不同类型盐渍土固化体的干缩与湿胀特性
Investigation on dry shrinkage and wet expansion of solidified saline soil containing different salts
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摘要: 采用三种固化剂对高含盐量的氯盐盐渍土和硫酸盐盐渍土进行固化,研究了它们的干缩和湿胀特性。结果表明,用矿渣和粉煤灰取代部分水泥,随后又增加粉煤灰的比例,可以连续降低固化土的干缩应变和干缩系数。矿渣和粉煤灰取代水泥后,水化活性减弱,产物减少,同时,体系内Ca2+的浓度降低,盐渍土中所含NaCl和Na2SO4对化学反应的促进作用减弱,化学反应程度以及由此引起的自由水到结合水的转化、孔隙特征的变化的差别缩小,因此,盐分引起的固化土的干缩应变和干缩系数的差别缩小。Na2SO4对固化土干缩应变和干缩系数的提高作用比NaCl明显。在低钙体系中,NaCl的物理作用比化学作用更突出。含NaCl的固化土试件在吸湿阶段具有明显的吸潮特性,但并不引起较大的膨胀。残存在土体中的Na2SO4在吸湿阶段可能发生剧烈膨胀而导致土体发生严重开裂。Abstract: Dry shrinkage and wet expansion characteristics of saline soils containing rich chlorine and sulfate,solidified by three sorts of soil stabilizers were investigated.It was shown that dry shrinkage and shrinkage coefficient of specimens decreased if partial cement was replaced by fly ash and slag,and then further by more fly ash.Compared with cement,the chemical activity of fly ash-slag stabilizer was lower and thereby less reaction products were produced.Furthermore,less calcium ions were provided so that the promoting effect of chlorine and sulfate on chemical reaction in soil was weakened,resulting in the differences of chemical reaction degree and therefore the transform from free water to bound water and also the pore characteristics between the specimens with salt and those without salt were reduced.So the difference caused by salts in dry shrinkage and shrinkage coefficient of specimens was also reduced.The positive effect of sodium sulfate on the increase of dry shrinkage and shrinkage coefficient was stronger than that of sodium chloride.In low calcium system,physical effect of chlorine was more obvious than its chemical effect.In moist environment,moisture absorption of the specimens with chlorine was obvious but without huge expansion.However,much rudimental sodium sulfate in soil might cause serious cracks in specimens by huge expansion.