To investigate the vertical bearing behavior of manually excavated large diameter belled concrete piles (LDBCPs), field loading tests were performed on a total of 16 LDBCPs, ranging from 0.8 to… Click to show full abstract
To investigate the vertical bearing behavior of manually excavated large diameter belled concrete piles (LDBCPs), field loading tests were performed on a total of 16 LDBCPs, ranging from 0.8 to 3.5 m in base diameter from 6.1 to 18.0 m in embedment length. The end bearing stratum is sand and gravel. The influence of pile dimensions (i.e., size of enlarged base D, embedment length L, and length-to-diameter ratio L/D) on the vertical bearing behavior of a belled pile is presented and discussed. Comparison is also made of the vertical bearing behavior of a belled pile and of a conventional straight pile under otherwise similar conditions. The results indicate that: 1) The vertical bearing capacity of a belled pile is significantly greater than that of a conventional straight pile provided the debris at the bottom of a belled pile is properly removed; 2) over 65% of the vertical bearing capacity for a belled pile is attributed to the tip resistance (Qe); 3) compared to the contribution of pile length L, increasing enlarged base D is a more effective way to increase the vertical ultimate bearing capacity of a belled pile (Qu); 4) the optimum length-to-enlarged base ratio (L/D) for belled piles to achieve maximum vertical bearing capacity is around 3.2.
               
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