Investigating the effect of coal macerals on the recovery rate of the flotation process- a case study

Alborz-Sharghi coal washing plant is one of the most significant coal producers in Iran, which has a low recovery rate in the flotation process. This paper investigates the effect of coal macerals types on the flotation recovery rate. For this purpose, a comprehensive sampling procedure was conducted on the feed of the flotation system. Afterwards, the required polished sections of the samples were prepared for detecting the macerals. After conducting a series of flotation tests on the samples, the recovery rate results were compared based on detected macerals on the polished sections. The results revealed that the flotation recovery rate increased with the rising vitrinite contents. However, it decreased with increasing fusinite and liptinite contents

Finite element simulation of fully grouted rock bolts behaviour across varied bore hole diameters

This paper introduces a finite element (FE) method to simulate the impact of confinement conditions on the axial load-bearing capacity of fully grouted rock bolts. The study utilises a combination of experimental and numerical modelling techniques. For this purpose, two different sizes of steel sleeves were used as confinements with a diameter of 23 mm and 50 mm. The samples were cured after embedding and grouting the bolt for 28 days. Subsequently, pull-out tests were conducted to assess the axial load-bearing capacity of the samples. The results showed a direct correlation between increased confinement diameter and higher values of ultimate pull-out capacities. In addition to the experimental tests, numerical models employing ABAQUS software were developed to simulate and analyse the debonding mechanism along the bolts. By defining the appropriate model geometry, materials properties, boundary conditions, and interactions, the simulation revealed that the debonding mechanism occurred at the bolt-grout interface. Eventually, a comparison between the load-displacement curves derived from the experimental tests and the numerical simulations highlighted the effectiveness of the numerical model in accurately representing the axial load transfer mechanism within the fully encapsulated rock bolts

Investigating the axial and shear performance of fiberglass rock bolts

This paper primarily evaluates the axial and shear performance of fully grouted fibreglass- reinforced polymer (FRP) rock bolting systems. For this purpose, a FRP rock bolt with a diameter of 20 mm was selected for examination. To evaluate the axial performance, several samples with a double- embedment length of 150 mm and an exposed length of 200 mm were cast using an 80 MPa cementitious grout and cured for 28 days. Pull-out tests were then conducted at a controlled rate of 1 mm/min with a 1000 KN MTS apparatus to determine the pull-out performance of the FRP bolts. Furthermore, a comparative analysis involved testing a 20 mm fully grouted steel rock bolt with a 150 mm encapsulation length, was conducted. The results indicated that the axial bearing capacity of the FRP bolts varied between 84 KN and 110 KN, while the steel bar exhibited a capacity of 144.5 KN. The load-displacement curves analysis showed that steel rebar rock bolts absorb more energy during the debonding process compared to the FRP bolts. Along with pull-out tests, the shear behaviour of the FRP bolts was also determined by conducting single and double-shearing tests. With this aim, after casting the concrete blocks in a double-shearing box, three different pretension values were applied to the samples. The results showed that pretension values had a direct impact on the displacement values, while they did not have a direct impact on the peak shear force values. Additionally, the tensile properties of the FRP and the steel bolts showed a different behaviour in the uniaxial tensile test