Faculty Publications

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Author: search.filters.author.Pal, S.K.

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    Studies on gravity backfilling method for blind backfilling of abandoned coal mines
    (TMMOB Maden Muhendisleri Odasi, 2015) Pal, S.K.; Panda, S.; Tripathi, A.K.
    In this paper a new, simple and low cost gravity backfilling method for stabilization of ground above abandoned underground mines is proposed. Laboratory investigations carried out on this simple gravity hydraulic blind backfilling method to fill up a fully transparent model of a section of a bord and pillar mine, have indicated that deposition of the filling material surrounding the inlet hole occurs in a regular shape with full packing up to the roof. Some empirical relationships on maximum volume of sand throughput and spread of sand around the inlet hole have been developed with a view to help the practicing engineers. In the field trial the spread of sand in different directions has been witnessed using an ROV camera fitted with a sonar imaging system. The shape and nature of deposited sand bed surrounding the feeder hole in field and laboratory studies are alike. The empirical relationships developed under field conditions have also been found to be similar to those of laboratory model.
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    MWD technique to estimate the uniaxial compressive strength of rocks
    (American Institute of Physics Inc. subs@aip.org, 2020) Lakshminarayana, C.R.; Tripathi, A.K.; Pal, S.K.
    The measurement of mechanical properties of rocks is an essential task to be carried out during the projects involving the rock engineering activities such as civil constructions, tunneling, excavations etc. Although the quantification of uniaxial compressive strength in the laboratory is much faithful, the availability of rock samples and their preparation according to ISRM standards is the major limitation. In this experimental investigation, the quantification of the uniaxial compressive strength (UCS) of rocks using the measurement while drilling (MWD) technique was attempted. During the drilling of dissimilar strength rocks for various combinations of drilling operational parameters, the value of thrust and torque were collected using the digital type drilling dynamometer. The prediction of the UCS was performed by developing a mathematical model considering the parameters used for operating the machine and corresponding thrust and torque values. The prediction capacity of developed model was evaluated using the value account for (VAF), root mean square error (RMSE) and mean absolute percentage error (MAPE). From the results it was concluded that the MWD technique could be a prominent tool for estimation of rock strength properties in future. © 2020 Author(s).
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    Quantification of Rock Strength Using the Mechanical Drilling Parameters
    (Springer Nature, 2020) Lakshminarayana, C.R.; Tripathi, A.K.; Pal, S.K.
    The estimation of rock strength is most often required for the preliminary stage of rock engineering projects. The determination of rock strength properties in the laboratory is reliable, but the availability of a number of fine quality core samples for lab testing is very difficult. In this study, an attempt is made to investigate the usability of variations of thrust developed at the rock-bit interface and vibration frequency generated in the drilling machine head for estimation of rock strength during the rotary drilling. The variation of thrust and vibration frequency during drilling is measured using sophisticated digital type drilling dynamometer and data acquisition system (DAQ) with accelerometer sensor respectively. The second order regression models were developed to predict the rock strength such as uniaxial compressive strength considering the machine operating parameters and measured variables. The evaluation of the prediction ability of the developed models was checked using the three performance indices known as VAF, RMSE, and MAPE. The results revealed that the approached method is highly efficient for estimation of rock strength during rotary drilling. © 2020, Springer Nature Switzerland AG.
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    Forestry reclamation of disturbed surface mine lands
    (2011) Tripathi, A.K.; Bhattacharya, J.; Pal, S.K.
    The goal of forestry reclamation is creation of naturally stable and productive forests on disturbed surface mine soil in as little time as possible which generate value for their owners and provide watershed protection, wildlife habitat, and other environmental services. This paper describes research conducted to study the forestry reclamation of disturbed surface mine lands. Soil data for forestry reclaimed land in Rheinish lignite area has also been compared to that of adjacent undisturbed forestry land to investigate the effectiveness of reclamation and soil management operations in restoring the disturbed surface mine land similar to adjacent undisturbed land.
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    A study on loose material filled PVC props as an alternative to conventional wooden supports
    (2011) Pal, S.K.; Kedia, R.; Trivedi, A.K.
    This paper describes the research conducted to design new type of props using PVC pipe and loose particles (cohesive and non-cohesive) as fill material. The design of the props is such that load is applied only to the inner core, of which a part of it is borne by the PVC because of the friction between inner and outer pipe. Rest of the load is transferred to the core, which pressurizes the pipe from inside. The reasoning behind constructing such props is that a pipe that is internally pressurized will be more rigid towards bending and hence take more load. This paper discusses experimental research work carried out on small as well as large scale props by varying L/D ratio (fixed in case of large scale props) and the type of fill material (cohesive and noncohesive) for testing their ultimate strength by loading them in different manners.
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    Reclamation and management of disturbed surface mining areas for agricultural purpose with emphasis on concurrent reclamation
    (2012) Tripathi, A.K.; Bhattacharya, J.; Pal, S.K.
    The extraction of natural resources has significant influence on the surrounding landscape and environment. Consequently in modern surface mines, reclamation is considered an important part of mining activities and is given as much importance as the extraction itself. The goals of reclamation are also integrated in the overall operational concept of surface mining. This paper discusses in detail the operations carried out to reclaim and manage the disturbed surface mine lands for agricultural purpose. Reclamation operations carried out in lignite mines in Germany for restoration of disturbed surface mining areas for agricultural purpose are also described.
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    Postmining soil development on spreader reclaimed land for agricultural purpose in Rheinish lignite area, Germany
    (2012) Tripathi, A.K.; Bhattacharya, J.; Pal, S.K.
    The goal [I] of agricultural reclamation in Rheinish lignite area, Germany is to restore arable soils with high capacity for crop production which ensures a permanent productivity with normal cultivation irrespective of current crop harvesting. Reclamation forms an integral component of the mine planning process and restoration of area disturbed due to mining in the region is given as much importance as the extraction of lignite itself. The soil materials for agricultural postmining land use are carefully selected and special care is taken while handling the soil so as to preserve the basic qualities. In this research, data obtained from agricultural reclaimed lands of different ages in Rheinish lignite area, Germany for various soil physical, chemical and biological parameters have been compared with nearby undisturbed soil data to study the postmining soil development with time.
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    Incorporating local image structure in normalized cut based graph partitioning for grouping of pixels
    (2013) Sen, D.; Gupta, N.; Pal, S.K.
    Graph partitioning for grouping of image pixels has been explored a lot, with normalized cut based graph partitioning being one of the popular ones. In order to have a credible allegiance to the perceptual grouping taking place in early human vision, we propose and study in this paper the incorporation of local image structure/context in normalized cut based graph partitioning for grouping of image pixels. Similarity and proximity, which have been studied earlier for grouping of image pixels, are only two among many perceptual cues that act during grouping in early human vision. In addition to the said two cues, we study three other such cues, namely, common fate, common region and continuity, and find indications of local image structure utilization during grouping of image pixels. Appropriate incorporation of local image structure/context is achieved by representing it using neighborhood in the form of histogram and fuzzy set. We demonstrate both qualitatively and quantitatively through experimental results that the incorporation of local image structure improves performance of grouping of image pixels. © 2013 Elsevier Inc. All rights reserved.
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    Model studies on the efficiency of gravity blind backfilling method and evaluation of a pre-jamming indication parameter
    (CAFET INNOVA Technical Society 1-2-18/103, Mohini Mansion, Gagan Mahal Road, Domalguda, Hyderabad 500029, 2016) Pal, S.K.; Mukhopadhyay, S.K.; Panda, S.; Tripathi, A.K.
    This paper discusses experimental research on a fully transparent scaled model of a section of a Bord and Pillar mine working carried out to study in detail the effectiveness of hydraulic blind backfilling as a solution to reduce subsidence problem above old underground water-logged coal mines. The relative influence of sand and water flow rates on the areas of filling from a single inlet point has been studied in detail. Automatic data acquisition system was installed in the model to continuously record the sand and water flow rates along with the inlet pressure of slurry at the entrance of the model. Pressure signature graphs have been plotted directly with the help of computer. Pressure signature analyses for various slurry flow rates and sand concentrations have been carried out. Investigation has also been carried out on evaluation of a pre-jamming indication parameter, which could be used for indication of the final stage of filling. © 2016 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.
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    Tuning the self-assembly and photophysical properties of bi-1,3,4-thiadiazole derivatives through electron donor-acceptor interactions and their application in OLEDs
    (Royal Society of Chemistry, 2017) Yadav, A.K.; Pradhan, B.; Ulla, H.; Nath, S.; De, J.; Pal, S.K.; Satyanarayan, M.N.; Ammathnadu Sudhakar, A.S.
    We report several shape anisotropic molecules that contain two centrally placed 1,3,4-thiadiazole units, which vary from each other with respect to the number and length of the flexible chains at the termini. The number, position and length of the peripheral chains connected to the termini showed an impact on the thermal behavior of these compounds. The compounds with two terminal tails exhibited an enantiotropic smectic C phase, whereas the compounds with four terminal tails turned out to be crystalline. Surprisingly, among the compounds with six terminal tails, only the compound with a longer terminal chain exhibited a columnar phase with oblique symmetry. It is also to be noted that only compounds with six terminal chains exhibited gelation in long chain hydrocarbons. The xerogel of the hexacatenar with six n-decyloxy chains showed an entangled network of nanofibers of several micrometers in length. The aggregation behavior of the hexacatenar in the hydrocarbon solvent is mainly supported by the attractive ?-? interactions of the aromatic cores and the van der Waals interactions offered by the peripheral flexible tails. The emission behavior is dependent on the number of peripheral tails and not on the length. Furthermore, one of the hexacatenars exhibited solvatochromic emissive behavior. This molecular design helps in the development of long molecular nanowires with a central conducting core and insulating peripheral sheath, which will be helpful for the application in organic electronic devices. The application potential of the columnar liquid crystal material was tested by the fabrication of organic light emitting diodes (OLEDs) either as a single emissive material or as a guest material in a host polymer. Higher efficiency and brightness were noticed in the host guest OLED, which exhibited a technologically important bright blue emission. © 2017 The Royal Society of Chemistry.