Study Of Dredged Sediments Solidification Mechanism Based On Water Transfer Model

Large amount of dredged materials (DM) may produce in dredging projects, solidification method can transfer it to useful soil resource effectively. As to the difficulties for quantitatively mechanism study, a new method was proposed to study the solidification mechanism from waster transfer angle. The particular content includes:(1) water transfer rule study during cement treated DM. The characteristics of cement solidification was analyzed firstly, a water phases classification method was proposed to classify water as free water, bound water and hydration water in solidified dredged material and cement hydration resultants. The soil-water suction potential index pF value was used to classify soil water, when pF value higher than 7.0, the water is hydration water. When pF value lies between 3.8 and 7.0, the water is bound water. Through the hydration water content and bound water content determination of different cement and curing time for three DMs, two water transfer models were built each for different cement content and different curing time. The water transfer models show cement reacts firstly with free water, the reaction can transfer free water to hydration water and bound water in cement hydration resultants. The hydration water in cement hydration resultants may be used to indicate the content of crystallized hydration resultants, while the bound water may be used to indicate the content of gel like hydration resultants.(2) Mechanical characteristics study of solidified DM. As to the three solidified DM at different cement content and curing time, unconfined compressive tests, iso-compression tests and consolidated undrained triaxial compression tests were done. Through tests the change rule of unconfined compressive strength, deformation, failure type, effective cohesion, deformation coefficient, structure failure stress, iso-compression coefficient and void ratio with cement content and curing time were make clear. Based on the analsis of mechanical behaviors of solidified DM, the conclusions of solidified DM strength comes from binding, filling and skeleton bracing actions of cement hydration resultants were drown.(3) Correlation analysis of water transfer content and mechanical properties. Through the quantitative analysis of hydration water content and bound water content- in cement hydration resultants with mechanical properties, the results show crystallized hydration resultants attribute to strength continuly, while when the content of gel like hydration resultants is small, the attribute is low, when the content increase to a certain value, the action of gel like hydration resultants exceed crystallized hydration resultants. When the two hydration resultants contents were small, the solidified DMs have no strength.