A series of drained triaxial compression tests were performed on sand samples for the determination of the angle of the internal friction (φ_d) in order to investigate the effects of sample disturbance on the φ_d a and also to study the 0 φ_d-N_1 relation in the range of N_1>30 for sandy soils, where Ni is the normalized SPT N-value by effective overburden pressure. The following were concluded. 1) Both the relative density and φ_d of TS sample (samples obtained by rotary-type triple-tube method) were affected by the sample disturbance. However, the effects of sample disturbance on φ_d is only 1.4 to 2.6 degrees, this is much less than that for liquefaction strength. 2) In the range of N_1≦30, the N_1-φ_d relationship for TS sample is totally corresponding to that for FS sample (by in-situ freezing method), and the relationship can also be represented by the empirical correlation proposed by Hatanaka and Uchida(l996) for FS sample. 3) Though the data is limited, the correlation of φ_<d(FS)>/ φ_d<(TS)>=1.06 can be seen for the natural sandy deposits in the range of N_1≦30. 4) In the range of N_1>30, the average value of the φ_d for TS and BL samples (by block sampling) is 38°, and there is no increase in φ_d with the increase of N_1. Based on the conclusion 3), the φ_d for in-situ sandy soils in Ni>30 can be converted from 38°to 40°. 5) The empirical correlation relating N_1 and φ_d in a wider range is tentatively proposed as φ_d=(20N_1)^<0.5>+20(3.5≦N_1≦20) and φ_d =40° (N_1>20) based on the test results and discussions shown above.
