Abstract: In order to study the bearing characteristic of static drill rooted energy piles under thermo-mechanical coupling conditions, a self-designed model test system has been used to evaluate the thermal response of the model pile in the clay-sand double-layered foundation. The results show that the temperature of the pile is non-uniformly distributed along the depth, and the radius of thermally affected region around the pile is 3 times of its diameter. Accumulated settlements are observed on the pile top and the surrounding soil surface after 3 heating-cooling cycles. Driven under the load of 25% of the ultimate bearing capacity on top, the cumulative settlement of single pile reached 3.12‰ of the pile diameter, which is 1.77 times that of the pile top under non loading condition. Larger additional thermal stress performs at the pile middle than both ends, and the null point (where lies maximum additional thermal stress) moves upward with the increase of the pile top load. In fact, it has been observed that under small load on the top, local tensile stress occurs in the pile body due to cooling. Therefore, the bearing characteristic of static drill rooted energy pile is of high relevance to temperature change, load on pile top and stress boundaries of pile ends, and that requires comprehensively consideration in engineering design to guarantee safety service of pile.

Key words: static drill rooted energy pile, thermo-mechanical coupling, additional thermal stress, model test, bearing characteristic