Vertical loading tests were performed on the bearing capacity of straight pile with enlarged grouted base using pressurized sand tank for studying the effects of the tip length and the strength of enlarged grouted base. The main conclusions are as follows. 1) When the tip length was zero, “bond failure” occurred in the early stage of loading regardless of the strength, and the pile head load reduced abruptly. 2) When the tip length was 0.83 times the pile diameter and the strength was 15 N/mm2, “punching failure” finally occurred, but the same bearing capacity was obtained as in the case when the tip length was 1.3 times the pile diameter. 3) When the tip length was 1.3 times the pile diameter, and the strength was 15 N/mm2, no “punching failure” occurred, and the pile head load continued to increase until the completion of loading.
