مجله زمین شناسی مهندسی
سال هشتم شماره 2 (تابستان 1393)

This paper presented the feasibility of developing and using artificial neural networks (ANNs) for modeling the monotonic large scale triaxial tests over angular، rounded rockfill and materials contained various percentages of fines as a construction material in some dams in Iran. The deviator stress/excess pore water pressure versus axial strain behaviors were firstly simulated by employing the ANNs. Reasonable agreements between the simulation results and the tests results were observed، indicating that the ANN is capable of capturing the behavior of gravely materials. The database used for development of the models comprises a series of 52 rows of pattern of strain-controlled triaxial tests for different conditions. A feed forward model using multi-layer perceptron (MLP)، for predicting undrained behavior of gravely soils was developed in MATLAB environment and the optimal ANN architecture (hidden nodes، transfer functions and training) is obtained by a trial-and-error approach in accordance to error indexes and real data. The results indicate that the ANNs models are able to accurately predict the behavior of gravely soil in CU monotonic condition. Then، the ability of ANNs to prediction of the maximum internal friction angle، maximum and residual deviator stresses and the excess pore water pressures at the corresponding strain level were investigated. Meanwhile، the artificial neural network generalization capability was also used to check the effects of items not tested، such as density and percentage smaller of 0. 2 mm.

The choice of a suitable bearing capacity of soil becomes the most important issue to be considered in any project. This paper describes analytical investigation conducted to evaluate the ultimate bearing capacity of adjacent footings in various spacings of footings. Bearing capacity of adjacent footings is determined based on virtual retaining wall method by applying equilibrium between active and passive forces. Results indicate the ultimate bearing capacity of each foundation changes due to the interference effect of the failure surface in the soil and it depends on footings spacing. In the present study، effect of soil type، depth of adjacent footings and reinforced soil is investigated on bearing capacity of adjacent footings. Results indicate closely spaced footings، can decrease or increase bearing capacity of adjacent footings with respect to single footings. Also، reinforced soil increases bearing capacity of closely spaced footings with respect to single footings on unreinforced soil، it depends on footings spacing. Finally، the predicted results are compared with those reported from experiments، analytical and numerical results performed by others، indicating an acceptable agreement.

This paper has evaluated the groundwater quality index of Lenjanat aquifer. Water quality index as a unique index is presented to describe overall water quality conditions using multiple water quality variables. Physical and chemical data of 66 water samples were used in this study. The results have been obtained by Comparing the qualitative features with the World Health Organization (WHO) standard and Industrial Research of Iran (ISIRI) standards. In calculating GQI، 7 parameters، including calcium (Ca)، magnesium (Mg)، sodium (Na)، chlorine (Cl)، sulfate (SO4)، total dissolved solids (TDS) and nitrate (NO3) have been used. Groundwater quality index shows the medium to relatively high groundwater quality in the study area. Minimum and maximum value of the index is calculated as respectively 55 and 93. Land use map shows that along the Zayanderood River and around the location of rice paddies، water quality reaches to the lowest quantity. Optimum index factor technique allows the selection of the best combination of parameters dictating the variability of groundwater quality.

Today the effects of grouting are usually confirmed by the results of permeability tests but this method is not enough to show the changes in mechanical properties of rock masses. Although many investigators use the in situ tests for evaluation of rock mass mechanical property improvement. But this tests are time consuming and expensive. Grouting reduces the permeability and improves the condition of joints and ultimately increases the rate of rock mass classification in rock engineering. So with measurement of rock mass quality index values (Q-value) in cores obtained from grouted boreholes، the efficiency and success in improving the mechanical properties of rock mass can be showed. This paper for first time introduces Q-logging as a simple method to assess the impact of grouting in improvement of the rock mass quality. Here in، the results of Q-Logging in trial injection panels in the Bakhtiary، Bazoft and Khersan II dams have been examined. The deformation modulus were calculated from the Q-Logging for before and after of grouting. Results show that there is a good agreement between calculated rock mass parameters based on the Q-Logging method and the measured from in-situ test in the studied site. This agreement confirms the efficiency and applicability of the Q- Logging method for assessment of grouting success as well as the estimation of the rock mass parameters in grouted areas. Also it has been shown that the deformation modulus in weak rock mass with low quality has been more improved than rock mass with beater quality.

The Sabzkouh water conveyance tunnel، with a length of approximately 11 Km to transferred 90 million cubic meters of water per year from the Sabzkouh area to Choghakhor Dam، about 80 Km south of Shahrekord in Chahar Mahal-e Bakhtiari province is under study. Because of the long length of this tunnel and also low rate excavation by traditional tunneling methods، the Tunnel Boring Machine has been a priority. Due to limitations of TBMs in complex and unfavorable geological conditions، based on the precise study performed، the machine was selected. The geological features and the geomechanical properties of rock masses play an important role to selection of proper TBM. In this paper، by estimation of the most important geomechanical properties and geological conditions of the rock masses، with the interpretations of geotechnical logs and the laboratory test results combined with field observations، the rock mass of the Sabzkouh tunnel، based on the three common engineering systems of RMR، Q and GSI was classified. According to classification systems، the rock masses are divided into three geotechnical zones. Based on the uniaxial strength of intact rock، the properties of discontinuities، fault thickness and shear zones، the underground water level and the squeezing intensity the performance of hard rock TBMs was performed. Finally، double shield TBM for the excavation of Sabzkouh tunnel is proposed

One of the most important issues in the design and implementation of engineering structures is to evaluate and investigate their durability against processes of consecutive wear، wet and dry. The durability of rock is resistance against chemical and physical weathering، the shape، size and status of the initial appearance in a long time and environmental conditions prevailing in the rock، hence it is important to evaluate the durability of rock. Since the device of standard durability (Franklin & Chandra، 1972) designed to evaluate and investigate durability of soft and argillites rocks. So، appears to be essential to design a durability device، which can evaluate hard rocks. For this purpose، Researchers of the Department of Geological Engineering، Tarbiat Modares University، durability device as «large-scale durability device» was designed and built which the length and diameter of the device، is 6 and 4. 3 times standard durability device، respectively، and needs 10 samples with weight of 400 to 600 g. In order to investigation the applicability of this device for hard rocks durability، we selected 17 building rocks samples of the igneous، sedimentary، metamorphic and pyroclastic rocks. Then their mineralogical، physical and mechanical properties were investigated. More، experiments of standard and large-scale durability up to 15 cycles were performed and data obtained were analyzed. The results show that، the large-scale durability device than standard durability، have more applicability for evaluating the durability of hard rocks.

One of the tests that is used for the characterization of soil abrasivity، is LCPC test. LCPC test device is designed for measuring the wear particles as small as pebbles (4-6. 3 mm). In this study، some of the most important abrasive minerals were collected from different parts of Iran for analyzing the effect of the geological parameters on the ability of abrasive minerals. Firstly، amount of index minerals abrasivity is measured according to three standards of AFNOR P18-553، AFNOR P18-579 and AFNOR P18-560 that are the preparation of samples for testing، procedure of laboratory tests and analysis of grain size with laboratory sieves. The effect of geological parameters affecting the wear rate of the sample، including five parameters of shape، size، angularity and saturation rate of the environment، has been studied. The effectiveness of these parameters on the abrasivity of samples are studied according to NF ISO 5725 relating to usage of statistics، the accuracy of test method، the repeatability and the ability to reproduce a standard way of testing within laboratory (based on classification index X 06-041). Finally، after ensuring significant effect of these parameters on the abrasivity of minerals by help of SPSS، abrasivity rates for types of minerals that have the hardness below 7 in the Mohs hardness scale، have been predicted.