Productivity Analysis of Raisebore RB-50X for Raise Slot Drilling at Extraction level GBC PT. Freeport Indonesia

PT Freeport Indonesia is the largest gold and copper mine in Indonesia, located in Mimika Regency, Papua Province. In its operation, PT. Freeport Indonesia applies two mining systems, namely open pit mining and underground mining. Underground Mine at PT. Freeport Indonesia consists of DOZ, Big Gosan, DMLZ, Kucing Liar, and GBC, with one of the methods applied by PT. Freeport Indonesia is a block caving method. The Grasberg Block Cave mine has entered the production stage since September 2018, but in its operation the GBC Mine is still developing its operational area to meet production targets (development). The development cycle (cycle development), which is the main operation carried out, namely drilling and blasting, loading & transporting (mucking & hauling), primary support, and secondary support. To support the main operations, it is necessary to have main support consisting of access and area, ventilation, water and water, electricity, pull of tests, surveys, and dewatering. In the blasting process at the drawbell, one free face is needed which functions as the direction of rock collapsing in the blasting process on the drawbell. Making free face or commonly known as slot raise using a rasiebore machine from PT. Redpath for slot raise drilling. Meanwhile, in the drilling stage, the slot raise has a problem that has resulted in delays in the drilling process for the RB-50X raisebore tool. The impact of the delay in making the slot raise resulted in not achieving the production target due to a delay in the blasting process, where the blasting process in the drawbell area functions to break the rock so that it falls and can be transported to the crusher to enter the rock sizing process.

The study of the curvature of the axis of the processed shaft when based in the centers using a steady rest

This paper presents the analysis and results of the study of a two-stage shaft fixed in dead centers and a rest device. Cutting forces act on the shaft, causing a bending moment. The analysis of the curvature of the axis of the workpiece, processed on a lathe when based in the centers, using a rest device, is carried out. The formula of elastic displacement of the workpiece axis at the place of the resulting cutting force is obtained. Diagrams of the stresses of the shaft axis displacements are constructed and a conclusion is made. The analysis showed that the greatest deflection is at the point of the cutting forces acting on the shaft. The quality of the part obtained after processing is characterized by accuracy. The parts mating in the product and, as a result, the overall reliability depends on how accurately the size and shape of the part will be maintained during processing. Parts with length of 10 to 12 times larger than the diameter are bent under the action of their own weight and cutting forces, as a result of which they get a barrel-like shape. It is possible to eliminate this by applying special devices for the machine. When processing long nonrigid workpieces, the tools, jigs and fixtures must evenly distribute the clamping force over the surface of the part. These conditions are well provided by technological equipment with pneumatic, hydraulic clamping devices, as well as with various collet clamps, split bushings, diaphragm or cartridges. When processing long non-rigid shafts, rest devices are used. The rest device plays the role of the main or secondary support when working with workpieces; it creates support for large, long parts during processing. It helps to avoid the risk of damage and deformation of the workpiece or the cutting elements of the machine, by giving the workpiece additional stability

Roadway Support in Deep “Three-Soft” Coal Seam: A Case Study in Yili Mining Area, China

This paper analyzes the large deformation of roadway in three-soft coal seam under the influence of tectonic stress. Taking the auxiliary conveying uphill roadway in Yili No. 1 Coal Mine as the engineering background, the deformation and failure mechanism of the surrounding rock and the supporting technology were studied. First, the characteristics of stress field and the surrounding rock properties of deep mining area were investigated through geostress measurement and rock mechanical test. Then, the roadway deformation and the loose circle of the supporting structure were obtained. Based on the results from measurement and theoretical analysis, we proposed a concept, i.e., “Stress adjustment-Strengthening-Grouting-Secondary support.” A numerical model was established to analyze the stress distribution and the state of plasticity in the surrounding rock. According to the results of the geostress measurement and the numerical simulation, a combined support scheme was proposed, i.e., “Yielding bolt & Shotcreting” as the primary support and “Prestressed grouting anchor cable & U-shaped shed” as the secondary support. Finally, the underground practice showed that the proposed support scheme can effectively control the large deformation and maintain the long-term stability of the roadway in deep and three-soft coal seam. The proposed technology has guiding significance for the support design under similar mining conditions.

ALAMILLO BRIDGE: CONSTRUCTION SIMULATION MODELS IN EZSTROBE

The Puente del Alamillo in Seville, Spain, designed by Santiago Calatrava, has a single pylon that rises at an angle away from the deck, and which together with the deck resembles a harp whose strings are the cable stays from the pylon to the deck. It is the only bridge of its kind in the world whose pylon is not back-anchored, and its deck and pylon balance at a single massive footing below the pylon. This design made construction of the bridge very risky because the unfinished bridge had to be kept in balance like a giant teeter-totter until it could rest at the secondary support away from the pylon. A total of three construction plans were investigated by the contractor with the first two rejected and the third used for construction. Previous research presented simulation models for these three plans in CYCLONE along with construction time estimates for the bridge deck and pylon. Unfortunately, the published simulation models had mistakes that led to incorrect statistical results and conclusions. This paper describes these mistakes and presents three simulation models in EZStrobe that produce appropriate statistics and conclusions. These models can be used as practical examples for the application of discrete-event simulation to construction.

Feasibility testing of a supported education programme for students with severe mental disorders

Introduction: Most supported education studies stop at discussing the academic problems of students with severe mental diseases (SMDs) without going into testing of appropriate and culturally relevant supported education interventions required for academic reintegration of students with SMDs. In this context, the researcher felt the need to test the feasibility of a need-based supported education programme (SEP) for students with SMDs to help them achieving higher education goals. Methodology: This study was reviewed and approved by the Institute’s Ethics Committee (NIMHANS) and it was also registered in the Clinical Trials Registry – India (CTRI): CTRI/2018/07/014828. The study used mixed (qualitative and quantitative) research methodology with a combined approach of Action Research and Case Study in providing SEP to students with SMDs. Fourteen ( n = 14) students who enrolled into the SEP were assessed on their self-esteem, sense of mastery, helping factors, needs and outcomes met from SEP. The SEP was provided for up to a maximum of 1 year based on the academic reintegration needs of the student. Results: The results indicated that there was a significant reduction in hindering factors (χ2 = 9.41, p < .01) and increase in helping factors (χ2 = 6.49, p < .05) and self-esteem (χ2 = 10.3, p < .01) over the period of 1 year of the study. Qualitative results further reiterated increase in helping factors along with positive outcomes such as enhanced primary and secondary support, reasonable accommodation at academic institutions, individual behavioural changes in academics and increased awareness and knowledge about mental illness and welfare benefits. Conclusion: The SEP was found to be feasible qualitatively and quantitatively in helping the students with SMDs to reintegrate into academics, improving their self-esteem, reducing their hindering factors, and improving their support system and helping factors.

INVESTIGATION OF MAINGATES STABILITY IN STEEP COAL SEAMS AT EXTRACTION LAYOUTS OF DEEP MINE

Purpose of work. Investigation of maingates stability in different methods of protection on the extraction layouts of a deep coal mine, which develops steeply inclined coal seams. Methods. To achieve this goal, mine experimental observation of maingates stability performed. Conditions for their maintenance are evaluated by the magnitude of the convergence of the side rocks on the contour and changes in the cross-sectional area of the gateroads. Results. As a result of the research the conditions of maingates stability in steep coal seams in protection by pillars or timber sets are substantiated. It is recorded that in the zone of influence of extraction operations, at a distance of l <60 m behind the mining face with the considered methods of protection, the support of the maingates is deformed within the yielding limits and has characteristic flexures the side of hanging wall. At a distance of l≥60 m, the cross-sectional area of the maingates is reduced to 50% of the initial values, and the amount of roof to floor convergence exceeds the flexibility of the support. The increase displacement of rock mass on the contour of the supported roadway behind the mining face depends on the strength and geometry of the secondary support structures above the maingate. Novelty. It is experimentally established that the change in the cross-sectional area of the maingate during protection by timber sets occurs linearly with increasing length of the extraction layout. Practical significance. To ensure the maingates stability, it is advisable to use non-pillar methods of protection, when using yielding secondary support systemsabove the roadway, or backfilling.

Problems of mining the prospective coal-bearing areas in Donbas

The prospective coal-bearing areas of Donbas in Ukraine have been identified. Their development will increase the energy security of Ukraine. It has been suggested that the development of these areas will involve mining the coal seams in a weak roof and floor environment, which are characterized by low compressive strength, lower density and a tendency to plastic deformations. The stability has been assessed of the rocks outcrop on the contour of mine roadways for mines operating in these areas. It has been determined that roof rocks in most of these mines belong to a range of groups from very unstable to moderately stable, and the bottom rocks are, in most cases, prone to swelling. This complicates the intensive prospective areas mining with the use of advanced technologies, as well as secondary support for retained goaf-side gateroads with limited yielding property. The mines have been determined, for which this issue is relevant when mining the seams with further increase in the depth. The mechanism of displacement in the secondary supports and has been exemplified and studied using the numerical method. The obtained results allowed us to substantiate the necessity of developing new technical solutions for the protection of gateroads under conditions of prospective Donbas areas.