Influence And Mechanism Analysis Of Water Envioonment On Engineering Performance Of Sodium And Calcium Soils

Excessive discharge of pollutants such as waste gas,waste liquid,waste residue and other pollutants make soil contamination worse.It also effects the soil properties and mechanical properties dramatically.The soil which is under the condition of mutative water environment can promote the research on the engineering properties and mechanism analysis,which can help people recognize the impact on environmental change further.In this study,sodium-based and calcium-based treatments were performed on cohesive soils.Dispersibility,disintegration properties,mechanical properties,permeability properties,and microstructure of sodium soil and calcium soil were tested in this study in different water environments,aiming to explain the mechanism how ion effect and alkaline solution effect the engineering performance of the soil.And then,a simplified model of interparticle force was established,following the main findings.?1?Fragmentation and disintegration tests show that the sodium soil is less stable than calcium soil in water.Sodium soil is dispersive in low-concentration alkaline solutions.However,due to the salt in the solution,it shows to be transitional and non-dispersive in the end,and it is more stable in the water.Calcium soil shows transitional when the solution is in low alkaline concentration and it shows to be transitional which there is Na⁺displacement.The more dispering the soil shows,the more amount of final disintegration is produced.?2?Compression tests and direct shear tests show that the calcium soil has higher cohesion,internal friction angle and compressive modulus to the sodium soil.Under the same concentration,the compressive modulus and cohesive force of soil samples in different salt solutions are ranking in NaCl>KCl>CaCl₂.And the compressive modulus and cohesion of the soil decreased with the increase of solution concentration.The compressive modulus of the calcium soil is higher than that of the sodium soil in the alkali solution.?3?Permeability tests and scanning electron microscope tests show that the permeability coefficient of sodium soil and calcium soil belong to low-permeability soil(K<1×10^-5cm/s).Since the calcium soil has more pores than the sodium soil,the calcium soil has stronger permeability.The increase of the solution concentration increases the condensation effect between the soil particles obviously,and the porosity in the soil increases.When the sodium soil was placed in NaCl solution,KCl solution and CaCl₂ solution,the permeability of the soil increased.The permeability coefficient of the calcium soil is lower than that of the sodium soil in the alkali solution.?4?Considering the type,concentration,acidity and alkalinity of ions in aqueous,a model in the interaction between soil particles,which includes electrostatic repulsion,hydration repulsion,pore water pressure,van der waals attraction,and cementing force.When repulsion equals gravity,the soil-water-electrolyte system is in balance.When repulsion greater than gravity,the soil is dispersive in the solution.When gravity greater than repulsion,the soil particles appear to agglomerate,due to the repulsive force is less than the attraction force.