| In recent years,with the development of China's mineral economy,mining activities have become more frequent.Stope abandon large quantities of slag and tailings to pile up at will,occupying agricultural land,seriously polluting water and land resources,and leading to kinds of geologic hazards.Xuanhua area is rich in mineral resources,mining has a long history,there's a lot of private mining,a large number of mining wastes have been formed over the years,they accumulated on the gullies and slopes,most of slag are loose and low mechanical strength,they are easy to induce clastic flow disaster in case of short time heavy rainfall,they pose a major threat to the safety of people's lives and property.Through the data and field investigation,combined with the field investigation and remote sensing image interpretation,the geological environment of Xuanhua area is summarized systematically,the effects of rainfall,landform and geological structure on the clastic flow disaster are analyzed,the distribution and accumulation characteristics of slag in Xuanhua area were ascertained.Combined with the tests of typical slag,studied on the physical and mechanical properties and mineralogical properties of slag,analysis of the relationship between the two and critical moisture content.Based on the above research,studied on the factors affecting the start of slag,discussed the induction mechanism of slag and the initiation mode of clastic flow.PFC software was used to simulate the sliding state of slag in different water content and monitor the speed of its decline,verified with the startup mechanism of slag,look forward to providing scientific basis for the disaster warning of clastic flow in Xuanhua area.The main achievements of the study are as follows:(1)There are a large number of slag deposits in Xuanhua area,they spread all over the area,account for about 6.5% of the total area.Slag accumulated on the gullies and slopes,they can be divided into two forms: slag accumulation and tailings reservoir.(2)The results of tests on mineralogical and physical mechanical properties of slag indicate : The strength of slag is affected by the granule gradation and permeability of slag soil,it is closely related to the types and contents of clay minerals in slag.(3)The critical moisture content of clastic flowis determined.Through the shear strength tests of the same moisture content with different dry densities and the same dry density with different moisture content,the correlation between the cohesive force of slag,the angle of internal friction and the moisture content was obtained,and the critical moisture content of the slag was determined.(4)The starting mechanism and hazard model of slag flow are put forward.When loose slag encounters short-term heavy rainfall,surface water power is strong,rainwater percolates quickly in the slag-gravel sand,soil weight was increased,but because of well water swelling of clay minerals in slag,slag drainage was blocked,cause rapid increased in moisture content,and shear strength was reduced,when the slag lose its strength or the sliding force exceed the shear strength,the slag start to slide down to form slope debris flow.The slope deposit and secondary loess are scraped along the slide of the clastic flow,increased the amount of material and source the fine particles,then induce debris flow.Using PFC software to analyze the starting process and sliding speed of slag,the start-up mode of slag was verified. |
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