Study On Dispersive Mechanism And Improvement Of Dispersive Clay

Dispersive clay caused great destruction for some water conservancy and hydropower construction projects.The study baced on the dams construction of water conservancy and hydropower project,such as Ningxia and Shanxi provinces.aiming at the key problems to be solved of the dam core anti-seepage soils about dispersivity and basing on the fundamental theories of soil mechanics and soil science and soil physics and soil physical chemistry,taking the reaction of clay-water-electrolyte as the starting point,analyzed the physic- ochemical properties and water principle characteristic and Zeta potentials and dispersive characters of soil,studied the dispersive mechanism of the dispersive soil,improved the identification methods about the dispersive clay,and studied the modified measures in order to supply the scientific instruction for applying the dispersive soil.The comparing test is carried out between the soil samples of Yangling and Ningxia in this research.Firstly,experiment evaluate the physical and chemical properties and mineral compositio- n of the selected soil samples,with five kinds of dispersive clay identifying test,make sure the dispersion of soil Yangling samples (YL) and Ningxia samples(NX).And study the relations between dispersion and the physical and chemical properties and mineral composition of soil.Secondly,study on the effect on dispersion about the changing of medium envioriment. By changing the mediun of soil sample,combined with crumb test,double hydrometer test and Zeta potentials test,studied the changing of dispersion and Zeta potentials,and analysis the dispersive mechanism.The research indicate that the medium envoriment of dispersion always have a lot of Na+ and high pH,the changing tendency of Zeta potentials have some same points with pispersion's changing tendency,but there are some questions needed to deeply researched.Finaly,identify the dispersion of soil samples N1-6,according to the result of identifying test and current modifying methods,do the modifying test by adding different reagents for N6.The research indicate that lime is a nice modifier,and the saturated limewater can't modify soil's dispersion,and neither could CaCl2 or AlCl3,it needed further reseach.The key conclusions in this thesis can be summarized as follows:1. The dispersive mechanisms of dispersive soil in northen China lie in the adequate Na+ and the stronger alkalinity(pH>8.5)in the soil;it is not the necessary condition that how much montmorillonite contained in soil for dispersive.2. The study result that a certain content of Na+ and a certain pH value and a certain relationship are necessary conditions to make clay dispersive.3. The lime is the effective additive to improve the dispersive soil.The dispersive clay can be changed into the non-dispersive clay by mixing some limes.