Performing the power spectrum-area method to separate anomaly from background for induced polarization data: (a case study; Hamyj copper deposit,Iran)

Anomaly separation plays a critical role in mineral exploration. The power spectrum-area considers the spatial data which give rise to detecting the anomalies more significantly. Induced polarization data has been surveyed using dipole-dipole array in the Hamyj copper index. Electrode spacing was designed at about 20 m. The Hamyj index was explored based on the result of remote sensing and economic geology. Hamyj deposit is located about 80 km west of Birjand city, South Khorasan province, Iran. In this paper, the induced polarization from the concentration-place domain was transferred to the time-frequency domain by using two dimensional Fourier transforms in order to use the power spectrum-area method. Then, the power spectrums of induced polarization signals were calculated and differentiated by means of fractal geometry. The threshold of separation for the design of digital filter was used to filter the data. Threshold IP and filtered data was calculated by concentration-area method. Finally, IP data and filtered data were compared with each other and 72 percentages of the anomalous data corresponded significantly with each other. The results showed that the power spectrum-area method can eliminate noise; hence, anomalies can be highlighted more sharply. As far as this study is concerned, this method can be used to suggest the best places for drilling.     

Utilization of bituminous limestone ash from EL-LAJJUN area for engineering applications

The following work aims at minimizing the environmental impact of the solid wastes (ash) that is produced after the utilization of the bituminous limestone in thermal power stations and /or retort processes. Limy ash has been prepared from the El-Lajjun bituminous limestone by direct combustion at 1,200, 950, and 525°C respectively. The laboratory tests have been selected with respect to construction needs and possible post construction conditions. Utilization of the various types of ash in the stabilization problematic soils from Jordan as brown soils and the clayey marl has revealed optimum results. The unconfined compressive strength of the parent brown soil and the clayey marl has been raised from 5 kg/cm² to 50 and 25 kg/cm², respectively. The CBR value has been raised from 4.5 to 150% for both problematic soil types. Various mortars and construction elements can be produced at normal room curing temperature without the use of ordinary Portland cement (OPC). Low quality sub-base and base course can be mixed with ash to produce cement treated base (CTB) and roller compacted concrete (RCC) without OPC. Durable pavements, embankments can be constructed with very long life and low cost. CTB and RCC utilizing ash can be used in dam construction instead of normal soil in earth fill dams. The high alkalinity of El-Lajjun ash is considered as a disadvantage to be utilized in normal concrete mixes for structural purposes. Ash only can be mixed with aggregates to produce lean concrete like for blinding purposes to be prepared for foundation activities.     

Ensemble Spatial Interpolation: A New Approach to Natural or Anthropogenic Variable Assessment

Natural Resources Research - This paper presents a novel and versatile framework for building ensemble spatial interpolation functions. As with all ensemble methods, the central idea is to assemble...     

The effects of torsion and motion coupling in site response estimation

Soil amplification characteristics are investigated using data from the Chibaken‐Toho‐Oki earthquake and its aftershocks recorded at Chiba dense array in Japan. The frequency‐dependent amplification function of soil is calculated using uphole‐to‐downhole spectral ratio analysis, considering the horizontal components of shear wave. The identified spectral ratios consistently demonstrate the splitting of peaks in their resonance frequencies and low amplification values in comparison with a 1D model. The torsional behaviour and horizontal ground motion coupling are clarified as the reasons for these phenomena at the site. To prove the hypothesis, the torsional motion is directly evaluated using the data of the horizontal dense array in different depths at the site. The comparison between Fourier spectra of torsional motion and identified transfer functions reveals the peaks at the same frequencies. The wave equation including torsion and horizontal motion coupling is introduced and solved for the layered media by applying wave propagation theory. Using the developed model, the effects of torsional motion with horizontal motion coupling on soil transfer function are numerically examined. Splitting and low amplification at resonance frequencies are confirmed by the results of numerical analysis. Furthermore, the ground motion in two horizontal directions at the site is simulated using site geotechnical specification and optimizing the model parameters. The simulated and recorded motions demonstrate good agreement that is used to validate the hypothesis. In addition, the spectral density of torsional ground motions are compared with the calculated one and found to be well predicted by the model. Finally, the results are used to explain the overestimation of damping in back‐calculation of dynamic soil properties using vertical array data in small strain level. Copyright © 2003 John Wiley & Sons, Ltd.