بررسي خصوصيات زمين شناسي مهندسي رسوبات مسير خط دو تونل مترو اصفهان حدفاصل كهندژ تا ابن سينا با تاكيد بر پديده نشست ناشي از حفر تونل

eva‎luting the engineering geological characteritics of sediments in Isfahan metro line two tunnel from Kohandej to Ibnsina with emphasizes on subsidence phenomenan due to tunnel excavation

زمين شناسي

The present thesis examines engineering geology an‎d ground settlement induced by tunnel excavation along Line 2 of the Isfahan Metro. The study area is mainly located on Quaternary alluvial deposits, while only the southern margin of the city is underlain by Jurassic formations. The alluvial sediments consist of fluvial deposits, piedmont materials, an‎d alternating fine-grained an‎d coarse-grained layers with diverse mechanical an‎d hydrological characteristics that influence soil behavior. The tunnel route was divided into four distinct zones to conduct more precise settlement analysis an‎d soil characterization. Zone 2 was selec‎ted as the main focus of settlement eva‎luation due to the availability of more comprehensive data. In this zone, three boreholes—BHII5, BH-11, an‎d BHII-4—were examined in terms of mechanical an‎d physical soil parameters, including elastic modulus, cohesion, internal friction angle, plasticity index, moisture content, an‎d groundwater level. The results showed that cemented (conglomeratic) layers exhibit less settlement compared to clayey layers, an‎d the settlement magnitude is directly affected by the combined mechanical an‎d hydrological properties of the soil. The observed differences in settlement between the boreholes were justified by variations in elastic modulus, moisture content, an‎d soil cohesion. This study demonstrates that soil behavior along the tunnel alignment is simultaneously controlled by lithology, mechanical an‎d physical soil properties, an‎d groundwater conditions. Accurate determination of these parameters enables more reliable prediction of settlement, identification of critical sections along the tunnel path, an‎d conservative tunnel design. Moreover, the findings help reduce the risks associated with unexpected settlement an‎d ensure the safety of adjacent structures. It is recommended that further field investigations, sensitivity analysis of mechanical parameters, an‎d hydrogeological modeling be conducted to improve settlement prediction accuracy an‎d provide more comprehensive data for the design an‎d management of tunneling projects in similar alluvial environments.

5

156733