常温、常压、常态的大气环境下黏性土微观孔隙的缓慢变异特征

作为建筑材料和地基的土体处于常温、常压、常态的大气环境下,大气氧化过程是缓慢的、不易察觉的,但对土质长期劣化效果不容忽视.本文以此命题为出发点,以大气氧化过程中微观孔隙变化特征为突破口,联合扫描电镜测试、压汞法及氮吸附法研究大气环境作用对湛江黏土的微观结构改造作用及其对土性影响机理.研究表明,大气氧化后土色由青灰色、绿灰色变为淡黄棕、黄棕色,颗粒团聚程度增强,塑性降低,膨胀性与收缩性减弱,灵敏性与结构屈服强度明显降低.大气环境作用对d0.1?m孔隙组产生"缩合"效果,对d1?m孔隙组产生"胀散"效果,表现为氧化土的总孔隙体积减小,但d1?m的孔隙体积明显增大,局部出现断裂孔隙,"墨水瓶"型孔隙减少,开放性孔隙向封闭性孔隙转化.湛江黏土在大气影响下土性发生异变并不是土的矿物本性变化所引起,而是水-土-电解质-大气间的化学反应与运动导致颗粒联结形式更改进而重塑微观结构所导致,土的超微观结构形态变化是发生这一现象的根本因素.鉴于大气氧化过程导致的结构强度的减损效果对土体稳定性的影响是长期的且潜在危害较大,应加强监测环境物化因素变化对岩土工程的影响.

Research on variability characteristics of micropore of Zhanjiang clay under ambient temperature and pressure,normal atmospheric

Soils are generally used as building material and foundation, are normally under the atmospheric with ambient temperature and pressure, nevertheless, effect of oxidation of soil proceeding so slowly that it is no easy to perceive, long-term deterioration of soil properties, cannot be ignored. Zhanjiang Clay was taken as the object of study, studied the reformation effect on the micro-structures under the influence of the atmospheric and its impacting mechanism to soil properties, by scanning electron microscopy, mercury intrusion porosimetry and nitrogen absorption method. Research shows, after oxidized, the color of soil changes from grayish green and light grayish green to yellow and yellowish brown; while aggregation of soil particles increases, not only Swelling-shrinkage properties, but also plasticity of soil particles decreases, as for the sensitivity and structure yield strength reduced. Furthermore, atmospheric environment has an effect of shrinkage and closure on pores （d〈O.l gm）, and enlargement and dispersion on pores （d〉l ~tm）, which results in a decrease of total pores volume of oxidized clay. As far as pores （d〉1 μm） are concerned, pores volume increases remarking, with appearance of fracture porosity and reduction of ink-bottle type pores, as well as conversion from open pores to close ones. The transformation of soil properties by the influence of atmospheric is not caused by inherent changes of mineral, but the remodeling effect of micro-structures because of motion effects and chemical reactions of water-soil-electrolytes- atmosphere leading to coupling and transforming of soil particles. It is the variation of ultra-micro-structure that generates this phenomenon. Prolonged influence with comparatively large potential harmful impact on soil stability caused by damage effects on structural strength during oxidation, it turns out to be necessary to strengthen monitoring the effect on geotechnical engineering of physical and chemical factors in environment.