Experimental Study On Modification Of Dispersive Clay By In-situ Injection

Dispersive clay is widely distributed.Because water conservancy projects often use local material,it is inevitable to use dispersive clay as filling material for dikes and dams in many projects.However,the dispersive clay has the characteristics of low erosion resistance and water dispersion,which often results in engineering accidents with hidden damage location and rapid destruction process.Therefore,it is of great significance to study the modification of dispersive clays.In this paper,the optimum formulation of ACC modifier composed of AlCl₃,CCl₃COOH and CaCl₂ and the modification effect of in situ penetration were investigated.The modification effect of the modifier is comprehensively appraised by the dispersibility appraisal test?pinhole test,debris test,double hydrometer test,exchange sodium ion percentage test,pore water soluble cation test?.At the same time,combined with the performance-price ratio as a reference index,the modification ability of the dispersible clay modifier is evaluated,and the optimum proportion of the dispersible clay modifier is obtained.Based on the developed ACC modifier,the in-situ penetration modification experiment was further designed.The optimum scheme of in-situ penetration modification was explored by controlling the influencing factors such as the dosage of modifier,the compactness of soil and the curing time.Finally,the mechanism of in-situ modification was analyzed by scanning electron microscopy?SEM?,permeation test and solute transport simulation.The conclusions are as follows.?1?ACC modifier,as a chemical modifier of dispersive clay,can give full play to the advantages of the three materials and promote the overall improvement effect.When the mass fractions of the three modifiers are 0.01%AlCl₃,0.05%CaCl₂ and 0.05%CCl₃COOH,the modification effect is remarkable and the most economical.?2?In the study of influencing factors of in-situ penetration modification,the effect of in-situ modification are better with the increase of dosage of modification solution,and the effect of in-situ modification are worse with the increase of compactness.When the compactness is 96%and the dosage of the modifier is 4%?120g?,the sample with a infiltration area of 78.54 cm²?10cm diameter?can be completely modified to a depth of5cm,and the soil layer with a depth of 5-10cm can be modified to a transitional soil.?3?There are two main factors affecting the effect of in-situ modification of dispersive clays.One is the penetration range of the modification solution,the other is the physical and chemical reaction effect produced by the interaction between the modification solution and the clay.With the increase of compaction degree,the permeability coefficient of caly decreases,which is the main factor affecting the permeability of modified liquid.?4?The action mechanism of ACC modifier is that it can provide high valence cations to replace sodium ions in clay,reduce the thickness of electric double layer between grains,produce cementitious substances and reduce the alkalinity of soil,thus inhibiting the dispersion of clay.