The purpose of this paper is to investigate analytically the fully grouted rock bolt interaction with grout and rock in pullout test and to determine the load-displacement curve of the bolt head (beginning of the bonded section). Usually, the pullout test output is only the load-displacement curve. This paper discusses how to use this curve to determine the bolt-grout-rock interaction. For modeling bolt-grout interface behavior, coupling (compete for bonding), partial decoupling, decoupling with the residual shear strength, and complete decoupling have been considered. With increasing the applied load, two possible cases including complete pullout and bolt shank yielding are considered. Based on experimental results, a model for the shear stress along a fully grouted bolt is assumed. According to this model, the distribution of axial stress in the bolt and displacement of the bolt head is determined. It is also assumed that the bolt is sufficiently long, which is usually used in underground excavations. Based on the presented analytical method, the bolt head load-displacement curve is determined by assuming input parameters. This curve is compared with a pullout test result.

Many parameters such as hole diameter, thickness and bonding properties, mechanical properties of the rock mass, grout and rock bolts, profile bolt properties and pre-tension influence the load transfer mechanism of the grouted rock bolt. The author has been studying and reviewing the field of fully grouted rock bolts for more than 17 years and has published several articles in this field. Therefore, one of the most important goals of the author is to use statistical software and algorithms in the field of his previous studies. The purpose of this research was to optimize the load transfer mechanism of fully grouted rock bolts by using numerical modeling and genetic and PSO algorithms. For this purpose, ANSYS, SPSS and MATLAB software have been used in this research. Five types of rock bolts are used with different profiles. The rock bolts are modeled by ANSYS software, and then the results are defined by SPSS software using multiple regression as a linear relationship. Finally, using genetic and PSO algorithms, the load transfer mechanism of bolts has been investigated. The results showed that with the increase in profile down width, the load transfer mechanism increased and with the increase in thickness of the grout, the load transfer mechanism increased.

In this work, the effect of rock bolt angle on the shear behavior of Rock Bridges is investigated using the particle flow code in two dimensions (PFC2D) for three different Rock Bridge lengths. Firstly, the calibration of PF2D is performed to reproduce the gypsum sample. Then the numerical models with the dimensions of 100 mm * 100 mm are prepared. The Rock Bridge is created in the middle of the model by removal of the narrow bands of discs from it. The uniaxial compressive strength of the Rock Bridge is 7. 4 MPa. The Rock Bridge lengths are 30 mm, 50 mm, and 70 mm. The rock bolt is calibrated by a parallel bond. The tensile strength of the simulated rock bolt is 360 MPa. One rock bolt is implemented in the Rock Bridge. The rock bolt angles related to the horizontal axis are the changes from 0 to 75 degrees. Totally, 18 models are prepared. The shear test condition is added to the models. The normal stress is fixed at 2 MPa, and the shear load is added to the model till failure occurs. The results obtained show that in a fixed rock bolt angle, the tensile crack initiates from the joint tip and propagates parallel to the shear loading axis till coalescence to rock bolt. In a constant Rock Bridge length, the shear strength decreases with increase in the rock bolt angle. The highest shear strength occurs when the rock bolt angle is 0° .

A better understanding of rock mass behavior is an essential part of the design and construction of underground structures. Any improvement in the understanding of the behavior of rock mass will facilitate the improvement of the design in terms of the safety of the working environment, long-term safety of the structure, environmental effects, and sound management of public or private resources. Thus, in step one in this paper the experience gained from the application of the GDE (Geo Data Engineering) multiple graph approach for rock mass classification and assessment of its behavior through the course of excavation of the Alborz tunnel is presented. The predicted hazards are compared with the experienced problems and suggestions are given to be considered in future works of tunnel construction. In step two, the GDE multiple graph approach is compared to the rock mass behavior types proposed by Palmstrom & Stille (2007) in terms of the continuity of rock mass. The result of this comparison together with the data obtained from rock mass classification in the Alborz tunnel are used to develop a system that determines the applicability of the rock bolt supporting factor (RSF) in different rock mass behavior classes.

Rockbolts are one the best systems to stabilize plane failure of rock slopes. The passive bolts are loaded and activated when rock block slides while pre-tensioned types are initially loaded prior to any rock sliding. The pre-tensioned rock bolts make the rock layers pressed together and the friction between them is activated before slipping, and probably no displacement between the layers is occured. If a slippage occurs after the installation of a pre-tensioned rock-bolt, an excessive load is applied. In this paper, the bolt contribution generated by the pre-tensioned and passive rock-bolt in discontinuity is analytically simulated, and the effect of roughness angle, inclination of the bolt to the joint plane, pre-tensioned force, and strength of the rock are evaluated. For modeling, it is assumed the sliding imposes a bending moment to the rockbolt, which leads two plastic hinges to be created. The part of bolt between two hinges (located in either sides of the joint) is considered a beam with two cantilever supports, which is loaded by a uniform distribution generated by surrounding grout/ rock. The results show the pre-tensioned rock-bolts are effective when the resistance of the rock or grout around the bolt is high.

This study has been carried out on the stability analysis and the support systems design of the water conveyance tunnel and surge tank of Gotvand dam. The stability analysis of underground openings is one of the most important subjects in rock mechanics principles. There are four different methods for the analysis of underground openings. These are: closed form solutions, numerical methods, empirical methods and physical modeling. Nowadays the numerical and empirical methods are more widely used all over the world. In This research, analyses have been carried out by finite difference method (component of numerical methods) and Q and RMR (component of empirical methods) rock mass classifications. The numerical software used for analyzing the tunnel stability was Flac3D. This software is capable of determining the values of induced stresses and displacements around the underground openings. The results obtained from stability analyses show that the underground excavation is unstable; therefore, installation of a support system is necessary. After installation of support systems, the value of maximum displacement is less than Sakurai’s critical displacement, therefore, the underground excavation will be stable. The recommended support systems are:1) Installation of systematic grouted bolt by 7m long and spacing 1.5×1.5m with shotcrete by 150mm thick in surge tank2) ) Installation of systematic grouted bolt by 5m long and spacing 2×2 m and with shotcrete by 70mm in conveyance tunnel and box.