Permanent Lining Research Articles

US tunnel rim nears full circle : Byrd, T New Civ Engr17 Jan 1985, P29–31

Mount Baker Ridge Tunnel is being built in Seattle, to an external diameter of 25.3 m from the perimeter inwards by the stacked drift methd. Small horshoe section drifts at 2.9 m centres are being driven around the bore's circumference then filled with concrete to form a permanent lining. The 400 m long tunnel is being bored to take two roadway levels of a new interstate highway through the ridge in the least destructive manner. Piled circular access pits were firstly built at both portals, and then broken through using a roadheader. Subsurface settlement, which was limited to 25 mm was found to be 75 mm on the second drift at a depth of 60 m. This level was repeated in the third drift without any explanation, but the specified level has not been exceeded since. On average, 15 days are taken to reach the far portil when the 55 ton backhoe shields are carried round by truck. Concrete is pumped along a slick line suspended from the crown and withdrawn as the drift fills. A design review board and a disputes review board have been set up to settle any unexpected issues on site. (TRRL)

Shotcrete as permanent lining for the Furka Base Tunnel : Amberg, R; Sala, A Rock Mech Rock EngngV17, N1, Jan–March 1984, P1–14

Shotcrete as permanent lining for the Furka Base Tunnel : Amberg, R; Sala, A Rock Mech Rock EngngV17, N1, Jan–March 1984, P1–14

Schotcrete as permanent lining for the Furka base tunnel

The lining concept of the 15.4 km long one-track Furka railway tunnel is described with particular emphasis on shotcrete application as a permanent support Altogether 70000 m3 dry aggregate/ cement mix and 115000 rock bolts have been applied. The tunnel was lined at a rate of approx. 400 tunnel metres per month using up to five shotcrete machines simultaneously. Systematic quality control throughout the construction work indicated an average uniaxial compressive strength of shotcrete of 40 N/mm2. The support requirements were grouped into 16 different classes and an additional special class accounting for extreme geological conditions in some relatively short stretches.

Design of tunnel lining in rock for long term time effects

Excavation of underground openings in rock relieves the in situ state of stresses, providing an initiating mechanism for time-dependent deformation in shaly rocks to occur. The construction of a permanent lining restrains the rock movement, resulting in an increase with time of pressure acting on the lining.Closed form solutions for this problem of rock structure – time interaction of circular tunnels have been developed, taking into account (a) the state of initial stresses, (b) the time-dependent properties of the lining as well as the rock, and (c) the time lapsed between excavation and lining. Expressions for lining pressures, stresses, thrusts, and moments are given for both "no slip" and "full slip" interface conditions.The effects of material parameters, lining flexibilities, and time lapse on quantities of engineering interest are studied and their implications on design illustrated.The results of analysis are compared with the field observations made in three tunnels. It is shown that the theoretical results are consistent with the observed extent and location of cracking in these tunnels.It is suggested that the methods proposed may be used for design considerations of permanent linings of tunnels in rock exhibiting significant time-dependent deformation.

Erosion Control Along Transportation Routes in Northern Climates

The widespread occurrence of permafrost in northern climates dictates the use of specialized measures to protect the terrain from adverse impacts associated with the construction of transportation facilities. Through the adoption of appropriate construction techniques and by providing proper drainage and erosion control facilities within the right-of-way, serious environmental degradation can be avoided. The most appropriate type of erosion control measure is selected according to local terrain and drainage conditions, including a Soil Erosion Code (SEC). Erosion control begins with the provision of effective drainage across the right-of-way. Typical erosion control measures include the use of permanent linings such as granular blankets, rock riprap and gabions and temporary linings, such as plastic sheets and fiberglass rovings. Ditch checks, rock aprons, energy dissipators and siltation basins may be used to minimize erosion of exposed soils along the route and attendant siltation of streams. Cut slopes may be protected with insulation in ice-rich, fine-grained soils to ensure stability and prevent slump material from reaching the drainage system. Ultimately, long-term erosion protection along transportation corridors is provided through appropriate revegetation techniques, periodic surveillance and regular maintenance of drainage and erosion control facilities.Key words: erosion, erosion control, permafrost engineering, revegetation, transportation corridors

Provisional support, primary and permanent lining at the construction of the stations of the Budapest underground : Greschik, G K Proc 4th Congress International Society for Rock Mechanics, Montreux, 2–8 Sept 1979, Vol 1, P425–430. Publ Rotterdam, A A Balkema, 1979

Provisional support, primary and permanent lining at the construction of the stations of the Budapest underground : Greschik, G K Proc 4th Congress International Society for Rock Mechanics, Montreux, 2–8 Sept 1979, Vol 1, P425–430. Publ Rotterdam, A A Balkema, 1979

Anchored shotcrete used as permanent lining of underground openings in rock (in German) : Bischoff, N; Kellenberger, J; Hagmann, A J Proc 4th Congress International Society for Rock Mechanics, Montreux, 2–8 Sept 1979, Vol 1, P333–340. Publ Rotterdam, A A Balkema, 1979

Anchored shotcrete used as permanent lining of underground openings in rock (in German) : Bischoff, N; Kellenberger, J; Hagmann, A J Proc 4th Congress International Society for Rock Mechanics, Montreux, 2–8 Sept 1979, Vol 1, P333–340. Publ Rotterdam, A A Balkema, 1979

Soft ground tunnelling problems solved in German metros : Martinek, K Tunn Tunnlg, V11, N9, November 1979, P41–47

The construction of the first section of the S-bahn underground railway networks in Frankfurt and Stuttgart has provided the stimulus for the development of soft-ground tunnelling techniques. After its completion, the 6.1 km Frankfurt network will connect the eastern and southern suburban lines. Geological conditions consist of gravelly sands on a formation of clay marl. Four parallel single-track 7 M diameter tubes were shield-driven with a permanent lining of cast iron segments. Subsidence was avoided by the injection of mortar between the segments and soil. The covering gravel was consolidated by an injection of a bentonite suspension. The article details the use of cut-and-cover methods and the New Austrian Tunnelling Method at the crossing of the S-bahn station at Frankfurt station. A further 385 M tunnel was constructed by the NATM under main streets and buildings.

Use of shotcrete for permanent linings underground : Sjostrom, O Proc 1st International Symposium on Storage in Excavated Rock Caverns (Rockstore 77), Stockholm, 5–8 Sept 1977, V3, P585–591. Publ Oxford: Pergamon Press, 1978

Use of shotcrete for permanent linings underground : Sjostrom, O Proc 1st International Symposium on Storage in Excavated Rock Caverns (Rockstore 77), Stockholm, 5–8 Sept 1977, V3, P585–591. Publ Oxford: Pergamon Press, 1978

Measurements on a tunnel lining in very dense till

Measurements were made on a 4.3 m (14 ft) bored diameter, 3.0 m (10 ft) finished diameter tunnel for a sewer in Mississauga, Ontario. Measurements included deformation of the flexible temporary lining, pressures on the temporary and rigid concrete permanent linings, soil deformations and surface settlements as the tunnel was excavated, and the effect of the tunnel on groundwater levels.Because of the stiffness of the very dense till and the method of construction it was found that during the period of measurement the tunnel opening deformed and was largely self-supporting. Some increase of loads on the linings with time was observed, but the rate of increase was almost negligible after 6 months. The water table around the tunnel was lowered as the tunnel and the surrounding pea gravel fill acted as a drain.Indications are that the tunnel has nearly uniform all-around pressure on it, considerably less than the overburden pressure, and, therefore, that it could be considered in ring compression without bending moments in either lining. If bending moments are not present, the permanent lining could be reduced from the 460 mm (18 in.) used to half that thickness or less and still be quite conservative in supporting all-around loads equal to the overburden pressure and providing for wear.

Geotechnical performance of a tunnel in till

Two parallel tunnels were built in 1976 as part of the first phase of the Edmonton Rapid Transit System. The tunnels, approximately 250 m long, 6 m in diameter, and having centres 11 m apart have been driven in downtown Edmonton with an average of 7.5 m overburden above the crown. The tunnels were located entirely within a dense, jointed till sequence of Wisconsin age.The tunnels were advanced using a mole followed by two systems of soil support. The temporary supporting system consisted of steel ribs and timber lagging while the permanent lining was cast-in-place reinforced concrete. To reduce drag friction, the cutting profile of the mole is about 20 mm larger than the diameter of the shield. The steel ribs are expanded into place by hydraulic jacks.Two finite element analyses were performed. One predicted surface settlements and the other predicted lining stresses. The settlements predicted for a single tunnel agreed closely with observed values but the observed amount was considerably more than predicted for both tunnels. The reasons for this are suggested as being due to a cross tunnel connecting the two main tunnels and to a decrease in stiffness of the soil mass brought about by the moling of the first tunnel.in situ assessment of stresses in the ribs was not successful due largely to the fact that the ribs were not expanded entirely against the soil. Thus comparisons with predicted values could not be made and values of the earth pressure at rest could not be established. However, rib deformations were essentially complete within a few days thus confirming the essentially time-independent character of the deformational behavior of the till.

Tunnels in bedded rock with high horizontal stresses

Sustained growth in urban development in southern Ontario has led to an increased activity in tunnelling in rocks. These sedimentary rocks are bedded and anisotropic in behaviour, In situ horizontal stresses considerably higher than the vertical overburden pressure exist in these rock formations. The combination of these two factors, together with the difficulties encountered in recent tunnelling projects, necessitates a reappraisal of current design concepts.Theoretical studies show that, because of these two factors, high stress concentration occurs at the crown and invert, causing failure in the weaker layers of the bedded rocks. In addition, the pattern and sense of movement are reversed when compared to 'normal' conditions of in situ stress state.Field observations made in three tunnels are described. The instability at the roof and floor and the observed pattern of radial displacements are consistent with the approach employed.Some requirements for temporary support under these conditions are outlined. Available field data on the timedependent deformation of these openings are presented and the consequent influence on the choice of permanent lining is discussed.

Karl Terzaghi and the Chicago Subway

Terzaghi's engagement on the Chicago Subway, 1939-1941, influenced his decision to take up permanent residence in the United States and had a strong impact on the development of applied soil mechanics. So-called squeeze tests, in which the settlements and subsurface movements were correlated with construction procedures, permitted improvements in construction methods and decreases in lost ground. Measurement of loads in bracing of open cuts led to better understanding of behavior of soft clay in undrained shear. Full-scale test sections provided basis for more economical design of permanent tunnel lining. All these activities evolved under Terzaghi's stimulation and in turn helped formulate his conceptions of the ways in which soil mechanics should be applied in practice.