*2.3.4 Analysis 3D finite element method of open pit mine*


Analysis using the finite element method uses the same data as the analysis carried out with boundary equilibrium, namely rock characteristics, 3D slope

**Table 5.** *Influence of variable max iteration.*

*Three Dimensional Slope Stability Analysis of Open Pit Mine DOI: http://dx.doi.org/10.5772/intechopen.94088*

geometry and 3D geological models. Young and poisson ratio are input parameters in this analysis. If the boundary equilibrium analysis requires the position and shape of the slip plane, the analysis does not require these assumptions but uses the elements and nodes that are attached to the model. For an example of a 3D mesh model, see **Figure 19**. For this example, case a 4-node element type with a graded gradient is used.

**Figure 19.** *3D meshing model.*

then enter the material properties for each material and start entering the material strength reduction factor (SRF) value for each element, at this stage the material properties value can be increased or decreased depending on the error value (solid tolerance) obtained. Furthermore, an Elasto-plastic analysis was performed using the Mohr-Coulomb failure criterion to obtain a new error value (solid tolerance). If the error value is still above the maximum value within the allowable iteration calculation limit, the SRF value will be lowered until the error value is below the maximum limit. The recapitulate the analysis results can be seen in **Table 5.**

The analysis shows that the higher the maximum number of iterations, the SRF value also increases **Table 4**. As the SRF value increases, in the maximum number of iterations of 400 the SRF value constant at a value of 1.04, so this provides information that at a maximum of 400 iterations is the maximum optimal number of iterations. If seen from the effect of the number of iterations on the total displacement, the results will fluctuate, this is closely related to the srf value because the higher the srf value, the total displacement will also increase, but at 1.04 the srf value does not change/is consistent but the total displacement fluctuates because it is solid tolerance, the resulting solid tolerance also varies due to the use of different maximum iterations, this is because the slope conditions remain non-convergent (energy equilibrium is not achieved) above srf 1.04 in the number of iterations that have been set, however, solid tolerance will get closer to the maximum value, while for the computation time it is very clear that the higher the maximum number of iterations, the computation time will also increase, because it will take more time to search for convergence with the maximum iteration limit given, although the results will remain the same, that non-converging above 1.04 and the last converging value is 1.04.

Analysis using the finite element method uses the same data as the analysis carried out with boundary equilibrium, namely rock characteristics, 3D slope

**Max iteration SRF Max displacement (m) Computing time (s)** 10,000 1.04 8.60 110,459 1.04 8.74 57,990 1.04 8.48 26,214 1.04 24.29 14,622 1.04 14.34 6021 1.04 12.90 5422 1.04 12.72 4788 1.03 5.25 3650 1.03 5.42 3341 1.03 6.51 3159 1.01 1.70 2300 1.01 1.70 1969 1.00 1.67 1704 0.98 1.20 1541 0.68 1.09 1501

*2.3.4 Analysis 3D finite element method of open pit mine*

**Table 5.**

*Slope Engineering*

**96**

*Influence of variable max iteration.*

**Figure 20.** *3D restraint model.*

**Figure 21.** *3D FEM analysis result.*

After the model is successfully meshed, it is necessary to determine the limit of the resistance that works in the field of analysis to determine the internal force that works on the restraint installation which plays a role in determining the deformation limit of the model. For an example of the restraint model can be seen in **Figure 20**.

**References**

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*DOI: http://dx.doi.org/10.5772/intechopen.94088*

*Three Dimensional Slope Stability Analysis of Open Pit Mine*

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[3] A nagnosti, P: Three-dimensional stability of fill dams. Proceedings of the 7 th International Conference on foil Mechanics and Foundation Engineering,

[4] Baligh, M. M. and A zzouz, A. S: End effects on stability of cohesive slopes, "Journal of the Geotechnical Engineering Division, AS- CE, GT 11, pp. 1105-1117

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Analysis with the finite element method can see information about stress acting on the model and the total displacement (**Figure 21**).
