Journal of Engineering Geology

Identification of potential areas for the construction of underground dams in the country

Amir Saberinasr

One of the strategies for water storage in arid and semi-arid areas such as Iran is the construction of underground dams; however, identifying suitable sites for the construction of these structures remains a major challenge. The aim of this paper is to identify the optimal locations for the construction of underground dams using a geographic information system and multi-criteria decision making techniques. Firstly, thematic maps were prepared in ArcGIS environment including geological condition, land use, landslide potential, topography, water stress, aquifer area and distance from dam, village, qanat, stream, fault, airport and road. Hierarchical analysis and fuzzy logic methods were used to weight the prepared maps. By removing unsuitable and restricted areas for the construction of underground dams, a final potential map for this structure was prepared. The results show that the provinces of Razavi and South Khorasan, Kerman, Yazd, Sistan and Baluchistan, Hamedan, Qazvin, Zanjan, Markazi and Qom have greater potential for the construction of underground dams than other provinces in the country. Finally, to validate the results, a comparison was made between the results presented in this study and several successful underground dam projects in the country, showing a relatively close match between the potential map and the implemented structures.

Determining shallow subsurface geological structure using geophysical methods; case study of Abasabad site

Mohamad Davoodi

The determination ofgeological subsurface strata and shear wave velocity profiles is one of the most important engineering measures for seismic design and site effects studies. Recently, the use of seismic geophysical methods in engineering geological studies for this purpose has become widespread. In this paper, the accuracy and efficiency of seismic geophysical methods with active and passive seismic source in determining the subsurface geological structure of a selected site in the city of Abasabad in northern Iran have been studied. To this end, first, by conducting several exploratory boreholes, the subsurface geological structure of the study site up to a depth of 70 meters was carefully determined using engineering geological experiments. The results of this section showed that the shallow sediments of Abasabad site are mainly composed of sandy soils with four separate geological layers. In the next step, in two other separate boreholes, seismic geophysical experiments with active source of down-hole test were performed in order to accurately determine the shear wave velocity profile in different layers. In addition, in the next phase, using the array microtremor recording method, which is a new seismic geophysical method of passive-source type, to determine the subsurface geological structure of the study site in the form of shear wave velocity profiles. It should be noted that the array microtremor recording was performed using fifteen different arrangements of receptors (with different numbers and distances of receptors) and by two analyzing methods including F-K and SPAC. The results of these studies showed that both active and passive seismic geophysical methods had acceptable performance in determining the subsurface geological stratification of the site. It also could be inferred that the down-hole test with high accuracy determines the shear wave velocity in each layer compared to the array microtremor method but requires artificial production of seismic waves and borehole drilling. Array microtremor method without the need for drilling and production of artificial seismic waves has high efficiency in determining the subsurface layering and estimating the shear wave velocity of each layer and in general the results of this paper showed that in estimating the shear wave velocity compared to down-hole method shows up to 10% error.

Quantitative and qualitative modeling of the dynamic system of the multi-purpose dam reservoir using Vensim software by probabilistic simulation method

somayeh zarei doudeji

Due to Iran's weather conditions and lack of water resources, dam construction projects are particularly important for the country's development and progress. Water resources management based on system dynamics is capable of simulating complex water resources systems. This model for the simulation of water resources has various capabilities, such as increasing the speed of model development, the possibility of group development of the model, effective communication of the results, and increasing confidence in the model through user participation. In this research, the model of the dynamic system of the multipurpose dam of Qamshek in Hormozgan province has been simulated using the probabilistic simulation method. The purpose of this modelling is to realize different needs of the dam (domestic, environmental, industrial and agricultural) before its construction and to check the quality conditions of the reservoir. The study of the results of the quantitative modelling was done after calculating the annual and monthly percentage of volumetric and temporal supply of different needs and their source of supply. The results show that the volumetric supply percentage of domestic, environmental, industrial and agricultural needs of the dam is 95.53, 95.02, 94.18 and 93.14% respectively, and the temporal supply percentage of domestic, environmental, industrial and agricultural needs is 95.19, 94.94, 93.67 and 92.91% respectively, which are all within the acceptable range of the Ministry of Energy. Qualitative modelling of the dam was carried out for the most pessimistic case with a discharge electrical conductivity of 3000 and a base discharge of 10000 micromos/cm, on the basis of which the maximum electrical conductivity of the reservoir was calculated to be 11900 micromos/cm. Based on this research, it was found that by modelling based on model evaluation indicators, including percentage of volume supply and percentage of time supply of different needs, it is easy to quantify the effect of exploitation and management policies on the way of determination and allocation. Observed the quality of water resources and made the most optimal decision.

Assessment of alkali-silica reaction (ASR) in active aggregates using concrete petrography and the dri index

Seyyed Mahmoud Fatemi Aghda

The alkali-silica reaction of aggregates is one of the most significant factors in the destruction of concrete structures worldwide. This is due to chemical reactions between alkaline fluids in concrete voids and active silica minerals present in some aggregates. Considering that many physical, chemical and mechanical properties of concrete are related to aggregates, the role of aggregates in concrete is crucial. This research aims to investigate the compatibility of aggregate petrographic studies and accelerated prismatic mortar testing in predicting the reactivity of aggregates and determining the intensity of aggregate reactivity using the DRI index (a semi-quantitative complementary petrographic analysis). The study was carried out on laboratory samples of aggregates from mines around Tehran, using the ASTM C295, ASTM C1260 and ASTM C856-4 tests. The results showed that pyroclastic aggregates, which include sandy tuff, crystalline tuff (dacitic andesite) and glassy tuff, have the potential to cause an alkali-silica reaction due to their glassy background and microcrystalline silica. During the alkaline reaction tests of the aggregates, evidence of gel was found in cracks, holes and cement paste. In addition, the DRI index showed that the fine aggregates of both study areas were in the "slightly damaged" category and the coarse aggregates were in the "severely damaged" category.

Effect of crude oil on the dispersivity of fine-grained soils (Case study: soils of Arak Shazand refinery zone)

Ebrahim Asghari-Kaljahi

With the expansion of the petroleum industry and the aging of facilities and pipelines, oil spills are becoming more frequent. In addition to environmental impacts, oil spills can cause changes in the plasticity and dispersivity of soils. To investigate the potential for dispersion in fine-grained soils due to oil leakage, soil samples were collected from the Shazand Refinery area in Arak and mixed with 0, 5, 10, 15, and 20% by weight crude oil. Specimens were prepared at the maximum dry density obtained from the Proctor compaction test and, after curing, pinhole and double hydrometer tests were conducted. The results of the mentioned tests showed that the fine-grained soil tends to disperse with the addition of up to 15% oil, and this dispersion increases with further increases to 20%. Changes in the soil fabric with increasing oil content were investigated using scanning electron microscopy (SEM) images, and the results showed that the dispersion of soil particles increased with increasing oil content.

Assessment of the contamination potential in the Northern Dezful-Andimeshk aquifer with emphasis on intrinsic and specific vulnerability

Sepideh Shakour

One of the appropriate ways to prevent groundwater pollution is to identify vulnerable aquifer areas. The Dezful-Andimeshk Plain has two landfills that do not comply with the necessary standards for waste disposal and a river that recharges the aquifer, which can be potential pollutants for the aquifer. Therefore, evaluating the pollution potential of this aquifer is considered a necessity. To achieve this goal, for the first time in this area, the assessment of the aquifer pollution potential was carried out based on the intrinsic vulnerability (DRASTIC) and specific vulnerability (DLR), and finally, the potential contamination (PC) in the region was evaluated.. Based on the results, the value of the inherent vulnerability index ranges from 106 to 162 and has two vulnerability classes: moderate and high. The high vulnerability is related to the western margin of the plain and near the outlet of the plain, as well as in the middle of the plain with a northeast-southwest trend. The low vulnerability is associated with the northern and southern parts of the region. The specific vulnerability index ranges from 25 to 75, which, based on expert opinion, is classified into two classes: low and medium vulnerability. The highest intrinsic vulnerability is in the middle of the plain and around the Dez River. According to the results, the aquifer's PC ranges from 130 to 207 due to specific and intrinsic vulnerabilities. It is classified into three classes: medium, high, and very high, mainly affected by the river, land use, soil, and hydraulic conductivity.

Effect of Siahroud river on lead and nitrate pollution of groundwater in Ghaemshahr-Joybar plain

Hamid Reza Nassery

The study of the aquifer hydrogeochemical processes and the detailed investigation of the groundwater pollutants in order to control the pollution and prevent its environmental consequences are of special importance. The aim of this research is to investigate the effect of the Siahroud River on lead and nitrate contamination of groundwater in Qaimshahr-Joibar plain. For this purpose, two surface water samples were collected from Siahroud River, before and after Qaimshahr city, and 13 groundwater samples were collected from 13 wells, located in the bed of Siahroud river, in three periods during 2019-2020. The of nitrate, lead and dissolved oxygen concentrations of the samples were measured in the laboratory of Mazandaran Regional Water Company. The assessment of the pollution of water resources in the area shows that the discharge of urban, rural and industrial sewage and agricultural drains into the Siahroud River has caused an increase in the concentration of nitrate and lead ions in the groundwater. The Siahroud River has had an impact on groundwater pollution in the Qaimshahr plain in the upstream and some middle parts of the range due to the direction of groundwater flow and the exchange that exists between the river and the aquifer, as well as the direct discharge of pollutant sources to surface water.