The stability of road cut cliff face along SH-121: a case study

Rockfall is one of the major concerns along highways, settlements and forests around the globe. Amboli road cut hill is one such region which is highly vulnerable and suffers from recurrent rockfall mostly in the rainy season, which blocks the State Highway 121 for considerable period of time. The steep and highly jointed slope along the road makes the zone prone to failure due to rainwater action. This road experiences heavy traffic throughout the year as it is the only road connecting Goa to Satara and Kolhapur via Sawantwadi in Maharashtra State, India. Therefore, an attempt has been made in this study to understand the stability of the cliff face. A combination of field study and 2D computer simulation was performed to assess surface characteristics of the cliff face. Bounce height, translational kinetic energy, translational velocity and factor of safety for saturated condition have been estimated. The result of this study shows that the rock face is highly unstable taking into consideration the environmental condition and daily traffic. Proper preventive measures have also been suggested to arrest the movement of falling rocks before reaching the roads or valleys. It is a belief that if proper care is taken, then further uncertain rockfall hazards can be prevented.     

Flood risk mapping for the lower Narmada basin in India: a machine learning and IoT-based framework

Natural Hazards - Floods have a significant economic, social, and environmental impact in developing countries like India. Settlements in flood hazard zones increase flood risk due to a lack of...     

Strength and dilatancy of jointed rocks with granular fill

It is well recognised that the strength of rock masses depends upon the strain history, extent of discontinuities, orientation of plane of weakness, condition of joints, fill material in closely packed joints and extent of confinement. Several solutions are available for strength of jointed rock mass with a set of discontinuities. There is a great multiplicity in the proposed relationships for the strength of jointed rocks. In the present study, the author conceives the effect of increasing stresses to induce permanent strains. This permanent strain appears as micro crack, macro crack and fracture. A fully developed network of permanent deformations forms joint. The joint may contain deposits of hydraulic and hydrothermal origin commonly known as gouge. The joint factor numerically captures varied engineering possibilities of joints in a rock mass. The joints grow as an effect of loading. The growth of the joints is progressive in nature. It increases the joint factor, which modifies the failure stresses. The dilatancy explains the progressive failure of granular media. Hence, a mutual relationship conjoins effectively the strength of jointed rock and a dilatancy-dependent parameter known as relative dilatancy. This study provides a simple and integral solution for strength of jointed rocks, interpreted in relation to the commonly used soil, and rock parameters, used for a realistic design of structure on rock masses. It has scope for prediction of an equivalent strength for tri-axial and plane strain conditions for unconfined and confined rock masses using a simple technique.     

Assessment of future water provisioning and sediment load under climate and LULC change scenarios in a peninsular river basin,India

Assessment of the impact of changes in climate and land use and land cover (LULC) on ecosystem services (ES) is important for planning regional-scale strategies for sustainability and restoration of ES. The Upper Narmada River Basin (UNRB) in peninsular India has undergone rapid LULC change due to recent agricultural expansion. The impact of future climate and LULC change on ES in the UNRB is quantified and mapped using the Integrated Valuation of Ecosystem Services and Tradeoffs (InVEST 3.3.0) tool. Our results show that water yield is projected to increase under climate change (about 43% for representative concentration pathway 4.5 for 2031–2040), whereas it is projected to decrease under the LULC change scenario. Sediment export is projected to increase (by 54.53%) under LULC change for 2031–2040. Under the combined effect of climate and LULC change, both water yield and sediment export are expected to increase. Climate change has a greater impact on projected water yield than LULC change, whereas LULC has greater impact on sediment export. Spatial analysis suggests a similar trend of variation in relative difference (RD) of ES in adjacent sub-basins. The quantified changes in ES provisioning will benefit future land management, particularly for operation of the Rani Avanti Bai Sagar Reservoir downstream of the UNRB.     

A Spectro-radiometric Analysis of Ocean Colour Sensors and Proposal for a Miniature Hyper Spectral Imager for Future

Ocean colour sensors traditionally are of fixed spectral channel systems with specified bandwidth of about 20 nm in the visible region and about 40 nm in Near Infrared region. In these systems, it is known that a radiometric error of 1% in the measurement of top of the atmosphere signal may lead to an error of 10% in the retrieved ocean upwelling radiance. In this paper we investigated the range of wavelengths participating in signal collection (effective spectral pass band, ESPB) using relative spectral response data of various sensors flown earlier. ESPB values were computed for each spectral channel for various percentages of signal and the results showed that they are quite high compared to bandwidths specified. These values were found to vary with sensor and channel. ESPB shall be small for accurate computation of spectral radiance. As the knowledge of spectral profile of the signal in the range of ESPB helps in better estimation of spectral radiance at the intended wavelengths, a miniature high performance linear variable filter based hyperspectral sensor is proposed as an alternative. We present here the design concept and report the estimated performance of such sensor that can be realized even with commercial off the shelf components for operational implementation.     

A Study of Early/Slow VLF Perturbations Observed at Agra,India

We present here the results of sub-ionospheric VLF perturbations observed on NWC (19.8 kHz) transmitter signal propagating in the Earth-ionosphere waveguide, monitored at our low latitude station Agra. During the period of observation (June-December 2011), we found 89 cases of VLF perturbation, while only 73 cases showing early character associated with strong lightning discharges. Out of 73 events, 64 (~84%) of the early VLF perturbations are found to be early/slow in nature; the remaining 9 events are early/fast. The onset duration of these early/slow VLF perturbations is up to ~ 5 s. A total of 54 observed early events show amplitude change lying between ± 3.0 dB, and phase change ± 12 degree, respectively, and found to occur mainly during nighttime. One of the interesting results we found is that the events with larger recovery time lie far away from the VLF propagation path, while events with smaller duration of recovery are within the ± 50–100 km of signal path. The World Wide Lightning Location Network (WWLLN) data is analysed to find the location of causative lightning and temporal variation. The lightning discharge and associated processes that lead to early VLF events are discussed.     

Geochemical and isotope hydrological characterisation of geothermal resources at Godavari valley,India

Thermal waters at the Godavari valley geothermal field are located in the Khammam district of the Telangana state, India. The study area consists of several thermal water manifestations having temperature in the range 36–76 °C scattered over an area of ~35 km². The thermal waters are Na–HCO₃ type with moderate silica and TDS concentrations. In the present study, detailed geochemical (major and trace elements) and isotope hydrological investigations are carried out to understand the hydrogeochemical evolution of these thermal waters. Correlation analysis and principal component analysis (PCA) are performed to classify the thermal waters and to identify the different geochemical processes controlling the thermal water geochemistry. From correlation matrix, it is seen that TDS and EC of the thermal springs are mainly controlled by HCO₃ and Na ions. In PCA, thermal waters are grouped into two distinct clusters. One cluster represents thermal waters from deeper aquifer and other one from shallow aquifer. Lithium and boron concentrations are found to be similar followed by rubidium and caesium concentrations. Different ternary plots reveal rock–water interaction to be the dominant mechanism for controlling trace element concentrations. Stable isotopes (δ¹⁸O, δ²H) data indicate the meteoric origin of the thermal waters with no appreciable oxygen-18 shift. The low tritium values of the samples originating from deeper aquifer reveal the long residence time (>50 years) of the recharging waters. XRD results of the drill core samples show that quartz constitutes the major mineral phase, whereas kaolinite, dolomite, microcline, calcite, mica, etc. are present as minor constituents. Quartz geothermometer suggests a reservoir temperature of 100 ± 20 °C which is in good agreement with the values obtained from K–Mg and Mg-corrected K–Mg–Ca geothermometers.     

Possibility of Large Deposits of Gas Hydrates in Deeper Waters of India

The available geological and thermodynamic data, essential for the formation and accumulation of gas hydrates, have been integrated and broadly interpreted for the deeper waters of India. The preliminary studies indicate that, in all probability, vast gas hydrate resources exist in the shallow sediments under deep waters. The area of the Bay of Bengal and Arabian Sea, off the coast of India and Andaman Islands, have accumulated thick sediments, over 22 and 10 km, respec tively, during collision of the Indian Plate with the Tibetan Plate. Bottom Simulating Reflectors (BSRs), indicating the likely presence of gas hydrates, have been observed from multichannel and single-channel seismic reflec tion data west of the Andaman Islands and Kerala-Konkan offshore. The Indian continental shelf, slope, and rise areas have, at places, shown the presence of gas-charged sediments and gas seeps through faults. There are commercial oil and gas fields in the shallow waters of both the east and west coasts of India. These are indicative of generation of both biogenic as well as thermogenic gases in the offshore areas of India. For the first time, an attempt has been made to estimate in-place gas hydrate resources under deep waters of India beyond 600 m water depth to the legal continental shelf boundary, and to the Andaman Islands. The gas hydrate resources appear to be vast, and require extensive exploratory efforts for their precise mapping and quantitative assessment.