Abstract: Aiming at the durability problem of post grouted piles in the marine environment, micro cone penetration (MCPT), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), X-ray diffraction (XRD), and unconfined compressive strength (UCS) tests were conducted to study the strength change of cement stabilized calcareous sand with different curing times and cement ratios in the marine environment. The relationship between unconfined compressive strength and penetration resistance of cement stabilized calcareous sand was obtained and compared with the experimental results of cement stabilized siliceous sand, the micro-erosion mechanism of cement stabilized calcareous sand was revealed. The results show that according to the distribution characteristics of penetration resistance, the stabilized cement in seawater environment can be divided into eroded layer and non-eroded layer, and the erosion depth increases with the increase of curing time and the decrease of cement ratio. Compared with the non-eroded layer, with the increase of curing time, the porosity of the eroded layer increases, and the amount of hydration products decreases. At the same time, the Ca contents significantly decrease. In addition, according to the distribution laws of the temporal and spatial variation in the strength, the microstructure and the phase composition of the cement stabilized sand, it can be found that the strength change of the cement stabilized sand in seawater erosion environment is a common result of the strengthening effect of hydration reaction on the strength of cement stabilized soil and the weakening effect of erosion reaction on the strength of the cement stabilized sand. The research results can provide a reference for evaluating the durability and long-term stability of post grouted pile in calcareous sand.

Key words: post grouted pile, calcareous sand, cement stabilized soil, seawater erosion environment, micro cone penetration test, micro erosion mechanism