| Loess is a special soil with strong water sensitivity and fragile struture.Its particularity breeds the strong disaster sensitivity of loess as engineering carrier.The role of water is the root of loess disasters such as loess landslide,foundation instability and foundation pit collapse.So,from the point of view of soil mechanics of unsaturated soil,the hydraulic-mechanical properties of undisturbed loess were studied closely around the humidifying effect of water.Among them are compression characteristics,humidifying and collapsibility characteristics,shear strength characteristics and static carth pressure coefficient K0 characteristics.Major work and research results are described below.Based on the lateral limited compression test of undisturbed loess under different water action paths,The compressibility index of undisturbed loess under different suction and moisture content is determined,and the law of compressibility index changing with suction and moisture content is revealed.The effects of size effect,loading and unloading path andforce-water action path on the compression characteristics of undisturbed loess were studied.Based on the graded humidification test under normal vertical stress,Tne influence of different vertical stress and moisture content on humidifying characteristics is analyzed,and the variation of collapsibility coefficient and moisture content with vertical stress is revealed.The influence of force-water action path and size effect on humidifying property was studied.Analysis of the relationship between saturation and suction,moisture content and suction under different vertical stresses and the influence of vertical stress on VG model parameters;The relation curves of seepage coefficient with saturation and suction are discussed.Based on the K0 consolidation test under different forces water paths,Analyzing the lateral stress variation characteristics of loess during leading,unloading and reloading,and discussing the influence of moisture content,vertical stress,loading and unloading path and force water path on K0 characteristics,It is revealed that the static earth pressure coefficient is not a constant but closely related to it,and the expression of the relationship between static earth pressure coefficient and moisture content and vertical stress under loading conditions is proposed.Based on the direct shear tests controlling suction,The characteristics of deformation development and strength play during normal suction shear are studied.The influence of suction on shear deformation,volume deformation,shear strength and shear strength parameters is discussed.the Bishop effective stress parameters ? values of undisturbed loess under different suction and the adsorption internal friction angle cpb values of Fredlund double stress model are determined based on two methods of effective stress and double stress variables. |
PDF Full Text Request