نشریه زمین شناسی مهندسی ایران
سال یازدهم شماره 2 (تابستان 1397)

Considering the increase in population and the development of agricultural activities in the south-western plain of Tehran, which has led to an increase in underground water drainage, the assessment of the vulnerability of subsidence areas is of great importance. In this research, the vulnerability of south-western plain of Tehran to subsidence has been investigated using ALPRIFT method in ArcGIS and optimization of the ALPRIFT method has been performed using SVM. To implement the ALPRIFT method, effective parameters have been used to assess the subsidence susceptibility including aquifer media, land use, groundwater pumping, recharge, aquifer thickness, faults distance and groundwater decline, which are ranked in seven separate layers and Weighted the ALPRIFT index from the combination of these seven layers, which was estimated to be 173-77. In order to optimize the ALPRIFT method, the SVM model was used. For this purpose, the input data (ALPRIFT parameters) and output (vulnerability index) and the subsidence amount were related to the two groups of training and testing. After training the model, Using the subsidence amount, the model results were evaluated at the experimental stage. The results showed that the SVM model was able to improve the results of the original ALPRIFT method. In order to verify the results, the InSAR radar map and its correlation coefficient (R^2) with the vulnerability index and correlation index (CI) of the piezometers in the plain were used.

Bazideraz's water transfer tunnel is located in the Zagros structural zone. To excavation this tunnel, an EPB Hard Rock type TBM machine was used. The axis of the tunnel is located on an Anticline. In this anticline, there are various geological structures such as folding, fault, karst, and so on. The underlying studies of the design and implementation of exploratory specimens in the core of this anticline have been confined. In this research, for study of geological conditions during drilling, seismic prediction of tunnel (TSP) test was carried out at two positions of 287 + 3 and 577 + 5. In this geophysical method, seismic waves are used to illustrate geological structures. The distribution of shear waves in a three-dimensional tunnel model provides evidence of lithological changes (alternation of marl and shale and limestone layers) and the existence of several crushed zones along the drilling path. Bazideraz Tunnel is the first project in the world to use the TSP method to drill a EPB machine. In this study, the analysis of the operational parameters of the EPB machine and Observe rock mass during drilling was used to measure the accuracy of the TSP results. The fluctuations of the penetration rate, thrust and torque in the drilling path are in accordance with the low velocity and high velocity regions of the three-dimensional shear waves. Results of controlling the drilling materials indicate that the shear waves distribution models have a relative adaptation to the geological conditions in the drilling path.

Stabilizing of vertical slopes is one of the important problems in civil engineering. Different methods are being used for slope stabilizing that composite soil nailing is one of them. By using this method, shear resistance of soil increases that led to increases the stability of system. In this study a small-scaled physical model was prepared in which a strip footing adjacent to excavated wall was considered. Composite soil nailing including two row nails and one row anchors has been used in order to stabilize the excavated wall. Particle image velocimetry (PIV) has been undertaken to investigate the behavior of composite soil nailing with pre-stressed anchor system. First, the model has been prepared and elements were located in specific positions. Digital photographs were taken after each step of excavating and also after each step of footing loading. Using image processing on sequences of digital images, behavior of system was observed. Results show that for special length of anchors located in middle row, bearing capacity of footing increases and horizontal displacement of wall decreases. It was also observed that maximum horizontal displacement of wall occurs in lower part of that by using composite soil nailing with pre-stressed anchors, although in soil nailing, maximum horizontal displacement occurs in top of the wall.

In this study combination of GIS and HEC-RAS were used for flood zoning in the Chalus basin. For this purpose GIS data processing was done and the coordinate system was defined for the data and then the boundaries of the basin and sub-basin were determined with archydro. Using the extracted data TIN, DEM, mean slop and dip direction of rivers maps were produced and then using HEC-GEORAS, the data required for HEC-RAS software were prepared. Then the manning coefficient values, soil hydrologic groups and distribution maps of CN were extracted from land-use map and subsequently data transferred to the HEC-RAS and the values of manning in each of the cross sections were entered and boundary conditions were defined. Then HEC-RAS model was run in steady-state conditions. By overlaying different layers in GIS (such as the depth and velocity), dangerous areas during the flood were determined. Then the overlapping land-use map and velocity and depth layers, the land-use types at risk from flooding have been identified. Results presented that the floodplain area is equal to 8 and 24 percentage (Min. and Max). Most of the floodplain consists of rice land, building blocks, orchards, meadows and forests in the 2-year flood; therefore maximum damage happens for farmers and residences. By increasing the return period flood, the area of forest (that is placed within the floodplain) increases with higher ratio than building blocks, rice fields and pastures.

Tensile failures including tensile cracks on the upper part of instable slopes, earth fissures, tensile cracks in earth dams, and any kind of tensile failures resulted from tensile stresses within soil body are considered as important engineering geological features. Studying tensile strength and deformation characteristics of soils can have a great role in the prevention of adverse phenomena resulted from tensile failures in soils. The Varamin collapsible soils are subjected to tensile fractures and earth fissuring because of the tensile stresses raised from the land subsidence of the Varamin plain. Therefore, in this study, the strength and deformation characteristics of these soils were investigated at undisturbed, reconstituted and treated states. Results indicate that, when undisturbed collapsible soils are subjected to tensile stresses, they show a low tensile strength and behave brittle in tension. Reconstituted soils have a lower tensile strength in comparison with undisturbed soils and behave very soft and fail easily in tension. Treated soils have a higher tensile strength in comparison with undisturbed soils and behave more ductile in tension and tolerate more deformation before tensile failure. Results indicate that the treatment of the collapsible soils with stabilizer materials together with compaction is an efficient method for strengthening these soils against tensile stresses and for improving their performance in tension.

In this research by analyzing the signals of ultrasonic waves and obtaining the ultrasonic parameters in nine carbonate rocks from different parts of Iran, the ability of these parameters to assess the physical and mechanical properties and durability of rocks was investigated. For this purpose, firstly the petrographic, physical and mechanical properties of studied rocks were determined and then, in order to determine the durability of samples, long-term weathering tests of slake durability and wetting-drying up to 15 and 50 cycles were carried out, respectively. Moreover, a precise ultrasonic device capable to record wave signal was used and ultrasonic parameters of compressional wave velocity (VP), maximum amplitude (Amax), spatial attenuation (αs), and temporal attenuation (αs) were determined from recorded signals, before and after wetting-drying cycles. Results indicated that each of the ultrasonic parameters has different capabilities in rock characterization, such as VP can assess both physical and mechanical properties more accurate in comparison with other ultrasonic parameters. Results also indicated that Amax and αs detect the development of the microcracks resulted from wetting-drying cycles and the development of weathering within rocks more better than VP. On the other hand, αt is not sensitive to the weathering development in rock, while if this parameter is corrected and converted to αtc, it can detect the development of weathering within rocks.

Sungun copper mine is located in the East Azerbaijan province, 45 km north of Varzaqan County. In this research, in order to zonation of potentially unstable areas, slope mass rating (SMR), kinematical analysis and analytic hierarchy process (AHP) methods by using of Dips 6.0, Expert Choice and ArcGIS softwares were accomplished. In the study by using Analytical Hierarchy Process method, the effective general criterias on the failure of rock slopes and extraction benches including structural geology, geomechanics, groundwater condition of joints, morphology and degree of alteration were selected and ranked by forming a pairwise comparison matrix. Then the sub-criterias and alternatives are wheighted by using of overall row wheight method on the basis of their importance. Finally, by integration of obtained data layers in the ArcGIS system, the studied mine area was zoned in low, medium and higth category in terms of failure potentially. According to the results, the western, southern, southeast and scattered parts of the north area of the studied mine specially in mining benchs are more likely to rock slope failurs, which is in good agreement with field observations. The results showed that there is a fairly good agreement between the results of the methods used in this research. But due to the fact that in the hierarchical analysis method, other criteria involved in the failure are considered, and the result is more reliable.