نشریه زمین شناسی مهندسی ایران
سال نهم شماره 3 (پاییز و زمستان 1395)

Land subsidence is an important geological hazard closely related with the development of urban areas. Intensive groundwater extraction attributed to economic development, and population growth has been identified as the main cause of land subsidence in many cities worldwide, especially those in densely populated and economically developed urban areas. The first step in fundamental studies of this phenomenon is the preparation of the engineering - hydrogeological model. This model is a pictorial representation of the hydrogeological units and their boundaries, physical and mechanical characteristics.
For separation and correlation of soil layers is used the geological logs data and their geotechnical characteristics (atterberg limits, unified soil classification and shear wave velocity). Elastic constants of soil layers (shear modulus, young,s modulus, bulk modulus and passion,s ratio) based on the estimated density and conventional empirical formulas are obtained. Then, the layers that have similar characteristics in an engineering geological unit are defined. Based on this model, a multi-layered aquifer system in southwest plain of Tehran includes three aquifer units and three aquitard units. This study shows that the heterogeneity of soil layers is high. This feature will change from one region to another (Shahriyar-Tehran plain, Shahriyar to Eslamshahr).

The purpose of this study is assessment landslide susceptibility in the central part of the Nekarod watershed is located in the mazandaran province using fuzzy logic.For this purpose, initially slide points using aerial photographs and field visits identified and followed landslides distributionmap was prepared.Then each of the factors influencing landslide occurrence such as (slope degree, aspect, plan curvature, altitude, geology, land use, distance from faults, distance from roads, and distance from drainage) as a data layers in environment GIS digital and in order to perform the analysis based on fuzzy sets theory was used.Fuzzy analysis using the software Matlab 7.1, after determination membership functions for each of the factors influencing in landslide occurrence was performed and then this software outputs that degree of sensitivity calculated is for each pixel in map the study area to Arc Map environment transferred and landslide susceptibility zonation map using triangular membership function was prepared.Assessment results showed that landslide susceptibility map produced using triangular membership function, with qualitative together index (0/41483) is have high accuracy in the study area.

The compression index of soil masses is one of the important soil parameters that is essential for geotechnical designs. As the determination of the compression index from consolidation tests is relatively time-consuming, empirical formulas based on soil parameters can be useful. Over the decades, a number of empirical formulas have been proposed to relate the compressibility to other soil parameters, such as the natural water content, liquid limit, plasticity index, specific gravity, and others. In this study, first by simple and multi linear regression based on 115 case study, empirical formulas proposed to relate the compressibility to other soil parameters, such as the, liquid limit, plastic limit, plasticity index, void ratio at liquid limit, void ratio at plastic limit. An alternative approach, an artificial neural network (ANN) model, is proposed to estimate the compression index with numerous consolidation test sets. The compression index was modeled as a function of five variables including the plastic index, clay fraction, void ratio at liquid limit, void ratio at plastic limit and specific gravity. Finally, comparison between proposed models carried out. The ANN model has a significantly better performance than the empirical equations for the soil compression index.

One of important goals in projects of road and soil dams is to compact whatever more of soil. Compaction of soil with reducing in void ratio causes to improve technical properties such as resistance and permeability. Minimum void ratio depends on soil properties and compaction energy. The most important properties of a soil in this regard are soil particles shape and coefficient of uniformity. Now days, presentation of exact experimental equations in geotechnical engineering have special importance. Therefore in this study it is tried to propose an equation between void ratio and the effective parameters. There are a lot of papers in this field; but the results of those previous studies were not comprehensive. In this paper, an exactly equation for calculation of minimum void ratio was recommended for poorly graded soils. In this study, 42 soil samples with different shapes, coefficient of uniformity and size were prepared; then, using instruments and preparation chart, sphericity and roundness of samples were measured; next minimum void ratio of the samples were measured. At last, using 70 percent of data, an equation for calculating of minimum void ratio based on sphericity, roundness and coefficient of uniformity was presented. Also, using other results, validation of the equation was presented. The results were completely logical.

The wells drilling in various industries such as oil, gas and mining have always been faced with the instability problem and the solving this need to spend a lot of money. The instability of wall of wellbore can be minimized by controlling deformation and failure. In this paper, experimental investigation has been carried out in two different stress conditions on thick-walled hollow cylindrical samples of sandstone, argillaceous limestone and marl using modified Hoek’s cell to predict the deformation and shape of failure in the wall of wellbore.
In the first series of tests, axial stress is constant and confining stress is changing and the second series of tests condition is vice versa. Experimental results indicated that, the deformation and shape of failure strongly depends upon the magnitude and direction of the imposed stress in the wall of well. Also result illustrated that, under constant axial stress condition, the wall of well, for both sandstone and argillaceous limestone specimens, broke out toward inside the wall of wellbore. Under the constant confining stress condition for argillaceous limestone as well as marl specimens, the failure occurred with random distribution in three points, which meet at 120 degrees

The stabilization and improvement of the soil is a branch of geotechnical engineering by which improve the engineering and geotechnical characteristic (same as strength, ductility and bearing capacity) of the problematic soils. In this study, Micronized Calcium Carbonate and a Polymer named as Poly Vinyl Acetate as the two types of additives were used to stabilize the silty sand soil, and their effects on modulus of elasticity were studied. For this purpose, after performance the index tests, the Micronized Calcium Carbonate and Poly Vinyl Acetate with different percentages of 1, 2, 3 and 4 were added to the soil and with curing times of 1, 7, 14 and 28 days, uniaxial compressive strength were done on stabilized samples. Then elastic modulus of soil in different conditions (different additives percentage and curing time) were determined. Besides, SEM (Scanning Electron Microscopy) imaging were performed on the three soil to investigate the structural characteristic changes of each sample before and after the stabilizing samples. According to the tests results, in general increasing the additives to a certain percentage in a constant curing time, results in the enhancement of the elastic modulus of the soil and by increasing curing time at a constant percentage of additives, elastic modulus will increase significantly. The results show that the effect of Poly Vinyl Acetate on the enhancement of the elastic modulus of silty-sand soil is more than the Micronized powder of Calcium Carbonate

Nowadays, change in geotechnical properties of the soil by oil pollution is one of the challenges of geotechnic engineers. In this study, thre effect of gas-oil pollution on shear strength parameters and shear behavior of the grawelly soil will be studied with a series of large scale direct shear tests. So large scale direct shear test (with box size of 30cm×30cm) is performed in well graded clayey grawel and pollution percent of 0, 3, 6, 9 and 12 with two level of normal stress (presentative of the low and high depth) and two compaction state.
The results show that the friction angel increases with increasing pollution fistly, then remains in constant amount for the soil with less compaction (unit weight of 17 KN/m3). While for the soil with more compacted (unit weight of 19 KN/m3), it is constant at first, then decreases and finally remains in constant amount. Also increasing more than 9% in pollution has no effect on friction angel. Soil cohesion increases firstly and then remains in constant amount with increasing pollution for both of compaction state. Also despite changing dilation angel with pollution percent, general expansion and contraction behavior of the soil remains costant for both compaction states and different levels of normal stress.

Assessment and prediction of rock fragmentation by drilling and blasting operations, the most basic and most critical parameters affecting the economy of mine is considered. Choghart mine had one of the largest Iran iron ore mine that annual eight million tons of iron ore is extracted from it. In the mine mining operations, including drilling, blasting, loading, transportation and processing is done on a daily basis. Distribution of aggregation from blasting operations and resulting machinery production, mining costs may be reduced. There are several methods to determine the blasting fragmentation and currently, the use of image processing systems is appropriate and effective method for evaluating of blasting fragmentation. In this study, sieve analyzes of three patterns of explosive in Choghart mine and fragmentation curve obtained by the image processing method is compared and then this method for more accurate predictions in mine by factors of α and β is correct. The correction factors value respectively is 0.81108 and 0.82087.