Due to the increasing importance of geomorphologic conditions on the seismic ground response, the effect of liquefiable soils on seismic ground surface response is discussed. At first, the equivalent linear analysis based on total stress model in the frequency domain is carried out and then the nonlinear analyses based on total stress, effective stress model and considering the pore water pressure development in time domain are done in order to evaluate the differences between the several types of ground response analysis methods. DEEPSOIL.Ver5 software is used based on the latest achievements and various techniques in both solution domains. LNG port project in Assaluyeh, situated in south of Iran, is considered as a case study. Due to lack of the real data recorded near-field fault at the project site, the simulated method is used in order to create the artificial earthquake. Also three far-field earthquakes have been selected based on conventional seismic hazard studies for the seismic ground response analysis. Then, in order to better understanding of the obtained responses, the resulted responses spectra are compared with the acceleration design spectra provided in some valid codes. The result of this study indicates that the pulse effect in the horizontal component of acceleration perpendicular to the fault plane direction, affects severely the surface ground response of the near-field earthquake. The obtained results of the nonlinear modeling of the soil with excess pore water pressure build-up in the time-domain are extremely different from those of frequency-domain responses based on the equivalent linear method. In addition, because of the inherent linearity of equivalent linear analysis which can lead to spurious resonances in ground responses, the peak ground acceleration in the time-domain is lower than the frequency-domain.
Objective of the present research is to identify, analyze, and assess risk of Paveroud Dam during construction phase. Following collection and analysis of the information related to environmental conditions of the area of study and technical specifications of dam construction, a list of probable risk factors was prepared in the form of a questionnaire, and for verification, the questionnaires were provided to a group of specialists consisting of elites and professors specialized at the disciplines relevant to environment and civil engineering. Number of questionnaires was determined based on Cochran’s formula. In the first step, the expert group in the research was asked to score in Likert scale format so as to analyze the acquired responses and the risks present in the region. Having analyzed the scores using the findings of PHA method, TOPSIS technique was applied to prioritize the identified risks of Paveroud Dam. The results indicated that erosion had the highest priority among 36 risk factors. After prioritization among the risk factors, risk was also assessed using RAM-D technique in which “impact on Sorkhabad Protected Zone with 9 scores, “erosion” with 6 scores, and “work at high elevation” with 3 scores were recognized as three major risks of Paveroud Dam. In order to mitigate the effects of dam risks during construction phase, environmental management planning is crucial, and for this purpose, risk mitigation choices were recommended at the end aimed at coping with the identified risks.
Free vibration of soil often occurs during earthquakes. Since the vibration caused by earthquake does not have (steady state harmonic vibration) continuity, the alluvium vibrates with its natural frequency between two natural seismic waves. This study evaluates the effect of piles on the period of free vibration of a soil layer using numerical method. In the first stage, using analytical equations for calculation of vibration period of a soil layer and a column with continuous mass, the results were analyzed by the software. In the second step, piles with the same dimensions and distance were added step by step, and the vibration period for the soil layer with piles was calculated. The friction or floating effects of the piles on alluvial soil vibration period was also examined. The results show that as the number of piles increases, the differences between the results of one dimensional analysis of alluvium soil and the results of the software become different, and this creates the need for specific arrangements for seismic analysis of this kind of alluvium (with inserted piles). The results also suggest that end-bearing piles have a greater effect on alluvial soil vibration period, and with increased amount of the floating of these piles, these effects decline.
| Objective or result | Title | Step |
| Identifying the general geological characteristics | General geological investigation of the considered region | 1 |
| Determining the rock units and soil layers as well as their outcrops and investigating their appearance | Determining the appearance of the layers through field investigations | 2 |
| Determining the layer types and drawing the longitudinal and lateral profiles | Identifying subsurface layers | 3 |
| Determining the characteristics of geological units and their origin of emergence | Geological classification based on the steps involved in formation of units | 4 |
| a)Collecting the available information, b) controlling the available information, c) completing the information | Determining the geotechnical attributes of geological units | 5 |
| a) Presenting geological-geotechnical classification, b) presenting geological identification criteria to determine the type of a given unit at the site of the project | Presenting a geological-geotechnical classification for the considered region | 6 |
One of the effective parameters in the dynamic behavior of reinforced soil walls is the fundamental vibration frequency. In this paper, analytical expressions for the first three natural frequencies of a geosynthetic reinforced soil wall are obtained in the 3D domain, using plate vibration theory and the energy method. The interaction between reinforced soil and the wall is also considered by modeling the soil and the reinforcement as axial springs. The in-depth transverse vibration mode-shapes, which were impossible to analyze via 2D modeling, are also analyzed by employing plate vibration theory. Different behaviors of soil and reinforcements in tension and compression are also considered for the first time in a 3D analytical investigation to achieve a more realistic result. The effect of different parameters on the natural frequencies of geosynthetic reinforced soil walls are investigated, including the soil to reinforcement stiffness ratio, reinforcement to wall stiffness ratio, reinforcement length, backfill width and length to height ratio of the wall, using the proposed analytical expressions. Finally, the results obtained from the analytical expressions proposed are compared with results from the finite element software Abaqus and other researchers’ results, showing that the proposed method has high accuracy. The proposed method will be a beginning of the 3D analytical modeling of reinforced soil walls.
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