Advantages of employing multilevel monitoring wells for design of tunnels subjected to multi-aquifer alluvial Advantages of employing multilevel monitoring wells for design of tunnels subjected to multi-aquifer alluvial

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Vol18 No.1: 219-232

Title】Advantages of employing multilevel monitoring wells for design of tunnels subjected to multi-aquifer alluvial

Author】Mohsen GOLIAN1*; Ebrahim SHARIFI TESHNIZI2 ; Hamed TAVASOLI ROSTAMI1; Homayoon KATIBEH3;. Mario PARISE4;. Masoud MAHDAD5; Habib SAADAT6; Mehdi ABBASI2; Mahshid EBAD ARDESTANI1

Addresses】1 Tehran Science and Research Branch, Islamic Azad University, Tehran 1477893855, Iran; 2 Department of Geology, Faculty of Sciences, Ferdowsi University, Mashhad 917751436, Iran; 3 Mining and Metallurgical Engineering Department, Amirkabir University of Technology (Tehran Polytechnic), Tehran 1591639675, Iran; 4 Earth and Environmental Sciences Department, University Aldo Moro, Bari 70121, Italy; 5 Iran University of Science and Technology, Tehran 1684613114, Iran; 6 Shiraz University, Shiraz 8433471946, Iran

Corresponding author】Mohsen GOLIAN

Citation】Golian M, Sharifi Teshnizi E, Tavasoli Rostami H, et al. (2021) Advantages of employing multilevel monitoring wells for design of tunnels subjected to multi-aquifer alluvial. Journal of Mountain Science 18(1). https://doi.org/10.1007/s11629-020-6293-y

DOIhttps://doi.org/10.1007/s11629-020-6293-y

Abstract】For tunnels being excavated through multiple aquifer formations, having precise knowledge of the aquifers' hydraulic head becomes essential for determining groundwater inflow into the tunnel and analyzing its stability, specifically using multilevel monitoring systems. In the multi-aquifer alluvial section of the Glas tunnel (Iran), since the hydraulic head calculations were based on the data obtained from single-piezometer boreholes, the excavation risk was assessed to be at high level and the tunnel seemed to be unstable, thus an incorrect conclusion was derived from the misleading data. To take cost mitigation measuresinto account, it was necessary to calculate the hydraulic head at tunnel level accurately. By installing nested and clustered wells the mean hydraulic head was measured to be 70 m, significantly different from the 90 m previously determined by boreholes. Considering the updated value, the groundwater inflow and bulkhead load, formerly calculated as 0.65 m3/s and 9.5 bars, were determined to be 0.49 m3/s and 7.5 bars, respectively.

Keywords】Nested wells; Clustered wells; Hydraulic head; Pumping test; Mechanized tunneling; Iran