Selection of Tunnel Support System by Using Multi Criteria Decision-Making Tools

Selection of the optimum support system for underground openings such as tunnels is a complex process. In this paper, a new approach, based on a combination of the Analytical Hierarchy Process (AHP), the Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) and the Preference Ranking Organization METHod for Enrichment Evaluations (PROMETHEE) is introduced. For this purpose, the selection process is assumed to be a multi criteria decision-making problem. First, different support systems by using FLAC3D numerical code, based on technical, safety and stability parameters of the tunnel are specified. Then, taking economic and performance parameters as the decision criteria, by using the combination of AHP, TOPSIS, and PROMETHEE, the optimum support system is selected. As a real mine case study, this approach is used in the main access entry to C1 coal seam of Tabas collieries. Results clearly demonstrate that the proposed support system selection method is advantageous to other alternatives

3D strain softening modelling of coal pillars in a deep longwall mine

In longwall coal mines, the entries on both sides of the panel play a significant role in production rate and safety of operation. With increasing production amount, the rate of conveying material through such entries increases. Therefore, it is required to design wider entries. Support of these entries, particularly in deep mines is difficult. In this paper, by using FLAC3D program code a deep longwall coal mine is modeled. The coal seam has a strain softening property, and the analysis index of stress and deformation of ribsides and coal pillars at different loading levels are determined. Strain softening parameters is studied separately for each modeled coal pillar, and based on conventional formula the pillar strength are calculated. In a modeled longwall mine, the caving material at goaf zone are fully compact. The results shows that based on Mohr-Coulomb model, the strain softening occurs at maximum cohesion and friction, and at region of decreasing the strength of pillar in stress-strain curve. Because of 3D nature of analyses, the effect of front and side abutment load on stability of pillar are studied simultaneously. Therefore, the results of this study could be suitable criteria for appraisal of pillar design method at deep longwall coal mines

Seismic analysis of horseshoe tunnels under dynamic loads due to earthquakes

Due to seismic events, such as earthquakes, the elastic waves propagate through a medium. The impact of these waves on underground structures is to provide dynamic forces and moments that may affect the stability of underground structures. The aim of this paper is to analyse the effects of seismic loads on the stability of horseshoe tunnels. As a case study, the stability state of the main access entry to C1 coal seam of Tabas collieries in Iran are analyzed using Phase2 software in static and dynamic states. It is often assumed that the effect of earthquakes on underground structures such as tunnels is negligible but the results of this study show that the stress caused by seismic loads can be harmful to the tunnel stability. It is concluded that the stress and displacement balance of forces around the tunnel are adversely affected and due to redistribution of these forces that create undue concentration in some areas, instability occurs in the tunnel. The paper also concludes that increasing the stiffness of the support system can increase the effect of the seismic loads. The analysis provided in this paper together with the conclusions obtained can serve as useful tools for the tunnel design engineers, especially in areas susceptible to seismic phenomena

Estimation of Coal Pillar Strength by Finite Difference Model

Longwall mining is now predominately used in coal mines where somewhat difficult conditions exist. As in the case of all other underground mining methods, pillars are integral parts of the mining design. The choice of shape and dimensions of the pillars has significant impact on the recovery and hence on overall productivity of the mine. The process of pillar design in longwall mining entails the selection of a safety factor, which is done by estimating the magnitude of the load applied on the pillar and the load bearing capacity of such pillars. In this paper, finite difference modeling principles have been applied to a typical coal pillar. The pillar strength is then estimated with various width/height ratios. These results have been compared with the results obtained from the conventional methods of pillar design. The effect of roof and floor quality on the strength of the typical pillar has also been evaluated in the same manner. It is concluded that although the finite difference method is not always the perfect method for such estimation, but the results clearly demonstrate that it produces more acceptable design than the conventional method, especially under undesirable conditions regarding the interface between pillars, roof and floor. An additional advantage of such method is shown to be its capability of being applied in situations where complex parameters prevail

Optimization of Chain Pillars Design in Longwall Mining Method

Chain coal pillars are parts of the structure of longwall mining system that play a significant role in the stability of the entries. With mechanization and developments in the various aspects of the method, higher efficiency in optimization of the design of chain coal pillars seems appropriate. In this paper, the three main methods of chain pillar design, namely the empirical, analytical and numerical methods are compared. Real data from the Tabas-Iran coal mines have been used in order to make the comparison process reliable. It is concluded that the most apparent advantage of the empirical method is the reliability of the results whilst the use of numerical methods enjoys the advantage of flexibility. On the other hand, the analytical methods are complex unless simplifying assumptions are made that can substantially decrease the accuracy of result which is thought to be the main advantage of the design method. A new method is therefore introduced here that combines all of the three presently used methods and by doing so, the new method has all the advantages of the three while minimizing complexities and inaccuracies associated with the use of the individual methods

A New Approach for Determination of Tunnel Supporting System Using Analytical Hierarchy Process (AHP)

In underground mining, the selection of support system for mine tunnel development plays a significant role in safety and economics of operations. Traditionally, such selection is on the basis of the experience of the design engineer. Nevertheless, the validity of such selection is questionable. A new approach for selecting the optimum tunnel support system based on Analytical Hierarchy Process (AHP) is proposed. In this new approach, the selection of the tunnel support system is considered as a multi criteria decision-making problem. Firstly, by using the numerical Finite Difference Method (FDM), based on technical and stability parameters of the tunnel, different support systems are specified. Then, by considering the economics and performance indices of each support system, a decision tree based on AHP model is generated and the optimum support system is selected. As a field study, the method is applied to Tabas collieries in Iran. It is concluded that the proposed support system determination is advantageous compared to other alternatives. Therefore, the proposed approach can assist the engineer in selection of optimum tunnel support system in different underground mining situations

Collaboration in BIM-based construction networks: a qualitative model of influential factors

Purpose: The purpose of this paper is to present a modified model for collaboration in BIM-based construction networks (BbCNs). Though BIM is increasingly adopted and implemented across the construction industry, the problems associated with the lack of collaboration among teams in BbCNs remain a major hindrance to reaping the full potential of BIM. Previous studies have been conceptual in nature. This paper, therefore, attempts to modify and validate existing conceptual models that describe collaboration in BbCNs. Design/methodology/approach: To modify the conceptual model for collaboration in BbCNs, qualitative data through semi-structured interviews with BIM experts in the industry were collected and analysed using qualitative methods including the use of NVivo software. Findings: The proposed model includes influential factors and their sub-factors to collaboration in BbCNs, as well as considering their indicators. Findings reveal that several overlooked concepts, particularly unfavourable BIM contractual arrangements, act as the root causes of the unwillingness of team members in BbCNs to engage in collaborative efforts. Research limitations/implications: The study's findings must be viewed in light of several limitations. First, the interviewees in this study were based in Australia hence their perceptions of BIM collaboration are reflective of the sociotechnical setting of BIM-enabled projects in this country. Also, the findings are based on the perception of experts in the field, rather than analysis of performance measures or quantitative assessment of associations among collaboration outcomes and various factors. This, however, provides the field with fertile grounds for future research. Practical implications: The study benefits researchers by shifting the collaboration discourse in BIM-enabled projects from technology-related issues to the people and contractual-related domains. Moreover, the developed qualitative model provides industry professionals with a point of reference to improve collaboration on BIM-enabled projects. Social implications: The study benefits researchers by shifting the collaboration discourse in BIM-enabled projects from technology-related issues to the people and contractual-related domains. Moreover, the developed qualitative model provides industry professionals with a point of reference to improve collaboration on BIM-enabled projects. Originality/value: Arguments provided in this study highlight the necessity of considering the contractual arrangement of BIM-related projects and foster the willingness of team members to collaborate. This can be addressed using clear and comprehensive BIM execution plans and clearly explaining the role of BIM managers in the process

An investigation into collaboration in Building Information Modelling-based Construction Networks (BbCNs)

This study investigated inefficient collaboration in the Building Information Modelling (BIM) process. It developed a model by identifying influential factors to effective collaboration in BIM-enabled projects. The findings indicated that unlike the common belief, technology is not the main factor, but factors such as knowledge, training, ethics, and motivation etc. are more critical to effective collaboration in BIM-enabled projects

Coal Pillar Strength Based On The Ground Reaction Curve – A New Approach

In underground coal mining, particularly room-and-pillar methods, the coal pillars play a significant role in roof stability. If the pillar dimensions are increased, the pillar bearing capacity also increases, but more coal remains in the pillar and therefore the recovery of mining operation decreases. Therefore, determining the optimum pillar dimension based on technical, economical and performance parameters is important. In this paper, the coal pillar is designed by using the concept of ground reaction curve (GRC). For this purpose, the GRC for coal pillars is drawn and then the elastic and plastic zone of coal pillar behavior is determined. Based on elastic and plastic zone, different equations are presented to draw a pillar reaction curve and the process of coal pillar design based on GRC is explained. As a case study, this new technique is applied to study the coal pillar state in Tabas coal mine of Iran. The results show that the presented new approach is successfully used in the design of the optimum coal pillar dimensions, and also determines the elastic and plastic behavior limit, which is important especially for the logical design of yield pillars