Study On The Response Of Slope Soil To In-Situ Leaching In An Ion-Adsorption REE Mine Lot,Southern Jiangxi Province

Ion-adsorption REE is a kind of unique valuable resources of China.However,serious ecological environmental problems arise from the REE exploitation.In order to relieve the environmental destroy as well as soil and water loss,and to improve the REE utilization,the in-situ leaching technology has been compulsively carried out by government.But such in-situ exploitation often induces landslides.Thus,how to effectively prevent and control the landslides is an urgent issue which needs to be solved by the in-situ leaching technology.The lacks of deep understanding on the genetic mechanism of landslides in the in-situ leaching stopes is the root reason causing the difficulty of preventing and controlling the landslides.An Ion-adsorption REE deposit in Southern Jiangxi Province is studied in this thesis.The samples of ores and top soil have been systematically collected in the back wall of landslide.Through the X-ray diffraction analysis,chemical analysis,screening,laser particle size analysis as well as the mineral identification and microstructure study on the soil thin section,and combined with the leaching experiment,the temporal-spatial variation laws of mineral composition,size distribution and microstructure are studied in this thesis,to reveal the response of slope soil in mineral composition and structure to in-situ leaching,analysis the deformation and failure process of the slope soil,and then the genetic mechanism of landslides.The results show that the in-situ leaching can greatly facilitate the k-feldspar weathering,and form illite(hydromuscovite),which strengthen the expansibility and reduce the intensity of ores.Moreover,such process trends to decrease the particle size of ores,but the recrystallization of Si O2 which released in the weathering process not only increases the quartz composition,but also increase the its particle size,promoting the A-type particle structure of ores transferring to B-type structure and thus increasing the macropores.Under the condition of long-term and high-intensity injection,fine particles migrate downward along the micropores and fracture among the quartz particles.Due to the low connectivity between micropores and fractures caused by the highcomposition of clay minerals,such migration easily gives rise to the blocking of pores(fractures),increasing the water content,even to saturation,strengthen the expanding of clay minerals,further decreasing the intensity of ores,and the landslides occur by the injection pressure and its gravity.In addition,the favorable microtopography,such as valley wall and top of gully,and the strong rainfall are also the external condition and force that evoke the landslides.