海水环境下水泥土强度衰减过程室内试验研究

针对滨海相软土场地形成的水泥土的强度衰减问题，采用天然海水作为腐蚀介质对水泥土进行一维浸泡试验，通过微型贯入试验、扫描电镜（SEM）试验、能谱（EDS）分析、X射线衍射（XRD）试验、离子含量及pH值测试等多种试验手段研究水泥土强度的分布规律和衰减过程。根据贯入阻力随贯入深度的变化规律将水泥土分为劣化层和未劣化层。结果表明：随着养护时间的增长和水泥掺入比的减小，水泥土的劣化深度不断增大，至360 d时最大劣化深度达到8.7mm；与未劣化层相比，劣化层的孔径增大，孔隙增多，水泥水化产物减少；水泥土的pH值和Ca2+含量随着试样深度的增大而增大，Mg2+、SO42-、Cl-含量随试样深度的增大而减小。经海水养护后，水泥土中Ca2+含量沿试样深度方向的分布规律与强度变化规律相似。在本试验条件下，水泥土的强度衰减是海水中侵蚀性离子抑制水泥土强度增长过程和促使水泥土强度降低过程的共同结果，在此过程中Ca以离子形式溶出，最终导致水泥土的劣化深度不断增大。

Laboratory test on strength deterioration process of soil cement in seawater environment

The natural seawater was used as the corrosive medium to simulate the marine soft sites, and the micro-penetration test, the spectrum analysis (EDS), the X-ray diffraction (XRD) and the chemical tests were conducted to study the spatial and temporal distribution and the strength deterioration process of cement soil formed in the marine soft sites. The cement soil specimen can be divided into the deteriorated layer and the non-deteriorated layer. The results indicate that the deterioration depth increases with time and the cement mixing ratio. The maximum deterioration depth appeared at 360 days with the 8.7mm amplitude. Compared with the non-deteriorated layer, the micro-structural porosities are more and larger in the deteriorated layer, while the hydration products of the cement are less in the deteriorated layer. The pH and the Ca2+ concentration of cement soil both rise, while the concentrations of Mg2+, SO2-4 and Cl- decrease with the sample depth and the cement ratio. The variation of cement soil strength is consistent with the distribution of Ca2+ concentration along the penetration depth. Under the test conditions, the deterioration of cement soil is due to the combined action of the inhibiting strength increase and the promoting strength attenuation of cement soil. The Ca leaches in the form of ion and leads to the deterioration finally.