Assessment of seismic amplification factor of excavation with support system     

Tavakoli  Hamidreza  Kutanaei  Saman Soleimani  Hosseini  Seyed Hossein 《地震工程与工程振动(英文版)》2019,18(3):555-566

Retaining walls have been used in many construction projects such as for road and inclined surfaces protection. The damage caused by an earthquake depends on the fundamental frequency, amplitude and the duration of the seismic motion. These parameters strongly depend on the seismic properties of the layers that are near the surface. In the study of retaining walls, in addition to the influence of soil, the influence of topography is also important. In the present study, site response analysis is performed by using finite element software PLAXIS to obtain the effect of various factors such as embedded length of the sheet pile, underground water table, length and angle of the nail, shear wave velocity of soil on site effect and dynamic response. Moreover, for better understanding of the effect of the above parameters, the stability analysis was performed by using shear reduction method. The results show that an increase in the embedded length of the sheet pile and the length of nailing causes an increase in the amplification factor. Moreover, for shear-wave velocity in the range of 200-600 m/s, the amplification factor increases with increase of the shear-wave velocity due to the decrease of nonlinear behavior.  相似文献   

Prediction of the effect of water supplying from Shirindare dam on the Bojnourd aquifer using MODFLOW2000     

Hossein Mohammadzadeh  Majid Altafi Dadgar  Hamidreza Nassery 《Water Resources》2017,44(2):216-225

In recent years, the water demand has been increasing considerably in Bojnourd, capital of Northern Khorasan province in NE of Iran, and the extracted water from Bojnourd alluvial aquifer, with an area of 65 km², is not sufficient for residents. The required water is going to be supplied from Shirindare dam, located out of Bojnourd aquifer’s catchment area; therefore, the groundwater levels will rise in some parts of the aquifer, due to the return flow of supplied water, which will cause serious problems for the city. In this paper, the groundwater flow system of Bojnourd aquifer has been numerically simulated using MODFLOW code in GMS interface. The model, primarily, was calibrated for a steady state condition for the mean values of oneyear period (Sep. 2009 to Sep. 2010) which has a steady condition with low stresses on the aquifer. Then the model was run/calibrated for transient conditions for a two year period (Sep. 2007 to Sep. 2009). After determining the hydraulic properties of the aquifer and confirming their validity, different management scenarios, were applied to the model. Results reveal that groundwater levels in the urban area will rise by over 3 m, by infiltrating 40% of supplied water from the Shirindare dam into the aquifer. To manage the rising water levels, two different management scenarios were applied to the aquifer model. In doing so and with proper management of aquifer exploitation during critical situations, not only will the groundwater level drop; also the city of Bojnourd can develop urban landscaping by constructing sports/cultural camping area using the extra pumped water.  相似文献   

Seismic risk assessment considering cumulative damage due to aftershocks          下载免费PDF全文

Fatemeh Jalayer  Hossein Ebrahimian 《地震工程与结构动力学》2017,46(3):369-389

Calculating the limit state (LS) exceedance probability for a structure considering the main seismic event and the triggered aftershocks (AS) is complicated both by the time‐dependent rate of aftershock occurrence and also by the cumulative damage caused by the sequence of events. Taking advantage of a methodology developed previously by the authors for post‐mainshock (MS) risk assessment, the LS probability due to a sequence of mainshock and the triggered aftershocks is calculated for a given aftershock forecasting time window. The proposed formulation takes into account both the time‐dependent rate of aftershock occurrence and also the damage accumulation due to the triggered aftershocks. It is demonstrated that an existing reinforced concrete moment‐resisting frame with infills subjected to the main event and the triggered sequence exceeds the near‐collapse LS. On the other hand, the structure does not reach the onset of near‐collapse LS when the effect of triggered aftershocks is not considered. It is shown, based on simplifying assumptions, that the derived formulation yields asymptotically to the same Poisson‐type functional form used when the cumulative damage is not being considered. This leads to a range of approximate solutions by substituting the fragilities calculated for intact, MS‐damaged, and MS‐plus‐one‐AS‐damaged structures in the asymptotic simplified formulation. The latter two approximate solutions provide good agreement with the derived formulation. Even when the fragility of intact structure is employed, the approximate solution (considering only the time‐dependent rate of aftershock occurrence) leads to higher risk estimates compared with those obtained based on only the mainshock. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

Climate change impact on precipitation and cardinal temperatures in different climatic zones in Iran: analyzing the probable effects on cereal water-use efficiency   总被引：1，自引：1，他引：0  

Fatemeh?KarandishEmail author  Seyed?Saeed?Mousavi  Hossein?Tabari 《Stochastic Environmental Research and Risk Assessment (SERRA)》2017,31(8):2121-2146

Global greenhouse gases increase could be a threat to sustainable agriculture since it might affect both green water and air temperature. Using the outputs of 15 general circulation models (GCMs) under three SRES scenarios of A1B, A2 and B1, the projected annual and seasonal precipitation (P) and cardinal temperatures (T) were analyzed for five climatic zones in Iran. In addition, the probable effects of climate change on cereal production were studied using AquaCrop model. Data obtained from the GCMs were downscaled using LARS-WG for 52 synoptic stations up to 2100. An uncertainty analysis was done for the projected P and T associated to GCMs and SRES scenarios. Based on station observations, LARS-WG was capable enough for simulating both P and T for all the climatic zones. The majority of GCMs as well as the median of the ensemble for each scenario project positive P and T changes. In all the climatic zones, wet seasons have a higher P increase than dry seasons, with the highest increase (27.9–83.3%) corresponding to hyper-arid and arid regions. A few GCMs project a P reduction mainly in Mediterranean and hyper-humid climatic regions. The highest increase (11.2–44.5%) in minimum T occurred in Mediterranean climatic regions followed by semi-arid regions in which a concurrent increase in maximum T (2.9–14.6%) occurred. The largest uncertainty in P and cardinal T projection occurred in rainy seasons as well as in hyper-humid regions. The AquaCrop simulation results revealed that the increased cardinal T under global warming will cause 0–28.5% increase in cereal water requirement as well as 0–15% reduction in crop yield leading to 0–30% reduction in water use efficiency in 95% of the country.  相似文献   

Sparse Bayesian linearized amplitude-versus-angle inversion     

Amir Mollajan  Hossein Memarian  Beatriz Quintal 《Geophysical Prospecting》2019,67(7):1745-1763

The technique of seismic amplitude-versus-angle inversion has been widely used to estimate lithology and fluid properties in seismic exploration. The amplitude-versus-angle inversion problem is intrinsically ill-posed and generally stabilized by the use of L2-norm regularization methods but with drawback of smoothing important boundaries between adjacent layers. In this study, we propose a sparse Bayesian linearized solution for amplitude-versus-angle inversion problem to preserve the sharp geological interfaces. In this regard, a priori constraint term with two regularization functions is presented: the sparse constraint regularization and the low-frequency model information. In addition, to obtain high-resolution reflectivity estimation, the model parameters decorrelation technique combined with dipole decomposition method is employed. We validate the applicability of the presented method by both synthetic and real seismic data from the Gulf of Mexico. The accuracy improvement of the presented method is also confirmed by comparing the results with the commonly used Bayesian linearized amplitude-versus-angle inversion.  相似文献   

A Unified Computational Method for Simulating Dynamic Behavior of Planing Vessels     

Mohammad Saeed SEIF  Ebrahim JAHANBAKHSH  Roozbeh PANAHI  Mohammad Hossein KARIMI 《海洋工程》2009,(3):517-528

High speed planing hulls have complex hydrodynamic behaviors. The trim angle and drafts are very sensitive to speed and location of the center of gravity. Therefore, motion simulation for such vessels needs a strong coupling between rigid body motions and hydrodynamic analysis. In addition, free surface should be predicted with good accuracy for each time step. In this paper, velocity and pressure fields are coupled by use of the fractional step method. On the basis of integration of the two-phase viscous flow induced stresses over the hull, acting loads (forces and moments) are calculated. With the strategy of boundary-fitted body-attached mesh and calculation of 6-DoF motions in each time step, time history of ship motions including displacements, speeds and accelerations are evaluated. For the demonstration of the software capabilities, circular cylinder slamming is simulated as a simple type of water slamming. Then, a high-speed planing catamaran is investigated in the case of steady forward motion. All of the results are in good concordance with experimental data. The present method can be widely implemented in design as well as in performance prediction of high-speed vessels.  相似文献