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Failure Mode and Stability of Excavation Face on Shield Tunnel Undercrossing Existing Tunnel Xue, Fei; Zhang, Mengxi
Civil Engineering Journal Vol 5, No 9 (2019): September
Publisher : Salehan Institute of Higher Education

Show Abstract | Download Original | Original Source | Check in Google Scholar | Full PDF (935.125 KB) | DOI: 10.28991/cej-2019-03091394

Abstract

The supporting pressure value of excavation face directly determines the stable state of excavation face, and its value will directly lead to instability of excavation face if the value is too small. When the shield is underneath the existing tunnel, special attention should be paid to the support pressure setting of the shield working face. When setting support pressure, the rigidity constraint of existing tunnel on surrounding soil should be fully considered. In this paper, we used ABAQUS software to analyse the failure mode of the soil around the existing tunnel due to the instability of the excavation surface caused by the small pressure setting of the excavation face, which is caused by the small pressure setting of the excavation face. By using the method of theoretical analysis, we optimized the prism in the traditional wedge model to chamfer platform with different opening angles to make it closer to the actual situation, and calculated the critical support pressure of shield tunnel face when it passes through the built tunnel. The research results can provide a reference for the effective value of support force of shield excavation face when the shield tunnel passes under the existing tunnel at a short distance.
Using Asynchronous Discussion Forums to Enhance Engagement of Students in Online Teaching Chu, Guanying; Wang, Yu; Bu, Qinglei; Han, Bing; Xue, Fei; Lim, Enggee
Acta Pedagogia Asiana Volume 5 - Issue SI - 2026
Publisher : Tecno Scientifica Publisher

Show Abstract | Download Original | Original Source | Check in Google Scholar | DOI: 10.53623/apga.v5iSI.1049

Abstract

The shift towards HyFlex learning in the post-pandemic era has introduced new challenges for higher education, particularly in maintaining student engagement and motivation in online learning environments. This paper examines the potential of anonymous asynchronous online discussion forums (AODFs) to enhance participation and engagement in large online classes. We propose a new model of forum management that integrates question-answering and peer-to-peer interaction, allowing students to post questions anonymously while responses remain non-anonymous. The study investigates the evolving roles of teachers and students in promoting and participating in forum activities, adopting a “students as partners” perspective. Data from the implemented AODF indicate increased student participation and motivation, with a substantial portion of non-academic questions addressed through peer discussion. Challenges such as lurking behavior and the limitations of relying solely on technology are also highlighted. The study underscores the critical role of instructors in evaluating and adapting emerging technologies to meet student needs and foster a sense of community in online learning environments.