Evaluation of natural resource potential in semi-arid micro-watershed, eastern Rajasthan, using remote sensing and geographic information system

The natural resources are considered more efficient and appropriate for necessary survey and investigation for the assessment, subsequent planning and implementation of various developmental programmes. Hence, it is necessary to increase the land and water resources levels for future demands. Morphometric, land use/land cover and hydrogeomorphic analyses have been carried out by visual interpretation method of remote sensing data of IRS, 1D-LISS III and IRS, P6-LISS III, and FCCs of band combination 2, 3 and 4. The interpreted data is supplemented as well as cross checked by field visits. The remote sensing and GIS tool could be helpful in getting the precise and valuable spatial information in understanding the present scenario contemplating with the past data and predicting the future trends. Morphometric analysis was done to determine the drainage characteristics of Bankukara watershed. The drainage pattern of the study area is predominantly dendritic to sub-dendritic in nature; however, locally structurally controlled drainage pattern is also seen. The development of stream segments is affected by slope and local relief. The bifurcation ratio indicates that the drainage pattern is structurally controlled. The land use/land cover change detection for 2001 and 2005 showed an increase in uncultivated land by 1.37%, dense forest by 0.17%, wasteland by 1.46% and rock quarry by 0.10%. There has been a decrease in the area under cultivated land by 1.99%, open forest by 0.12%, open scrub by 0.54% and water body by 0.40%. Hydrogeomorphic units identified through visual interpretation of FCC include alluvial plain, valley fills, plateau, buried pediment, pediments and intermontane. Based on land use/land cover change detection and hydrogeomorphological mapping, the Bankukara watershed has qualitatively been categorized into four groundwater potential zones, viz. good to very good, moderate to good, poor to moderate and very poor to poor.     

A Modulated-Gradient Parametrization for the Large-Eddy Simulation of the Atmospheric Boundary Layer Using the Weather Research and Forecasting Model

The performance of the modulated-gradient subgrid-scale (SGS) model is investigated using large-eddy simulation (LES) of the neutral atmospheric boundary layer within the weather research and forecasting model. Since the model includes a finite-difference scheme for spatial derivatives, the discretization errors may affect the simulation results. We focus here on understanding the effects of finite-difference schemes on the momentum balance and the mean velocity distribution, and the requirement (or not) of the ad hoc canopy model. We find that, unlike the Smagorinsky and turbulent kinetic energy (TKE) models, the calculated mean velocity and vertical shear using the modulated-gradient model, are in good agreement with Monin–Obukhov similarity theory, without the need for an extra near-wall canopy model. The structure of the near-wall turbulent eddies is better resolved using the modulated-gradient model in comparison with the classical Smagorinsky and TKE models, which are too dissipative and yield unrealistic smoothing of the smallest resolved scales. Moreover, the SGS fluxes obtained from the modulated-gradient model are much smaller near the wall in comparison with those obtained from the regular Smagorinsky and TKE models. The apparent inability of the LES model in reproducing the mean streamwise component of the momentum balance using the total (resolved plus SGS) stress near the surface is probably due to the effect of the discretization errors, which can be calculated a posteriori using the Taylor-series expansion of the resolved velocity field. Overall, we demonstrate that the modulated-gradient model is less dissipative and yields more accurate results in comparison with the classical Smagorinsky model, with similar computational costs.     

An application of waveform denoising for microseismic data using polarization–linearity and time–frequency thresholding

Noise suppression or signal‐to‐noise ratio enhancement is often desired for better processing results from a microseismic dataset. In this paper, a polarization–linearity and time–frequency‐thresholding‐based approach is used for denoising waveforms. A polarization–linearity filter is initially applied to preserve the signal intervals and suppress the noise amplitudes. This is followed by time–frequency thresholding for further signal‐to‐noise ratio enhancement in the S transform domain. The parameterisation for both polarization filter and time–frequency thresholding is also discussed. Finally, real microseismic data examples are shown to demonstrate the improvements in processing results when denoised waveforms are considered in the workflow. The results indicate that current denoising approach effectively suppresses the background noise and preserves the vector fidelity of signal waveform. Consequently, the quality of event detection, arrival‐time picking, and hypocenter location improves.     

Dynamic buckling of braces in concentrically braced frames

Axially loaded members might experience compressive forces above their static buckling capacity because of dynamic buckling under rapid shortening. Although the subject is studied in the context of engineering mechanics, it has not been thoroughly investigated in the field of earthquake engineering. Such dynamic overshoots in the compressive capacity can also be observed for braces of concentrically braced frames (CBFs) during earthquakes. Consequently, a comprehensive investigation is conducted in this study regarding the effects of dynamic buckling of braces on the seismic behavior of steel CBFs. After providing a theoretical background, recent dynamic experiments on braces and CBFs are simulated and discussed to investigate the occurrence of dynamic overshoot during these tests. Eight archetype CBFs are then designed, modeled, and subjected to a large set of ground motions to provide a quantified insight on the frequency and anticipated level of dynamic overshoot in the compressive capacity of braces during earthquakes. Results of a total of 1600 nonlinear time history analyses revealed that dynamic overshoots occur frequently in braces and affect the behavior of CBFs notably. Considerable increases are recorded in forces transmitted to other members of CBFs as a consequence of such dynamic overshoots. Importance of incorporating these dynamic overshoots in the capacity design procedure of columns, beams, and gusset plates is highlighted. Furthermore, results of a parametric study are presented and summarized in the form of a simple formula that can be used as a guide for estimating the level of dynamic overshoot.     

Performance-based analysis and design for internal stability of MSE walls

ABSTRACT

Mechanically stabilized earth (MSE) walls must be designed with adequate margins of safety against internal stability failure described by tensile strength and pullout limit states. Probabilities of failure (or reliability index) will vary strongly with the accuracy of the underlying models that appear in limit state performance functions. In this paper, prior work by the authors and co-workers on this topic is reviewed. Relative performance is explored in the context of the reliability (or probability of failure) of steel and polymeric reinforcing elements in MSE walls using limit state performance functions with load and resistance models having different accuracy.     

Stability Analysis of Landslide near Dewal Village along Murree-Muzaffarabad Road,Pakistan

This study presents a detailed geological and geotechnical analysis of Dewal landslide along Murree-Muzaffarabad road, Pakistan. The study area is situated in a tectonically active region of the earth where mass movements like rock fall, rockslides and slumps cause adverse economic loss through disruption of travelling on roads. The study has the main focus on factors responsible for its instability together with stability analysis using limit equilibrium method by use of computer program Slide (version 5.0). The input parameters of rock mass was evaluated by field investigations and laboratory testing. To analyze the net deposit and net slide mass of the landslide area, multi-date point’s data of 2008 and 2012 of the slide area was obtained and their digital elevation models were generated by using Inverse distance weighting (IDW) technique in ArcGIS 9.3. The study has concluded that the present slope instability is the function of a specific deformation pattern in the rock units (leading towards the possibility of a shear plane under the slid mass), surface and subsurface drainage and the engineering behavior of the overburden and underlying rock units. This study recommends several protection parameters for landslide and suggests that detailed investigation of Dewal landslide is required for long term stability.     

A geoelectrical and hydrogeological study for the assessment of groundwater resources in Wadi Al Bih, UAE

Drilling information, historical water table levels, groundwater salinity records of the existing water wells in Wadi Al Bih area, United Arab Emirates, were stored in a geodatabase and used to characterize the geological and hydrogeological settings of this area. A 2D earth resistivity imaging survey was conducted for the first time in the Northern UAE to determine the potential of the Quaternary aquifer and its groundwater quality in the areas where there are no monitoring wells. The results of the chemical analyses of the collected groundwater samples together with the inversion results of the resistivity data were used to draw a total salinity map and determine the spatial variations in groundwater quality. The inversion results of the 2D earth resistivity imaging data indicated that the Quaternary aquifer in the study area is in a good connection with the underlying carbonate aquifer. It also indicated that the carbonate aquifer is of major regional and vertical extension and it contains the fresh water in this area. The data stored in the developed database were used to produce different types of geopotential maps.