Study On Deformation Characteristics Of Undisturbed Loess Under True Triaxial Compression And Humidification

During the formation of natural loess deposits,a large-pore overhead structural system will be produced under arid or semi-arid climatic conditions.The special structure of loess is an important factor that determines its mechanical properties.With the development of the western region,a large number of actual projects have been carried out in the loess area.Due to rainfall,irrigation,and rising groundwater levels,the collapsible loess will have different degrees of humidification and deformation problems,resulting in landslides,road cracks and foundations.Uneven settlement and building tilt hazards.In this paper,the uniaxial compression and single-line method of true triaxial humidification and collapsibility tests of undisturbed and remolded loess were carried out.The humidification deformation law and its cause of undisturbed loess under true triaxial complex stress conditions were mainly studied.(1)The unconfined compression test of undisturbed and remolded loess with different water content shows that the stress-strain curves of undisturbed loess with different water content show softening type,and the curve of remolded loess changes from softening type to weak hardening with increasing water content The reason is that the disturbance of remodeling will lead to the destruction of the internal bond of the loess,forming a new structure;as the water content increases,the undisturbed uniaxial compressive strength and undisturbed structure index of the reshaped loess become smaller,and the When the water content is low,the rate of decrease is fast,which means that the lower the initial water content,the more sensitive the structure decreases to water.(2)Carry out the humidification and collapsing test of the true triaxial single-line method under the condition that the main principal stress parameters are constant and the different stress ratios and spherical stresses.It is concluded that when the intermediate principal stress parameters and stress ratio are constant,the spherical stress increases and the humidification The amount of deformation increases and gradually tends to be gentle;the medium principal stress parameter and the average spherical stress are constant,the stress ratio increases,the amount of humidified deformation increases,and the humidified deformation of the loess slightly humidified when the large stress ratio is large.Calculation formulas of humidified body strain and humidified shear strain reflecting the influence of force and water on humidification deformation were established.Moisture deformation of the loess is the mechanical response of the soil structure under the action of force and water,which is accompanied by the healing and development of the soil structure after damage.(3)A true triaxial single-line humidification and collapsibility test was carried out under the conditions of constant spherical stress and different intermediate principal stress parameters and stress ratios,which showed that with the increase of the intermediate principal stress parameters,the humidified body strain and shear strain were both equal It gradually increases,similar to the law of different stress ratios.However,the law of humidification and deformation in different principal stress directions is different,which is related to the change of stress ratio or medium principal stress parameter,and the change of the stress in the three principal stress directions of the soil;when the medium principal stress parameter or stress is relatively large,the humidification is in the small principal stress The direction of stress is more prone to bulging deformation.