Microstructure Characteristics of Modified Loess before and after Drying-wetting Cycle
The chemical solidification of loess utilizes the substances generated by the reaction between the soil particles and the additives to improve the engineering geological characteristics of the soil,which has been widely used.The X-ray diffraction test,scanning electron microscope(SEM)test and mercury intrusion porosimetry(MIP)test were conducted to investigate the mineral compositions,microstructures and strengths of loess soils modified with calcium lignosulfonate,sodium lignosulfonate,sodium silicate and quick lime,and compacted loess.The drying-wetting cycle tests were performed to assess the water stability of modified loess soils.The results show that the clinochlore and gaultite that existed in compacted loess were undetected,and the mass per cent of quartz and albite in modified loess was increased from 70％to above 78％.The obvious microstructure change would result from the addition of various modifiers in loess,characterized by the decrease of pore contents,redistribution of pores and transformation of connection between soil particles.There is a negative correlation between unconfined compression strength and plane porosity.After 10 cycles of drying-wetting,the cumulative pore volume of modified loess soils was decreased,but the mean pore diameter and pore distribution showed different trends.The unconfined compression strength of modified soils decreased overall following drying-wetting cycles.Collectively,the results from both the micro-and macro-analyses indicated that the drying-wetting cycle would cause the deterioration of the geotechnical properties of modified and compacter loess.However,the calcium lignosulfonate-modified loess exhibits good surface integrity and its strength remains reasonably high after 10 drying-wetting cycles,suggesting that calcium lignosulfonate has an important function in improving the mechanical properties and resistance to drying-wetting cycles of loess.
万方数据
维普
