Engineering geology and geotechnical characterization of Tabriz Metro Line 2, Iran

The present study was performed in order to determine the engineering geology and geotechnical details of soils and rocks along Tabriz Metro Line 2(TML2) by using the information and raw data which were acquired by borehole drilling and all field and laboratory tests in the study area. The minimum and maximum depths of the boreholes were 15 and 40 m, respectively. The results of their analysis revealed that geologically, the areas of metro route, mainly formed by alternating layers of claystone, siltstone, marl, and conglomerate, covered mainly by the alluvial deposits and in addition to older, dextral, strike-slip North Tabriz Fault (NTF) which is a major and most important geological structure of Tabriz area, there are also many minor and generally young and seismically active faults. The results of investigation on the groundwater depth in boreholes of TML2 also indicated that the groundwater depth varies between 1.5 and 30 m, along the route of metro. Eventually, based on the standard penetration test values (N-SPT), it was revealed that soils of the western parts of TML2 are in the group of dense to very dense, the central parts are in the group of very dense (Bazaar area) and dense (Fahmideh area), and the eastern parts are very dense. And finally the results achieved from determining groundwater sulfate values according to Concrete Code of Iran (CCI) indicated that the amount of soluble sulfate in the soil is mild to extremely high. Accordingly, the amount of sulfate increases from the western to the eastern parts. So that, this value is between 200 and 26,500 ppm. Based on these studies, the average of sulfate in the western, central and eastern parts is, respectively, 1118, 1275 and 4840 ppm. Thus, the groundwater in the east part is highly aggressive, and deterioration of concrete lining of the tunnel is expected in the near future.

Simple and Non-Linear Regression Techniques Used in Sandy-Clayey Soils to Predict the Pressuremeter Modulus and Limit Pressure: A Case Study of Tabriz Subway

Nowadays, some common field tests consist of SPT test and pressuremeter test are performed in investigating the geotechnical parameters of projects such as tunneling. Due to the high cost of pressuremter test performance and its time-consuming procedure, using some empirical relations between SPT and Pressuremeter tests are recommended for primarily study of the project. The purpose of this study is to perform regression analyses between the NSPT and the uniaxial compression strength test and the pressuremeter test parameters obtained from a geotechnical investigation performed in route of 2nd line of Tabriz metro. Correlations were carried out for sandy and clayey soils separately. A series of simple and nonlinear multiple regression analyses are performed and as a result of analyses, several empirical equations are developed. It is shown that the empirical equations developed in this study are statistically acceptable.