Study On The Collapsibility Of Typical Loess Under Unsaturated Humidified Conditions

The traditional evaluation and research on loess collapsibility are based on the completely saturated state.In practical engineering practice,the loess has undergone obvious additional deformation when it is not saturated,which is called humidification deformation.Under the leadership of the national“the Belt and Road Initiatives”,more construction will be built in the central and northwest parts of the country.In these areas,the shallow buried undisturbed loess,or fill loess slope treatment,foundation construction,land subsidence treatment and other engineering construction will face different degrees of loess humidification deformation which is difficult to monitor.It is necessary to study the humidification and deformation of loess in order to provide a reference for engineering construction.Here,we analyse undisturbed loess（Q₃）in tongchuan region of Shanxi province as the research object.Analyze the change law of soil moisture content and collapsibility under unsaturated humidification conditions.Define the unsaturated humidification collapsibility coefficient through laboratory experiments;Use ABAQUS software to numerically simulate the deformation characteristics of the unsaturated loess soil under the conditions of seepage and consolidation,analyze the law of humidification deformation over time.The main research contents are as follows:1.Determine the basic properties of the soil samples such as moisture content,specific gravity,density,liquid plastic limit,material composition and microstructure.The particle size of the sample is mainly powder,high proportion of primary minerals,and the clay minerals are dominated by the mixed layer of Imonite.The collapsibility coefficient is 0.078,which is a strong collapsibility;the self-weight collapsibility coefficient is 0.005,which is a non-weight collapsible loess.The microscopic type of the sample is a framework-like structure,with mainly powder particles as the framework,which constitutes a loose and relatively uniform type of larger pores.2.Using self-made acrylic device to carry out the unsaturated humidification process of the soil column,measure the moisture content value at different positions of the soil column at different times.Analyze the change law of soil moisture content under the unsaturated humidification condition.3.Take samples from different positions of the test loess soil column to test unsaturated humidification coefficient.Analyze the influence of target water content,humidification time and test pressure on the unsaturated humidification coefficient and the overall unsaturated humidification of the soil column.4.Use ABAQUS numerical simulation software to simulate the seepage and consolidation of the loess site with a certain degree of saturation,analyze the cumulative humidification deformation of the loess soil layer under seepage and consolidation conditions over time.