نشریه زمین شناسی مهندسی ایران
سال دوازدهم شماره 2 (تابستان 1398)

In order to study the physical and mechanical properties of available soils in the Khor-Arab Abad road, the seven sampling stations were selected along the way at the distance of 10Km from each other that located on the edge of the road. Then lime is usually the first option for soil stabilization in road construction projects as an economic reason. Considering the existence of Magnesium Oxide production factory in southern Khorasan province, this option has been studied also as a stabilizing agent in the present study.the existence of the Qaleh-Zari copper mine near Khor-Arab Abad road was a motivation to study the application of utilizing copper waste of processing factory for stabilizing soil .In order to specify the optimum amount of lime, the samples containing 2%, 5% and 10% of Lime were prepared. The optimum percentage was selected to be 5% according to previous studies and related recommendations was proposed 2% of lime adding to half of the samples as an accelerator for magnesite and copper waste respectively. Three additive combinations of 5% lime, 5% fine-grained magnesite with 5% lime, 5% copper waste have shown the best performance in order to increase CBR, uniformity of effect on all samples and non-inflation of 7 days treated samples. In terms of uniformity of performance on increasing CBR, the condition of fine- grained magnesite situation is better than copper waste and weaker than lime.

Fast growing of engineering infrastructure to meet human requirements is directly related to the need for a resistant soil to carry out construction load. On the other hand, the importance of environmental issues has led to an ever-increasing demand for new and environmentally friendly methods for soil remediation. The method of microbial induced calcium carbonate precipitation (MICP) is considered by the researchers as one of the most environmentally friendly methods. The purpose of this study was to investigate the effect of MICP on the uniaxial strength of carbonate sand. Therefore, samples of Bushehr carbonate sand were cured after the injection of bacteria and cement solution. Then a uniaxial compression tests were carried out to evaluate the compressive strength. Also, the effect of cement solution concentration and curing time on the results of MICP method was investigated. The results show that maximum uniaxial strength of sand stabilized with MICP is about 3.5 kg/cm2, which indicates the proper performance of MICP method for stabilization of carbonate sand. The UCS of the samples depends on the concentration of cement solution. Stabilized samples with a higher cementation of concentration solution had more uniaxial resistance than samples with lower cement concentrations. The curing time more than 14 days did not significantly affect the uniaxial resistance.

The Hajilar earth dam is under construction near the Kharvana Town of Varzaghan County. The height of this earth dam is 95 meters from foundation level. During dam studies have been identified 11 borrow material sources. As for, the evaporative formations outcrops in the project region and the presence of field evidence such as erosion of the sluice, erosion of the jars, the formation of pit and tunnel in the soil, and the flooding of the water after rainfall, it is necessary to study the potential of the dispersion of fine-grained soils in the area. In this research, the soil characteristics of five borrow sources of the clayey core of dam have been investigated, with emphasis on parent rocks, mineralogy and dispersive tests. For this purpose, field investigation and sampling and determination of parent rock related to borrow material resources, dispersive tests such as Crumb, double hydrometer, Pinhole and chemical analysis were performed on the samples. The results of this study show that clayey soils with the origin of Neogene evaporation deposits in the Leylab plain have a high dispersive potential and are classified according to the results of pinhole tests in group D1. Based on the results of double hydrometer tests, the percentage of dispersion in the Leylab plain is between 45 and 68%. The fine-grained soils around the Hajilar River, which are often the source of igneous rocks, have a low dispersive to non-dispersive.

Rock mass classification is one of the most important and practical criteria in designing of underground excavations and estimating the related support systems. RMR and Q classifications are the most utilized rock mass classification systems in which different geological surveys and rock mechanics studies have been required for precise determination of their numeric values. Considering the significance of these two classification systems, costly and time-consuming process of data collection in order to determine the required parameters to calculate these systems, development of valid relations between the above classification systems is essential. In this research, different empirical relations in the forms of linear, polynomial, exponential, logarithmic and power equations between the RMR and Q classification systems are firstly developed based on the measured data in the several parts of the Marivan Azad dam tailrace. Then, the logarithmic relation is proposed as the most precision and reliable empirical relation between the above classification systems based on the determination coefficient criterion, significance level and F-test in the ANOVA. Proposed relation is similar to the Bieniawski equation but some modifications have been made in its coefficients for localization and obtaining the better results. Finally, results verification using the evaluation performance indices showed that estimation accuracy of the proposed relation and its conformity with the measured values are better than those of the previous relations and has the higher conformity with the measured data.

The presence of marly soils causes various problems in the implementation of engineering projects. Therefore, treatment of these soils, using various types of additives, has become to one of the most important research topics in the field of geotechnics. Hence, this study has been done with aim of investigating the effect of treatment by lime and nanoparticle on the engineering behavior of marly soils located around the Sonqor city. After taking marly soil samples from the study area, the samples were transferred to the laboratory and their physical, chemical and mechanical properties have been investigated before and after stabilization by the lime and nanocomposite additives. Based on the obtained results, the soil plasticity index decreases by increasing lime percentage due to pozzolanic reactions. Also, with increasing lime percentage and curing time, the modulus of elasticity and the uniaxial compressive strength have been increased. The results showed that with increasing the percentage of nanocomposite up to 4%, due to the filling of the soil's pore space by nanocomposite particles, the compressive strength of the soil increases, and after that a decreasing trend is observed as a result of the flocculation of the particles. Finally, it was found that addition of lime has more efficiency in improving the strength properties than the nanocomposite.

Dispersive soils are among the most important problematic soils in earth structures, especially earth dam projects. Lime and aluminum sulfate are common and traditional additives for stabilization of dispersive soils due to the proper replacement of calcium or aluminum ions instead of sodium ions. Considering the progress of nanotechnology and using its in soil improvement, in this study, nano-sized aluminum oxide powder was used to improve dispersive soil. Five different nano material ratios (0, 0.2, 0.4, 0.8 and 1% by weight of dry clay) were mixed with a dispersive clay and four different lime contents (0, 2, 4 and 6% by weight of dry clay) and the dispersion potential of mixtures are obtained from double hydrometer test. The results show that increasing nano Al2O3 greatly reduced the percentage of dispersion. Adding 1% nano-Al2O3 in dispersive clay has diminished 64% the potential of dispersion. In samples with containing 2% lime, only 0.2% of the nano material has been able to place the soil in non-dispersive category.