Thermo-mechanical response of static drilled rooted energy piles under monotonic cooling cycle

Static drilled rooted piles are a new type of composite piles consisting of precast piles with cement soil. This paper investigates the thermo-mechanical response of static drilled rooted energy piles (SEP) versus ordinary energy piles (OEP) under monotonic cooling cycle (20 cooling) using indoor modeling tests. This paper investigates temperature distribution, additional thermal stresses, additional thermal shaft friction, pile top displacement, and bearing capacity changes of piles and soil. Due to different constraints OEP and SEP exhibit different thermo-mechanical response. The results showed that after 20 cooling cycles, the maximum additional thermal stresses reached 0.43 MPa and 0.48 MPa for OEP and SEP, respectively. The normalized displacements of the piles were -1.45 % and -0.53 %, respectively. Comparing the ultimate bearing capacity before and after cooling cycle, the OEP and SEP were reduced by 15 % and 8 %, respectively, and the shear strength test of the peripile soil verified the effect of temperature cycling on the strength of the peripile soil. In practice, the adverse effects of monotonic cooling circulation on the superstructure of the building should be taken into account in the design.