開端鋼管ぐいの支持力に関する考察 (その 2)

抄録

In this Part 2, the results of load test of steel pipe piles were examined statistically, and a new formula on the allowable bearing capacity of steel pipe piles was introduced. Fig.13 represents the relation between the values of allowable bearing capacity R_<at> determined by the load tests shown in Table 3 and the values R_<ac> calculated by modified Meyerhof formula Eq.(16) based on the assumption that the tip of pipe is perfectly closed. The figure indicates that the ratio R_<ac>/R_<at>=1.23 for the diameter being smaller than about 500mm and the ratio is 2.08 for the diameter being larger than about 600mm. And from Fig.14 it will be seen that the values of ratio are caused by overestimate of the tip resistance in Eq.(16). Through the discussion in Part 1 it was crarified that frictional resistance of the inner soil column at the ultimate bearing capacity in actual field test may be restricted only in the range of length driven into the dense sandy stratum of the bottom one-tenth of full length of pile. And it is shown that the effect of arching action will be in the same range of length and beneath the tip of thninwall of pile as shown in Fig.16 for the pipe pile whose diameter is smaller than about 500mm. Accordingly, considering these two points, the authers proposed a new formula on the allowable bearing capacity, Eq.(18)〜Eq.(20). Fig.21 indicates that the new formula gives fairly good estimate to the results of load test.