Load settlement characteristics of a piled raft in sand

• Main Author: Chan, Junxiong.
• Other Authors: Teh Cee Ing
• Format: Final Year Project
• Language: English
• Published: 2010
• Subjects: DRNTU::Engineering::Civil engineering::Geotechnical
• Online Access: http://hdl.handle.net/10356/39752
• Institution: Nanyang Technological University

A model test tank and a loading frame with jacking load were used for the test of model piled raft system. A total of 20 tests were conducted to study the load settlement characteristics of a piled raft foundation with the use of piles as settlement reducers. Both piled raft system and pile raft unit cells were included in the tests. The tests were conducted under the same soil density, same soil volume from silo and also same surcharge load from the loading machine. The experiment conducted on the raft was used to determine the ultimate bearing capacity of raft on different thickness. The raft was loaded to a depth of 0.1B, deemed as the ultimate capacity. This was if the raft was loaded continuously, there will not be an ultimate value on the trend of the curve and the applied load will continue to increase until the loading plate comes in contact with the sand. Unit cell tests were conducted as a basis of comparison against the piled raft tests. Two sizes of unit cell piled raft were tested. The unit cell tests consist of loading on footings, single pile, pile group and pile raft tests. The data recorded were plotted to study on the load-settlement characteristics. For a piled raft foundations, piles of four different lengths were used in the tests. The individual piles were loaded to determine the load-settlement characteristics. The use of pile with different length allows the effect of pile length on piled raft to be studied. Besides the varying of pile length, the effect of pile arrangement or spacing on the raft was also studied in this experiment. The variation of pile spacing with a fixed length of pile showed that with the increase of pile-to-pile spacing, the settlement carried by the piled raft system under a given load could be reduced. The same trend was also observed for a smaller number of piles, raft settlement decreases with the spacing. Finally, the numbers of piles in the raft were varied from 5, 9, 16, 25 to 49 piles. The tests showed that with the load taken increases with the increase in the number of piles. Another similar experiment was conducted with a single pile unit cell and 4 piled raft. Results showed the presence of interaction between piles and the factor increases with the number of piles.