Journal of the Geological Society of India最新文献

Present study was related to land degradation after landslide and risk analysis of Lower Kosi watershed in Central Himalaya using RS and GIS. The study was aimed to identifying the relation of land use with landslide activity in Himalayan terrain and landslide management. The landslide inventory map was prepared for the detailed study with the help of Google Earth Image and field verifications. Landslide had been sub-categorized into two categories; natural and road induced. The land use map was prepared from Google Earth image followed by toposheets. Statistical analysis of landslide frequency and density as well as frequency and density ratios were applied. The collected data was evaluated in combination with GIS. The relationship between land use categories and landslide occurrences was determined. The landslide frequency ratio (FR) and density ratio (DR) were analyzed. The FR and DR value of 1 is an average value. Hence, the value of ratio more than 1 signifies a strong relationship between landslides and the given factor while ratio values less than 1 registers a poor relationship. The FR and DR values were >1.0 in the areas of fallow land, barren/rocky land, agricultural land and open forest revealing a strong relation to landslide processes while the lesser values of FR and DR in ‘dense forest’ area determines the impact of sufficient vegetation cover on the least occurrence of landslides. This study may be applicable for new and existing land use planning projects as the adopted methodology provides rapid estimation of landslide vulnerability of the area.

With the increase in the pace of development, the demand for tunnels has increased in recent years. Analysing the stability of a tunnel in a fractured rock mass is a very challenging and cumbersome activity. The tunnel stability depends on the strength of the rock, joints bolt strength, in-situ stresses, and their orientation. This paper focuses on constructing tunnels in fractured/jointed rock mass. Three different software namely Rocscience Phase2 (finite element based), FLAC^3D (finite volume based) and PFC^3D (distinct element based), were used to analyse the performance and stability under static and dynamic loading conditions. The geomaterial properties used for the analysis were taken from data obtained after laboratory testing and based on available literature. The effect of joint orientation and bolt length was analysed using Phase 2 assuming plain strain conditions. The effect of earthquake and performance of fully grouted, energy absorbing and deformation-controlled bolts under seismic loading conditions were compared using FLAC^3D. While the 3D distinct element analysis of geometry was performed using PFC^3D to evaluate the effect of joints and their orientation. The performance of the different types of bolts was also analysed numerically. The behaviour of bolts can be customised using the ‘fish‘function. The results indicate that analysis must incorporate the fusion of various numerical simulation techniques like finite element-, finite volume- and distinct element-based methods for more reliable results.

The study of radionuclides is very important in our daily life as these impose health implications to the general public. In present study the estimation of radionuclides in Ganderbal and Budgam districts of Kashmir Province using NaI(Tl) gamma-ray spectrometer has been carried out. Radium, thorium, and potassium activity concentrations have been observed to range from 25±3 to 33±5 Bqkg⁻¹, 3±2 to 11±3 Bqkg⁻¹ and 415±63 to 601±80 Bqkg⁻¹with average values of 29 Bqkg⁻¹, 5 Bqkg⁻¹ and 514 Bqkg⁻¹, respectively. The radium equivalent activity (Ra_eq) for the soil samples has been evaluated and was found in the range of 107 to 128 Bqkg⁻¹ with the mean value of 116 Bqkg⁻¹. It has been inferred that the radium equivalent activity (Ra_eq) lies in the permissible limits of 370 Bqkg⁻¹ set by United Nations Scientific Committee on the Effects of Atomic Radiation. Absorbed dose and annual effective dose (indoor and outdoor) values were found to vary from 34 to 43 nGyh⁻¹, 0.17 to 0.21 mSv and 0.04 to 0.05 mSv, respectively. Also, hazard indices (external and internal) are calculated from the specific concentration of radium, thorium and potassium which are found less than unity as recommended by organization for economic cooperation and development (OECD). Therefore, it can be concluded that the present study area does not pose any health implication to the general public.

The accurate identification of rock layer interfaces from wireline logs is one of the crucial issue of geological interpretation as we face difficulties in traditional interpretations due to the presence of various kind of high and low frequencies in the log data. Determination of rock boundaries in shallow marine sediments is very important to understand several issues related to the exploration of conventional and non-conventional hydrocarbons. Presently a combined wavelet and Fourier transform-based approach was demonstrated to discriminate the rock layers from wireline log data in Krishna-Godavari basin, which were acquired during the India National Gas Hydrate Program Expedition 02 (NGHP-Exp.-02). Initially, we selected the suitable mother wavelets and optimum level of decomposition to perform the wavelet transform by computing the error between the original log signal(s) and approximation coefficients (cA’s) of the decomposed signal(s) at several decomposition levels. Subsequently, discrete wavelet transform (DWT) of a particular decomposition level was applied to the log signals to obtain the detail coefficients (cD’s), which contain the high-frequency components of the log signals. Further, these high-frequency components of the log signals were utilized in frequency spectrum-based filtering approaches. This approach was adapted to yield information about the abrupt changes occurring in the log signals across the studied depth interval. The combined application of Fourier and wavelet transforms to shallow marine log data demonstrates that this approach is an efficient tool for delineating rock layer boundaries.