Influence and Evaluation of Potential Fractured Zone by Surrounding Rockmass Deformation during Deep Tunneling Blasting Excavation

Jixue Zhou, Junhong Huang, Yi luo, Xinping Li


Daliang tunnel on Lanzhou-Xinjiang high-speed railway is a typical tunneling project with adverse geological conditions, especially fractured zones during blasting excavation. A major collapse disaster was caused due to an unexpected fractured zone, which was excavated and supported improperly. Field test data of surrounding rockmass displacement is analyzed for changes alone tunnel axis and with time. Deformation curve versus time for tunnel sections with surrounding rockmass in consistent and relatively high integrity shows one inflection point, where deformation rate changes from increase to decrease. It revealed by numerical analysis that before exposed by blasting excavation, rockmass near fractured zone has shown much deformation. Inflection point can always by observed on the total deformation curve, while it appears earlier when nearer to the fractured zone. When the inclination angle of the fractured zone is small, the location of inflection point on deformation-time curve is more sensitive to the change of inclination angle. Existence of a fractured zone in vicinity ahead can be evaluated for choosing proper blasting excavation and support method.


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