TBM Tunneling - Rock Mechanics Based on an Anisotropic Jointed Rock Model - page 674

crete can be constructed using a Gripper TBM. The shotcrete membrane is usually
installed in the backup area. The internal lining is installed after completion of the
tunnel or far behind the temporary face. It can be constructed as impermeable con-
crete structure or with a sealing foil between the shotcrete membrane and the cast-
in-place concrete lining to avoid water inflow into the tunnel during operation (Fig.
21.12, upper).
Using a shielded TBM, the lining segments are erected under the protection of the
tail skin. Two different construction methods are used, single lining and double lining.
In the single lining construction method the segmental ring represents the temporary
support as well as the final lining. The longitudinal and circumferential joints are sealed
with gaskets (Fig. 21.12, lower left). In the double lining construction method the lining
consists of an external segmental ring and an internal cast-in-place concrete lining. Be-
tween the external and internal lining a sealing foil is arranged. When applying the dou-
ble lining construction method the annular gap is frequently filled pneumatically with
pea gravel. The latter can be post-grouted with cement-based suspension (Fig. 21.12,
lower right).

21.2 Stability of the Temporary Face and Shield Design, Example

21.2.1 Project
The railway line along the western coast of Sweden, the so-called “West Coast Line”,
connects Copenhagen via Malmö and Gothenburg with Oslo. Within the overall mod-
ernization of the Swedish railway network, the West Coast Line was extended to a
double-track line and upgraded for high-speed trains. A major bottleneck of this con-
nection was the bypass of the Hallandsas ridge formed by a single track line with lim-
ited capacity and a maximum speed of 80 km/h only. With the construction of the
Hallandsas tunnel, the line crosses the Hallandsas ridge with two single track tubes, and
the speed is increased to 200 km/h (Fig. 21.13).

Hallandsas ridge, being a horst, is under-crossed by this tunnel with an overburden of
up to 150 m. The two tunnel tubes were constructed with an internal diameter of ap-
prox. 9 m and a length of 8.6 km each (Figs. 21.13 and 21.14). The tubes were connected
with cross-cuts at 500 m intervals or less.
During construction between 2004 and 2007 problems occurred in connection with wa-
ter inflow into the tunnel, lack of stability of the temporary face and extreme wear of
the cutterhead and other TBM components. These led to large delays and cost increases.

In the following, the reasons for the encountered problems are outlined, with the inten-
tion of avoiding such problems in the future as far as possible. This presentation to a
large extent follows an article published by Lundman et al. (2009).