Preliminary Study On Mechanism Of In-situ Leach Altering The Engineering Properties Of REE Ore And Causing Landslide

Ion-adsorption REE deposit is a kind of unique valuable resources of china. However, its exploitation has brought some serious environmental problems. In contrast to the eliminated pool leaching technique and heap leaching technique, the present in-situ leaching technique avoid the activity of "move mountains", thus can protect the vegetation better, reduce the water loss and soil erosion, and improve the recovery rate of resources. But such technique may cause slope stability problems. In-situ leaching often induces landslide disasters, which impose direct impacts on the safety production and economic benefit of the mine. They may also destroy farmland, and even cause casualties and property losses. Thus, they attract extensive attention of society.Some researches had focused on the mechanism of in-situ leaching induced landslides, and most scholars considered that in-situ leaching leading to the local supersaturation, changes of physically mechanical properties and intensity reduction of the slope soil is the main reasons for the formation of landslides. But the genetic analyses of the previous studies were often carried out by general inference based on the site observation, lacking of experimental data to support whether or not and how the leaching process changing the physically mechanical properties of rare earth ores and eventually leading to landslides.The Xiangbiao REE deposit in southern Jiangxi Province was studied in this thesis. Several landslides had induced to occur by in-situ leaching in this deposit. On the basis of geological field investigation, the tailing samples were collected from the fresh sliding surface of 1# Landslide with 2m depth interval by the method of cutting hole. A sample of unleached rare earth ore was also collected in the location with a straight line distance less than 100 m from the 1# Landslide. The experimental studies of main engineering properties such as the chemical composition, mineral composition, particle size composition, density, liquid limit, plastic limit, swelling and mechanical properties were carried out to the samples after a few days’ drying under the sunlight. The results showed that leaching process had altered the engeering properites of the REE ore in chemical composition, mineral composition, particle size distribution, structure and mechanical properties. It was suggested that intensive chemical reaction had taken place during the the process of leaching leading to the great intensity reduction of REE ore. The results also showed that the particle size distribution of the tailings samples changed regularly with depth. It clearly revealed that significant amount of particles between 3 ~ 0.031 mm in size had migrated from top to bottom and caused pore blocking. Therefore, it was inferred that the pore blocking induced the local orebody saturation, which resulted further reduction in intensity of REE ore and eventually led to the 1 # Landslide. Key Words:in-situ leach; Ion-adsorption REE deposit; engineering property; mechanism of...