The Ingenieur Vol 57 January-March 2014 The Ingenieur Vol 57 January-March 2014 | Página 15

Figure 5 – Remedial Works at Lepoh Fault

Figure 6 – Face Collapse at TBM 2

Figure 7 - Rock and Ingress Water Temp

Figure 8 - Temperature of Water, Air and Rock

The cause of the high temperature is still
under investigation by local universities.
Measurements of rock and water temperature
were taken at regular intervals. The data obtained
was analysed for health and safety reasons of the
workers working in the tunnel. Figure 9 shows the
measurements recorded in the tunnel.
To overcome the low productivity of the
workers and hazardous working environment,
additional chillers and air conditioning units were
installed to reduce the ambient temperature inside
the tunnel.
Special vests were used by the workers during
working. As a result the ambient temperature was
reduced to desirable limits. Figure 10 shows the
results of the ambient temperature after additional
chillers were installed to overcome the high
temperature.
High Water Ingress
Groundwater ingress caused problems in the TBM1 and TBM-2 and these were generally dealt with
by providing adequate dewatering measures.
The amount of the ingress water during
tunnel excavation was estimated as relatively
small based on the results of series of geological
investigations and the ground water analysis. The
counter measures were mainly focused on ensuring
the tunnel face was stabilised during excavation.
However, it imperative to be prepared for the worst
case scenario of a large amount of water inflowing
into tunnel, caused by unexpected poor ground
conditions, or the collapse of the work face under
a river. With this in mind, several countermeasures
were taken both inside and outside the tunnel.
A dewatering system with a capacity of 10 tons
per minute was installed at the Junction of Adit1 tunnel and the Main tunnel at the beginning
of the project. However, in order to treat a larger
amount of unexpected water inflow up to 20m3/
min a stop-log utility was prepared at the Junction
to secure enough time for evacuation of the main
machineries and for installation of additional
dewatering equipment.
During the excavation at TBM 1, the ingress
water the total quantity exceeded 16m3/min. A
similarly problem was experienced at TBM 2. As
a result the working area was flooded. The high
water ingress at both TBM’s made it impossible for
the excavation work to continue for safety reasons

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