مجله زمین شناسی مهندسی
سال نهم شماره 1 (بهار 1394)

This paper presents a case study of the instability mechanism، re-qualification and reinforcement method adopted to pass through a collapsed zone of a sabzkuh water conveyance tunnel in southwest Iran. The instability problems were encountered during tunnel excavation due to the failure to recognize the fact that alteration in stress field and resulting deformation could cause dilation and increase in the permeability of sand and gravel layers، local fault gouge zones، landslide surface and in turn significant reduction in shear strength and collapse in tunnel. IPE Arch Support Technique (IAST) is for the first time used for T1 part of Sabzkuh tunnel design in order to reinforce the ground around tunnel and to crossing zone falling. However، since the design and construction work with IAST have been done on the basis of only the practical experience of engineers، it needs to analyze quantitatively the reinforcement effect of IAST. In this study، Finite Element Method was applied for analysis of the quantitative reinforcement effect with deformation modulus of ground، IPE length and size. As a result، the settlement increases as length increases and decreases with the increase of the deformation modulus of ground and IPE size.

The main objective of this research is to investigate on the mechanism of cement-clay-heavy metal contaminant interaction at different time intervals from micro-structural point of view. To achieve the above mentioned objective series of buffering capacity measurements, batch equilibrium and XRD experiments were performed on different mixtures of bentonite+contaminant+cement. The results of this study indicate that three process of contaminant retention by clay particles, chemical precipitation, and pozzolanic interaction in solidification process contribute to contaminant retention. Furthermore, the evaluation of XRD analysis indicates that in solidified samples with less than 10% cement, the main reason for reduction in peak intensity of clay fraction is due to the presence of heavy metals. This is attributed to the low pH of lead heavy metal rich electrolyte. However, as the percentage of cement increases, the clay solubility is the main reason for reduction in peak intensity of montmorillonite in XRD test.

Kandovan village is the one of the tourist attractions in East Azarbaijan province of Iran. Rural houses have been excavated within the rocks of cone-shaped Pyroclastic rocks several hundred years ago. The cone-shaped rocks of Kandovan are susceptible to weathering، erosion and degradation because its special geological properties. Present paper has been discussed weathering and erosion in theses rocks using field studies and laboratory tests. Kandovan rock mass has low resistance against weathering and erosion because its components are plagioclase minerals and pumice fragments with low resistance and low welding and sorting، high sphericity and rounding. Although weathering and erosion along existing joints and fractures is the most important causative agent of cone-shaped forms but there is the possibility of further damage of houses due to continuing weathering and erosion processes. High porosity of rocks has caused that it to have a high capacity for water absorption. High water absorption percent and high sensitivity against expansion and contraction by freezing-thawing and wetting-drying cycles and low hardness and internal strength of Kandovan rock mass causes weathering and disintegration due to environmental impacts. Furthermore، weak texture of pyroclastic rocks causes easy erosion of rock by surface waters and wind.

One of the most useful procedure to soil stabilization is lime. Soil improvement using lime is a quick and simple approach which could be included in large and small projects. The objective of soil ‘Improvement’ with quicklime is to achieve an immediate reaction، which significantly strengthens the soil due to the removal of moisture and a chemical change in clays. In order to do parametric study on the influence of the lime on shear strength preparing the samples is important. In this paper، in addition to considering method of samples preparation، effect of lime content، water content and processing time on the shear strength of clay using direct shear test is investigated. The results indicate that method of samples preparation is effective and is identified that there is an optimum lime and moisture content which maximize shear strength.

The Dynamic Probing is an important test in site investigation and geotechnical studies. It is used for determination of situation and specification of soil layers when the depth of exploration is moderate. In our country the last few years the use of this test has been widely used to replace the standard penetration test. In this paper، the experiences to use of types of dynamic probing rigs and the errors and mistakes that can occur in these experiments is discussed. Then the accuracy of this test is studied to evaluate the specification of fine-grained soils. The most important innovation of this research is the proposition of the new correlations between cone dynamic resistance and undrained shear strength and so compaction percent in fine-grained soils. Finally، it is hoped the results of this research can be used to correction existing errors in usage of dynamic probing test. The paper encourages the wider application and further development of this test for site investigation in fine-grained soils.

In this study active faults in the region of Shahid Rajai dam of sari with 100 km radius was categorized on based fractal dimension of faulting and Earthquake and also evaluating of slip rate and investigate those activity rate. Using the fractal dimension of faulting and earthquake with squares method (Box-counting) and finally by classification this fractals dimension، the faults of North Alborz، Damghan and Garmsar more activity faults in the region of study area during 100 years late which based on activity degree of faulting and Earthquake with method of fractal analysis which based on assessment of activity degree of faulting and earthquake with method of fractal analysis also set in BD grade and this activity was confirmation. For assessment of slip rate beginning the seismicity parameters (a&b) of study area was determination، then these parameters were normalized for each fault. Based on existing relationships and having a&b for each fault، the seismic moment those fault was calculated. According to The relationships for calculating the rate of seismic moment، slip rate of each fault has been estimate and based on faults in study area was classification. The Faults with very low slip rate and high return period of earthquake could cause occurrence large earhquakes which earthquake of 856 A. D Qumes and causing smith therefore Damghan Fault could this fault know. Thereupon Therefore expectance larger slip in the future on faults such as Astaneh، Rameh، Cheshme-Ali and etc Will have. High slip rate along the New faults introduced (Khorram-Abad، Majid، etc.) in this area is noteworthy that according to occurrence the earthquakes in the privacy of their fault، the high slip rate is reasonable.

Concentrations of potentially toxic elements and PAHs have been studied in 126 soil samples in the Bushehr province. The results of contamination factor (CF) reveal that Cu، Mo and Zn have very high contamination factor. The results of enrichment factor (EF) show that As، Mo، Cd، Pb، Cu and Zn are enriched compared to the average abundances of background level and mean shale values. The principal component analysis (PCA) was used to assess the relationships among different of elements. The strong association of elements such as Cr، Ni، Al، V and Sc in soils suggests a common source، i. e. derivation from parent rock units. The significant correlation and moderate positive loading of Zn، Se، As، Mo and Cu with PAHs content indicate that the concentrations of these elements in soil samples are influenced by anthropogenic activities. High positive loading of CEC with Pb and Cd and moderate loading with Cr، Co، Ni and Co، indicate that CEC content play a significant role in the distribution of these elements in the soils.

The purpose of this paper is to propose a new correlation coefficient of bearing capacity of rectangular foundation is located on the nearby slopes. In this context، the dominant model of an experimental study of a slope sand box made of steel and is located on a strip foundation. After vertical loading،The applied load and displacement of foundation were recorded and tension - settlement curve is drawn. Finally، based on the ultimate bearing capacity is determined as follows. Used in this research was the gravel and sand BABOLSAR In all experiments، the relative density of 50%. Based on the results، followed by the distance to the edge of the slope and inclination angle on ultimate bearing capacity of the foundation and its variation with different parameters is discussed. The results indicate that with increasing distance from the edge of the slope، Bearing capacity increases linearly. Also with increasing slope angle، the bearing capacity has declined linearly. Finally a new equation to estimate the bearing capacity of shallow foundations near slopes for conditions of this paper is presented.

The purpose of current study is development of an intelligent model for estimation of shear wave velocity in limestone. Shear wave velocity is one of the most important rock dynamic parameters. Because rocks have complicated structure، direct determination of this parameter takes time، spends expenditure and requires accuracy. On the other hand، there are no precise equations for indirect determination of it and most of them are empirical. In this study، by using data sets of several dams of Iran adaptive neuro-fuzzy inference system (ANFIS) and gene expression programming (GEP) methods، model and equation are rendered for prediction of shear wave velocity in limestone. Totally، 170 sets of data were used for modeling. From these data sets، 136 ones were utilized for building the intelligent model، and 34 were used for their performance evaluation. Compressional wave velocity، density and porosity، were considered as input parameters. In the relevant predictions، the values of R2 and RMSE for ANFIS model were consecutively 0. 958 and 113. 620. These values for GEP equation were 0. 928 and 110. 006. Because these results have accuracy، they could be used for prediction of shear wave velocity for limestone in the future.