Stereological Analysis of Fracture Networks along Cylindrical Galleries

The intersections between three-dimensional fracture networks consisting of constant- and variable-size disks with a gallery were systematically analyzed. Exact and approximate analytical formulae were derived for the numbers of partial or full intersections. These predictions were verified by Monte Carlo simulations. Trace length distributions were studied by numerical techniques for various disk distributions. These simulations showed that differences between various disk distributions are very small when trace length distributions with the same average and standard deviations are compared.     

Spatial patterns in thunderstorm rainfall events and their coupling with watershed hydrological response

Weather radar systems provide detailed information on spatial rainfall patterns known to play a significant role in runoff generation processes. In the current study, we present an innovative approach to exploit spatial rainfall information of air mass thunderstorms and link it with a watershed hydrological model. Observed radar data are decomposed into sets of rain cells conceptualized as circular Gaussian elements and the associated rain cell parameters, namely, location, maximal intensity and decay factor, are input into a hydrological model. Rain cells were retrieved from radar data for several thunderstorms over southern Arizona. Spatial characteristics of the resulting rain fields were evaluated using data from a dense rain gauge network. For an extreme case study in a semi-arid watershed, rain cells were derived and fed as input into a hydrological model to compute runoff response. A major factor in this event was found to be a single intense rain cell (out of the five cells decomposed from the storm). The path of this cell near watershed tributaries and toward the outlet enhanced generation of high flow. Furthermore, sensitivity analysis to cell characteristics indicated that peak discharge could be a factor of two higher if the cell was initiated just a few kilometers aside.     

On the relative performance of spectrum superposition methods considering modal interaction effects

The contribution of modal interaction in the various available spectrum superposition methods is accounted via the modal cross-correlation coefficient, which has been defined in several different approximate ways. Further, in these methods, to define the final expressions directly in terms of the response spectrum amplitudes, the peak factors for all the modal responses are approximated to be equal to the peak factor for the total structural response. However, these assumptions have been found to be violated significantly in many cases and do not hold good in general. Therefore, some recent studies have attempted to improve upon these assumptions. In this paper, detailed investigations are made to study the relative performance of the various available methods considering the modal interaction effects. To find out which of the available methods, in general, gives the better results, the response of a five-storey asymmetric hypothetical building, characterized by significant interaction effects, has been computed from different methods for several widely differing input excitations and the results have been compared with the exact time-history solution.     

Geochemical factors controlling the chemical nature of water and sediments in the Gomti River, India

 R-mode factor analysis of the recently acquired data on water and sediment chemistry has been performed. Basic chemical parameters have been merged together which aid in interpreting a few empirical geochemical factors controlling the chemical nature of water and sediments of the Gomti River, a major Himalayan tributary of the Ganges drainage basin. Water chemistry seems to be controlled by three factors: bicarbonate, rainfall and silicate and phosphate factors. Sediment chemistry is largely controlled by the following four factors: clay, adsorption/desorption, Fe-Mn hydroxide and mercury factors. These factors show spatial and temporal variability in terms of their R-scores. Received: 8 September 1997 · Accepted: 15 December 1997     

Landslide zoning in a part of the Garhwal Himalayas

 The Himalayas are undergoing constant rupturing in the thrust belt zone in the Garhwal Himalayas, due to which earthquake and mass movement activity is triggered. These processes of mass movement and landslides have been constantly modifying the landscape. Landslides are one of the indicators of the geomorphological modifications taking place in this active and fragile terrain. This work is aimed at providing another example of landslide susceptibility mapping based on geological and geomorphological attributes. The data collected from aerial photographs, topographic sheets and the image suggests that there is a correlation between the distribution of landslides and some of the geological and geomorphological factors, for example, the distance from an active fault, relative relief and slope. Parameters like factor of safety, altitude, relief, slope and the distance from the fault lineament have been included in the study. A rating system has been applied to the factors for arriving at a quantitative estimate of landslide susceptibility for each physiographic unit. Since terrain classification forms the foundation of this work, the entire study can be grouped into two sequential activities: (1) the terrain classification and (2) landslide susceptibility mapping. The result is the landslide susceptibility zoning map presented. The landslides have not been classified with respect to time and may represent the final result of the on-going geological, geomorphological and seismic activity since the Holocene period or late Pleistocene time when the glaciers retreated. The area chosen for the study lies between Badri gad and Barni gad in Yamuna valley region of the Garhwal Himalaya where a very large scale investment is in the pipe line for Hydroelectric power generation. Received: 12 August 1993 · Accepted: 13 January 1998     

Prediction of peak particle velocity and peak air pressure generated by buried explosion

Summary Three sets of different formulae expressed as functions of dynamic elastic constants of rock and some design parameters involved in a buried explosion are derived explicitly for the prediction of peak particle velocity (PPV) and peak air pressure (PAP). Separate equations are derived to estimate PPV and PAP for inside, outside, and at the boundary of the crater zone. The equations incorporate the physical parameters including (i) longitudinal wave velocity, (ii) shear wave velocity, (iii) density of rock, (iv) characteristic impedance of air, (v) detonation pressure of explosive, (vi) depth of hole, (vii) radius of hole, (viii) distance of the measuring transducer. Suggested equations are tested for a few hard and medium-hard rocks. Characteristic features and important conclusions are described.     

Some aspects of cast blasting techniques for dam construction

Summary A proposal is under consideration to construct a dam on an experimental basis by a cast (or directional) blasting technique, DBT. The dam site is located at Bharari Khad, a tributary of the Sutlaz river in Himachal Pradesh. Site investigations have been completed and a large scale blast has been designed for construction of the experimental dam.The paper describes the basic design concept of DBT and application of throw and caving methods for construction of dams. The preliminary tests required to design the blasting pattern are detailed. The technique has a great potential because it reduces construction cost and time particularly in inaccessible mountain regions.