out on models of (1 pile), (1x2), (1x3), (2x3), (3 x3), (3 piles triangular), (4 piles diamond), (5 piles), and (9 pile circle), as well as to tests on an unpiled raft. Test variables were pile length, number of piles, and sand density. It is noticed that when the piles increased to nine piles in the group, the bearing capacity increased by 40%. The effect starts to increase when one pile is just placed under the raft as the bearing capacity of the piled raft increased by 3% and 7% when the pile length is 15D and, 20D, respectively. The reduction in the settlement is also observed to be smaller and no economic advantage is achieved with more increase in the number of piles. If the number of piles reaches (6) piles, the influence of the piled raft on settlement reduction disappears.
Effect of Relative Density on Behavior of Single Pile and Piles Groups Embedded with Different Lengths in Sand
Engineering and Technology Journal,
2016, Volume 34, Issue 6, Pages 1206-1220
The present research investigates the effect of axial relative density on the ultimate load of model piles with different lengths driven in dry sandy soil having small scale model piles.
The materials used in this study are divided into three parts they are; sandy soil, steel piles and aluminum pile caps.A total number of 27 model tests are carried out using three relative densities (33%, 60%, and 80%) corresponding to loose, medium and dense sand, respectively.
A square section steel solid model piles are used with 18 mm width and (320, 420, 520) mm embedded length (Ld). A 6B distance between the piles center to center is selected to eliminate the effect of group interaction.
Two pile groups' configuration (1×2) and (2 × 2) are considered in this study connected by aluminum caps with smooth surface having a thickness of 25 mm.
The load applied on the models is measured by a pressure transducer connected to the main line of the hydraulic pressure system and applying up to failure. During all the experimental tests, the loading rate is kept at 3 mm/min.
It was founded that relative density has more impact on (2×2) pile group than on (1×2) pile group and single pile. The average rate of increase in the ultimate load from loose to medium is about 15% greater than the average rate of increase from medium to dense. Also, the ultimate load of pile increased about 96% with changing the sand density from loose to medium sand for single and piles group while the average increment is about 81% from medium to dense. The increase in embedded length of pile caused increasing the ultimate load capacity and decreasing the settlement ratio. The average rate of increase in the ultimate load when the embeddedlength changes from 32 cm to 42 cm is about 4% less than the average rate of increase when the embedded length changes from 42 cm to 52 cm. Also, use of (1×2) piles group instead of a single pile, the average rate of increase is about 6% less than the average rate of increase when change from (1×2) group to (2×2) pile group.
Finally, when the number of piles changes from single pile to (1×2) piles group, and to (2×2) piles group, the average of increase of ultimate load is about 102.5% and 108.5% respectively.