Delineation of waterlogged area in inaccessible underground workings at Hingir Rampur Colliery using 2D resistivity imaging: a case study

Resistivity imaging (RI) survey was carried out along two profiles in the Hingir-Rampur Colliery to assess how far it would be practical to extend the workings in Seam I towards the waterlogged previous workings, whilst leaving at least 60 m of coal between the two sections of mine. In order to corroborate the results of the geophysical survey, two boreholes were drilled along the profiles. Analysis confirmed hard, compact and dry strata between 60 and 146 m depth.     

Performance of ceramic-block fire stops for power cable installations

Fire losses due to cable fire in thermal power plants and industrial units are mounting. Fire in cable galleries is caused either by an external source or internal heating due to overloading or poor cable insulation. Most of the power cables are laid in groups that run on trays. In the event of fire, cable insulation melts and cable conductors come into contact and generate sparks. The resulting flame spreads through cables and engulf other groups of cables. This leads to damage in control rooms and distribution units that causes power generation disruption and plant shutdown.To minimize the damage and system disturbance due to fire, a new system for cable installation has been developed. The system involves construction of fire stop walls using fire-resistant cavity blocks, heat-resistant wool, and fire-resistant sealant.     

Geotechnical study for optimizing the slope design of a deep open-pit mine,India

The study was undertaken to determine the optimal overall slope angle of a lead–zinc mine, which could extend down to a depth of 170 m. Detailed geotechnical investigations were conducted, including geotechnical mapping of existing benches to establish the geometrical and mechanical properties of the discontinuities, the drilling of eight boreholes and the establishment of the physico-mechanical properties of the intact rock. Based on these data, limit equilibrium and numerical simulation techniques were applied to assess the stability of the slopes and determine an optimal slope angle. It was concluded that the overall foot-wall and hanging-wall slopes should be 42 and 48° respectively.      

An analytical solution to wellbore stability using Mogi-Coulomb failure criterion

Deep wellbores/boreholes are generally drilled into rocks for oil and gas exploration, monitoring of tectonic stresses purposes. Wellbore and tunnel in depth are generally in true triaxial stress state, even if the ground is under axisymmetric loading condition. Stability of such wellbores is very critical and collapse of wellbore must be avoided. Mogi-Coulomb failure criterion is a better representation of rock strength under true triaxial condition. In this paper, an analytical solution is proposed using Mogi-Coulomb failure criterion. The solution is obtained for rock mass exhibiting elastic-perfectly plastic or elastic-brittle-plastic behaviour considering in-plane isotropic stresses. The proposed solution is then compared with exact analytical solution for incompressible material and experimental results of thick-wall cylinder. It is shown that the results obtained by the proposed analytical solution are in good agreement with the experimental results and exact analytical solution. A reduction of about 13%–20% in plastic zone from the proposed closed-form solution is observed, as compared to the results from the finite element method (FEM) based Mohr-Coulomb criterion. Next, the influences of various parameters such as Poisson's ratio, internal pressure (mud weight), dilation angle, and out-of-plane stress are studied in terms of stress and deformation responses of wellbore. The results of the parametric study reveal that variation in the out-of-plane stress has an inverse relation with the radius of plastic zone. Poisson's ratio does not have an appreciable influence on the tangential stress, radial stress and radial deformation. Dilation angle has a direct relation with the deformation. Internal pressure is found to have an inverse relation with the radial deformation and the radius of plastic zone.     

Slope instability analysis in Phyllitic rock in the Lesser Himalayan using three different modeling approach

Bulletin of Engineering Geology and the Environment - The numerical methods for slope stability problems always have a serious concern related to their continuum and discontinuum nature. In...     

Electron microscope studies of nano-domain structures in Ru-based magneto-superconductors: RuSr(2)Gd(1.5)Ce(0.5)Cu(2)O(10-delta) (Ru-1222) and RuSr(2)GdCu(2)O(8) (Ru-1212)

Microstructures of the RuSr(2)Gd(1.5)Ce(0.5)Cu(2)O(10-delta) (Ru-1222) and RuSr(2)GdCu(2)O(8) (Ru-1212) magneto-superconductors have been investigated by using selected-area electron diffraction, convergent-beam electron diffraction, dark-field electron microscopy and high-resolution electron microscopy at room temperature. Both Ru-1212 and Ru-1222 consist of nm-size domains stacked along the [Formula: see text] direction, where the domains are formed by two types of superstructures due to ordering of rotated RuO(6) octahedra about the c-axis. In Ru-1212, both primitive-and body-centered tetragonal superstructures (the possible space groups: P4/mbm and I4/mcm) are derived to form the corresponding nm-domains. It is of great interest that Ru-1212 consists of domains of two crystallographically different superstructures, while the similar domains observed in Ru-1222 have crystallographically identical superstructure with an orthorhombic symmetry (possible space group: Aeam), related by 90 degrees rotation around the c-axis (Yokosawa et al., 2003, submitted for publication).     

Performance of membrane compensated multirecess hydrostatic/hybrid flexible journal bearing system considering various recess shapes

The paper describes a theoretical study concerning the performance of an externally pressurized multirecess hydrostatic/hybrid flexible journal bearing system by varying the geometric shape of recess and using the membrane flow valve restrictor as a compensating element. The four different recess geometries of the bearing studied in the present study are a square recessed bearing, a circular recessed bearing, an elliptical recessed bearing and a triangular recessed bearing. The equation governing the flow of lubricant in a journal bearing together with 3D elasticity equation and restrictor flow equation are solved by using the Finite Element Method. The study describes the effect of recess shape, bearing flexibility and a method of compensation on the performance characteristics of a hydrostatic/hybrid journal bearing system. A comparative performance of the membrane compensated hydrostatic/hybrid journal bearing system has also been studied vis-à-vis capillary, orifice and constant flow valve restrictors. The results presented in this study amply demonstrate that the shape of recess/pocket of a hydrostatic/hybrid flexible journal bearing system affects the performance of the bearing quite appreciably and a proper selection of recess shape along with a suitable compensating device is needed to get an improved performance from the bearing.     

Synthetic polyurea extreme‐pressure greases

This paper describes the preparation of synthetic polyurea greases and evaluates their performance. The polyurea greases were prepared in situ by reacting diisocyanate with monoamines and ethylene diamine in the presence of a synthetic base oil (polyalphaolefin). Two different extreme‐pressure (EP) additives blended with the prepared polyurea greases were evaluated for their EP activity in four‐ball and Timken tests. The additivated greases gave higher loads, and higher values of weld load in the four‐ball test as compared to the polyurea grease without additive. The blended greases were also found to pass rust, corrosion, oxidative stability, and shear stability tests. The topography of the wear‐scar surfaces was investigated using scanning electron microscopy.     

Frequency channeling: a concept to increase the frequency and control the PPV of blast-induced ground vibration waves in multi-hole blast in a surface mine

Bulletin of Engineering Geology and the Environment - Vibrations induced due to blasting in mines may damage the nearby houses and disturb the habitants. The monitoring, prediction, and control of...     

Different glazing systems and their impact on human thermal comfort—Indian scenario

In the present communication, fifteen different glazing systems ranging from 3 mm single glazed clear glass to double glazed with low-e and solar control coating, have been analysed in terms of their human thermal comfort impact. Thermal comfort is measured in term of PMV (predicted mean vote) and PPD (predicted percentage of dissatisfied). Study encompasses all the six climatic zones of India. By using OPTICS 5.0 and WINDOW 5.0, U-values, solar heat gain coefficient, inside glazing surface temperatures and inside solar radiation have been computed. Depending upon different climatic zones, six sets of different design conditions, in terms of ambient temperatures, solar radiation and wind velocity, have been chosen. Typical values of metabolic rate and clothing insulation taken are 1.2 met and 0.5 clo for summer and 1.0 met and 1.0 clo for winter, respectively. Inside room air velocity is taken as 0.15 m s⁻¹ round the year. Room temperature is taken as 20 °C in winter and 25 °C in summer. It is found that for cold station (e.g. Leh) all glazings except solar control glazings, ensure thermal comfort and total PPD is less than 10% (|PMV|?0.5). For warm and hot climates, solar control glazings are thermally suitable. Results for winter night of Delhi shows that all the 15 glazings are inadequate for thermal comfort and PPD, due to cold feeling, varies between 27% and 33% approximately.