numerical modeling

Slope stability is critical for infrastructure safety, particularly in seismically active regions. This work evaluates the stability of a slope along the Baroti-Reyur road in Himachal Pradesh, located in Zone 5, using a novel combination of Limit Equilibrium Methods (LEMs) and Finite Element Methods (FEMs). The analysis examines natural slope conditions and the impact of sustainable mitigation measures, including retaining structures and bioengineering techniques, under the static and dynamic conditions. The soil model incorporated a modulus of elasticity (E) of 90,000 kN/m², and a poisson's ratio (v) of 0.3 to reflect realistic slope-soil-structure interactions. Retaining structures such as gravity, cantilever, and gabion walls (4 m, 6 m, and 5 m high) were constructed using M30 RCC and Fe500 steel. Bioengineering measures featured deep-rooted grasses like Vetiver and Broom grass to improve soil cohesion (c), shrubs like Lantana camara for surface stability, and trees like Albizia lebbeck to reinforce deeper soil layers. These vegetation-based interventions enhanced slope resilience, while promoting ecological restoration. Theoretical LEM analysis revealed marginal stability, with static FOS values of 1.1 and pseudo-static FOS of 1.05. GEO5 pseudo-static analysis indicated critically low FOS value of 0.88 for dynamic saturated conditions, improving to 2.01 with retaining structures. FEM analysis using PLAXIS 2D provided more detailed insights, capturing complex soil-structure interactions with a static FOS of 1.028 and dynamic FOS of 0.994. By combining FEM with sustainable mitigation strategies, this work offers a framework for resilient slope stabilization, ensuring safety, while promoting environmental sustainability in seismically active regions.

In recent years, the demand for new trenchless methods has dramatically risen. Pipe jacking is a trenchless method widely used in recent years. Ground deformation is one of the significant parameters that may lead to unrepairable harm to facilities and even people. So, ground deformation analysis is necessary for safety and design reasons. The present study analyzes the factors affecting ground deformation during pipe jacking. This is a descriptive-interventional study. Pipe jacking causes soil displacement in three dimensions (3-D). Therefore, 3-D numerical methods were applied for analysis. In this study, numerical simulation was performed using PLAXIS finite element numerical software, taking the case study into account. The effect of each parameter on the ground deformation pattern was studied in three directions; the uplift and their exact position were then analyzed. It should be noted that displacement analyses were performed in two areas: pipe crown and ground surface. Also, the relation of each parameter was estimated with the ground subsidence. Finally, the effect of each different factor and their sensitivity index were determined using sensitivity analysis. The highest subsidence occurs at the end of the shield due to stress relaxation. Considering the results, it was found that the relationship between the internal friction angle and subsidence is linear and direct. The relationship between the elastic modulus and subsidence is also linear but indirect. The results indicate that the most sensitive factor of ground deformation is the diameter, but the least sensitive factor is the face pressure.

Unlike the mechanical properties of intact rock, which can be obtained on a laboratory scale, estimating the mechanical properties of the jointed rock mass is very difficult due to the presence of different joints and the complexity of the joints. Therefore, to calculate the mechanical parameters of the jointed rock mass and use the continuous media theory of the jointed rock mass, it is necessary to calculate the Representative Element Volume (REV) of the rock mass. In this study, the Discrete Element Method (DEM) and the mechanical index of strength were used to investigate the effect of persistent and non-persistent joint angles, as well as model size on the REV in x, y, and z directions. The numerical results showed that by changing the joint angles and side length, both the strength and the REV of the rock mass were affected. The maximum representative side length for the persistent joint in the x and z directions occurred at angles of 60° and 75°, respectively. The minimum strength was obtained for joints in the x and z directions at a 45° angle. Finally, the REV for persistent and non-persistent joints is calculated as 10*0.5*8m and 4*0.5*4m, respectively.

The present study proposes a suitable support system for the underground tunnels of the gold deposits of Mazraeh-Shadi in the East Azerbaijan Province of Iran using numerical modeling. The stability of the tunnels was evaluated using the data obtained from the numerical modeling, the ground reaction curve (GRC), the longitudinal deformation profile (LDP), permissible displacements according to the Sakurai relationships, and the load imposed on the support system of the tunnels. Due to the very large dimensions and high computational costs, the adits were modeled at the depths of 1830 and 1870 meters. According to the results and the diagram of the proposed support system based on Q and the cross-section of the tunnel, a support system made from fiber shotcrete with a thickness of 90-120 mm, along with rock bolts regularly installed, is proposed. At the intersections and the tunnel portal, a stronger support system had to be used, and in the tunnel portal the reinforcement system, such as the implementation of shotcrete on the sloped surface, should be taken.  At the level of 1870 meters, implementing shotcrete with a thickness of 12 cm and a safety factor of 1.2 was sufficient. At the level of 1830 meters, the shotcrete required to be strengthened. For this purpose, a layer of steel mesh or a restraining lattice with a spacing of 2 meters was used. The proposed support system is sufficient and appropriate given the relatively small dimension of the tunnels and their temporary use and according to the Sakurai criterion, the experimental methods, and the engineering judgment.

Accurate assessment of horizontal earth pressure acting upon retaining walls is crucial for the effective and secure design of these constructions. Not only active earth pressure, but the arching phenomenon also plays a significant role in passive earth pressure distribution. In this study, using the finite difference method (FDM), some numerical models are simulated to examine the influence of soil strength properties and a wall inclination on the earth pressure and ground deformation. The development of shear bands as well as the trajectories of principal stress inside the backfill are investigated. The results of this study show that the failure surface behind the retaining wall under passive mode is generally nonlinear and will become linear only if the wall surface is frictionless. Among the existing theories, the stress distribution provided by the classical theory of Coulomb (1776) shows a better agreement with the numerical data compared to arching-based theories and the classical theory of Rankine (1857). Considering the root mean square error (RMSE) falling within the approximate range of 0.2 to 0.5, it can be inferred that the numerical modeling results demonstrate acceptable agreement with Coulomb theory. These findings are consistent with the experimental results of Fang et al. (2002).

Today, numerous surface and underground mining and construction projects can be found worldwide, built on a rock bed and surrounded by rock. Open pit mines are considered the primary sector for mineral production in the mining industry. The issue of slope stability is crucial for the economy and safety of open pit mines. Slope stability should be based on the determination of tectonic and lithological parameters and the determination of mine boundaries. It is illogical to allocate one slope for the entire walls of the mine, which are made of different materials and have different structural conditions. The purpose of slope stability analysis is to maintain a stable slope while mining activities continue. This research was conducted on slope stability analysis in the No. 4 Gol-e-Gohar mine in Sirjan. Geotechnical characteristics and necessary information for numerical modeling were obtained through mine visits, surveys, and tests on rock samples from exploratory boreholes. Based on two-dimensional modeling using PHASE 2D software, the CSFH behavior model (cohesion softening - friction hardening) for the northern wall will enhance the overall strength of the rock mass. However, this behavior model is not suitable for medium and weak-quality rocks. For rocks with softening behavior, the CSFS behavior model (cohesion softening - friction softening) provides more realistic results. Furthermore, to investigate the effect of schistosity plates, transisotropic behavior parameters were determined based on direct cutting tests on schistosity surfaces, and stability analysis was conducted. It was concluded that the orientation of the Turq surfaces in schist layers has a significant effect on the strength of these layers, leading to larger displacement values than other models.