Research Of Similarity Model Test On Open Pit To Underground Mining For Slope Deformation

Geomechanical model test is a kind of scale rule research method to specific geotechnical engineering problems based on the similarity principle,it can really simulate the complicated underground structure,geological structure and stratum combination.So we can through it to study some special rules and phenomenon,which can be related to the reality by the similarity theory.This paper was based on Yanqianshan Iron Mine which was transiting from open pit to underground mining.Slope deformation and failure which caused by underground mining can be researched through the model test.The main research contents and results were as follows:(1)The engineering geological properties were analyzed through data collection,and choosing a representative area as the typical section of the model test.According to the engineering geological characteristics of the selected section and field test conditions,the geometric similarity ratio between the model and its prototype was 1:200,and the density similarity ratio between the model and its prototype was 1:1.The physical and mechanical properties of rock similar material were derived according to the similarity theory.The similar material composed of cement,quartz sand,barite powder,iron powder and gypsum,the quality ratio between them for 1:28:28:6.67:3,and then stirring in water which is 10% of the total quality.(2)A physical model test system was designed,which was used to simulate the process of underground mining,it is composed of model box and the system to simulate sublevel caving without bottom pillars;The 3D laser scanning technology and distributed optical fiber monitoring technology were introduced into model test,which were used to monitor deformation,in addition artificial measurement was also included.(3)Model test of open-pit to underground mining,the test shows that:(1)As the test for the degree of strata movement and slope deformation which caused by underground mining was more and more bigger,the joint failure that caused by the excavation process were controlled by the steep dip layered rock mass structure,which presented the rip-collapse failure;(2)Strata movement and slope deformation that caused by underground mining presented three stages: first stage,at mined-out areas the gravity redistribution of thesurrounding rock would lead to a slight cracked and relaxed rock mass;Second stage was the stage of tension crack getting through,and the development stage of crushed zone;Third stage,dumping damage was occurred along the steep dip fracture and towards the mined-out areas;(3)Strata movement and slope deformation was caused by gravity redistribution,and controlled by the steep dip layered rock mass structure,but the level of dumping damage was controlled by the crack,not controlled by the strata.