Finite-difference based response surface methodology to optimize tailgate support systems in longwall coal mining

AbstractDesigning a suitable support system is of great importance in longwall mining to ensure the safe and stable working conditions over the entire life of the mine. In high-speed mechanized longwall mining, the most vulnerable zones to failure are roof strata in the vicinity of the tailgate roadway and T-junctions. Severe roof displacements are occurred in the tailgate roadway due to the high-stress concentrations around the exposed roof span. In this respect, Response Surface Methodology (RSM) was utilized to optimize tailgate support systems in the Tabas longwall coal mine, northeast of Iran. The nine geomechanical parameters were obtained through the field and laboratory studies including density, uniaxial compressive strength, angle of internal friction, cohesion, shear strength, tensile strength, Young’s modulus, slake durability index, and rock mass rating. A design of experiment was developed through considering a Central Composite Design (CCD) on the independent variables. The 149 experiments are resulted based on the output of CCD, and were introduced to a software package of finite difference numerical method to calculate the maximum roof displacements (dmax) in each experiment as the response of design. Therefore, the geomechanical variables are merged and consolidated into a modified quadratic equation for prediction of the dmax. The proposed model was executed in four approaches of linear, two-factor interaction, quadratic, and cubic. The best squared correlation coefficient was obtained as 0.96. The prediction capability of the model was examined by testing on some unseen real data that were monitored at the mine. The proposed model appears to give a high goodness of fit with the accuracy of 0.90. These results indicate the accuracy and reliability of the developed model, which may be considered as a reliable tool for optimizing or redesigning the support systems in longwall tailgates. Analysis of variance (ANOVA) was performed to identify the key variables affecting the dmax, and to recognize their pairwise interaction effects. The key parameters influencing the dmax are respectively found to be slake durability index, Young’s modulus, uniaxial compressive strength, and rock mass rating.</jats:p

ODABIR OPTIMALNOGA SCENARIJA ZA ISTOVREMENU PRIMJENU DIJAMANTNE ŽIČNE PILE I LANČANE SJEKAČICE U KAMENOLOMU ARHITEKTONSKO-GRAĐEVNOGA KAMENA KORIŠTENJEM METODE VIŠEKRITERIJSKOGA ODLUČIVANJA SECA

Currently, diamond wire cutting is used in most dimensional stone mines to extract stone blocks. Despite the capabilities of diamond wire cutting, stone extraction is associated with limitations or productivity loss in some cases. For this purpose, different scenarios resulting from the combination of diamond wire cutting and chainsaw machines had been investigated by discrete-event simulation in this research with the aim of improving the productivity of mining operations, and the best scenario was selected using the multi-criteria decision-making method of Simultaneous Evaluation of Criteria and Alternatives (SECA). In this research, the Shayan dimensional stone mine was selected as a case study, and based on the information related to mining operations, ten scenarios were defined for cutting the stone blocks. In the first scenario, a diamond wire cutting was alone used to cut all three sides of the block. In the second scenario, in addition to the diamond wire cutting, a chainsaw machine was added to the mining process to cut the back face of the block. In the third to sixth scenarios, in addition to the diamond wire cutting to cut side faces, a chainsaw machine was added to the mining process to cut the bottom face of the block. Depending on the continuity and intactness of the rock mass, and the need for horizontal drilling, the block dimensions varied across these scenarios. In the seventh to ninth scenarios, in addition to the diamond wire cutting to cut side faces, two chainsaw machines were used to cut both the back and the bottom faces of the block. These scenarios may differ in terms of the stone’s intactness, the need for horizontal drilling, and block dimensions. Finally, in the tenth scenario, both the back and bottom faces were cut using two chainsaw machines, while the side faces were cut using two squaring chainsaw machines. In order to find the best scenario to achieve the optimal technical and economic conditions, the SECA decision-making method was used due to the presence of several influential criteria. Based on the available information, four criteria including the production rate, capital cost, operating costs, and productivity were considered to compare the defined scenarios. According to the results, the final weights of the criteria were respectively equal to 0.228, 0.32, 0.239, and 0.213. Based on the criteria weights and the performance of each scenario across the criteria, the final scores of the scenarios were determined, and ultimately, the second scenario with a score of 0.655 emerged as the optimal configuration for the Shayan mine due to its balanced performance across all criteria.Rezanje dijamantnom žicom danas se koristi u većini kamenoloma arhitektonsko-građevnoga kamena za eksploataciju kamenih blokova. Unatoč većem kapacitetu rezanja dijamantnom žicom eksploatacija kamena u nekim se slučajevima suočava s ograničenjima ili padom produktivnosti. Zbog toga su u ovome istraživanju proučavani različiti scenariji kombinacije rezanja dijamantnom žičnom pilom i lančanom sjekačicom u svrhu poboljšanja produktivnosti rudarskih radova, a najbolji scenarij odabran je korištenjem višekriterijske metode donošenja odluka (simultaneous evaluation of criteria and alternatives, SECA). Za studiju slučaja odabran je kamenolom arhitektonsko-građevnoga kamena Shayan, a na temelju informacija vezanih uz rudarske radove definirano je deset scenarija rezanja kamenih blokova. U prvome scenariju dijamantna žična pila korištena je za rezanje svih triju strana bloka. U drugome scenariju, uz rezanje dijamantne žične pile, uključena je lančana sjekačica za rezanje stražnje strane bloka. Od trećega do šestoga scenarija, uz korištenje dijamantne žične pile za rezanje bočnih strana, lančana sjekačica dodana je u procesu rezanja donje strane bloka. U tim scenarijima dimenzije bloka varirale su ovisno o kontinuitetu i cjelovitosti stijenske mase i potrebi za horizontalnim bušenjem. Od sedmoga do devetoga scenarija, uz korištenje dijamantne žične pile za rezanje bočnih strana, dvije lančane sjekačice korištene su za rezanje stražnje i donje strane bloka. Ti se scenariji mogu razlikovati u pogledu cjelovitosti kamena, potrebe za horizontalnim bušenjem i dimenzija bloka. U desetome scenariju stražnja i donja strana izrezane su pomoću dviju lančanih sjekačica, dok su bočne strane izrezane pomoću lančane sjekačice za oblikovanje blokova. Kako bi se pronašao najbolji scenarij za postizanje optimalnih tehničkih i ekonomskih efekata, korištena je SECA metoda odlučivanja koja ima nekoliko ključnih kriterija. Na temelju dostupnih informacija za usporedbu definiranih scenarija u obzir su uzeta četiri kriterija: stopa proizvodnje, trošak kapitala, operativni troškovi i produktivnost. Na temelju rezultata, konačne težine kriterija iznosile su redom 0,228, 0,32, 0,239 i 0,213. Na temelju pondera kriterija i izvedbe svakoga scenarija po kriterijima određeno je konačno rangiranje scenarija pa se na kraju drugi scenarij s ocjenom 0,655 pokazao kao optimalna konfiguracija za kamenolom Shayan zbog svoje uravnotežene izvedbe po svim kriterijima