Effect Of Ion-electrokinetic Consolidation On Soil Shear Strength Characteristics In Collapsing Hill

As an extremely harmful type of water and soil loss,collapsing hill has always been concerned by experts and scholars.The quantity of the traditional collapsing hill governance model is large and the cost is high.It often needs to excavate the wall of the collapsing hill,which can easily lead to secondary erosion.Whether an in-situ remediation method with smaller project quantity can be found has become a key issue in the management of collapsing hill erosion.Therefore,this study provides a new idea for the treatment of collapsing hill by revealing the feasibility of electrokinetic consolidating collapsing hill and exploring the relationship between ions and the soil shear characteristics of collapsing hill.Based on the ion effect,three different layers of collapsing hill soil were taken as the research object,through the indoor experiment to analyse the regularity of shear characteristics of collapsing hill soil after adsorbed different ions(K+,Ca2+,Fe3+)and electrokinetic consolidation.The results were as follow:(1)After ion adsorption,the shear strength values were measured under the same conditions.It was found that K+ did not strengthen the soil in three soil layers.Fe3+ entered the soil and formed Fe(OH)3 colloids,which improved the soil cohesion to a certain extent.The effect of Ca2+on the improvement of soil cohesion was the most significant,and the effect was best when the additive amount was 10 g/kg.(2)The shear strength of the soil in red soil layer decreased after the first increased with the increase of soil moisture content.The shear strength of blank red soil layer reached its peak when the water content was 25%,while the maximum shear strength of the red soil layer with Ca2+ appeared when the soil moisture content reached 20%.The relationship between soil cohesion and soil moisture content in red soil layer was the same as between shear strength.In both treatments,the internal friction angle of red soil layer decreased significantly with the increase of the soil moisture content.(3)With the increase of the soil moisture content,the shear strength of sandy soil layer showed a trend of decrease,and dropped to zero when the soil moisture content was 30%.In both treatments,the cohesion of sandy soil layer decreased with the increase of the soil moisture content.When the soil moisture content was 10%,the cohesion of sandy soil layer with Ca2+ adsorbed was 115.07%higher than that of the blank,and had the best consolidation effect.In both treatments,the internal friction angles of sandy soil layer were stable and did not produce large fluctuations with the increase of soil moisture content.(4)The relationship between shear strength and moisture content in detritus layer soil was similar to that in red soil layer.The internal friction angle of adsorbed Ca2+ detritus layer soil was relatively stable after the soil moisture content exceeded to 15%,and the internal friction angle of blank detritus layer soil decreased gradually with the increase of soil moisture content.(5)After the electrokinetic consolidation(CaC12),the shear strength of the soil in three soil layers improved significantly.Compared with the direct addition of CaCl2,the improvement effect of the cohesion of three soil layers after electrokinetic consolidation performed as detritus layer>sandy soil layer>red soil layer,and the red soil layers' effect were close.There was no significant change in the internal friction angle of the collapsing hill soil before and after electrokinetic consolidation.In summary,K+,Ca2+ and Fe3+ have different effects on the soil shear characteristics of collapsing hill.The use of CaCl2 solution for electrokinetic consolidation of the collapsing hill is feasible.