Research Of Similarity Model Test On Open Pit To Underground Mining With Super High-steep Slope

Similar model test of rock mass is mainly used to study the mechanical characteristics and deformation mechanism of rock mass related to underground structure, it can really simulate the complicated underground structure, geological structure and stratum combination. Some special rules and phenomenon can be found in the model test, and can be confirmed with the theoretical research, but because of long duration, large investment, high difficulty, therefore the physical model test is rarely used in underground engineering.Open-pit to underground mining is the inevitable trend of the development of domestic and foreign open pit mines. In the process of mining, high steep slope and underground mining influence and restrict each other, their mutual influence mechanism is the guarantee and theoretical basis of safety production. It is necessary to adopt the model test to research the stability and potential mechanism of deformation-failure to high slope and underground stope under the influence of underground mining. At present, the similar material model test is facing many technical problems, such as the limitations of similar material, rationality of fault fracture zone simulation, measurement technology and so on, the solution to these problems is the key point of this research.This article is main contents of the National Natural Science Fund Project "the research of mutual influence mechanism between high-steep slope and underground mining"(41072219), taking Daye iron open-pit to underground mining conditions as the basis, follow the principles of similarity theory, starting from the research of model test technology, developed the rock similar material, completed the design of model test, analysis and compare the model test results with numerical calculation software. The main research contents and results are as follows:(1) The research of engineering geological properties and model generalization.①The engineering geological properties are analyzed through data collection, geological investigation and indoor-outdoor tests of the east open-pit stope of Daye iron mine.②Choosing the1-2profile between26～31#exploration line at the Shizishan mining area as the typical section of model test, the rock mass of the profile can be generalized as diorite, marble, magnetite and backfill, the fault fracture zone can be generalized as F9and F25fault.(2)Similarity theory analysis and the development of similar materials.①Selected geometry’s similar constant as300, the physical and mechanical properties of rock similar material are derived according to the similarity theory.②A new kind of similar material of underground caving mining model test which consists of iron ore powder, barite powder, quartz sand, unsaturated resin, gypsum, etc was developed through a lot of material mechanics test which are high availability.(3) Study on the physicochemical properties of rock similar material.②The test of physical and mechanical properties of similar material show that the density of similar material range from2.37to2.83g/cm3, the elastic modulus range from11.423to127.935MPa, the compressive strength range from0.091to0.884MPa, the cohesion range from2.3to12.01kPa and the friction angle range from15.93°to38.59°②The sensitivity of every factor is analyzed by using variance and range analysis method. It concluded that the weight ratio of iron ore powder has control effect on density and internal friction angle, and the weight ratio of unsaturated resin has control effect on compressive strength, elastic modulus and cohesion.③The analysis results of the rock similar material by using environmental scanning electron microscope show that the particles are irregular shape, spherical less, poor roundness, pore connectivity and containing different degree of cementation.④The analysis results of the rock similar material by using X ray fluorescence spectrometry show that the60%contents of the similar material are ferric oxide and barium oxide. So the chemical activity of similar materials are low, the physical and mechanical properties are stability under natural environment.The physicochemical properties of rock similar materials show that the physical and mechanical properties of similar materials are stability and the materials can meet the the needs of marble, diorite and iron ore for Daye Iron Mine’s underground caving mining model test.(4)Development of physical model experiment system.①The overall scheme of the complete model test is designed. The model block production device is developed to solve the forming problem of rock similar material block which are high gravity, low deformation modulus, low strength.②According to the characteristics of open mining and sublevel caving mining, similarity mining technology and mining plan of model test is designed under the existing experimental conditions.③According to the research need,12dialgage,39strain foil,2soil pressure cell and59photographic objective are arranged in the model surface to monitor the model test process.(5)Model test of open-pit to underground mining.①Study on mechanical characteristics of slope in the process of open-pit to underground mining process. In process of underground mining, the horizontal displacement of slope grow rapidly. The displacement of northern slope is always greater than the total value of the south slope. The largest vertical displacement appears on the top of northern slope, the value of about-0.15mm that is-45mm equivalent to prototype, the largest horizontal displacement appears at the toe of north slope. The value of about-0.23mm that is-69mm equivalent to prototype. The principal stress of slope are pulling stress and parallel to slope surface. The southern slope are more stability than northern slope.②Study on mechanical characteristics of the surrounding rock of stope in the process of open-pit to underground mining process. During the process of open-pit to underground mining, the displacement of surrounding rock decrease with the elevation reduction and horizontal distance from the center. Before mining to a certain level, the rock maximum stress of a level increase slowly with the increase of mining depth, when mining to the level, the rock maximum stress jump to the maximum value, after mining below the level, the rock maximum stress decreases with the increase of mining depth.(6)Research on digital photogrammetry technology in model tests. Research shows that: Digital photographic measurement technology applies to large deformation and displacement measurement, it can dynamically monitor the process of this model test, analysis the deformation trend at each part of model. The results provide the new testing technology for experimental study of model test and will be conducive to the application and development of model test.(7)Study on numerical simulation compare with model test. Choosing the typical cross section of physical model test as the research object, using the FLAC software to analyse the comparison between numerical simulation and physical experiment. The results show that:①Because of the unloading effect in open pit mining process, the phenomenon of displacement and stress rebound appear at the toe of slope.②The largest vertical displacement appears on the top of northern slope.③Displacement of surrounding rock and the slope increase gradually during the underground mining. The maximum principal stress are in layered distribution and gradually increasing from bottle to top of the slope.④The mechanical characteristics of the slope and the surrounding rock of stope in the process of open-pit to underground mining process described in numerical simulation is the same with the results of model test. Both the results studied by model test and numerical simulation can be verified with each other.