Rock support systems have become widely dominant components in underground hard rock mines. They are used to maintain the stability of underground openings and reinforce disturbed rock masses after creating an excavation or starting mining activity. Thus, the objective of this study is to examine the effect of support types on the performance stability of underground tunnels that exist in hard rock mines, in terms of deformation, the extent of failure zones and the strength of the rock mass surrounding the tunnel. This, in turn, will help in the selection of an appropriate support system that mitigates the stress-deformation conditions around the tunnel. Herein, four models have been built using the RS2D program, simulated and introduced to evaluate the behaviour of an underground tunnel with different rock support systems. The first model is simulated without any support system, whereas, rock bolts have been installed in the second model. The third model applied only shotcrete, while rock bolts and shotcrete are combined together in the fourth model. The results are presented and discussed in terms of strength factor, the extent of yielding zones and rock mass displacement/convergence. The results show that tunnel stability suffers when there is no rock support at all, while, it is significantly improved when the rock support system is installed. The optimum improvement is obtained when both shotcrete and rock bolts are employed together.

Rock support systems have become widely dominant components in underground hard rock mines. They are used to maintain the stability of underground openings and reinforce disturbed rock masses after creating an excavation or starting mining activity. Thus, the objective of this study is to examine the effect of support types on the performance stability of underground tunnels that exist in hard rock mines, in terms of deformation, the extent of failure zones and the strength of the rock mass surrounding the tunnel. This, in turn, will help in the selection of an appropriate support system that mitigates the stress-deformation conditions around the tunnel. Herein, four models have been built using the RS2D program, simulated and introduced to evaluate the behaviour of an underground tunnel with different rock support systems. The first model is simulated without any support system, whereas, rock bolts have been installed in the second model. The third model applied only shotcrete, while rock bolts and shotcrete are combined together in the fourth model. The results are presented and discussed in terms of strength factor, the extent of yielding zones and rock mass displacement/convergence. The results show that tunnel stability suffers when there is no rock support at all, while, it is significantly improved when the rock support system is installed. The optimum improvement is obtained when both shotcrete and rock bolts are employed together.

Unplanned ore dilution negatively affects overall mine profitability by increasing operating costs (e.g., mucking, haulage, crushing, hoisting, milling, waste treatment, and low-grade ore upgrading). Eliminating ore dilution requires identifying and controlling the major causal factors, which are related to in-situ stress regimes, depth of stope undercut, ore dip/orientation, stope geometry, and quality of the host rock mass. In-situ stress regimes and depth of stope undercut were examined in a previous publication (see Part I). The results showed that the stability of the stope hanging wall significantly deteriorates when in situ stress regimes and depth of stope undercutting of the access drift increase. Conversely, the extent of plastic zones increases with such an increase. Also, the depth of stope undercutting has no impact on the deformation development of the rock mass. The objective of this paper is to assess stope hanging wall (HW) stability and ore dilution with respect to ore inclination and stope geometry in sublevel, open stoping, narrow-vein mines. A series of two-dimensional elasto-plastic numerical models was built to examine the effect of ore dip angle and stope geometry (height and width) on stope HW stability and ore dilution in a highly stressed environment (in-situ stress ratio = 2.5). The results are presented, discussed, and compared in terms of depth of relaxation zones, extent of plastic failure zones, and total displacement with respect to four stope dip angles (45°, 60°, 75°, and 85°), three stope widths (5, 7.5, and 10 m), and three stope heights (20, 30, and 40 m). Results show that stope HW stability improves when ore dip angle increases (i.e., steeply dipping ore deposits) because the depth of relaxation zones and extent of failure zones decreases. Dip angle had a negligible effect on HW deformation. Less dilution occurred at very steep (85°) inclination angles. At different ore dip angles, stope HW stability greatly deteriorated with increasing stope width and improved with decreasing stope height.

Abstract Purpose. This study aims to evaluate the slope stability of open pit comprising massive and jointed rock mass. Methods. Mohr-Coulomb yield function (MC) with shear strength reduction technique (SSRT) are incorporated in finite element analysis (FEA) and four different slopes with varying geometry and geological structural features with an ultimate slope angle of 34° are analyzed using the two-dimensional FEA Program RS2D. The first slope comprises blocky rock mass; the second slope has a network of joints parallel to slope face; the third slope has a parallel joint networks dip out the slope face, and the last slope has a cross-joints network. Findings. The critical strength reduction factor (CSRF) indicates whether the slope face is stable (if CSRF ≥ 1) or not. The minimum CSRF of 0.53 (e.g. compared to 0.55 for parallel joints dip out to the slope face, 0.58 for joints parallel to slope face and 0.65 with no joint existed) is obtained with cross-joints network existed. The CSRF (e.g., CSRF = 0.49) reduces when the MC slip criterion is adopted with the jointed rock mass. Originality. This study attempts new stability indicator namely critical strength reduction factor (CSRF) embedded in shear strength reduction technique (SSRT), based on finite element (FEM) to assess the slope of open pit with respect to presence of geological discontinuities. Practical implications. The slope stability of rock mass is significant to design parameters in open pit mines. Unexpected instability is eventually costly, hazardous to personnel/machinery, disrupted to the mining operation and time-consuming. Therefore, this study Provides a methodology for the application of shear strength reduction technique (SSRT) when evaluating the slope stability of open pit mines with respect to existence of geological features. As a result, the mine planners and engineers will be able to know a head of time when and where necessary support is needed.

Abstract Purpose. This study aims to evaluate the slope stability of open pit comprising massive and jointed rock mass. Methods. Mohr-Coulomb yield function (MC) with shear strength reduction technique (SSRT) are incorporated in finite element analysis (FEA) and four different slopes with varying geometry and geological structural features with an ultimate slope angle of 34° are analyzed using the two-dimensional FEA Program RS2D. The first slope comprises blocky rock mass; the second slope has a network of joints parallel to slope face; the third slope has a parallel joint networks dip out the slope face, and the last slope has a cross-joints network. Findings. The critical strength reduction factor (CSRF) indicates whether the slope face is stable (if CSRF ≥ 1) or not. The minimum CSRF of 0.53 (e.g. compared to 0.55 for parallel joints dip out to the slope face, 0.58 for joints parallel to slope face and 0.65 with no joint existed) is obtained with cross-joints network existed. The CSRF (e.g., CSRF = 0.49) reduces when the MC slip criterion is adopted with the jointed rock mass. Originality. This study attempts new stability indicator namely critical strength reduction factor (CSRF) embedded in shear strength reduction technique (SSRT), based on finite element (FEM) to assess the slope of open pit with respect to presence of geological discontinuities. Practical implications. The slope stability of rock mass is significant to design parameters in open pit mines. Unexpected instability is eventually costly, hazardous to personnel/machinery, disrupted to the mining operation and time-consuming. Therefore, this study Provides a methodology for the application of shear strength reduction technique (SSRT) when evaluating the slope stability of open pit mines with respect to existence of geological features. As a result, the mine planners and engineers will be able to know a head of time when and where necessary support is needed.

Abstract Purpose. This study aims to evaluate the slope stability of open pit comprising massive and jointed rock mass. Methods. Mohr-Coulomb yield function (MC) with shear strength reduction technique (SSRT) are incorporated in finite element analysis (FEA) and four different slopes with varying geometry and geological structural features with an ultimate slope angle of 34° are analyzed using the two-dimensional FEA Program RS2D. The first slope comprises blocky rock mass; the second slope has a network of joints parallel to slope face; the third slope has a parallel joint networks dip out the slope face, and the last slope has a cross-joints network. Findings. The critical strength reduction factor (CSRF) indicates whether the slope face is stable (if CSRF ≥ 1) or not. The minimum CSRF of 0.53 (e.g. compared to 0.55 for parallel joints dip out to the slope face, 0.58 for joints parallel to slope face and 0.65 with no joint existed) is obtained with cross-joints network existed. The CSRF (e.g., CSRF = 0.49) reduces when the MC slip criterion is adopted with the jointed rock mass. Originality. This study attempts new stability indicator namely critical strength reduction factor (CSRF) embedded in shear strength reduction technique (SSRT), based on finite element (FEM) to assess the slope of open pit with respect to presence of geological discontinuities. Practical implications. The slope stability of rock mass is significant to design parameters in open pit mines. Unexpected instability is eventually costly, hazardous to personnel/machinery, disrupted to the mining operation and time-consuming. Therefore, this study Provides a methodology for the application of shear strength reduction technique (SSRT) when evaluating the slope stability of open pit mines with respect to existence of geological features. As a result, the mine planners and engineers will be able to know a head of time when and where necessary support is needed.

This paper presents a three-dimensional Finite Element Analysis (3D FEA) on reinforced concrete beams tested experimentally by other researcher for investigating the effectiveness of hybrid reinforcement (FRP bars and steel bars) as a main reinforcement to enhance the flexural behavior of concrete beams. To provide a new model which can simulate the performance of concrete beam reinforced with steel and FRP bars accurately, all of the beam components were included in the model and element which composing the model and mesh size were chosen carefully. The user-programmable features in ANSYS 13.0 were used for model analysis. The developed model showed a good agreement with the corresponding experimental result. A parametric study is carried out to investigate the influence of FRP to steel reinforcement ratio, FRP bars type, Location of FRP and steel bars and concrete strength in the behavior of hybrid FRP-RC beams.

Because of the shortcomings of the externally bonded system that mainly consists of epoxy and FRP sheets, the fabric-reinforced cementitious matrix, (FRCM) represents a viable solution in the strengthening of reinforced concrete beams. The FRCM layers consist of fabric mesh embedded in an inorganic stabilized cementitious mortar. Many experimental studies examined the impact of strengthening of RC beams with the FRCM layers, but the numerical investigations are limited. This study is therefore aimed at introducing a numerical study investigating the behavior of RC beams reinforced with FRCM layer. The main goal of this paper is to verify the FEM results with the experimental results that are available in the previous study [1], and to provide a parametric study. The investigated beams in this paper are 150 mm × 250 mm× 3000 mm with two reinforcement ratios. One, two, and three-layers of PBO, (P-Phenylene Benzobis Oxazole) FRCM were investigated as strengthening of the simulated beams were strengthened with. The numerical validation included load-deflection curve, load –strain of both concrete and PBO- FRCM, strain distribution, cracks series and failure mode. The built model gave an accurately prediction of the attitude of the investigated beams. The results also indicated that the rise in the reinforcement ratio or the amount of FRCM layers contributed to improving behavior under both ultimate and serviceability limit states.

A literature fast survey shows that the topic of strengthening concrete columns with fiber-reinforced polymer (FRP) composites has not been sufficiently covered in the available textbooks. Most of the previously published textbooks, which discussed the FRP-confined or strengthened concrete columns (see Fig. 6.1), focused on the behavior and design of circular cross-sections under concentric or eccentric axial loading. The majority of the textbooks focused on confined plain concrete columns. To the best of the author’s knowledge, none of the published textbooks sufficiently studied the available stress–strain models that describe the behavior of the FRP-confined concrete. This chapter presents the following additional contributions to the existing published textbooks about FRP composites as external reinforcements for reinforced concrete (RC) columns: (1) a comprehensive discussion on the stress–strain behavior and modeling of FRP-confined concrete circular and rectangular/square cross-columns, (2) enhancing the ductility of the RC columns using external FRP jacketing, (3) effects of exposure to short and long-term environmental conditions on the behavior of FRP composites used to strengthen the existing columns, (4) ductility design methods of FRP-confined RC columns, and (5) evaluation of the performance of FRP-confined columns considering a damage-controllable mechanical model proposed for the FRP-RC structures.

Fiber-reinforced polymer (FRP) sheets have been increasingly used to reinforce and repair tunnel linings and the slabs of viaducts owing to their advantages. In these FRP-strengthened structures, both in-plane shear stress and out-of-plane normal stress are imposed on the interface between the FRP sheets and concrete. Concrete spalls from the concrete surface owing to different failure mechanisms. To study the bonding and debonding mechanism behind spalling failure, a punching–peeling test against the spalling of concrete pieces is an important tool. In this chapter, the peeling behavior and the spalling resistance of FRP sheets externally bonded to concrete plates and beams are introduced, based on available experimental and analytical investigations. An extremely useful analytical technique for this problem is also introduced in this chapter.