نشریه زمین شناسی مهندسی ایران
سال دوازدهم شماره 1 (بهار 1398)

The purpose of this research is investigation the effect of lime on the residual soils in the southern area of the Faghireh village of southern Hamadan. The study area is located in the mountain range of Alvand and Kyvarstan in south of Hamadan. The topography of the region is hilly and formed from the weathered units. To investigate of lime effect on studied soils, maximum dry unit weight, optimum water content, pH and uniaxial compressive strength of stabilized soils with different percentages of lime was determined. The results show that increasing lime percentage and curing time, increases optimum water content and decreases maximum dry unit weight, and also improved the resistance properties of stabilized soil. According to the results, optimum lime percentages were 5% and 7%, and the curing time for the stabilized soils in the Faghireh area of Hamedan were obtained for 28 days. Then, the effects of freez-thaw cycles were investigated by using uniaxial compressive strength tests, direct shear, weight loss due to freezing and determining the swelling of samples. The results show a reduction in uniaxial compressive strength in freez-thow cycles. Also, the cohesion of the samples are decreased and the internal friction angle of the samples are increased, and the weight loss and swelling due to the freezing of the stabilized samples are less than the base soil.

Improvement of poor soils as an inevitable issue plays an important role in civil engineering projects. In this paper, the effect of adding metakaolin on Atterberg limits and uniaxial compressive strength of sandy clay soil was investigated. For this purpose, uniaxial compressive strength tests have been done on non-stabilized and stabilized soil samples with 5, 10, 15, 20 and 25% of metakaolin at curing times including immediately after mixing, as well as 7, 14 and 28 days. The Atterberg limits test have been also conducted on stabilized soil samples with 5, 15 and 25 at immediately after mixing. The results show that increasing the percentage of metakaolin increases the liquid and plasticity limits of sandy clay. So that the amount of plasticity limit of soil is less than the liquidity and thus the soil plasticity index increase. Stabilized samples with 25% metakaolin increased by 1.33 and 1.40 times, respectively, for liquid and plasticity limits, due to the highest change in the Atterberg limits of sandy clay soil. The study of stabilized soil in plasticity chart shows that by adding of metakaolin, the soil's position in this chart is negligible. Also, increasing the percentage of metakaolin and the curing time increases uniaxial compressive strength of the sandy clay. The highest strength rate for 25% of metakaolin occurred at 28 days. Also, studying the failure planes and the failure rate of the tested specimens shows that with increasing metakaolin, the failure of the specimens occurs faster after reaching the final strength.

Performance prediction of diamond wire saws and estimation of sawability are important in the cost estimation and the planning rock cutting projects. In this paper, the performance prediction of diamond wire saws in cutting carbonate rocks is considered on 14 different carbonate rocks in stone quarries. Uniaxial compressive strength (UCS), Brazilian tensile strength (BCS), Schmidt hammer value (SHv), Los Angeles (LA) abrasion and production rate (Ph) of diamond wire saws are determined in separated reference. The scope of this study is to evaluate the capability of two different methods in order to predict production rate of carbonate rock using diamond wire saw. A non-linear model presented by Ataei et al. and new proposed non-linear model are presented. An application of Imperialist Competitive Algorithm (ICA) is used to determine the non-linear production rate estimator coefficients. According to the calculated statistical error between the forecasted and real measured values of production rate, ICA-based model has the lower values of MAPE, MAE, VARE, MEDAE and RMSE than the previous model in the literature, while it has the higher value of VAF than the previous model in the literature. It is concluded that the production rate of carbonate rock using diamond wire saw can reliably be estimated using the developed model.

Microbial induced carbonate precipitation (MCIP) is an environmentally and suitable method for soil remediation. In this method, urea is hydrolyzed by the urease enzyme, that is splashed from Sporosrcina Pasteurii bacteria. The calcium carbonate is formed in the presence of calcium ion. Calcium carbonate connects the soil particle like a bridge and improve its engineering characteristics. In the present research, the effect of MICP on the permeability of carbonated sand was investigated. The effect of factors such as concentration of the cementation solution, curing time and relative density on soil permeability have been studied. To consider the effect of different factors on the MICP performance, number of samples have been treated with MICP method and then constant head permeability test were conducted on the treated samples. the results show that as the concentration of cement solution was increased, the permeability of the samples was decreased. Loose Samples resulted in more decrease in permeability with respect to the dense samples. Also, bacterial activity was increased with time and after 14 days the variation in permeability was reduced. The highest rate of permeability reduction was around 60% for the sample prepared in loose state and cured with one molar concentration of cementation solution for 28 days

According to increasing demand of the country for more production rates and output from oil reservoirs, it's necessary to re-activate the oil wells in Iran. Oil production in overtime Reduces, The reason of this event is decreased reservoir's Pressure and Closure the cracks and microscopic holes. Hydraulic fracture as a method for stimulating oil reservoirs related to various factors including the characteristics of the environment which the fracture grows. Mechanical properties of the layers recognized as the one of the most effective parameters on the progress of hydraulic fracture and its geometry. In this study, we try to indagate the various factors involved in hydraulic fracture and the effect of each of them on hydraulic fracture until reduce both operation costs and better and more efficient failure. In this research, numerical modeling was done by ABAQUS software in 10 different cases and then, the effect of the each input parameters on the hydraulic fracture pressure was investigated by performing sensitivity analysis. Actually these input parameters are well's data and including Young's modulus, minimum and maximum horizontal stress, vertical stress, tensile strength, poison’s ratio and pore pressure. Required information is obtained from excavated wells in carbonate rocks in Iran. The results show's minimum horizontal stress has the most effect on the hydraulic fracture pressure and parameters such as vertical stress and Young's modulus are not effective in determination of hydraulic fracture pressure.

Dispersivity is a physico-chemical phenomenon whereby clay soil particles lose their cohesion in the presence of water and repel each other, so that the particles become suspended in water and easily washed with very little energy from the environment. Potential dispersivity in a given soil depends on several factors, including: type of clay minerals, pH, organic matters, temperature, moisture percentage, type and concentration of ions existing in the soil pore water and the characteristics of eroding fluid and usually there are high amounts of sodium cation. Soil dispersivity evidence can be alluded to the development of erosional shapes on steep and flat areas; since these erosional shapes were observed upon the Gachsaran formation in Masjed Soleyman petrochemical site, so sampling was carried out from different parts of the site in order to assess the causes of erosion. Then, by performing physical and chemical tests as well as the tests to characterize soil dispersivity, it was observed that the amount of sodium cation is low and soil itself is non-dispersive. By observing the gypsum mineral, voids and free spaces available in manual and microscopic samples, their gypsum content was determined. Again, by its relation with field observations, it was revealed that erosion shapes induced by leaching, dissolution and ultimately the soil to be hollowed in the result of gypsum mineral presence that has been contributed in developing a kind of mechanical erosion in the region.