Sharif Digital Repository

Construction of underground structures in urban areas is a very challenging work. There are generally two methods of construction, an open cut-and-cover and underground method. To eliminate the subsurface and surface disturbance and street traffic problems, underground method is preferred. The stress redistribution caused by underground excavation induces movements and deformation in the earth mass and ultimately at the ground surface. This is more pronounced in large space excavations. Generally pre-supporting system is used to control ground deformation and thus enhance its stability. In this paper an innovative pre-supporting system is presented. Concrete Arch Pre-supporting System (CAPS)... 

Construction of underground structures in urban areas is a very challenging work. There are generally two methods of their construction, an open cut-and-cover and underground method. To eliminate the subsurface and surface disturbance and street traffic problems, underground method is preferred. The stress redistribution caused by underground excavation induces movements in the earth mass and ultimately at the ground surface. This is more pronounced in large space excavations. Generally pre-supporting system is used to control ground deformation and thus enhance its stability. In this paper an innovative pre-supporting system is presented. Concrete Arch Pre-supporting System (CAPS) is... 

Construction of underground structures in urban areas is a very challenging work. There are generally two methods of their construction, an open cut-and-cover and underground method. To eliminate the subsurface and surface disturbance and street traffic problems, underground method is preferred. The stress redistribution caused by underground excavation induces movements in the earth mass and ultimately at the ground surface. This is more pronounced in large space excavations. Generally pre-supporting system is used to control ground deformation and thus enhance its stability. In this paper an innovative pre-supporting system is presented. Concrete Arch Pre-supporting System (CAPS) is... 

Subway metro systems are one of the most efficient modes of mass transportation, especially in heavily populated areas. A series of 3D Finite Element Analysis (FEA) has been carried out to investigate the interaction between mechanized twin tunnels excavated beneath the highly congested streets of Shiraz (Iran). Firstly, the reference numerical model has been verified using the measured data of surface settlement control pins. The effects of driving of the new closed shield tunnel on the evolution of stress fields in the existing segmental lining as well as the ground surface settlements in the reference numerical model have been then quantified. Lastly, the effects of influencing factors... 

Subway metro systems are one of the most efficient modes of mass transportation, especially in heavily populated areas. A series of 3D Finite Element Analysis (FEA) has been carried out to investigate the interaction between mechanized twin tunnels excavated beneath the highly congested streets of Shiraz (Iran). Firstly, the reference numerical model has been verified using the measured data of surface settlement control pins. The effects of driving of the new closed shield tunnel on the evolution of stress fields in the existing segmental lining as well as the ground surface settlements in the reference numerical model have been then quantified. Lastly, the effects of influencing factors... 

This paper presents results from a series of constant normal load direct shear tests on artificially created rock joints, in an attempt to quantify the effects of different factors that contribute to the shear strength along "ideal" rock joints. Particular focus is given to the effect of asperity orientation with respect to the direction of shearing. In many historical rock joint shear strength criteria, the effect of a joint's roughness on the joint shear strength is described based on analysis of only a single profile in the direction of shearing. More recent studies have observed that the distribution of sheared area on a joint surface during shear is significantly affected by the... 

The increase of underground space applications, as a solution for congested urban areas makes it inevitable to cross closely spaced underground structures. The analysis of new TBM EPB-bored tunnel under existing underground station was conducted by 3D finite element method. The influence of new tunneling was investigated on the deformation and moments of final lining of existing underground station. The effectiveness of interaction analysis depends on factors such as station overburden, existing station supporting stiffness and traffic loads. In this paper, a parametric study was conducted to study ground movements and lining moments. It is shown that moment increase is significant when the... 

The increase of underground space applications, as a solution for congested urban areas makes it inevitable to cross closely spaced underground structures. The analysis of new TBM EPB-bored tunnel under existing underground station was conducted by 3D finite element method. The influence of new tunneling was investigated on the deformation and moments of final lining of existing underground station. The effectiveness of interaction analysis depends on factors such as station overburden, existing station supporting stiffness and traffic loads. In this paper, a parametric study was conducted to study ground movements and lining moments. It is shown that moment increase is significant when the... 

A method for construction of large underground spaces based on a new pre-supporting system is introduced. In this paper Mansour Station, in Line 1 of Tabriz Metro (Tabriz Urban Railway Organization, TURO); Iran has been studied using this method. Mansour Station have some special characteristics such as shallow depth, soft surrounding soil, wide span and heavy street traffic, thus requires a method of underground construction that can control the stability of the underground space and the ground settlement. This method includes a pre-supporting system that is called Concrete Arch Pre-supporting System (CAPS). Construction of CAPS is mainly based on construction method of old Iranian small... 

Settlement is one of the most important effects of tunnelling. In order to minimize this effect, it is necessary to arrange for circumstances to keep the strain and stress state of undisturbed soil within a tight limit. To achieve this, it is common nowadays to use closed face pressurized shields such as EPB TBMs. In this type of shield, face stability and ground settlement control is maintained by pressurizing the tunnel face with adjustment of cutter head thrust and muck removal discharge. In this paper, numerical modeling of excavation of twin tunnels in Tabriz subway is addressed with respect to the effect of EPB tunnelling in settlement control. Settlement and lining thrust are... 

Multinational Enterprises (MNEs) use social media to reach a global audience. Simultaneously, Corporate Social Responsibility (CSR) has become an important feature of MNEs’ communications with stakeholders via social media. It is, therefore, important to understand the country and industry level differences in how stakeholders engage with CSR communications of MNEs via social media. We examine this across four countries and three industries by focusing on stakeholders’ engagement with CSR (vs. non-CSR) posts on Twitter. We find significant differences across industries within countries for three separate aspects of behavioural engagement (likes, retweets and replies). In addition, CSR posts... 

Recently, Luc defined a dual program for a multiple objective linear program. The dual problem is also a multiple objective linear problem and the weak duality and strong duality theorems for these primal and dual problems have been established. Here, we use these results to prove some relationships between multiple objective linear primal and dual problems. We extend the available results on single objective linear primal and dual problems to multiple objective linear primal and dual problems. Complementary slackness conditions for efficient solutions, and conditions for the existence of weakly efficient solution sets and existence of strictly primal and dual feasible points are... 

Recently, Luc defined a dual program for a multiple objective linear program. The dual problem is also a multiple objective linear problem and the weak duality and strong duality theorems for these primal and dual problems have been established. Here, we use these results to prove some relationships between multiple objective linear primal and dual problems. We extend the available results on single objective linear primal and dual problems to multiple objective linear primal and dual problems. Complementary slackness conditions for efficient solutions, and conditions for the existence of weakly efficient solution sets and existence of strictly primal and dual feasible points are... 

We propose and analyse a nonmonotone quasi-Newton algorithm for unconstrained strongly convex multiobjective optimization. In our method, we allow for the decrease of a convex combination of recent function values. We establish the global convergence and local superlinear rate of convergence under reasonable assumptions. We implement our scheme in the context of BFGS quasi-Newton method for solving unconstrained multiobjective optimization problems. Our numerical results show that the nonmonotone quasi-Newton algorithm uses fewer function evaluations than the monotone quasi-Newton algorithm. © 2020 Informa UK Limited, trading as Taylor & Francis Group