• A K Verma

      Articles written in Journal of Earth System Science

    • A comparative study of ANN and Neuro-fuzzy for the prediction of dynamic constant of rockmass

      T N Singh R Kanchan A K Verma K Saigal

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      Physico-mechanical properties of rocks have great significance in all operational parts in mining activities, from exploration to final dispatch of material. Compressional wave velocity (p-wave velocity) and anisotropic behaviour of rocks are two such properties which help to understand the rock response under varying stress conditions. They also influence the breakage mechanism of rock. There are different methods to determine thep-wave velocity and anisotropyin situ and in the laboratory. These methods are cumbersome and time consuming. Fuzzy set theory, Fuzzy logic and Neural Networks techniques seem very well suited for typical geotechnical problems. In conjunction with statistics and conventional mathematical methods, hybrid methods can be developed that may prove to be a step forward in modeling geotechnical problems. Here, we have developed and compared two different models, Neuro-fuzzy systems (combination of fuzzy and artificial neural network systems) and Artificial neural network systems, for the prediction of compressional wave velocity.

    • Reply to the comments by Tarkan Erdik and Zekai Şen on ‘A comparative study of ANN and neuro-fuzzy for the prediction of dynamic constant of rockmass’

      T N Singh R Kanchan A K Verma K Saigal

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    • Influence of shear velocity on frictional characteristics of rock surface

      T N Singh A K Verma Tanmay Kumar Avi Dutt

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      Understanding the fundamental issues related with the effect of shear velocity on frictional characteristics at the interface of rock surfaces is an important issue. In this paper, strain-rate dependence on friction is investigated in relation to sliding behaviour under normal load. The phenomenon of stick-slip of granite and shaly sandstone with a tribometer at constant rate of strain under normal loads was observed.

      Friction at the interface of the rock samples was developed by increasing shear strain at a constant rate by applying constant velocity using the tribometer. For shaly sandstone, state parameters (𝑎 and 𝑏) played a major role in determining the friction values and roughness of the contact surfaces as well. Higher values of 𝑏 for shaly sandstone may be attributed to the fact that its surface had a greater number of pronounced asperities. Rubbing between the surfaces does not mean that surface becomes smoother. This is because of variation of friction between surfaces.

    • Reorientation of lineation in the Central Crystalline Zone, Munsiari–Milam area of the Kumaun Greater Himalaya

      A K Verma A R Bhattacharya

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      During large scale ductile shear deformation, linear features of the rocks tend to be reoriented towards the direction of bulk shear. This is demonstrated in a crustal scale shear zone of the Himalaya, the Main Central Thrust (MCT), typically exposed in the Munsiari–Milam area of eastern Kumaun Greater Himalaya. Along the MCT, the crystalline rocks of the Greater Himalaya are thrust over the younger sedimentary belt of the Lesser Himalaya. In the study area, the scatter of lineation orientation in the vicinity of the MCT has been observed to drastically reduce within 27° in a zone of about 18 km (about 13 km in the crystalline rocks and about 5 km in the sedimentary rocks). Beyond this zone, the scatter is very high, up to 70° or more. The low scatter of lineation orientation around the MCT could be related to the strong ductile shear deformation associated with the movement along this thrust due to which the linear features got reoriented towards the direction of bulk shear. Away from this zone, ductile shearing had negligible or no effect on the rocks and, therefore, the scatter of lineation remains very high.

    • Study of thermo-hydro-mechanical processes at a potential site of an Indian nuclear waste repository

      Sachin Maheshwar A K Verma T N Singh R K Bajpai

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      A detailed scientific study is required for the disposal of high-level radioactive wastes because they generate extremely high heat during their half-life period. Although, several methods have been proposed for the disposal of nuclear wastes, deep underground repository is considered to be a suitable option.

      In this paper, field investigation has been done near to Bhima basin of peninsular India. Detailed fracture analysis near the borehole shows very prominent maxima of fractures striking N55°E coinciding with the trace of master basement cover metasediment fault. Physico-mechanical properties of rocks have been determined in the laboratory.

      The host rock chosen is granite and engineered barrier near the canister is proposed to be clay. A thermo-hydro-mechanical (THM) analysis has been done to study the effect of heat on deformations, stresses and pore-pressure variation in granite and clay barriers. For this purpose, finite difference method has been used. Suitable rheological models have been used to model elastic canister and elasto-plastic engineered barrier and host rock. It has been found that both temperature and stresses at any point in the rockmass is below the design criteria which are 100°C for temperature and 0.2 for damage number.

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