Abstract: This paper presented the test results of two large diameter short-belled piers, a deep loading test and a friction pile in sand-cobble layer at the same test site, and accordingly gives a study on the belled piers (embedded depth of 6.20 m-6.75 m) load transfer behavior. The analysis shows that the pier ultimate bearing capacity can be confirmed by direct test method and indirect test method. S3 pier (bearing layer is cobble layer) ultimate bearing capacity is 7 250 kN, end resistance is 6 890 kN, taking up 95 % of the ultimate bearing capacity, and S2 pier (bearing layer is sand layer) ultimate bearing capacity is merely 2 330 kN, end resistance taking up 85 %. When the settlement of loading pier is about 1.46 mm, the skin frictions of pier S3 and S2 have achieved ultimate state; but when the end resistance in ultimate state, the settlement of pier S3 and S2 are 92.64 mm and 21.07 mm; respectively. The vertical bearing capacity of belled pile is greater than the pure friction pile and shaft as their diameters are equal.

Key words: sand-cobble layer, large diameter short-belled pier, end resistance, vertical bearing capacity, static load test