孔隙水盐分溶脱过程天然沉积软粘土工程性质演化及机理研究

In the geotechnical practices of offshore engineerings, the desalination of pore water by the freshwaters or rainfalls leads to the variation of the behaviors of the soft marine clays. But presently, the desalination effect of pore waters on soil behaviors is still unclear which will cause engineering disasters. Noted that as the soft marine clay just beside the coastlines in the regression depositional environment at Lianyungang area is selected as the studied materials for the high salinity in the pore water. In the experiment design, the desalination effect of pore waters on the physical properties is first studied by the artificial and natural soils by controlling or determining its mineral composition, particle size distribution, specific surface area and porewater salinity etc. Later, a specific oedometer/triaxial shearing test is developed to conduct the pore water percolation with low concentrations of the solutions. During the percolation tests, the deformation will be observed and then the SEM and MIP tests are carried out to study the influence of desalination process. After percolation, the loading and unloading (and shearing) procedure is performed to compare the difference between pore water leaching and not, and to clarify the pore water effect on mechanical behavior. With the above studied results, the Modified Cambridge Model in the p'-q plane will be expanded again to the p'-q-∏ plane aimed to consider the desalination effect of pore water where ∏ is the osmotic suction. Noted that in this session, the pore water effect to physical properties is also considered. Furthermore, the site investigation with RCPTu, borehole and pore water analysis are arranged in the zone of Lianyungang marine clay to verify the soil behavior evolution during the salinity leaching process.In addtion, the case of embankment instability due to pore water desalination in Canada will be adpoted to verify the proposed model. Above all, the results of this research can improve the safety of offshore geotechnical engineerings, avoid the potential disasters and deepen the understanding of the soil behavior.

近海岩土工程实践表明，孔隙水盐分受地表淡水或降雨的侵蚀而发生溶脱，导致软粘土工程性质变异。由于目前对盐分溶脱过程软粘土工程性质演化机理不明，为工程灾变埋下隐患。项目以海退成因的连云港海相软土为载体，通过改变矿物成分、粒径、比表面积和孔隙水盐分条件，探究孔隙水盐分溶脱过程软粘土物理性质的演化规律；设计特殊的换盐装置，跟踪盐分溶脱前后土体力学性质和微观结构等方面的变化，明晰该过程中力学参数的劣化机制，探讨微观结构与力学性质变化的相关关系；综合盐分溶脱前后土体物理力学性质的变化规律，拓展修正剑桥模型。在连云港海相软土分布区域开展现场和室内的试验，实证盐分溶脱过程软粘土工程性质演化规律与机制,同时收集国内外盐分溶脱导致路基/地基失稳案例验证本研究提出的模型。项目研究将明晰孔隙水盐分溶脱过程软粘土工程性质演化规律与机理，并加深对软粘土力学行为的认识，从而提高近岸土工结构物安全和避免工程灾害。

近海岩土工程实践表明，孔隙水盐分受地表淡水或降雨的侵蚀而发生溶脱，导致软粘土工程性质变异，但由于目前对盐分溶脱过程软粘土工程性质演化机理不明，为工程灾变埋下隐患。本研究以海退成因的连云港海相软土为载体，通过改变矿物成分、粒径、比表面积和孔隙水盐分条件，首先开展了人工软黏土的盐分效应的研究，明确了孔隙水盐分、软粘土级配与矿物成分耦合作用下，人工软黏土工程性质的演化规律，建立了考虑孔隙水盐分效应的人工软黏土的本构模型；设计了特殊的换盐装置，跟踪盐分溶脱过程中天然沉积软黏土体力学性质和微观结构等方面的变化，发现了溶脱环境下滤出孔隙水富含土壤胶体，这可能是海相软粘土强结构性的重要原因；探讨了微观结构与力学性质变化的相关关系，综合盐分溶脱前后土体物理力学性质的变化规律，明晰了溶脱过程中力学参数的劣化机制，尝试给出溶脱过程中考虑沉积软黏土结构变异的本构模型。在连云港海相软土分布区域开展现场和室内的试验，实证了盐分溶脱过程软粘土工程性质演化规律与机制，开展了数值模拟工作，给出近海土工结构安全性能的演化规律。研究成果不仅明晰了孔隙水盐分溶脱过程软粘土工程性质演化规律与机理，还深化了对软粘土力学行为的认识。