A NEW METHOD FOR PREDICTING 3D FRACTURES
AT NEXT TUNNEL EXCAVATION SPACE FOR PERPENDICULAR SETS TO TUNNEL AXIS
Phí
Trường Thành
Hanoi University of Natural
Resources and Environment
Abstract: The fractures in rock would strongly affect rock mass stability, if
the rock mass is excavated. Therefore, understanding of fracture distribution
to predict the presence of them in rock mass before excavating is necessary.
However, predicting fracture locations ahead is not easy, especially parallel
fractures to tunnel excavation face and it will not be predicted, if the rock
mass has not excavated yet. This paper proposes a new methodology for analyzing
fracture spacings and predicting fracture locations at next tunnel excavation
space for perpendicular sets to tunnel axis based on fracture spacings from
previous excavated faces. The fracture spacings are determined as distances
between central projection points of fracture traces at each excavation face on
the line that is normal to average plane of set orientation. The analyzing
fracture spacings is carried out by simply plotting fracture spacings in
sequential manner (cumulative plot). The predicting fracture locations at next
excavation space is to solve inversed problem; It is carried out by inserting
fracture cluster based on distribution of previous fracture spacings on
cumulative plot. At the same time, the 3D fractures will be automatically
plotted at the next tunnel excavation space adding fracture cluster. The result
of applying this methodology at BongHwang tunnel, Chungbuk
province, Korea using Tunnel Mapper tools have
shown the utility of this method.
Keywords: Fracture spacings, Fracture distribution, Predicting fracture,
Fracture set, Tunnel excavation.