Characteristics Of Strength Of The Interface Between Disturbed Loess And Compacted Loess

In recent years,a large number of land reclamation projects,including mountains cutting and trenches filling engineering and land creating engineering,have been launched in loess area of western China for alleviate the problems of land shortage and soil erosion.Large-scale interface between compacted soil and undisturbed soil(shortly referred to as the interface)is produced in the engineering,which is the weak areas in whole engineering.Cracks and gullies in the interface easily caused by uneven settlement created by the deformation difference of undisturbed soil and compacted soil and water scouring,which may lead to landslides,endangering the safety of people's property.The strength characteristics of the interface are studied and the mechanism of lime-modified was analyzed and the excellent lime dosage was given by compression test and direct shear test,based on the strength and deformation characteristics of loess in this study.The research conclusions follow as,(1)The greater the compaction of the loess,the smaller the compressive strain.The higher the moisture content,the greater the compressive strain,but the effect of moisture content on compressibility decreases with increasing compaction.The ?–p curves of compacted loess are hyperbolic.The interface failure caused by cumulative effect of uneven deformation of undisturbed loess and compacted loess.(2)The internal friction angle of the interface increases with increased compaction and decreases with increased moisture content.The cohesive force increases with increased compaction and decreases with increased moisture content.The change in the moisture content has a more significant effect on the shear strength compared with the influence of the change of compaction.The shear strength of compacted loess is always greater than the interface,and the increase of moisture content will gradually reduce the difference of those shear strength indexes in same compaction condition.When moisture content is high,the difference is almost 0.the sudden decrease of the friction angle of compacted soil slightly lags behind the interface in the moisture content increasing.(3)The internal friction angle of the interface with lime increases with the increase of lime content,and the increase is significant in 2% dosage.The cohesive force increases with the increase of lime content,and the increase is significant in 4% dosage.Lower moisture content is easy to exert the reinforcing effect of lime,and it is beneficial to exert the late strength of the lime-interface.(4)The stress-strain relationship curve of the lime-interface gradually changes from strain hardening to strain softening with the increase of lime content.When the lime content is more than 6%,it shows brittleness.The age has a significant effect on the shear strength of the lime-interface,but there is little effect on the shear strength of the interface of loess.The shear strength of the lime-interface increases with the increase of age.(5)SEM tests show that the structural and overhead pore structure of the lime-interface improved significantly with the increase of lime content and age.The formation of shear strength of lime-interface is mainly due to ion exchange,carbonation and ashing.