IOSR-JAGG   Volume-1 ~ Issue-3 ~ MAY-JUN-2013

Abstract: Placers are deposits of detrital materials in which valuable minerals have been concentrated by the oceanographic processes of waves and currents. These minerals are important economic source as they are useful in many industries for various purposes. India has rich placer mineral deposits at many locations along the long coastline of more than 6000 km. Contrary to the deposits of other countries, Indian deposits of placer are multi mineral in nature consisting of ilmenite, rutile, leucoxene, zircon, monazite, sillimanite garnet, kyanite, magnetite, casseterite, etc. In this study a pilot mining system of capacity 50 tons per hour operating at a maximum depth of 10 meters has been designed and developed to investigate the effect of different parameters, e.g., water jet velocity, distance from the nozzle tip to the mineral bed, time of operation, on the concentration of mineral sand in the discharge water. The solid concentration obtained is 10.6% (v/v) for a water jet velocity of 20 m/s. It has been observed that the solid concentration in the delivery line increases upto 14.8% with the change in the distance between the nozzle tip and the mineral bed.

Keywords: Placer mining; dredge output; mineral sand; translation velocity; soil shear strength

Abstract: A shallow sub-surface electrical resistivity survey (ERS) was carried out at Shaukat Khanum Memorial Cancer Hospital and Research Centre (SKMCH&RC), Peshawar, Pakistan. The main objective of the survey was to capture a clearer picture of the near-surface geologic sequence to study geophysically the attributes (depth & thickness) indirectly of particular horizon lying within five meters beneath the earth's surface for an engineering study supported by actual values (bore hole data and measured values at field). Vertical electrical sounding (VES) data was acquired using Shlumberger configuration with maximum current electrodes separation (ABmax) of 16 feet in order to resolve clearly the target geoelectric layer in the very immediate vicinity of exposed geologic cross section of an excavation designed for construction of basement of massive civil structure (SKMCH&RC). Geophysical electrical resistivity technique mapped the particular layer's depth and associated thickness having values of 4.42m and 2.87 m respectively. VES results (depth & thickness) were validated by the actual field values obtained from measuring tape as well as borehole information of the studied site. Comparison showed that geophysical electrical survey technique imaged the target geologic layer accurately with uncertainty of 0.3 feet only. This study deduced the presence of inhomogeneous near-surface media covering the depth range (< 1 – 5m) where building foundations are usually placed. The error of 0.3 feet in estimation of both parameters guarantees the successful applicability of said geophysical tool in near-surface engineering geophysical investigations with high accuracy in non-destructive, cost effective and faster way. One of the objectives of the study was to introduce ERS technique and encourage utilization of other geophysical tools for such sort of engineering works at Pakistan to avoid any geotechnical hazard.

Keywords: Depth & thickness, Electrical resistivity survey (ERS), Foundation bed, geotechnical hazard, Shallow sub-surface, Vertical electrical sounding (VES), Khyber Pakhtunkhwa, Pakistan.

Abstract: People living in Ibadan, Southwestern Nigeria have started shifting their focus on construction of buildings towards villages that are close to the metropolis. It is therefore imperative to carry out this research in order to recommend the types of structures to be erected at Adumasun area, Oniye, Southwestern Nigeria when the time comes in order to avoid catastrophic failure that might have happened thereafter. The aim of this research is to carry out vertical electrical sounding geophysical survey at Adumasun area, Oniye, Southwestern Nigeria with a view to determining the fracture distribution within the study area. The study area is located between latitude 070 37′ 55.37″ to 070 38′ 00″ North and longitude 0030 11′ 10.2″ to 0030 11′ 16.8″ East. Schlumberger electrode array was employed for the study using R 50 Resistivity meter for the data acquisition. The geoelectric survey comprised of ten depth soundings, with maximum current electrode spacing (AB) of 200m. 40% of the modeled curves are A-type, 50% are H-type, and 10% are KH-type. The geoelectric sections obtained from the sounding curves revealed 3-layer and 4-layer earth models respectively. The models showed that the subsurface layers were categorized into the topsoil, the second layer, and the third layer (where it is present). One-third of the study area showed fresh bedrock while two-third showed fractured bedrock. Areas underlying with fresh bedrock and thin overburden thickness are recommended for the construction of high-rise buildings while areas with fractured basement and thick overburden thickness are recommended for the construction of low-rise buildings. It is concluded that the study area is averagely competent for the construction of high-rise buildings and low-rise buildings depending on where individual builders are located. Keywords:- Fractured Basement, Fresh Bedrock, Geoelectric Section, Overburden Thickness, Precambrian Basement Complex, Vertical Electrical Sounding.