ENGINEERING GEOLOGY
Year:2016 | Volume:8 | Issue:3-4|Papers Count:8

Studying geological engineering characteristics of rock formations is imperative. The aim of this paper was to understand the geological engineering characteristics of Kermanshah city's cherty radiolarites rock bed which interacts with abundant linear and concentrated constructions. Physical and mechanical tests were performed on these rocks, including dry and saturated density, porosity, water absorption, uniaxial compressive strength, Brazilian tensile strength, Schmidt hammer and compressed wave velocity. As tectonical condition and brittleness of the researched rocks made the sampling difficult, the researchers firstly attempted to determine the statistical condition of data by evaluating statistical data distribution, performing the Kolmogorov-Smirnov test and 95% Validation of the CI, and then meaningful relationships among them were obtained. The results showed that obtained data from the tests followed normal or normal logarithm distribution and were in the 95% validation of CI range. Also, obtained experimental equations have proper coefficients for indirect estimation of mechanical and physical elements.

In This study, the microtremore data were used for recognition and mapping the South Mashhad fault zone. For this, in 27 points and 5 profiles normal to the mountain of south Mashhad single stations microtremore data were measured and by the dominant frequency are estimated using the spectral ratio (HVSR) method. Then Map of the period and its variations drawn In the highlands south of the city and the Stations with sudden change in the amount of frequency are marked on the map. Moreover, anisotropy of dominant frequency and amplification in all stations are checked and the station with high anisotropies of amplification marked. Finally, by comparing the results of both methods with reviews the area borehole and evidence of fault activity on aerial photographs, location of Mashhad fault zone are proposed. The results have good agreements with site evidence and aerial photo interpretation.

Using of underground spaces for transportation have been inevitable with considering to population growth, energy saving and environmental polluting issues especially in metropolis and its need to have modern systems. Tunneling under urban environment which involves old residential building with high density, different infrastructures, monuments and unknown buried subterranean has a specific challenges in spite of using modern tunneling machines. There are different parameters which determine the influence to adjacent structures due to mechanized tunneling. Risk assessment procedures form a key component of pre-construction studies for underground projects. In this paper, main parameters which cause to hazards and damage to adjacent structures in tunneling by using of pressurized TBM (EPB) in urban areas have been presented and classified corresponding to their abundance on the Tabriz metro line 1. The project is 17.2 kilometers long which is includes 8 kilometers twin tunnel is part of metropolitan transportation development of Tabriz city. This line is consisted of 17 underground stations and passes underneath the historical city center. Mechanical tunneling of Tabriz metro line 1 twin tunnels with 6.88m in diameter is under construction by using of two EPB-TBM under special urban area including of old residential buildings, different infrastructures and geological challenges (mix faced condition, buried holes, disturbed ground during varies earthquakes, abrasive ground) and continuous needs for TBMs maintenance in hyperbaric condition. For evaluation of varies hazards on the Tabriz metro line 1 in the studied area, different events have been registered. In order to measurement of settlements in adjacent building, targets along the tunneling line on building walls installed and their movements have been monitored. The variation of displacement in depth were monitored via installation of extensimeter in the tunnel line. It was found that as well as surface subsidence and other parameters which accounting to tunneling risk assessment efforts, there are some hazards which could enhance the risks in tunneling works in urban area. As experienced in Tabriz metro line 1, presence of wells and unknown buried underground spaces could be enhance the tunneling influence and risks to the adjacent structures. It was conclude that cracks in building due to surface subsidence with 45 percent is the main hazard. The permeation and flow of foam (soil conditioner additives) and grouts to adjacent buildings via holes and unknown spaces with 11 percent was the other hazard which has experienced on the Tabriz metro L1. It was seen that maximum displacement occured during passing of first TBM in tunneling crown level.

Pumped storage reservoirs are one of the newest systems in saving electricity. According to importance of convey water for placed the turbine and knowing that, almost of instability of underground area is for ignorance in some engineering geology parameters, we have decided to investigate this parameters. In this research we have been studied the engineering geology parameters along tunnel, changing in some of these parameters are shown in Rockwork 2008. After all with the new classification called IRMR the engineering geology parameters of rock mass have been studied, compare the result with classic classification, RMR and GSI shown that the outlet and entrance of tunnel are under bad situation. At the next, studied of joint for recognized the wedge base on finite element method have been investigate. Eventually with emphasis on rock bursting, squeezing and geomechanic studied the admissible advancement step for two section of tunnel base on FLAC 3D have been carried out. Using such studied make safety in services and reduce the spent-time.

Nowadays, the need to enhance the exploitation of hydrocarbon resources due to importance and increase in the rate of consumption of this material is more crucial than ever. On the other hand, the rock formations with low effective porosity, which are considered as hydrocarbon reservoirs prevented to have a suitable productivity of these reservoirs. Hydraulic fracturing is known as a process of initiation and propagation of fractures caused by fluid injection into the part of the boreholes in rock formations, which has an important role in increasing of the exploitation of hydrocarbon reservoirs with low efficiency. Initiation and propagation fractures have a high dependency to the parameters and properties of reservoir rocks. Among these parameters can mention, such as rock material, rock tensile strength, pore pressure and etc. Importance tensile strength of rock for predicting the breakdown pressure of hydraulic fracturing test is remarkable and this parameter is a function of lithology of reservoir rock. Hence, in this study with sampling at typical section of Asmari formation, evaluation of breakdown pressure parameter as a function of rock tensile strength and lithology parameters has been paid. The ratio of hydraulic fracturing tensile strength to Brazilian test tensile strength and Point load test allows prediction of the tensile strength and is an important parameter for simulation of hydraulic fracturing test results. Comparison of these ratios shows that the tensile strength parameter is dependent on the test method. Rock tensile strength that obtained from hydraulic fracturing test is 20.08 MPa and proportion between tensile strength of hydraulic fracturing test to Brazilian test is equal to 2.35. Slight differences in the distribution of data and regression coefficient 0.9 are due to the small karst cavities, relatively low porosity and intragranular voids because of fossils in the rock structure. All evidences, including the results of physical and mechanical properties reveal the influence of lithology on the results of tensile strength obtained from hydraulic fracturing test.

Coefficient of consolidation (CV) is one of the important parameters used in geotechnical design. This parameter is usually achieved from one dimensional consolidation test in laboratory. Cone penetration Test (CPT) is an in situ test, in this test can be measure pore water pressure with time this test has previously been introducing dissipation test. Teh (1987), Houlsby and Teh (1988), Teh and Houlsby (1991) and Jones and Rust (1995) have been proposed different methods to determine CV from CPTu results. In this paper, have been used 43 dissipation tests and 35 one dimension laboratory consolidation tests that were conducted in three areas in southern Iran and are compared CV are obtained from CPTu test by from 4 methods listed above with each other’s and one dimensional laboratory consolidation test. The results show that CV obtained from laboratory test is higher than the value obtained by from Teh & Houlsby (1991) method and lower than the value obtained from others methods. The similarity of results obtained from laboratory test in terms of amount and trend are closer to results obtained from Teh & Houlsby (1991) method. The empirical relationships between laboratory and in situ CV are proposed. For all equations, coefficient of correlation is higher than 0.7. The highest value is belong to Houlsby & Teh (1988) method and the least value is belong to the Jones & Rust (1995) method. Once the empirical equation is proposed for each site indecently, coefficient of correlation in all methods is high but while the empirical equation is proposed for all sites together coefficient of correlation is decrease. Thus these empirical equations are influenced by the characteristics of each area so for each area must be independently evaluated and empirical equation are proposed.

In this article the effects of various factors on steel corrosion in soil has been investigated by statistical analyses. Due to lack of such data in Iran, we used corrosion data from NBS studies, conducted between 1922 to1947. In order to determine the portion of each factor in soil corrosion, a multivariate regression analysis was carried out between each one of the corrosion factors and mean mass loss of the buried steel pipes. Finally the best model has been determined based on the P value criteria shown in F test and T test tables. This analysis repeated for the average time of 1.5, 11.5 years and the average of the entire test (18 years) after burial. Results of correlation matrix show that the highest correlations are among test year and then total acidity respectively, and the rest of variables (chloride and sulphate ion content, moisture, precipitation, resistivity, and the pH) have been rejected. The final model is exponential model and its correctness has been confirmed according to standardized residuals analysis. Since the data are related to long term and real-world conditions, the results are consequential.