In a real case story a tunnel collapsed. when simulating the problem by a numerical model using a 3D software Plaxis, at the stage of computation corresponding to the collapse, we noticed large displacements in the soil mass above the shell of the tunnel. is it sufficient to argue that the modelling the collapse was evident.
hello dear Ahmed in numerical method and its better to say in all area we have a solution to modeled the collapse in soil or structure
in software when you defined the criteria and some limits the software do the solving and when the parameters reach to this limits give you massage that the run finished.
so if you define the parameters for software that means the collapse or failure limitation when its stresses or strains and etc reached to this limit your soil structure collapsed or failure in your structure occurred. like J-K method and so on.
i am so sorry because my writing not good. apologize me dear friend.
hello dear Ahmed in numerical method and its better to say in all area we have a solution to modeled the collapse in soil or structure
in software when you defined the criteria and some limits the software do the solving and when the parameters reach to this limits give you massage that the run finished.
so if you define the parameters for software that means the collapse or failure limitation when its stresses or strains and etc reached to this limit your soil structure collapsed or failure in your structure occurred. like J-K method and so on.
i am so sorry because my writing not good. apologize me dear friend.
Hello Mr. Rouiliو
In fact, in most numerical software probable collapse zone can be detected. In some of them the plastic points are checked and in some of the others the maximum shear strain rate zones are investigated. However, if you're looking for simulating simultaneous fracture zone too, PFC software can be the most suitable.
Dear Mr. Ahmed,
Greetings,
Geotechnically, and in FEM software such as Plaxis, you can model the collapse of the structure by using SSR (Shear Strength Reduction) method, this allows you to determine your ultimate strength of the subsurface against the external loading which causes the collapse, this will provide you the exact failure loading or the ultimate strength instead of trial and errors approach, and then you can compare it with your mechanical and structural loading of your structures. If Rock is presented in your formations, then you have to use another software in conjunction with plaxis, to utilize DEM analysis.
FE programs like PLAXIS can only do continuum analysis, in which the failure can be judged through the concentration of shear strains but the real failure that includes large strains with separation of zones and cracks, as happens in real tunnels cannot be visualized. The only way to simulate the failure reasonably close to as it occurs in field is through discontinuum programs like UDEC and 3DEC.
Instability in the context of mining has been studied extensively using numerical methods. Among the methods is the finite difference method, employed in discrete element codes such as PFC and UDEC. These codes seem to capture the mechanics of unstable failure reasonably well. Consider the work of Gu, R., Garvey, R., Kias, E., Ozbay, U., and Poeck, E. for reference.
Adding to the question raised by Mr. Ahmed Rouili, How effective is the use of FLAC in simulating the collapse of underground structures?
Numerical analysis can't capture the inherent geological uncertainity in tunnelling.
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