A number of cylindrical fallouts were observed in a tunnel under construction and temporary grouting as well as immediate backfilling was performed in order to control cavity expansion. The exact dimension of the largest fallout, i.e., height, cannot be measured due to limited access to the site and, therefore, experimental as well as empirical approaches were employed to estimate the fallout size. Additional boreholes were drilled immediately after the installation of permanent reinforcement and the accuracy of the proposed Tunnel Electromagnetic Prospecting System (TEPS), a non-destructive experimental testing method used to estimate the fallout volume, is verified with borehole core data. It is found that the empirical approach based on a bulking factor is easy to apply if a reference value is available. It is also proven that the TEPS method, which is fairly simple and inexpensive during the test process, gives satisfactory results when compared with borehole data. Finally, an effective reinforcement design is considered and the safety of the reinforced fallout area is evaluated through numerical analysis. Future work will be concentrated on the refinement of the measured data from TEPS and the reinforcement effect of the auxiliary techniques utilized in the fallout area.
[1]
Byung-Sik Chun,et al.
Induction of tunnel reinforcement selection rules by using decision tree technique
,
2006
.
[2]
C. D. Martin,et al.
Estimating the potential for spalling around a deep nuclear waste repository in crystalline rock
,
2009
.
[3]
Süleyman Dalgıç,et al.
The influence of weak rocks on excavation and support of the Beykoz Tunnel, Turkey
,
2000
.
[4]
Gye-Chun Cho,et al.
Detection of Anomalies in Particulate Materials Using Electrical Resistivity Survey-Enhanced Algorithm
,
2008
.
[5]
Leandro R. Alejano,et al.
Multi-approach back-analysis of a roof bed collapse in a mining room excavated in stratified rock
,
2008
.
[6]
Massimiliano Fraldi,et al.
Limit analysis of collapse mechanisms in cavities and tunnels according to the Hoek-Brown failure criterion
,
2009
.
[7]
Catrin Edelbro,et al.
Numerical modelling of observed fallouts in hard rock masses using an instantaneous cohesion-softening friction-hardening model
,
2009
.