مجله زمین شناسی مهندسی
سال هشتم شماره 4 (زمستان 1393)

Evaluation of strong ground motion up beneath the construction is important in both geo technical engineering (site effect) and earthquake engineering aspects (analysis of earth behavior). The most precise methods of micro zonation in geotechnical engineering is based on one dimensional dynamic analysis، in which ground surface is supposed to be horizontal، however in many cases، because of variety of topography conditions، recorded responses are different on the top of topography and their corners. In this study، FLAC 2D software as a finite difference software، is used to analysis the trapezoidal hill with different shape ratios. These topography models are analyzed by far field earthquake records، and their dimensionless amplification ratios are compared with obtained results of one dimensional analysis. Assessment of these two analysis methods in some points on the topography and around it، demonstrated considerable differences that evident necessity of two dimensional analysis in earthquake geo technical engineering.

Subsurface dams are technologies that are adaptable to nature and can be efficient for water resources management، especially for preventing unused underground water from exiting. These dams are structures that block the natural flow of underground water and cause water supplies to be underground. Further that investigated the engineering geological and geotechnical characteristics of reservoir alluvium have been important. In this study investigated characteristic of reservoir alluviums Mastbandy underground dam located in 15 kilometer to the south west of Ardestan. Therefore determined physic and mechanic characteristics alluviums reservoir coverer in form laboratory and field. The results of the experiments show that alluvium are of the kind which is dense granular and non-uniform with no plasticity. These sediments regarding permeability are categorized as being medium to high. Careful porosity gain of this tests in face creation underground dam surface، that is capacity reservoir equal about 200000 cubic meter. Load and unload as a result of charging and discharging of water، lead to settlement. For attention that reservoir particles are to form more often by sand and gravel and small quantity of silt. Settlement on the alluviums reservoir are from the type at once. For attention mechanical parameters gain، rate settlement for unit area in case that reservoir is decharge of the water equal to 16 milimeter.

Direct observations from past earthquakes، experiences and modeling carried out by researchers، have shown that the ground motion during earthquakes is impacted by a great variety of factors such as specific site-soil behavior، source and path effects. With respect to the subject، the nonlinear behavior of Urmia city’s sediment has been studied in this paper. First the methodology of soil nonlinear response analysis، including the constitutive model and dynamic equation of motion for horizontally layered soils and it’s time domain solution has been investigated. Afterwards، geotechnical properties of underlying soil for Urmia city have been interpreted. Seismic hazard maps of seismic geotechnical bedrock have prepared for 3 hazard levels. One- dimensional ground response analysis has conducted. Synthesized acceleration time histories for analysis according to regional seismic hazard analysis and the maximum ground acceleration and response spectra in ground surface have been calculated and compared with maximum ground acceleration and response spectra of bedrock and then the amplification spectra of the surface was obtained. Finally according to geotechnical information and estimated amplification factors، the Urmia city is divided into five regions and amplification spectrum for each region has been proposed.

Knowing engineering geological characteristics of carbonate formations are necessary for database. In this research، using petrological study and mechanical tests on 5 types of Ilam-Sarvak formations limestones in Khorramabad city، their engineering geological characteristics were determined and the relations between physical and mechanical properties have been analyzed. IBM SPSS Statistics (version 19. 0) software was used for determination of relations. The relations have high correlation. According to study of thin sections our rocks are biomicrite. Limestones of Ilam-Sarvak formations have high hardening and low porosity. These rocks are in medium to high density، very resistant durability index، medium to high UCS and high point load strength category. These rocks are also impermeable. Based on the UCS، modulus ratio of the intact rock engineering classification the limestones are CM and CL. According to solubility test، the solution velocity constant was 1. 39×10-6 m/s.

The Minab (Esteghlal) dam site is located in east of Minab city in Hormozgan province and in the vicinity of active fault of Minab. Joint studies in the ten stations on the rocks masses around the reservoir of dam demonstrations the four main joint sets. For assessment of this idea، the permeability of rock masses outcrops in the reservoir is estimated by HC experimental model. For this، the RQD، GSI and other characteristics of discontinuities in rocky outcrops in dam reservoir are measured in field studies. The results show that the permeability of left and rock dam embankments change from 9. 14 × 10-6 up to 2. 02 × 10-5 m/s. Also the water lost for three different condition of minimum، mean and maximum level of water table are 0. 14، 0. 20 and 0. 29 m3/s. The results indicate that the discontinuities with trend of east – west and northeast – southwest and also shear fault zone of Minab have main effects in leakage of reservoir

The collapsible soils are usually known as soils with open structure and weak bonding between particles. The behavior of such soils is similar to very loose soils. This type of soils، when saturated without any changes in loading or subjecting vibratory loads، experiences huge settlements. The present research، deals with investigation on collapsible soils located in the North East of Mashhad. The results of laboratory and in situ tests show that collapsible soil in this region was very sensitive to the increasing of moisture degree. This means that an increase in soil moisture content، significant excess settlement occurs during short time. This indicates that soil in this region suffers from high potential collapsibility. The huge soil settlement will lead the stability of existing structures to be at risk. It is، therefore، necessary the collapsible soil in the region to be improved. For soil improvement، many techniques including moisture mitigation and soil replacement or compaction may be employed. Also stabilization of soil with lime، cement or coarse aggregates are practical methods. The most effective method can be employed according to the site specification، structural characteristics and economic constructions. The results of the present research indicate that stabilization of soil lime is the most appropriate method for increasing bearing capacity of soil and reducing structural settlement.

By the time the grow of global population، increasing human demand for agricultural products and optimal use of water and preventing environmental degradation caused by industrial and agricultural pollutants made nowadays the modeling of water flow and contaminant migration in porous media is of great importance. For water flow and contaminant migration modeling we need detailed knowledge of the porous medium hydraulic parameters including hydraulic conductivity and water retention characteristic curve. Also on agricultural issues such as seed germination and continuing growth، information on the soil hydraulic properties، physical and thermal conductivity and In order to accurately predict the effect of soil temperature on the growth of grain، water retention in the soil is necessary. In the present study using geophysical and thermal studies the characterization of hydraulic parameters of unsaturated porous media was studied. The study area is located 45 km West of Tehran and the northwestern city of Karaj (Hesarak District) on the campus of Kharazmi University. Warm Water with temperature of 50° C injected and ambient temperature data recorded during the 3255 seconds began by installing a second thermal sensor used to collect the data needed for the inverse solution. From 48 temperature data which have been collected from the injection water in the ring and 48 data from sensor installed at depths of 50 cm were used for thermal hydraulic parameters estimation. In this study، the injection of saltwater into a 2 × 2 m hole into the aquifer was used and the saltwater movement mapped with geoelectrical methods. At this stage 121 geoelectrical Soundage with Wenner-Shlumberger configuration were used. The Soundage was used to determine the direction and velocity of the salt water، the lithology، depth and thickness of unsaturated zone.