Experimental study on improvement design of loess curing in engineering environment

摘要

This paper investigated the characteristics of improved loess curing in engineering environment. Loess was divided into silt and silty clay, and lime and lime-fly ash were selected as admixture materials. Direct shear tests and permeability tests were performed to research the rules in strength and permeability. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) tests were performed to analyze the improved mechanism. The conclusions are as follows: (1) compared with results curing in laboratory conditions, the fast change periods of strength and permeability starts later and continues longer time for each improved type when curing in engineering environment. For fast change periods of strength, the remolded compacted loess and 2:8 lime-treated loess are between 14 similar to 28 days, 3:7 in 14 similar to 90 days, and lime-fly ash-treated loess in 28 similar to 180 days. As far as permeability is concerned, the permeability coefficient of lime-treated loess and lime-fly ash-treated loess reaches 10(-7)cm/s in 90 days and 180 days, respectively. (2) Over the long term, the improvement effect still occurs at a slow rate. From 180 to 1090 days, the strength of lime-treated loess and lime-fly ash-treated loess increased by 13.2 similar to 16.5%, and their permeability coefficients decreased by 4 similar to 7.7%. (3) The properties of untreated loess have a significant role in strength and permeability, and silt and silty clay own different effect ways. (4) Curing conditions and untreated loess properties results to differences of improved loess in age standard and improvement effect, these effects should be considered in engineering projects.