**5. Numerical analysis**

*Slope Engineering*

**Figure 4.**

*Tunnel face schematization.*

The state of stress in the ground is considerably greater than the strength properties of the material even in the zone around the face. For this consideration based for the results of the diagnosis phase, the techniques to be applied for the applica-

Both methods assure the rigidity of the core of ground ahead of the face, and therefore the conditions of stability in that ground, have a decisive effect on that deformation response and determine how an arch effect is triggered and conse-

tion of the supporting pressure on the Tunnel faces are as follows:

*Relation between the stability coefficient and the face supporting according to [12].*

quently the tone of the stress–strain response in the whole tunnel.

**6**

• Shotcrete;

**Figure 5.**

• Fiber glass bolting.

In engineering practice, different design methods tend to be used; in this study, advanced numerical modeling was used due to its ability to predict vertical and longitudinal deformations; as well as the failure mechanisms at the front of the tunnel face [14, 15]. It can indeed be used to simultaneously take into account constraints and anisotropic materials, tunnel advance stages and any pre-containment and cavity containment intervention. In this work, the use of a calculation code through finite element method according to the execution situation [16–18]. The numerical parameter used in the simulation as already mentioned in the **Table 3** resulting from the geotechnical investigation of the zone in question, where the behavior criteria used in the simulation is Drucker-Prager criterion, which as a generalization of the Mohr–Coulomb criterion for soils. The criterion is based on the assumption that the octahedral shear stress at failure, it depends linearly on the octahedral normal stress through material constants. The results indicate that the action of the surrounding terrain on the tunnel based on the attack section R. The main input parameters are the mesh network of elements which determines the domain to which the analysis applies, the geomechanical properties of each element, the surrounding conditions and the loads acting (**Figure 6**).

Numerical simulations allowed obtaining practical results of the radial and longitudinal displacements in the figure and table below:

#### **5.1 Longitudinal displacement**

The following diagram shows the extrusion of different attack section based on the distance in front of the face (**Figure 7**).

#### **5.2 Radial displacements vertical displacements**

The vertical and longitudinal deformations and changes of the critical zone that occur in the tunnel are linked to attack section R. When the maximum value of the attack section "R" is equal to 5 m, the corresponding Maximum Vertical Displacement (Ux) is equal to 0.53 m, and Longitudinal Deformation in front of the Tunnel face can reach a maximum of 65 m.

In the case where the radius R = 3.5 m attack, the maximum vertical displacement (Ux) is 0.2 m. So, it is 3 times less than the previous case, and similarly for Longitudinal Deformation in front of the Tunnel face which does not exceed 50 m. it is shown that simulation results are consistent with the observed extent and those obtained in literature. (**Figure 8**).

**Figure 6.** *Model and meshing.*

**Figure 7.** *Uz displacement curves based on the attack section R.*
