Study On The Relationship Between The Variation Of Soil Mass And The Genesis Of Landslide In Ion-type Rare-earth In-situ Leaching Slope

As one of the national non-renewable strategic resources,ionic rare earths are widely used in various industries due to their unique physical and chemical properties.In order to meet the needs of various sectors and export supplies,China needs to mine large quantities of rare earths every year.However,the huge production and sales volume creates not only wealth but also ecological and environmental problems.At present,landslides still occur at in-situ leach sites,and most scholars at this stage have analysed their occurrence qualitatively through field investigations and basic knowledge that they are caused by fluid injection and rainfall,while fewer studies have combined particle size distribution with permeability and analysed the causes of landslides through specific indoor test data.Taking the landslides in ion-type rare-earth in-situ leaching slope of Wenlong stopeⅠ in Longnan,Ganzhou as the research object,and based on detailed field investigation and systematic sampling,combined with indoor soil tests,this thesis studies the particle size distribution,permeability and shear strength of the soil mass,and comprehensively analyzes the relationship between the variation of soil mass and the cause of landslide.The main conclusions are as follows:(1)Leaching is indeed the root cause of the landslide of the in-situ leaching stope.The sliding surface is spread along the interface between weathered granite and residual overburden,rather than along the " leaching liquid level"(upper interface affected by leaching liquid)in the ore body.(2)The particle size distribution of the landslide soils at the leach site is dominated by gravel and fines,with a relatively small amount of sand.The overall gravel content does not vary much,while the sand content increases and then decreases down the slope,finally converging at the foot of the slope,and the fines content gradually decreases.(3)The permeability coefficient at standard temperature of the specimen decreases with increasing fines content and decreases to a lesser extent.When the difference in particle size distribution between coarse particles is not significant,it has a smaller effect on the permeability of the specimen than fine particles.(4)The shear strength and cohesion of the specimens increase with the increase of the fines content within the range of 25%～35%,when the fines content exceeds 35%,the shear strength and cohesion of the specimens decrease with the increase of the fines content,the angle of internal friction remains basically the same within the test fines content;The shear strength of the specimens generally decreases with increasing moisture content,the cohesion increases with increasing moisture content in the range of 5%～15%,and decreases with increasing moisture content when the moisture content exceeds 15%,while the angle of internal friction decreases first with increasing moisture content,but basically remains the same when the moisture content exceeds 15%.(5)Under the continuous action of rainfall and liquid injection,the migration of fine particles changes the particle size distribution and pore structure of the slope body,resulting in a relative water barrier in the slope body.The pore water pressure in the upper part of the slope body is at a high level and difficult to reduce,which in turn reduces the shear strength of the upper soil body,forming a softening zone and eventually a landslide occurs.