Effect of different media environment on dispersion of clay and treatment with lime on the dispersive soil | 不同介质环境对黏土分散性的影响及分散性黏土改性研究

Chinese. 研究不同介质环境对黏土分散性的影响，探究黏土的分散机理，确定改良黏土分散性的生石灰适宜掺量。基于非分散性土和分散性土的物理化学特性差异，模拟不同的介质环境，对非分散性黏土和分散性黏土进行碎块试验，研究介质环境对黏土分散性的影响；以不同掺量的生石灰对分散性土进行改性，并通过碎块试验和针孔试验评判改性效果，探求生石灰的适宜掺量。非分散性土在一定浓度的高Na+碱性环境下表现分散性。在含NaOH环境中，非分散黏土在pH=10.5、Na+浓度为0.3 mmol/L时开始表现分散性；在Na2CO3环境中，非分散黏土在pH=10.13、Na+浓度为0.1 mmol/L时开始表现分散性；在NaHCO3、KOH、KHCO3 、K2CO3以及NaCl等中性介质环境中，非分散性黏土不表现分散性。分散性土在中性盐溶液下分散性会减弱，随着盐浓度的增加最终丧失分散性。在NaCl和CaCl2环境中，分散性黏土分散性减弱的临界浓度分别为5和1 mmol/L。生石灰掺量为0~2.0 g/kg时，对分散性黏土改性效果不明显；生石灰掺量≥2.5 g/kg时，对分散性黏土具有显著的改性效果。适当浓度的Na+在一定的碱性环境中能促进分散，而适当浓度的阳离子（包括Na+在内）在非碱性环境中能抑制分散；生石灰是一种优良的分散性土改性剂。

English. The research was to study the effect of different media environment on dispersion of clay, explore the dispersive mechanism and find out the proper mixing ratio of lime to modify the dispersive clay. Based on the differences of physical and chemical characters between dispersive clay and non-dispersive clay, the dispersive properties of the clay soil were studied under the conditions of the different medium environment which simulated with the crumb test. The dispersive clay with lime was treated, and the results of the treatment were judged by crumb and pinhole test to seek proper quantity of lime. The results show that the non-dispersive clay presents dispersive property when it is in high-natrium alkaline condition. When it is in NaOH and in Na2CO3 environment, the corresponding critical concentration is 0.3 mmol/L and 0.1 mmol/L, with the pH 10.5 and 10.13, the concentration of Na+ 0.3 mmol/L and 0.2 mmol/L respectively. But when it is in NaHCO3, KOH, KHCO3, K2CO3, NaCl and other neuter environment, the non-dispersive clay behaves normally. The dispersive clay’s dispersive property becomes weak as the salt solution consistence rises and behaves non-dispersive in the end. When it is in NaCl and CaCl2 media environment, the critical solution density is 5 mmol/L and 1 mmol/L respectively. The lime is an effective additive when the content of lime is up to 0.25 g/kg with mass ratio, the dispersive clay becomes the non-dispersive clay. The study indicates that proper concentration of Na+ in the alkaline environment could promote dispersive property; and appropriate concentrations of cation (including Na+), in a non-alkaline environment can inhibit the dispersion. The lime is an effective additive for the dispersive soil.