Experimental Investigation of Curing-Age-Dependent Bearing Capacity Evolution and Load-Transfer Mechanisms of Short-Core SDCM Piles

The vertical bearing capacity of stiffened deep cement mixing (SDCM) piles is strongly influenced by curing age, making the determination of appropriate loading timing an important issue in engineering practice. To investigate this effect, a series of axial compression tests was conducted on floating short-core SDCM piles cured for 14 d to 90 d using a specially developed multi-pile curing device and loading system. The curing-age-dependent load–displacement response and load-transfer behavior were analyzed. Unconfined compression tests were also performed on the cemented soil to assess strength development. The experimental results show that the ultimate bearing capacity increased rapidly within the first 28 d and gradually approached a stabilized value of 3024 N after about 60 d, following either an exponential or hyperbolic evolution trend. In addition, the strength and stiffness of the cemented soil exhibited continued growth, increasing by approximately 38% and 25%, respectively, from 28 d to 90 d. At the early curing stage, the increase in ultimate bearing capacity was mainly governed by the strength development of the cemented soil, whereas the stabilized value at later stages was jointly controlled by the strength of the surrounding soil and the characteristics of the cemented soil–soil interface. With increasing curing age, the progressive hardening of the cemented soil enhanced the load-transfer contribution of the DCM column and promoted more uniform mobilization of shaft resistance along the pile. These findings provide useful guidance for determining appropriate loading schedules and for the design and construction control of SDCM pile foundations.