Faculty Publications

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Effect of High Temperature on the Compressional Wave Velocity of Two Sandstones with Different Grain Sizes
(Springer Science and Business Media Deutschland GmbH, 2024) Manikanta, V.; Hasainar, H.; Badiger, N.K.; Kothari, V.; Bhat, A.; Srinivasan, V.
Understanding rock behaviour at high temperatures can serve as vital information in restoring fire-damaged monumental structures. This knowledge is essential for engineering and construction purposes, as it allows for assessing rock stability and potential hazards and developing appropriate safety measures in areas with high temperatures. This study investigates the effect of different temperatures on two sandstones with varying grain sizes. The rock was first heated to a range of temperatures such as 35, 250, 500, 750, and 1000Â Â°C. To identify the thermal damage of the rock samples, the Ultrasonic Pulse Velocity measurement instrument is used to identify the inner cracks. This research discusses the application of Ultrasonic Pulse velocity (UPV) to identify thermal damage and analyse related parameters of two different sandstones. The ultrasonic method is one of the simple and reliable techniques to understand the damage conditions of rocks. There were significant variations in the P-wave velocity with thermal treatment, it is observed that a negative trend developed in the primary wave velocity as the temperature increased. They give qualitative and quantitative inferences on the extent of damage caused by various environmental parameters, particularly heating. The data obtained from the present study were compared to check the confidence of regression models. The mean absolute percentage error method, the root mean square error method (RMSE), was carried out on thermal damage of rock samples. Probabilistic analysis was also conducted to estimate the damage on rocks at different confidence levels. Â© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.
An Investigation on the Influence of Thermal Damage on the Physical, Mechanical and Acoustic Behavior of Indian Gondwana Shale
(Springer, 2020) Srinivasan, V.; Tripathy, A.; Gupta, T.; Singh, T.N.
In the present study, the effect of thermal treatment on the physical, mechanical and fracturing behavior of Gondwana shale samples from India was investigated. Acoustic Emission signals were used to identify the changes brought in by temperature variations on the crack damage zones and failure attributes in shale. The results suggested that mechanical parameters such as uniaxial compressive strength, tensile strength (?t), elastic modulus, mode-I fracture toughness (KIC), cohesion, and brittleness index (B1) exhibited a strong negative correlation with thermal damage (Dt). But, the internal angle of friction and brittleness index (B2) showed a reasonable positive relation with thermal treatment. The deformation of the shale was dominated by its clay mineral enrichment, the characteristics of which changed with heating. The intensity of fracturing as observed from acoustic signals was chiefly controlled by the orientation of bedding planes and the degree of thermal treatment. The initiation and propagation of macro-crack were found to be greatly influenced by the degree of thermal damage. Under compression, thermally damaged samples showed similar deformation pattern, while under Brazilian tensile load, the deformation path became inconsistent with increasing temperatures. It was observed that thermal damage in tested shale decreased the layer compaction, which eased the fracturing intensity, thereby reducing the overall strength of the samples. The present investigation concludes that even a slight change of the thermal conditions can substantially alter shale fracturing behavior and failure attributes posing serious safety concerns of deep geo-engineering structures. © 2020, Springer-Verlag GmbH Austria, part of Springer Nature.
Experimental study on failure and fracturing attributes of granite after thermal treatments with different cooling conditions
(Elsevier B.V., 2022) Srinivasan, V.; Hasainar, H.; Singh, T.N.
Thermal damage is one of the fundamental mechanisms affecting the stability of rocks encountered in many deep geo-engineering ventures such as nuclear waste isolation, geothermal extraction etc. In the present study, the findings on influence of heating and subsequent cooling conditions on the fracturing and mechanical behaviour of an Indian granite are discussed. The granite samples from Jalore region of India were heated from room temperature to 600 °C followed by slow cooling and water quenching treatments. It was observed that rapid cooling through quenching had a greater impact on strength, elastic properties than slow cooling rate. Moreover, a drastic shift in terms of fracturing thresholds was witnessed, as a function of both temperature and sudden thermal shock experienced by rock at higher cooling rate. The simultaneous AE monitoring results suggested an early crack damage at higher thermal regimes. With help of microscopic observations, it was observed that inter-granular crack boundaries widened with increasing thermal damage experienced by minerals under both cooling conditions. However, the fracturing process was intense under rapid cooling treatment due to the invasion of water due to quenching which accelerated severe intra-crack growths, especially at higher thermal stress because of the rapid cooling rate than the slow cooling. The increased intensity of thermal cracks with temperatures and with variation in cooling rate was inferred as the primary reason for decay of rock characteristics. This was very well supplemented by decay in strength properties and changes in fracturing attributes of the tested granite as inferred from acoustic monitoring. © 2022

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