IR@CIMFR - Central Institute of Mining and Fuel Research (CSIR)
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The impact of high temperature on compressive strength and density of two types of granites from India
No full textPhysical properties of rocks have significant engineering value. Compressive strength and density of rocks are used in many rock mechanics related studies pertaining to civil and mining activities, stability of the excavation and estimation of the support required. In addition, rocks like granite are used as a building material and are encountered in many civil and infrastructure projects. However , these properties vary with increase or decrease in their temperature. A host of data exists on heat treatment of different rocks. in order to augment such studies and to further the know- how in this discipline, a comprehensive analysis of 56 samples if two types of granites from India was taken up in this study. The test for compressive strength and density with increase in temperature from 35C to 600 c were devised and conducted. The results revealed that the behavior of two groups of the granite varied in a noticeable range on a linear scale. A reduction of 45% to 49% in strength from room temperature to 600c in the two types of granites points to the loss of strength with increasing temperature. A reduction of 4.3% to 6.3% in density of the samples on heating can be considered to be mild. The rearrangement of grains, loss of water content initially and increase in volume on further heating are considered to be the major reasons for reduction of such physical properties in a linear manner. Colour changes have also observed in the heating process which needs to be explained in future
Integration of Numerical and Empirical Approaches for Assessment of Apt Support Design for Various Underground Openings of Chromite Mine
No full textThe underachievement of support systems in roof bolts layout design is one of the dominant causative factors of roof fall in underground mines. Various factors triggering the roof failure are the presence of laminated roof, the geological plane of weaknesses, the time lag in support installation, inefficient grouting/bonding of roof bolts, improper estimation of roof bolt length, the concentration of the induced stresses due to mining activities, etc. The roof fall concerns mining engineers as it seriously affects safety and productivity. Hence the stability of the openings has to be considered as apriority to suspend the movement of overly in glayered strata by application of adequate support. Application of rock mass classification system helps in guiding suitable roof support design for apt Search Log in
stabilization of the mine openings. The study has been carried out to assess the befitting support design of various openings in underground chromite mine considering applicable rock mass classification systems namely Bieniawski’s Geomechanical System and Barton’s Q — system inclusive of numerical analysis. The values of rock load obtained by Bieniawski’s geo mechanical system was on the higher side. Thus, in view of the safety and stability of engineering structures, Bieniawski’s geo mechanical system was considered for the design of a support system. Rock load was determined for different dimensions of under ground openings such as decline, cross-cut junctions, cross-cut roadways, ore drive, footwall drive, and haulage junctions, wherein width variation resulted in influencing rock load. Safety factor has also been analysed with respect to the width of the opening to demarcate stable and semi-stable zone
Even partially amorphous Pd2Ni2P metallic glass significantly promotes hydrogen evolution electrocatalysis
No full textMetallic glasses are expected to be endowed with higher electrocatalytic activity, with respect to their crystalline counterparts, due to the presence of a high density of under-coordinated sites. However, glasses made of metals, as opposed to metal oxide/sulfides are harder to synthesize, with the challenge increasing with amorphousness. In light of these issues, we calibrate the increase in hydrogen evolution reactivity using the Pd2Ni2P bulk metallic glass composition as a model system. This composition has a good glass-forming ability and is interesting from a catalytic point of view, as Ni and P lie on the opposite leg of the HER volcano plot with respect to Pd. Partially amorphous (PA) Pd2Ni2P alloy displayed a five-fold higher specific electrocatalytic activity on per unit electrochemical surface area (ECSA) basis compared to its crystalline (C) counterpart. This magnitude of specific electrocatalytic activity, which is on par with that for pure Pd, has been achieved with just 40% of the precious metal, leading to a considerable saving in cost. The homogeneous single-phase structure of the highly electro-active partially amorphous alloy leads to higher electrochemical stability than its polycrystalline counterpart. This finding implies that many compositions ignored traditionally due to their poor electrocatalytic activity or stability can now be reconsidered in amorphous forms, thus expanding the material space of valuable catalysts
Experimental and CFD Simulation Techniques for Coal Dust Explosibility: A Review
No full textCoal is a low-cost and high-calorific-value fuel. The coal mining industry worldwide has been suffering from severe accidents due to coal dust explosion hazards since its inception. Statistically, it was observed that 12,489 fatalities had occurred in 104 reported mining accidents from coal dust explosions during 1900–2020. There are numerous methods for detection, prevention, and control of coal dust explosions in mines. The underground mining environment is unpredictable and has an array of variables. These undulating factors make it difficult to prevent or control the coal dust explosion hazard. However, coal mining is done aggressively throughout the world, especially in developing countries as coal is a major source of thermal energy used in power plants contributing to about 38% (IEA, (2019), World Energy Outlook, IEA, Paris https://www.iea.org/reports/world-energy-outlook-2019.) of world electricity. Worldwide, coal dust explosibility studies are carried out in experimental mines, laboratories, and simulations. The complexity, lack of proper infrastructure, and unavailability of laboratory equipment sometimes make it difficult to study coal dust explosibility. The authors have discussed in detail and proposed that the CFD modelling can be a viable option for studying and evaluating coal dust explosibility
Silkworm Protein-Hydroxyapatite Blend Films for Tissue Engineering Applications
No full textA unique protein extracted from discarded silkworms was reinforced with hydroxyapatite (HA) and made into films for potential tissue engineering applications. After reeling of silk, the silkworms are treated as waste and disposed. However, the silkworms contain up to 25–30 % proteins, 40 % oil and 20–25 % carbohydrates and are inexpensive and a renewable resource for various biopolymers. Proteins extracted from silkworms had purity of 90 %, molecular weights of about 30 kDa and were soluble in a weak alkali. The proteins could be made into films using a simple compression molding technique. Hydroxyapatite (HA) was synthesized and added to the proteins to promote cell growth for tissue engineering applications. The changes in the structure, properties and enhancement in cell viability and growth due to the addition of HA were studied. The ability of the films to differentiate osteoblast cells was determined using ALP assay and calcium activity tests. Results showed that the addition of HA increased the tensile properties including the strength (3.5 to 5.5 MPa, elongation from 3.3 to 5.7 % and modulus from 153 to 242 MPa). However, no significant change was observed in terms of cell attachment, growth or viability. Yet, the inclusion of HA did not increase the cytotoxicity and hence, is considered to be beneficial to obtain silkworm protein-based films
Optimization of NiFeCrCoCu high entropy alloy nanoparticle – graphene (HEA-G) composite for the enhanced electrochemical sensitivity towards urea oxidation
No full textGraphene as a single or few-layered 2D material acts as a stable and efficient substrate to build effective nanocomposite catalysts for numerous applications. In this study, a few layers of exfoliated graphene sheets are engineered with novel high entropy alloy (HEA) nanoparticles through mechanical milling technique followed by sonication. Three different HEA-Graphene (HEA-G) composites were produced with the metal-to-graphene weight ratio of 50:50, 70:30 and 90:10. As-synthesized HEA-G composites were extensively characterized through microscopy (AFM and TEM) and spectroscopic (Raman) techniques to understand the HEA nanoparticle formation and distribution over the surface of graphene sheets. Further, the catalytic behaviour of HEA-G composites was examined using cyclic voltammetry (CV) and chronoamperometry (CA) to understand the non-enzymatic oxidation of urea using the HEA-G composites. The onset of the catalytic behaviour was observed with the composite 50:50 which was increased till 70:30 composite. However, the 90:10 composition exhibited minimal catalytic response compared to the other two composites. The composite 70:30 being the best performer was used to derive sensitivity based on the oxidation of urea which was found to be 37.4
Am M−1 cm−2. The current study opens the window to explore a new class of all possible HEA nanocomposites for electrocatalytic applications
Prediction of Strata Monitoring System in Underground Coal Mines Using IoT
No full textUnderground coal mines are known for being one of the most hazardous sectors due to its working environment. The mine workers are usually prone to many risk factors leading to heavy casualties. As per the statistical records of Directorate General of Mines Safety, roof fall is one of the major causes of accident in Indian underground coal mines. One of the critical contributing factors of such accidents is lack of roof fall prediction system, thereby leading to failure to withdraw or removal of working persons before the actual failure. Real-time monitoring of strata movement and analysing the acquired data for predicting possible roof fall well in advance through an effective intelligent system can certainly pave way in reducing the accidents due to roof fall.
The paper presents an integrated strata management system for continuous monitoring of strata behaviour and analysing the data using artificial intelligence for prediction of failure of strata ahead of time.
This web-based monitoring system initially sets the customizable threshold values according to the mine conditions followed by continuously monitoring of the strata conditions including triggering an alarm system when the retrieved data crosses the set threshold limit
Appropriate Support Design for Incline Lip Opening and Drivages in Fragile Rock Mass Formation: An Empirical and Numerical Based Case Study
No full textThe production of underground coal is directly
related to the safety of the mine. When any fatality
occurs, mostly due to roof fall and side fall,
production of the mines gets affected. In India roof
fall in underground mines still contributes a fair
amount of percentage, i.e., in and around 40%
towards the fatalities of the accident. Thus the roof
fall in underground mines has to be minimized by
the application of a rational and appropriate
support system. The design of support for soft rock
formation still drives a real concern for engineers as
it requires lots of effort, hard work and experience.
In this study, support design is given for the incline
lip opening in fragile and soft rock geological
formation. The study on the apt support for incline
drivages has also been conducted. Rock load has
been estimated applying CMRI rock mass
classification, Bieniawski’s Geomechanical System
and numerical modeling. On comparing rock load
obtained by CMRI rock mass classification has been
observed on upper side. To ensure the safety and
stability of incline drivages, CMRI rock mass
classification has been considered to design a
support system so as to maintain factor of safety
above two
Implication of Electrical Resistivity Tomography for Precise Demarcation of Pothole Subsidence Potential Zone Over Shallow Depth Coal Mine Workings
No full textPothole, an undesirable catastrophic consequence, is a common phenomenon in old coal mine workings, especially at shallow depth endangering habitats and surface structures. Precise identification of pothole potential zone is vital to prevent any major setbacks. Limited sub-surface information leads to branching out from the realistic ground conditions resulting in improper inferences. Resistivity imaging system is a favourable tool for gathering and strengthening technical information to demarcate the potential areas of pothole occurrence as it has proven ability to translate the characteristic of strata. Geological disturbance, one of the causes for pothole, has been located precisely by electrical resistivity survey at the study site. The overlying rock type has been correlated with resistivity range and validated with borehole lithology. Considering influencing parameters for pothole i.e. position of underground workings, geological disturbance and nature of near surface strata potential locations of the pothole likely to occur has been demarcated based on resistivity characteristics. Two potholes occurred in the past also helped in strengthening in interpretation
Predicting and Optimising the Strength of Cemented Paste Fills Through Bayesian Network Model
No full textThe techno-economic and social benefits of cemented paste backfill (CPB) resulted in its wide acceptance by the mining industry. The Ordinary Portland Cement (OPC) remains the key binder but to diminish its economical constraints, suitability of alternate binders has been examined worldwide. The present study aimed to investigate the effect of partial replacement of OPC with fly ash on the CPB’s strength and to determine the most optimal mix to achieve the required strength (1 MPa at 28 days of curing) at the most cost-effective way using the Bayesian network (BN). The CPB mixes were prepared at 72 wt.% solid concentration with mill tailings (87–91%), OPC (6–13%), and fly ash (0–4%), and instantly after mixing, fresh (slump, bleeding, density) CPB properties were measured. The strength was tested at 7, 14, 28, and 56 days of curing and initially analysed through traditional model. The traditional models follow the aleatory principle and are considered not appropriate for geotechnical engineering. Hence, the BN model was developed and tested. The reliability of two classifiers in learning model structure was compared which gives Naïve Bayes as the highest reliable tool. The CPB’s strength is most sensitive to the OPC content. The most consistent mix(s) is mill tailings: 87–88%, OPC: 9–11%, fly ash: 1–4%. Adding fly ash at 89–91wt% mill tailings possesses high failure probability of the CPB. The collinearity test indicates that the fines percentage and chemical composition of CPB’s ingredients are highly correlated with its slump, bleeding, and strength development