RESEARCH ON ADVANCE SUPPORT CONSTRUCTION TECHNOLOGY FOR SHALLOW BURIED BIASED PRESSURE AND SMALL CLEAR DISTANCE TUNNELS
To address the complex stress forms and construction technical challenges associated with shallow-bur-ied,offset,close-distance tunnels,this study is based on the Luojiao tunnel project in Chongqing.It establishes a calculation formula for the plastic zone of surrounding rock based on the Kastner formula and a mechanical model for advanced small pipe support based on Pasternak theory.By combining theoretical analysis and numerical simula-tion,a numerical analysis model for shallow-buried,offset,close-distance tunnels is developed,and the construc-tion techniques under two conditions with and without advanced support are studied.The results indicate that ad-vanced support with pipe can effectively reduce the deformation of the tunnel surrounding rock and the development of the plastic zone,significantly enhancing the self-stability of the surrounding rock.After implementing advanced pipe support,the maximum settlement deformation of the surrounding rock decreased from 9.88 mm to 6.63 mm,and the strain in the plastic zone was reduced by 21.5%.The maximum stress in the steel arch framework was found at the stepping section of the main tunnel in the right hole,with a value of 132.57 MPa,which is below the design strength of 235 MPa.This study provides practical references for the construction of similar close-distance tunnels in the future.
shallow buried bias voltagesmall clear distance tunneladvance support
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