海水环境下钙质砂水泥土加固体的微观侵蚀机制试验研究

Experimental study on micro-erosion mechanism of cement stabilized calcareous sand under seawater environment

针对海洋环境下钙质砂中的后压浆桩耐久性问题,通过微型贯入、扫描电镜、能谱、X射线衍射及无侧限抗压强度等多种试验手段,研究了养护时间与水泥掺量对海水环境下钙质砂水泥土加固体的强度变化规律,建立了钙质砂水泥土加固体的无侧限抗压强度与贯入阻力的关系,并与硅质砂水泥土加固体的试验结果进行了对比,揭示了钙质砂水泥土加固体的微观侵蚀机制。结果表明,根据贯入阻力的分布特征,可将海水环境中水泥土加固体分为侵蚀层与未侵蚀层,侵蚀深度随养护时间的增长和水泥掺量的减少而增加;与未侵蚀层相比,随着养护时间的增长,侵蚀层的孔隙增加,水化产物减少,且Ca的含量明显降低。根据水泥土加固体的强度时空变化、微观结构及物相成分的分布规律发现,海水侵蚀环境下水泥土加固体的强度变化是水化反应对水泥土加固体强度的增强作用和侵蚀反应对水泥土加固体强度的削弱作用的共同结果。研究成果可为评价钙质砂中的后压浆桩耐久性与长期安全稳定性提供参考依据。

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.