The effect of topography on stability of shallow tunnels case study: The diversion and conveyance tunnels of Safa Dam

نویسندگانAhad Ziaei- Kaveh Ahangari
نشریهTransportation Geotechnics
ارائه به نام دانشگاهDepartment of Mining Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran
شماره صفحات126-135
شماره سریال14
نوع مقالهFull Paper
تاریخ انتشار2018-03-01
رتبه نشریهISI
نوع نشریهچاپی
کشور محل چاپایران
چکیده مقاله<p dir="ltr" style="text-align: justify;">Due to ignoring the role of real&nbsp;<a href="https://www.sciencedirect.com/topics/social-sciences/topography" title="Learn more about Topography">topography</a>&nbsp;in the&nbsp;<a href="https://www.sciencedirect.com/topics/engineering/numerical-modelling" title="Learn more about Numerical Modelling">numerical modeling</a>&nbsp;carried out for back analysis and considering that in the tunnel longitudinal profile the distance of tunnel&nbsp;<a href="https://www.sciencedirect.com/topics/social-sciences/structural-elements-buildings" title="Learn more about Structural Elements (Buildings)">roof</a>&nbsp;to the&nbsp;<a href="https://www.sciencedirect.com/topics/engineering/ground-surface" title="Learn more about Ground Surface">ground surface</a>&nbsp;is the maximum, some results inaccuracy may occur. This issue is especially critical for cases when two tunnels or&nbsp;<a href="https://www.sciencedirect.com/topics/engineering/underground-structures" title="Learn more about Underground Structures">underground structures</a>&nbsp;are constructed next to each other. The purpose of the present research is to study the role of real topography on the obtained results of back analysis and determine the accurate geomechanical parameters of the rock mass using back analysis based on convergencemeter data. For this aim, 8 instrumentation sections were modeled using FLAC<sup>3D</sup>&nbsp;5.0 and the real topography was determined. Next, another numerical model was built to study the role of real topography and the obtained modeling results were compared for cases with and without real topography; where a significant difference was obtained between the results. In the case of ignoring real topography, the&nbsp;<a href="https://www.sciencedirect.com/topics/engineering/error-function" title="Learn more about Error Function">error function</a>&nbsp;obtained from monitoring and&nbsp;<a href="https://www.sciencedirect.com/topics/social-sciences/numerical-analysis" title="Learn more about Numerical Analysis">numerical method</a>&nbsp;results are between 1.5 and 10 times more than the case of considering real topography, suggesting the significant role of real topography. Furthermore,&nbsp;<a href="https://www.sciencedirect.com/topics/engineering/stability-analysis" title="Learn more about Stability Analysis">stability analysis</a>&nbsp;and optimization of tunnels&nbsp;<a href="https://www.sciencedirect.com/topics/earth-and-planetary-sciences/support-system" title="Learn more about Support System">support system</a>&nbsp;performed in this study using the real topography data. The results showed that removing the designed&nbsp;<a href="https://www.sciencedirect.com/topics/engineering/rock-bolt" title="Learn more about Rock Bolt">rock bolts</a>&nbsp;the tunnel was still stable through other designed supports.</p>

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