Faculty Publications

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    Computer aided slope stability analysis
    (2006) Sastry, V.R.; Ram Chandar, K.; Santosh, M.
    Primary purpose of slope stability analysis in most of the engineering applications is to provide safe and economic design of slopes that prevent failure. The analysis technique chosen depends on both site conditions and potential mode of failure which depends upon the rock mass characteristics. Various slope stability analysis techniques include physical, numerical and analytical methods. Physical modeling is a time consuming process and a costly affair, while analytical method involves past experiences, it is site specific and depends upon various parameters which are difficult to quantify. Numerical analysis with sophisticated softwares provides an accurate solution within short duration. This paper presents an in-house developed software package called "V-slope" to analyze and interpret the slope with options for suggesting suitable safety measures based on the nature of slope. Slip circle and tension crack techniques were considered for analysis. The slope profile for different factor of safety (FOS) values will be displayed on the screen for easy understanding. In case the FOS is lower than the required, the V-slope gives suggestive measures. In case of temporary slopes the only way by which slope failure can be prevented is by decreasing the slope angle and in such cases the program gives additional volume of material to be excavated and the likely additional cost incurred for various slope angle options. For permanent slopes, option is provided for designing the soil nails, i.e. number of bolts required, length, diameter and spacing of the bolts etc. Finally the V-slope is compared with a comprehensive commercial software package Slide and the results were found very much satisfactory.
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    Reservoir formation damage during various phases of oil and gas recovery- an overview
    (2012) Puthalath, P.; Murthy, C.S.N.; Surendranathan, A.O.
    When a reservoir of oil or gas is discovered under the ground, and reservoir engineers and drilling engineers are employed to tap that reservoir, often, they inadvertently damage it. Formation damage is an undesirable operational and economic problem that can occur during the various phases of oil and gas recovery from subsurface reservoirs including production, drilling, stimulation techniques and work over operations. The formation of a reservoir can be damaged by unforeseen rock, fluid, particle interactions etc and alterations caused by reservoir fluid, flow, and stress conditions. For example, the chemicals that the engineers have injected into the reservoir, the drilling mud used in drilling, or even by stress from the drill bit itself may cause formation damage. Control and remediation of formation damage are among the most important issues to be resolved for efficient exploitation of petroleum reservoirs and cost management. Formation damage seems to be inevitable and whether formation damage can be prevented, removed economically, or must be accepted as the price for drilling and producing a well will depend upon many factors. In this paper a general characteristics of formation damage during various stages of oil exploration are discussed. © 2012 CAFET-INNOVA TECHNICAL SOCIETY. All rights reserved.
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    Behaviour of large underground cavern during construction in himalayas - a case study
    (CAFET INNOVA Technical Society cafetinnova@gmail.com 1-2-18/103, Mohini Mansion, Gagan Mahal Road, Domalguda, Hyderabad 500029, 2014) Naik, S.R.; Sastry, V.R.
    Construction of large underground caverns in Himalayas is challenging due to complex geological and insitu stress conditions. Understanding the behaviour of such caverns during construction stage is possible only with extensive instrumentation. A case study of a large cavern under construction in Himalayan region in Bhutan is considered. Results from various types of instruments are discussed in this paper. Instrumentation data shows that Himalayan rock mass particularly with phyllitic quartzite exhibits large deformations thus requiring careful selection of support and excavation methodology. © 2014 CAFET-INNOVA TECHNICAL SOCIETY.
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    A numerical modelling approach to assess the behaviour of underground cavern subjected to blast loads
    (China University of Mining and Technology, 2018) Kuili, S.; Sastry, V.R.
    The paper gives an insight into the behaviour of large underground caverns which are subjected to blast loads. Caverns are generally constructed in hard rock formation which compels us to use blasting methods for the excavation works. Comparative study was done between models with intact rock mass and discontinuities to assess the stability of cavern as a result of blast loads. Numerical modelling was performed with 3 dimensional distinct element code (3DEC) to analyse the performance of cavern walls in terms of displacement and to compute peak particle velocities (PPV) both around the cavern periphery and at surface of models. Results showed that the velocity wave with higher frequency exhibited large displacements around the periphery of cavern. Computation of PPV showed that model with horizontal joint sets showed lower PPV in comparison to model with intact rock mass. PPV values were also analysed on the surface for model consisting vertical joints spaced at 4 m intervals. Comparative study of PPV on surface vertically above the blast location between models with horizontal joints spaced at 4 m and vertical joints at 4 m intervals were conducted. Results depicted higher magnitudes of PPV for model with vertical joints in comparison to model with horizontal joints. © 2018
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    Estimation of Rock Strength Properties Using Selected Mechanical Parameters Obtained During the Rotary Drilling
    (Springer, 2019) Lakshminarayana, C.R.; Tripathi, A.K.; Pal, S.K.
    During the preliminary stage of rock engineering projects, the estimation of mechanical properties of rocks is most often required. The requirement of a large number of high-quality rock core samples is the major drawback when the mechanical rock properties are to be determined in a well-established rock mechanics laboratory. In this study, an attempt is made to estimate the uniaxial compressive strength and Brazilian tensile strength of sedimentary rocks using the selected mechanical drilling operating parameters obtained during the rotary drilling. The operating measured parameters such as the weight on bit or thrust and the vibration frequency induced at machine or drill head were acquired using the drill tool dynamometer and sound/vibration data acquisition system, respectively. The mathematical models were developed considering the drilling operational parameters (drill bit diameter, drill bit speed and penetration rate) and measured mechanical parameters (thrust and vibration frequency). The prediction potential of the developed models was assessed by the prediction performance indices. The outcome results revealed that the developed mathematical model using the approached method is significant and can be conveniently used for the estimation of mechanical properties of rocks during the rotary drilling. © 2019, The Institution of Engineers (India).
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    An experimental study on rock damage and its influence in rock stress memory in a metamorphic rock
    (Springer, 2020) Srinivasan, V.; Gupta, T.; Ansari, T.A.; Singh, T.N.
    Rock stress memory, often referred as Kaiser effect, in rocks can be an effective tool to estimate the in situ stress conditions, if the uncertainties in rock damage and its behavior during loading conditions are properly understood. In view of this, the present study is an attempt to investigate the variations in rock stress memory, i.e., the Kaiser effect in a metamorphic rock under multi-stage uniaxial compression. The khondalite rock samples from Eastern Ghats Mobile Belt (EGMB) belonging to southeastern part of Indian subcontinent having complex geological history are examined. The effects of multi-stage compression on the damage evolution and subsequent variations in rock stress memory are investigated. The samples were categorized into different levels of rock stress memory, depending on the stress the rock was able to withhold after loading stages. The damage evolution in the tested rocks was predominantly controlled either by initial loading or failure stress. Higher damage imparted by initial loading and intense fracturing could be the possible reason for poor stress memory function in the investigated rock. Felicity ratio, an indicative of rock damage with stages of loading, supported the observation that rock damage was dominant during initial loading stage. Rock heterogeneity has played a dominant role in decay of Kaiser effect, with intense fracturing during subsequent loading stages in the investigated rocks. To summarize, Kaiser effect can be used to infer rock damage and stress conditions, provided the geological history of the region is also taken into consideration. With rocks from complex geological conditions, Kaiser effect or rock stress memory should be supported by other tools to infer in situ stress, but the method can be effectively used to understand the stress changes and damage mechanism of multiple loading. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.
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    Rock strength characterization using measurement while drilling technique
    (Springer, 2020) Lakshminarayana, C.R.; Tripathi, A.K.; Pal, S.K.
    The approximation of strength properties of rocks most often requires during the preliminary phase of any engineering projects related to rock mechanics. The main disadvantage of evaluating the rock properties in a testing laboratory is the prerequisite for high-quality rock core with many numbers. In this empirical method, the essential strength properties of rocks would measure during the rock drilling process using some identified machine variables along with the acoustic parameter. The machine operating variables such as thrust and torque and acoustic vibration parameter collecting at the machine head were used to develop rock strength models. A drill-type dynamometer was employed to gauge the machine variables and the NI-9234 data acquisition system for gauging the vibration parameter. The evaluation of the mathematical models for their efficiency shows that the applied empirical approach could determine the strength properties with fewer errors and can use as an alternative method for measuring the compressive and tensile strength of sedimentary rocks in the laboratory without using core samples. © 2020, Indian Geotechnical Society.
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    Demonstration of structure-from-motion (SfM) and multi-view stereo (MVS) close range photogrammetry technique for scour hole analysis
    (Springer, 2021) Mali, V.K.; Venu, P.; Nagaraj, M.K.; Kuiry, S.N.
    Comprehensive data collection remains a challenge in the field of sediment research. The manual acquisition of fine-gridded data is almost infeasible even for a laboratory setup. Therefore, this paper demonstrates a simple and cost-effective SfM–MVS technique to acquire accurate morphological data. This data further can be used for assessing the scour development around a bridge pier. For this purpose, the experiments are conducted for clear-water scour around circular and hexagonal piers for three different discharges. Before the start of the experimental run, a set of overlapped images is taken using the digital camera. Once the experiment run is completed, the water in the flume is completely drained off and then again another set of overlapped photos are taken. A total of eight ground control points (GCPs) is used to transform the generated relative three-dimensional cloud points to the absolute local coordinate system. Eventually, the high-spatial resolution digital elevation models (DEMs) are generated using the SfM–MVS photogrammetry technique. A statistical analysis is performed between the checkpoints (observed data) and DEM predicted points, which revealed that the generated DEMs show high accuracy in all the cases. It is therefore concluded that the SfM–MVS technique can be applied to understand the morghological changes around any shape of the piers. Thus, the proposed image analysis method can be adopted for obtaining the high spatial resolution data for sediment transport research. © 2021, Indian Academy of Sciences.
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    An overview of the applications of soft computing methods for predicting the physico-mechanical properties of rocks from indirect methods
    (Inderscience Publishers, 2023) Bijay Mihir Kunar, S.; Chandar, K.R.
    Rocks are widely used in infrastructure constructions like roads, tunnels, buildings, and dams. Understanding physico-mechanical properties of rocks is vital for selecting suitable rocks, yet some properties pose challenges in determination. High-quality core samples and precise instruments are necessary for accurate assessment. Predicting the physico-mechanical properties of rocks is a key research area in rock mechanics. Researchers have employed diverse methods, including laboratory tests, non-destructive tests, and mineralogical and petrographical characteristics, to determine rock properties. This article reviews the use of soft computing methods, artificial intelligence, and machine learning to predict rock properties through indirect methods. Indirect methods involve engineering indices tests, mineralogical and petrographical characteristics, and additional approaches such as electrical properties, crushability indices, thermal characteristics, and grinding characteristics. The article also proposes various artificial intelligence and machine learning techniques as potential future directions in prediction of rock properties. © © 2023 Inderscience Enterprises Ltd.
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    A Numerical Modelling Approach to Assess Deformations of Horseshoe Cavern on Account of Rock Mass Characteristics and Discontinuities
    (Materials and Energy Research Center, 2023) Kuili, S.; Sastry, V.R.
    Caverns are massive underground openings excavated for purposes like defense installations and nuclear waste disposal which becomes challenging for weak strata consisting of fractured rock masses and may result in future calamities. This study is dedicated to ascertain stability of a horseshoe cavern in different types of granitic rock masses as well as fractured rocks. Two different types of granitic formations are accounted and displacements obtained along cavern periphery have been illustrated in the preliminary part of this study. An increment in vertical displacement at the crown of 260% and lateral displacement of almost 170% for both walls were observed for moderately weathered rock. Further, implications due to orientation and frequency of joint sets on the displacements incurred has also been explored. This study acquires its novelty by considering combinations of joint sets with varying spacings for investigating their implications on cavern walls. Presence of discontinuities depicted that horizontal joint spaced closely increased the deformation magnitude which reduced with decrement in joint frequency. Subsequently, along with horizontal joints at 4m interval, vertical and oblique joints sets were also incorporated at different frequencies. Consideration of vertical joints at 2m spacing with horizontal joints resulted in 313.2% increase in vertical displacement at cavern crown as well as 340% and 363% increase in lateral deformation at the left and right wall, respectively in comparison to intact rock. In case of oblique joints spaced at 2m with horizontal joints, increment in vertical deformation at the crown proliferated to 329% in comparison to intact rock. © 2023 Materials and Energy Research Center. All rights reserved.