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Cement mortar-expanded precast (CMEP) piles comprise a new class of expansion pile technology. To reveal their vertical bearing properties, full-scale research on the bearing performance of expanded piles under different pile top pressure modes and pre-bored conditions has been carried out. Test results have shown that pile top pressure mode had little effect on the bearing performance of expanded precast piles, but significantly affected internal load transfer mechanism. When internal precast pile was under pressure alone, the axial force of inner precast pile was relatively high. When the full section of pile top was loaded, precast pile axial force was reduced by about 20-50%. Furthermore, different pre-bored conditions could cause different pile end support conditions, significantly impacting the performance of expanded pile bearing. The ultimate bearing capacity of expansion piles with super core (SC) pile, equal core (EC) pile and less core (LC) pile were 1200, 880 and 906 kN, respectively. However, all three expanded pile types had about 12% higher bearing capacity than conventional strong composite piles. The failure modes of all test piles under ultimate load were overall subsidence, indicating that the shear capacity of the interface between inner precast pile and outer cement mortar was greater than shear action between outer cement mortar and surrounding soil. When the strength of outer grouting material was greater than 15 MPa, the interface damage of inner precast pile and outer material may not be considered.

来源平台：INTERNATIONAL JOURNAL OF CIVIL ENGINEERING