(1. Institute of Geotechnical Engineering，Southeast University，Nanjing，Jiangsu 210096，China；
2. Capital Construction Office of Southeast University，Nanjing，Jiangsu 210096，China)
Abstract：Investigations on the thermo-mechanical behaviors of precast high strength concrete(PHC) pipe piles，especially surrounded by multi-layer strata，are relatively few. Based on in-situ prototype tests，piezocone penetration tests and drill sampling method，the thermal and mechanical responses of a full-scale PHC energy pile in layered soil were analyzed. The results show that the temperature of piles distributes relatively uniform with an average increase of 20.0 ℃. The temperature of the pile near the ends or high conductive soil layers is lower，indicating obvious influence of inhomogeneous heat transfer ability of layered soils on the temperature of the pile. The compressive stress is generated in the pile body. The maximum stress is 4.70 MPa p and the stress at the bottom of the pile is 3.77 MPa. The neutral point locates at 16.3 m depth which is about 2/3 of the pile length，and the position keeps stable during the test. Compared with other field tests，it was found that the additional stress of the pile body is related to the strength of the surrounding soil and the pile type. The negative shaft friction develops in the upper part of the pile and positive shaft friction occurs in the lower part. The negative shaft friction is larger than the positive，which may be due to the difference between the pile-soil relative displacements of both ends of the pile. According to the results，a simplified distribution of pile-soil relative displacement and pile body stress was proposed.
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2019, Vol. 38 
