Experimental study on the bearing characteristics of reamed precast piles in pile-slab subgrade

To reveal the bearing characteristics and load transfer mechanism of reamed precast concrete (RPC) piles with pre-bored grouting in the pile-slab subgrade, and to study the influence of the reamed section size, pile top bearing mode, and section combination form on the synergistic effect of the internal precast pile-external reamed material-surrounding soil, static load tests were carried out on 9 test piles in two test areas. The test area A consisted of 5 RPC piles with reamed diameters of 0～1 200 mm bearing on internal pipe piles, and the test area B consisted of 2 small-diameter RPC piles bearing on internal pipe piles and full-section bearing and 2 largediameter RPC piles bearing on internal pipe piles. The test results show that the external cement mortar can effectively transfer the load from the internal pipe pile to the surrounding soil and improve the overall bearing performance. When the thickness of cement mortar increases from 10 cm to 25 cm, the settlement of the pile top at the same load level decreased by about 44.3% to 59.5%. However, with the further increase in the thickness of cement mortar, this trend is not obvious. The reasonable range of the thickness of external cement mortar under test conditions is 15～25 cm. Under the internal pipe pile bearing condition, the interfacial resistance between the pipe pile and cement mortar is large at both ends and small in the middle. Under the combined action of the internal pipe pile and the lateral resistance of surrounding soil, tensile stress may appear near the pile top when the thickness of cement mortar is less than 15 cm. Under the full-section bearing condition, the interfacial resistance between the pipe pile and cement mortar at the pile top is relatively insignificantly affected by the displacement of the pile top, but it increases gradually with depth. The overall bearing performance of RPC piles under the two bearing modes is roughly equivalent. Increasing the diameter of internal precast piles can significantly improve the bearing performance of RPC piles. The load transfer law of large-diameter RPC piles is similar to that of small-diameter RPC piles. The test results are of great significance for the application of RPC piles with pre-bored grouting in the pile-slab subgrade. © 2023, Central South University Press. All rights reserved.