Triaxial Test Study Of NaCl Solution On Saturated Remodeled Clay

Any human productions and life are carried out in the rock-soil mass of crustal surface,while all rock-soil is composed of multiple components.Due to the charged surface of rock-soil medium,ion exchange occurs easily when the soil is fully contacted with the solution under the action of natural and human factors,which changing the pore fluid composition and concentration within the soil.And the original stress balance between the system of soil-water-electrolyte is destroyed,that makes the soil deformation and strength characteristics changed,showing a strong chemical-mechanical coupling effect,and it has an important impact on various geotechnical engineering.However,the existing theories of rock and soil mechanics have obvious limitations to solve the geotechnical engineering problems.So,exploring the influence of chemical environment change of pore water on soil engineering characteristics and its mechanism,(especially clay soil)can provide theoretical basis for related engineering problems,and also play an active role in promoting the development of the discipline of rock and soil mechanics.In this paper,clays with kaolinite as the main clay mineral composition is based as research object.Through the NaCl salt solution saturated remolding clay isotropic compression test,triaxial consolidation drainage test and mercury injection test,this dissertation systematically studies the mechanism and influence of the chemical composition and concentration of pore water on the deformation and strength characteristics of clay.At the same time,osmotic suction is used to replace the physical concentration and composition of pore solution to characterize the effect of chemical action on soil.The study finds that:First of all,the osmotic suction has a significant effect on the isotropic compressive properties of clay,which is mainly reflected in the influence on the initial elastic compression line slope and yield stress.Wherein: the initial elastic compression coefficient increases with increasing of osmotic suction and the yield stress is gradually reduced.While the elastic-plastic segment compressibility and the rebound coefficient are not greatly affected by the osmotic suction that can be ignored.Secondly,the osmotic suction significantly affects the strength properties of the clay.It shows that the shear strength decreases first and then increases with the increase of osmotic suction,but it is always lower than that of pore solution for distilled water.The reason is that the strength of soil is controlled by the change of intergranular stress and structure.When the concentration of salt solution increases,the intergranular stress increases to strengthen the strength of soil,but at the same time,it also changes the structure of soil and weakens the strength of soil.The contribution of the above two to the strength is opposite with the concentration of salt solution.When the concentration of the pore solution is lower than a certain limit,the influence of structure dominates the soil strength,but when the concentration exceeds this limit,the particle rearrangement will weaken the influence of structure,and the intergranular gravitation will increase,eventually making the shear strength slightly rise.Thirdly,the deformation of the soil is significantly affected by the osmotic suction.With the same stress,the greater the suction suction,the more significant the soil deformation is.And the shear deformation would slightly decreases when it reaches a peak,the reason is that during shear process,the soil is compacted and the soil particles are staggered,which results in a certain lateral expansion and slight recovery of the volume.Fourthly,the pore diameter distribution curves of clay under different osmotic suction are all unimodal pore structures,and the peak point was lower than the soil of distilled water and shifted to the right.With the increase of salt content,the development of electric double layer is inhibited,which promotes the transformation of clay particles from F-F dispersed structure to large pore E-E or E-F flocculated structure.