Effect Of Different Compaction Factors On Compaction Characteristics And Shear Strength Of Loess Silt

Most cities in the loess region of China have been developed along the narrow river valley,such as Luliang,Yan'an,Lanzhou,Taiyuan,etc.These urban areas are located in river valleies,which led to extremely scarce of constract lands.The shortage of construction land limits the development of these cities.Therefore,a large number of filling projects appeared in the Loess region,and the loess soil have inevitably been used as filling materials for roadbed and foundation.However,due to the particularity of loess,when loess is used as filling material in engineering,some engineering accidents often occur,which would affect on the safe operations of upper structures,once the improper filling quality control.Therefore it is position sense for filling understanding its property and ensuring filling engineering quality to study the compacting behaviors and strength of loess silt under different compacting methods and compacting parameter.In this thesis,the compacting tests of two methods were concluded on the loessy silt,and the direct shearing tests were conducted on the compacted silt,in order to study the effect water content,compact energy,compact method,layer thickness and etc.on the shear strength of compacted samples.The following conclusions were drawn out:(1)The compacting feature of loessy silt is agreed with the compacting feature of cohesive soil,that is,the optimal water content decrease and maximum dry density increases with the compacting energy increasing.In the range of this project,the effect of the compacting method on the compacting efficacy is the most obvious under the same compacting energy,and the result compacted by conventional compaction method is better than that by single blow compaction method.The thickness of layer is second effect factor,and the thicker the layer thickness is,the better of the compaction efficacy.(2)The shearing strength of compacted lossey silt is positive corrected with the compacting efficacy.Under the same condition,the shear stress and shearing displacement presents work softening at compacting water content less than optimal water content.However,the relation of shear stress and shearing displacement presents work hardening,at compacting water content more than optimal water content.And,the strengths at a long term become more or less same.(3)The cohesive force of compacted sample possesses a positive relationship with sample dry density,that is,it increases with the increment of dry density.But,the increment extent also relates with compacting water content.The extent at compacting water content less than optimal water content is less than that at compacting water content more than optimal water content.(4)In general,the friction angles are almost similar.Under the condition of same dry density,the friction angle for the sample with compacting water content less than optimal water content is bigger than that with compacting water content more than optimal water content.