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The tunnel passes through the Pindos flysch formation, which consists of argillaceous schist and claystone with occasional sandstone. There is intense closed folding and related breakage as well as closely spaced thick shear zones containing soft clayey material. Intense weathering phenomena were also encountered. Large-scale deformation and slippage of the foot of the support occurred due to the squeezing potential of the ground in relation to the deep overburden (150 m). Monitoring of the excavation stages was carried out using extensometers, convergence measurement and floor heave measurement. Tests to determine the swelling potential of the rock were also undertaken. It was found that the original 6 m long rock bolts did not extend outside the plasticized zone of the rock mass, resulting in propagation of the loosening zone and deformation. Rock bolts with a length similar to the tunnel diameter (9-12 m) were installed to tackle the problem., The tunnel passes through the Pindos flysch formation, which consists of argillaceous schist and claystone with occasional sandstone. There is intense closed folding and related breakage as well as closely spaced thick shear zones containing soft clayey material. Intense weathering phenomena were also encountered. Large-scale deformation and slippage of the foot of the support occurred due to the squeezing potential of the ground in relation to the deep overburden (150 m). Monitoring of the excavation stages was carried out using extensometers, convergence measurement and floor heave measurement. Tests to determine the swelling potential of the rock were also undertaken. It was found that the original 6 m long rock bolts did not extend outside the plasticized zone of the rock mass, resulting in propagation of the loosening zone and deformation. Rock bolts with a length similar to the tunnel diameter (9-12 m) were installed to tackle the problem.

The project involves the construction of a 6 km long road tunnel, passing beneath the Hvalfjordur fjord, through basalts with intercalating sedimentary beds and coarse-grained sediments and conglomerates. Two relatively dense subvertical fault and dyke systems exist and groundwater flows are expected to be pronounced where these cross the tunnel. Grouting ahead of the tunnel face is being carried out to alleviate this. Seismic surveys indicate that the sediments are up to 100 m thick and that a deep trench has been cut into the bedrock near the northern shore of the fjord. Seismic risk analysis has been carried out to evaluate the effects of possible fault movements on the tunnel. Tunnelling will be by drill and blast, with cut and cover being used for the portals. Both plain and fibre-reinforced set-mix shotcretes are being used for support, with double corrosion-protected rock bolts. Excavation started in June 1996 and the tunnel is due to be completed in 1998/9., The project involves the construction of a 6 km long road tunnel, passing beneath the Hvalfjordur fjord, through basalts with intercalating sedimentary beds and coarse-grained sediments and conglomerates. Two relatively dense subvertical fault and dyke systems exist and groundwater flows are expected to be pronounced where these cross the tunnel. Grouting ahead of the tunnel face is being carried out to alleviate this. Seismic surveys indicate that the sediments are up to 100 m thick and that a deep trench has been cut into the bedrock near the northern shore of the fjord. Seismic risk analysis has been carried out to evaluate the effects of possible fault movements on the tunnel. Tunnelling will be by drill and blast, with cut and cover being used for the portals. Both plain and fibre-reinforced set-mix shotcretes are being used for support, with double corrosion-protected rock bolts. Excavation started in June 1996 and the tunnel is due to be completed in 1998/9.

A new 2.1 km road link is to be built which will include a 780 m long single carriageway two-lane road tunnel excavated through chalk. 240 m will be constructed using cut and cover and the rest will be bored and have a sprayed concrete lining. Preliminary ground investigations were carried out to build up an initial picture of conditions along the tunnel route. Large diameter coring, both horizontal and vertical, was used for more detailed studies of fracture frequency, chalk grade, strength and stiffness. The surface wave geophysics technique was used through areas where intrusive ground investigation was not permitted. Plate bearing tests were also carried out but results from these were found to be unreliable. Results suggest that loose rock conditions could occur adjacent to faults along the tunnel route and where persistent, dilated subhorizontal discontinuities are present. Anisotropy in in-situ chalk stiffness is also anticipated throughout the tunnel., A new 2.1 km road link is to be built which will include a 780 m long single carriageway two-lane road tunnel excavated through chalk. 240 m will be constructed using cut and cover and the rest will be bored and have a sprayed concrete lining. Preliminary ground investigations were carried out to build up an initial picture of conditions along the tunnel route. Large diameter coring, both horizontal and vertical, was used for more detailed studies of fracture frequency, chalk grade, strength and stiffness. The surface wave geophysics technique was used through areas where intrusive ground investigation was not permitted. Plate bearing tests were also carried out but results from these were found to be unreliable. Results suggest that loose rock conditions could occur adjacent to faults along the tunnel route and where persistent, dilated subhorizontal discontinuities are present. Anisotropy in in-situ chalk stiffness is also anticipated throughout the tunnel.

The road tunnel, in Holland, is to be built by TBM under the river Oude Maas through soft soils. Laboratory studies have been undertaken to predict, measure and evaluate lining behaviour in the tunnel. Different structural models of a circular concrete segmental tunnel lining were analysed, with models varying from simple bedded beam models to sophisticated 3-D finite element models. Rotational stiffness of the joints is one of the essential input parameters. It was possible to obtain a range of deformations, bending moments, shear forces and hoop forces in segmental lining under structural loads including joints influence on tunnel lining behaviour. A comparison is presented between the laboratory experiments of the joints and the numerical modelling., The road tunnel, in Holland, is to be built by TBM under the river Oude Maas through soft soils. Laboratory studies have been undertaken to predict, measure and evaluate lining behaviour in the tunnel. Different structural models of a circular concrete segmental tunnel lining were analysed, with models varying from simple bedded beam models to sophisticated 3-D finite element models. Rotational stiffness of the joints is one of the essential input parameters. It was possible to obtain a range of deformations, bending moments, shear forces and hoop forces in segmental lining under structural loads including joints influence on tunnel lining behaviour. A comparison is presented between the laboratory experiments of the joints and the numerical modelling.

The Norwegian Public Roads Administration is carrying out research into the durability of sprayed concrete linings. Aspects covered include linings in entrance zones, sub-sea tunnels and frost zones, rock bursts, fire protection, dry rock, rock support behind water and frost protection constructions and material technology and implementation. It has been found that the production and application of the concrete has a major influence on durability, with reduced durability occurring due to deviation from the original implementation procedure. Low permeability, correct thickness and material quality are key durability factors. The concept of instrumentation, documentation and verification can be used to help develop sprayed concrete systems by documenting the real behaviour of the linings and verifying the design assumptions. Monitoring should be carried out of structure safety, water infiltration/leakage, mechanical properties, bonding, bolting, corrosion and degradation., The Norwegian Public Roads Administration is carrying out research into the durability of sprayed concrete linings. Aspects covered include linings in entrance zones, sub-sea tunnels and frost zones, rock bursts, fire protection, dry rock, rock support behind water and frost protection constructions and material technology and implementation. It has been found that the production and application of the concrete has a major influence on durability, with reduced durability occurring due to deviation from the original implementation procedure. Low permeability, correct thickness and material quality are key durability factors. The concept of instrumentation, documentation and verification can be used to help develop sprayed concrete systems by documenting the real behaviour of the linings and verifying the design assumptions. Monitoring should be carried out of structure safety, water infiltration/leakage, mechanical properties, bonding, bolting, corrosion and degradation.

179 tunnels have been built in South Africa since 1970: 47 water tunnels, 56 associated with dams and pumped storage schemes, 3 road tunnels, 55 railway tunnels and 18 service tunnels. Some of the larger projects are the Orange-Fish, Jonkershoek, Steenbras, Palmiet, Huguenot and Hex River tunnels in Cape Province, the Inanda Wiggins, Drakensburg and Blackhill to Richards Bay tunnels in Natal and the Lesotho highlands water project. Most tunnels have been driven using tunnel boring machines, with shield driving equipment only being necessary for 8 tunnels. Future tunnelling will probably be limited mainly to water resource development projects. Tables are presented giving details of existing and planned tunnels in South Africa., 179 tunnels have been built in South Africa since 1970: 47 water tunnels, 56 associated with dams and pumped storage schemes, 3 road tunnels, 55 railway tunnels and 18 service tunnels. Some of the larger projects are the Orange-Fish, Jonkershoek, Steenbras, Palmiet, Huguenot and Hex River tunnels in Cape Province, the Inanda Wiggins, Drakensburg and Blackhill to Richards Bay tunnels in Natal and the Lesotho highlands water project. Most tunnels have been driven using tunnel boring machines, with shield driving equipment only being necessary for 8 tunnels. Future tunnelling will probably be limited mainly to water resource development projects. Tables are presented giving details of existing and planned tunnels in South Africa.

Two significant collapses occurred during construction of a motorway tunnel through sandstones and shales. The first occurred at the intersection of two fault zones with the stratum above the tunnel being thinly-bedded shale. The tunnels were being driven using drill and blast with a reinforced shotcrete lining and rockbolt primary support system and an in-situ concrete secondary liner. An inflow of water of around 0.5 l/s was noted ten days before the first collapse and distortion of the steel rib occurred. Settlement and other damage was observed a week later, extra bolts were used and water flow declined. The collapse occurred on 12 October 1995, blocking the passage. Water flow at the time of collapse was estimated at around 25 l/s, indicating that the tunnel had driven into a water-bearing layer below the water table. The collapsed material inside the tunnel was strengthened by grouting, inserting drainage pipes and installing bolts, wire mesh and shotcrete. Tunnel drivage recommenced through the rock fall and the position of the old face was recovered on March 5 1996. A second collapse occurred a month later. Probe drilling is being carried out and the voids located are being filled with concrete prior to the recommencement of tunnelling., Two significant collapses occurred during construction of a motorway tunnel through sandstones and shales. The first occurred at the intersection of two fault zones with the stratum above the tunnel being thinly-bedded shale. The tunnels were being driven using drill and blast with a reinforced shotcrete lining and rockbolt primary support system and an in-situ concrete secondary liner. An inflow of water of around 0.5 l/s was noted ten days before the first collapse and distortion of the steel rib occurred. Settlement and other damage was observed a week later, extra bolts were used and water flow declined. The collapse occurred on 12 October 1995, blocking the passage. Water flow at the time of collapse was estimated at around 25 l/s, indicating that the tunnel had driven into a water-bearing layer below the water table. The collapsed material inside the tunnel was strengthened by grouting, inserting drainage pipes and installing bolts, wire mesh and shotcrete. Tunnel drivage recommenced through the rock fall and the position of the old face was recovered on March 5 1996. A second collapse occurred a month later. Probe drilling is being carried out and the voids located are being filled with concrete prior to the recommencement of tunnelling.

A report is given on the planning, design and execution of work to drive a fullface tunnel of 100m2 cross-section through very soft soil. Embedded stones and unchosive layers added to the difficulties that were encountered. The results of ground surveying by boreholes formed the basis of the planning and design of a test tunnel. The results that were obtained from driving the test tunnel showed more favourable soil characteristics and lower ground pressures that had to be taken into account in the design., A report is given on the planning, design and execution of work to drive a fullface tunnel of 100m2 cross-section through very soft soil. Embedded stones and unchosive layers added to the difficulties that were encountered. The results of ground surveying by boreholes formed the basis of the planning and design of a test tunnel. The results that were obtained from driving the test tunnel showed more favourable soil characteristics and lower ground pressures that had to be taken into account in the design.

The Seelisberg tunnel is the current biggest single structure in the Swiss national road network. Each of the two bores has a length of 9.3km. The tunnel cuts the edge between the Vierwaldstattersee and the urnersee. The alignment was selected mainly on the bases of topographical and geological conditions., The Seelisberg tunnel is the current biggest single structure in the Swiss national road network. Each of the two bores has a length of 9.3km. The tunnel cuts the edge between the Vierwaldstattersee and the urnersee. The alignment was selected mainly on the bases of topographical and geological conditions.

The Milchbuck tunnel will take urban motorway SN 1 under a heavily built-up part of Zurich. Besides the difficult ground conditions along this section, there is the additional problem that the large tunnel will pass under some roads and buildings with only 6-8 m of cover. The freezing method was selected for the tunnelling of this section, which removed the need for the large-scale and costly underpinning of buildings., The Milchbuck tunnel will take urban motorway SN 1 under a heavily built-up part of Zurich. Besides the difficult ground conditions along this section, there is the additional problem that the large tunnel will pass under some roads and buildings with only 6-8 m of cover. The freezing method was selected for the tunnelling of this section, which removed the need for the large-scale and costly underpinning of buildings.

Innovative efforts have concerned, in particular, preliminary investigations and reconnaissance work (8 exploration galleries were excavated for 17 tunnels), excavation technology (use of explosives in urban sites and near working structures; use of roadheaders), and control procedures for support stability (strain and pressure measurements). In general, the principles of the New Austrian Tunnelling Method have been applied in construction work. Contractors associated with the works played a major role in the improvements that have been made., Innovative efforts have concerned, in particular, preliminary investigations and reconnaissance work (8 exploration galleries were excavated for 17 tunnels), excavation technology (use of explosives in urban sites and near working structures; use of roadheaders), and control procedures for support stability (strain and pressure measurements). In general, the principles of the New Austrian Tunnelling Method have been applied in construction work. Contractors associated with the works played a major role in the improvements that have been made.

During construction the geotechnical working team employed a systematic use of the Barton, Bieniawski and Wickham geomechanics classification schemes, at the same time checking the convergence deformations of all tunnels. Quality indexes from the three classifications are compared to give correlations from data that have emerged during excavation to date. A relationship between rock bolt behaviour and specific rock qualities is established, and convergence measurements are analysed in terms of rock quality., During construction the geotechnical working team employed a systematic use of the Barton, Bieniawski and Wickham geomechanics classification schemes, at the same time checking the convergence deformations of all tunnels. Quality indexes from the three classifications are compared to give correlations from data that have emerged during excavation to date. A relationship between rock bolt behaviour and specific rock qualities is established, and convergence measurements are analysed in terms of rock quality.