Papers by Abdollah Sohrabi-Bidar
Cement grouting is a common method for sealing and consolidating dam foundations. Since grouting ... more Cement grouting is a common method for sealing and consolidating dam foundations. Since grouting is a cost and timeconsuming process, understanding the amount of cement consumption is essential to estimate the cost of any dam construction. The geological setting is one of the main factors affecting the amount of cement take. In this paper, an attempt has been made to investigate the relation between the amount of cement take and the values of Rock Quality Designation (RQD), permeability, joint spacing, and joint aperture, measured in pilot holes drilled at the Khersan II Dam site (west Iran). The amount of cement take shows a direct relation with the values of permeability and joint aperture but presents a reverse relation with the values of RQD and joint spacing. Among the mentioned parameters, the Lugeon value has the highest correlation with cement consumption, however, poor correlation indicates the influence of other factors. To reduce the influence of other factors, the values of cement take were normalized to the injection pressure and then its correlation with the mentioned parameters was investigated again. Results show a significant improvement, especially between the normalized cement take and Lugeon values, resulted in at least the coefficient of determination of 0.7. After validation, the presented equation could be used to estimate the value of cement consumption at similar dam sites.
Journal of Computational Methods In Engineering
Archives of Hydro-Engineering and Environmental Mechanics
Dam construction is one of the most popular solutions for managing water resources. In recent yea... more Dam construction is one of the most popular solutions for managing water resources. In recent years, changes in patterns of regional seismicity associated with large impoundment dams have raised concerns among environmentalists. In this study, five large dams located in Iran were studied from this perspective. The Gutenberg-Richter, linear regression and T-test were used to examine the seismic changes in the radius of 100 km of each of the dams during a twenty-five-year period before and after the construction of the dams. The results revealed that the seismicity level and relative density of large and small earthquakes in three of these dams have increased after dam construction. A significant difference between the magnitude of earthquakes, as well as the number of earthquakes before and after the construction of dams in the region, was recognized. However, the results of the T-test statistical analysis indicated that the mean depth of the earthquakes and their distance from the d...
A brief review of previous studies shows that topographic features play an important role in the ... more A brief review of previous studies shows that topographic features play an important role in the amplification (de-amplification) of seismic waves. Most researchers who have focused on topographic effects have paid attention to the distribution of amplification on isolated features, whereas what is seen in nature is often more complicated. it is known that 2D or 3D geological structures further contribute to the amplification of seismic ground motion. the main objective of this study is an investigation of the influence of adjacent hills on seismic responses. First, a parametric study has been performed, considering five models (consisting of one to five 2D symmetric homogeneous semi-sinusoidal hills), which are subjected to vertical incident waves. The 2D numerical results show that the largest values of spectral amplification for a series of 2D semi-sinusoidal hills are observed at the crest stations of the central hill, and it increases when the number of hills increases symmetri...
Scientific Quarterly Journal of Iranian Association of Engineering Geology, Feb 20, 2020
Scientific Quarterly Journal of Iranian Association of Engineering Geology, Feb 20, 2015
Scientific Quarterly Journal of Iranian Association of Engineering Geology, Feb 20, 2020
ABSTRACT: In this paper, an advanced formulation of time-domain two-dimensional Boundary Element ... more ABSTRACT: In this paper, an advanced formulation of time-domain two-dimensional Boundary Element Method (BEM) for linear elastodynamics is used to carry out site response analysis of topographic structures subjected to incident P-, SV-, and Rayleigh waves. A modified set of well behaved full space two-dimensional elastodynamic convoluted kernels is presented and employed, that has a higher degree of accuracy than those presented by the previous researchers. Numerical results are presented, including cases of half-plane, canyon and ridge sections, subjected to the different body and surface waves.
Journal of Seismology and Earthquake Engineering, 2019
Following the November 12, 2017 Sarpol-e Zahab earthquake with a magnitude of 7.3 in Richter scal... more Following the November 12, 2017 Sarpol-e Zahab earthquake with a magnitude of 7.3 in Richter scale, emergency inspection of dams has been performed for dams located at the epicentral distance of 125 km, according to the ICOLD recommendations. In the mentioned zone, there are 16 impounded operational storage dams. Inspected dams had no apparent significant damages and only some thin cracks had been observed in Tange-Hamam Dam that is a non-homogenous embankment dam and the closest operational dam to the epicenter of the earthquake, with a distance of 25 km from the epicenter. There were some defects such as longitudinal cracks and some tiny transversal cracks on the crest of the dam as well as some vertical cracks in the spillway's left approach wall. Regarding the observed evidence, more precise investigations of the dambehavior were performed through the instrumentation data. Settlement measuring on magnetic plates shows the settlement of 13 cmnear the embankment surface at the...
There are valuable investigations on the amplification effects of the topography on the seismic r... more There are valuable investigations on the amplification effects of the topography on the seismic response in the frequency domain; however, a question is that how one can estimate the amplification of time domain peak ground acceleration (PGA), peak ground velocity (PGV), and peak ground displacement (PGD) over the topographic structures. In this study, the numerical approach has been used for the evaluation of time domain peak ground motion parameters amplification on a two-dimensional Gaussian-shaped hill in a typical rocky medium. Five normalized geometries, as well as the twelve normalized vertical incident motions, have been used. Incident motions are SV wave of Ricker type. Time domain responses of displacements, velocities, and accelerations have been calculated and analyzed in selected points of the hills. Tabulated results illustrate a significant role of geometry on the patterns of the amplification, and that almost the top of the hill amplifies and the hill toe de-amplifie...
Journal of Seismology and Earthquake Engineering, 2018
This study aims to rigorously examine the influences of the vertically propagating recorded stron... more This study aims to rigorously examine the influences of the vertically propagating recorded strong ground motions on the trapezoidal-shaped hills in different sizes and shape ratios. In order to generalize the results of the study, one-dimensional as well as two-dimensional analyses are conducted. Then, intended results are represented in dimensionless form as a result of which amplification ratio patterns are extracted and compared with each other in terms of displacement, velocity, and acceleration. Similarly, corresponding response spectra ratios are derived on significant points on hill-crest, hill-side, and beside of that, and juxtaposed in diagrams. Results of the assessment are put together with that of recent studies and predictions of the reliable codes. An adequate agreement between maximum values of amplification ratios obtained in time-domain analyses and spectral analyses makes us hopeful to think of connecting time-domain parameters with spectra-related ones to propose...
تزریق سیمان روشی متداول برای آببندی و تحکیم پی و تکیهگاههای سد میباشد. در پروژههای سدسازی مع... more تزریق سیمان روشی متداول برای آببندی و تحکیم پی و تکیهگاههای سد میباشد. در پروژههای سدسازی معمولا بخش مهمی از منابع اختصاص یافته، صرف عملیات تزریق میگردد؛ بنابراین نداشتن برآوردی از مقادیر خورند سیمان میتواند در برنامهریزی اجرای پروژه مؤثر باشد. یکی از عوامل اصلی مؤثر بر تزریق و مقدار خورند سیمان، مشخصات جایگاه زمینشناسی است. در این مقاله، با استفاده از دادههای پانل تزریق آزمایشی در سنگهای آهکی تکیهگاه چپ سد خرسان II، رابطه بین خورند سیمان و چهار پارامتر شاخص کیفی سنگ، عدد لوژن، فاصلهداری درزهها و بازشدگی درزهها مورد بررسی قرار گرفته است. نتایج نشان میدهد که خورند سیمان دارای رابطهای معکوس با شاخص کیفی و فاصلهداری درزهها است، اما با عدد لوژن و بازشدگی درزهها رابطه مستقیم دارد. در بین پارامترهای ذکر شده، عدد لوژن دارای بیشترین همبستگی با خورند سیمان است، با اینحال، همبستگی ضعیف نشانگر اثرگذاری عوامل دیگری نیز میباشد. با توجه به این مسئله مقادیر خورند سیمان به میزان فشار تزریق نرمال گردیده و همبستگی آن با پارامترهای مورد اشاره بررسی شد. نتایج، بهبود قابل توجی، به ...
Journal of Applied Geophysics, 2021
In recent decades, numerous observations of the connection between sedimentary basins structure a... more In recent decades, numerous observations of the connection between sedimentary basins structure and severity and variability of damages during earthquake events have sparked a series of studies for characterization of such subsurface structures. However, these investigations were always accompanied with cost concerns and executive restrictions. Among non-destructive and cost effective approaches which have been developed in seismic response evaluations, usage of microtremor has attracted considerable attentions. In the current study, we have focused on inversion of microtremor acquired in the Qom basin, Iran. As the area is known to be seismically active, our main contribution is the construction of a three-dimensional model of the sedimentary basin in terms of shear wave velocity, which extends and integrates the previous knowledge (limited to the Vs30) down to the bedrock. Additionally, we provided further evidence of several possible faults in the area, one of which has been introduced earlier but poorly investigated so far: the "Qomrud" Fault. The results of a series of previous studies on the area, comprising down-hole surveys, electrical resistivity surveys, surface seismic refractions and surficial borehole excavations have been used, either to form a more precise initial model for inversion process or to evaluate the outputs. Additionally, we investigated possibility of obtaining the distribution of the Vs30 in the area directly from inversion of HVSR curves. It revealed that, although for relatively shallow bedrocks (80-100 m) the differences of achieved velocities is lower than 10-15%, in deep sediments, the Vs30 from microtremor is largely overestimated. Furthermore, we discussed the applicability of empirical relationships for estimating bed-rock depth in the investigated basin.
Earthquake Engineering and Engineering Vibration, 2020
This study focuses on investigating spatial variation of ground motion that has great influence o... more This study focuses on investigating spatial variation of ground motion that has great influence on the dynamic behavior of the large structures located on the surface topography. One of the most effective parameters on the spatial variation of ground motion is the difference between the arrival time of seismic waves in different points located on the abutments. In this research, a three-dimensional model of the Pacoima Dam site is prepared. The time domain 3D boundary element method is used to apply non-uniform excitation at the dam supports. This model is subjected to vertically propagating incident SH and P waves. The time delay can be characterized by calculating the value of the time delay for which the cross-correlation between two records is maximized. Finally, to obtain the time delay in a topographic site, a function considering effective parameters such as the height from the canyon base, wave velocity and predominant frequency, is presented. Furthermore, a code was developed for generating the spatially variation of seismic ground motions. The results show that the proposed functions have an acceptable accuracy in estimating the time delay to generate non-uniform ground motion.
Soils and Foundations, 2019
This study investigates different methods for generating non-uniform support acceleration at actu... more This study investigates different methods for generating non-uniform support acceleration at actual topographic sites. The factors affecting the non-uniform excitation of a topographic site include the time delay between the arrival times of incident waves at different soil depths, causing a phase difference, and the coherence function. The existing coherence models are based on data recorded on flat surfaces and are not suitable for surfaces with topographic features. Therefore, in the present study, models of a canyon site subjected to Ricker waves with different predominant frequencies, shear wave velocities, and shape ratios have been developed, and the results of boundary element analyses in the time domain (using the BEMSA code) have been obtained at different elevations on the canyon surface. Then, by conducting a statistical analysis employing the symbolic regression method on the results of numerous presumed cases, the relationships for calculating the time delay between the support responses and the coherence function of V-shaped canyons were obtained. To verify the accuracy of the proposed relationships, the results were compared with the records from the Pacoima Dam site during two different earthquakes and a good agreement was obtained between the results. Eventually, by implementing the proposed relationships in the random vibration method, the non-uniform acceleration of the site was simulated. The results indicate that the proposed relationships have an appropriate level of accuracy for calculating the time delay and the spectral coherence function of V-shaped canyons.
Journal of Rock Mechanics and Geotechnical Engineering, 2019
In this context, a new boundary element algorithm based on the time-convoluted traction kernels i... more In this context, a new boundary element algorithm based on the time-convoluted traction kernels is employed to evaluate the spatially varying earthquake ground motions of the Pacoima dam in the USA subjected to SH, SV and P incident waves. An accurate three-dimensional (3D) model of the dam canyon is implemented into the computer code BEMSA to investigate the seismic response of the dam. The analyses are performed in time domain with a linearly elastic constitutive model for the medium. This modeling procedure has been validated by the results reported in the existing literature. According to the results of this study, the response of the dam to earthquake waves is generally influenced by predominant frequency of the incident motion, surface topography, relative distance of observation points, and type of the incident seismic wave. For the cases considered, the incident SV wave has led to the maximum amplification of incident motions, especially at the left side of the dam. The results indicate that the proposed procedure can be employed for accurate prediction of a dam response during an earthquake.
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Papers by Abdollah Sohrabi-Bidar