Optimization Of Numerical Simulation For Stope Structure Parameters Of Thick Ore Body Based On Stress Boundary Method

With the rapid development of computer technology, numerical simulation analysis has been widely used in the research and design of geotechnical and underground projects. It not only costs less than physical model but also can calculate and analyze parameters quantitatively during recovery, which include stress in the surrounding rock, law of displacement changes as well as variations of plastic zone. Then it is able to determine their dynamic changes in each step of recovery and judge the stability of the surrounding rock.The fact that the initial stress field generated by numerical simulation is in line with the actual one is the basic condition that numerical simulation of underground projects works. Although measurement on site is the most direct way to obtain geostatic stress data, the results reflect only partial stress field around each measured point. Furthermore, it's unable to measure a large area because of the limitation of field or funding. This paper has studied Wuzhuang iron mine, the main achievements is as follows:First, it states the failure mechanism and the instability criterion of surrounding rock in stopes. It also analyses rock strength criteria, limited displacement criterion and transfixion of plastic zone criterion, all of which are currently commonly used. There are many factors that influence the stability of surrounding rock in stopes, and the relationship between them is complex, so this paper judges the stability synthetically using the three criterions above.Second, combining with the limited observed value of geostatic stress in project region, this paper uses the stress boundary method for initial stress field fitting. This method provides a new idea for simulation of initial stress field in geotechnical engineering with FLAC^3D. This idea can be described as follows: during the development of the initial stress state, it doesn't specify velocity boundary conditions for the calculation model, instead, according to the limited observed value of geostatic stress, it only illuminates stress boundary conditions on the surface of the model and keeps them invariable.Third, by analyzing the limitation of elastic solution for initial stress field at a time, this paper presents the elastic-plastic solution by stages with two steps, which is more flexible and will make the initial stress field fit the actual one better.Fourth, using the initial stress field obtained with the method above, this paper calculates thirty schemes substantially by numerical simulation. These schemes involve different structural parameters of stope. In addition, this paper makes a detailed comparison of stress in the surrounding rock, law of displacement changes as well as the distribution of plastic zone in all stopes.Fifth, based on the results above, curve of relationship between the stope span and the roof tensile stress, curve of relationship between the stope length and the roof tensile stress and curved surface of influence for the roof tensile stress made by the two factors above, have been drawled. These illuminate that the impact that the span of stope makes is far greater than what the length of stope does, although the two factors all influence the stability of stope roof rock. And the stability is decided by not only the exposed size but also the shape of exposed surface. Therefore, for steep thick ore body, this paper proposes the philosophy of designcalled "large panel, small span".