Vivek Sharma; Pardeep Kumar; Ravi Kumar Kumar Sharma
Abstract
Himachal Pradesh state is located in seismically active western Himalayas (India) and its seven districts are in seismic zone V and other in zone IV as per the seismic code of India. Ninety% area of Hamirpur district, the studied area, lies in zone V. Peak ground acceleration (PGA) is one of the most ...
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Himachal Pradesh state is located in seismically active western Himalayas (India) and its seven districts are in seismic zone V and other in zone IV as per the seismic code of India. Ninety% area of Hamirpur district, the studied area, lies in zone V. Peak ground acceleration (PGA) is one of the most important seismic response parameters in structural seismic design, largely influenced by the sub-soil and input seismic motion characteristics. In the present work, the primary objective is to identify the areas in the district that are prone to amplification of peak ground acceleration and can be delineated for infrastructural planning. Peak ground acceleration is one of the most important parameters used in seismic design of the structures. It is estimated using the computer programme ProShake, wherein the soil parameters from 181 borehole profiles up to 30 m depth and software in-built standard earthquake input motions of magnitude 6.9, 7.0, and 7.2 used as the input parameters. The output peak ground acceleration range from 0.24 g to 0.72 g at the ground surface and from 0.21 g to 0.54 g at a depth of 10 m. There is an attenuation of peak ground acceleration at 30 m depth. The estimation of peak ground acceleration will play an important role in delineating the starta having higher peak ground acceleration amplification. This information can be effectively used for planning of important infrastructure projects like hospitals, educational institutions, and commercial establishments in an economical way in the studied area.
Exploration
Vivek Sharma; Ravi Kumar Sharma; Pardeep Kumar
Abstract
In the present work, the empirical correlations between standard penetration test (SPT) N-values versus shear modulus (Gmax), and Peak Ground Acceleration (PGA) amplifications for sub-Himalayan district-Hamirpur, Himachal Pradesh (India) consisting of highly variable soil/rock strata at different ...
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In the present work, the empirical correlations between standard penetration test (SPT) N-values versus shear modulus (Gmax), and Peak Ground Acceleration (PGA) amplifications for sub-Himalayan district-Hamirpur, Himachal Pradesh (India) consisting of highly variable soil/rock strata at different depths and across the terrain are evaluated. In the first stage, the N values obtained from SPTs are conducted in the field at 184 locations covering the studied area. The shear wave velocity for each soil profile of each borehole is calculated using the best available correlation in the literature. Further, the seismic response parameters are evaluated for these values using the ProShake software. Finally, the empirical relationships between maximum shear modulus and SPT value for different soil types are determined along with the ground motion amplifications. The amplification factor for Bhoranj sub-division varies from 1.40 to 2.60 and from 1.28 to 2.30, 1.20 to 2.10, 1.22 to 1.85, and 1.22 to 1.70 for Barsar, Nadaun, Hamirpur, and Sujanpur, respectively. The studied area consists of variable soil strata including clay, silt, sand, conglomerate, sandstone, and mixture thereof. The correlation between shear modulus and N value is coherent with already reported correlations for regular soils. The amplification factor reported for the sites plays an important role in planning infrastructure in the region. The correlations between maximum shear modulus (Gmax) and SPT value for hilly terrain comprising of highly complex geological formations such as mixed soil and fractured rocks presented in the study are not available in the research work carried out earlier.
Sh. Maleki; H. R. Ramazi; M. J. Ameri Shahrabi
Abstract
Shear wave velocity (Vs) is considered as a key parameter in determination of the subsurface geomechanical properties in any hydrocarbon-bearing reservoir. During a well logging operation, the magnitude of Vs can be directly measured through the dipole shear sonic imager (DSI) logs. On a negative note, ...
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Shear wave velocity (Vs) is considered as a key parameter in determination of the subsurface geomechanical properties in any hydrocarbon-bearing reservoir. During a well logging operation, the magnitude of Vs can be directly measured through the dipole shear sonic imager (DSI) logs. On a negative note, this method not only is limited to one dimensional (1D) interpretation, it also appears to be relatively costly. In this research work, the magnitude of Vs is calculated using one set of controversial petrophysical logs (compressional wave velocity) for an oil reservoir situated in the south part of Iran. To do this, initially, the pertinent empirical correlations between the compressional (Vp) and shear wave velocities are extracted for DSI logs. Then those empirical correlations are deployed in order to calculate the values of Vs within a series of thirty wells, in which their Vp values are already recorded. Afterwards, the Kriging estimator along with the Back Propagation Neural Network (BPNN) technique are utilized to calculate the values of Vs throughout the whole reservoir. Eventually, the results obtained from the two aforementioned techniques are compared with each other. Comparing those results, it turns out that the Kriging estimation technique presents more accurate values of Vs than the BPNN technique. Hence, the supremacy of the Kriging estimation technique over the BPNN technique must be regarded to achieve a further reliable magnitude of Vs in the subjected oil field. This application can also be considered in any other oil field with similar geomechanical and geological circumstances.
