1、翻 译 部 分英文原文Spiling bolts and reinforced ribs of sprayed concrete replace concrete LiningKristin H. Holmy, Bent AagaardThis article discusses how and when spiling bolts and reinforced ribs of sprayed concrete should be used to achieve safe progress in poor rock mass conditions. It is discussed when b
2、olting and reinforced ribs of sprayed concrete can replace cast in place concrete as permanent rock support. Examples from the challenging Fryatunnel illustrate how this was achieved in poor to extremely poor rock mass conditions. Numerical models comparing sprayed concrete and cast in place concret
3、e are briefly reported.Keywords: Tunnelling; Rock support; Spiling bolts; Reinforced ribs of sprayed concrete; Concrete lining1. IntroductionThe use of spiling bolts, sprayed concrete and reinforced ribs of sprayed concrete close to the tunnel face has increased in Norwegian tunnels over the last 10
4、 years. It is a consequence of projects with demanding excavation conditions, where tunnelling in weak rock and passing of weakness zones have been substantial.In the same period, the development of sprayed concrete in terms of quality has been fast. Among other things, an alkalifree accelerator whi
5、ch gives the sprayed concrete higher early strength has been developed. Alkali-free sprayed concrete has opened the possibility for spraying thicker layers of sprayed concrete in one round, and is therefore, suitable for support in connection with weakness zones.In Norway there exists a tradition fo
6、r flexible decision on primary support as the tunnel is being excavated. Therefore, many different support alternatives for excavating through weakness zones have been developed. The development has been fast, and it is now important to try to sum up the experience gained about the use of spiling bo
7、lts and reinforced ribs of sprayed concrete in connection with the passing of weakness zones.The fact that spiling bolts and reinforced ribs of sprayed concrete are about to replace concrete lining will be discussed in this paper based on experience from the 5.3 km long Frya tunnel. Some points of v
8、iew on how to make use of spiling bolts and reinforced ribs of sprayed concrete when excavating through weakness zones are given. Also some examples are included that show how the use of numerical modelling can shed light on possible differences between the mode of operation for sprayed concrete in
9、combination with bolts/ribs vs. concrete lining.2. The Frya sub-sea tunnelIn this paper the Fr0ya sub-sea tunnel is used as main example. It is therefore, adequate to present some facts about the Fr0ya tunnel.The Frya sub-sea Tunnel is 5.3 km long and connects the two islands Hitra and Fr0ya on the
10、north-west coast of Norway, West of Trondheim, see Fig. 1. Deepest point is 155 m below sea level, and it has a major part (3.6 km) below the sea, where the rock overburden varies between 37 and 155 m. The two-lane tunnel has a cross sectional area of 50 m2. The maximum gradient is 10.Fig. 1. The Fr
11、ya tunnel, connecting the two islands Hitra and Frya, and the Hitra tunnel connecting the islands to the mainland Norway.The Frya tunnel is the second sub-sea tunnel of the Hitra-Frya Mainland Fixed Link. The 5.7 km long and 264 m deep Hitra tunnel was completed in 1994.The total tunnel cost for the
12、 Fr0ya tunnel (including preinvestigations and contract administration) was 417 million NOK (52 million Euro, 8 NOK= 1 Euro) which equals 78700 NOK/m tunnel. The tunnelling works started in February 1998, with hole-through in September 1999, and opening of the tunnel for traffic in June 2000.Compare
13、d to other, similar projects, rather compre-hensive pre-investigations were carried out. The refraction seismic measurements have shown more of low velocity (weakness) zones than for any of the other sub-sea tunnels constructed in Norway, see Fig. 2. A main geological feature is the Tarva fault whic
14、h can be followed more than 150 km towards NW on the Norwegian mainland. The material in many zones consists of soil-like material (clay, silt, sand and gravel). Often, the clay material shows a high degree of swelling with low strength and low friction properties.The metamorphic rocks in the area a
15、re of Precambrian age with gradual transitions between various gneisses, such as granitic gneiss, micagneiss, and migmatite. The strike of the bedrocks is mainly ENE-WSW with steep dip towards NW.3. Spiling boltsIn this paper, the term spiling bolts refers to the use of rock bolts ahead of the tunne
16、l face. The bolts areinstalled outside the theoretical blasting profile in a fan shaped pattern, often oriented approximately 15 relatively to the tunnel axis, see Fig. 3.Spiling bolts are used to secure the stability before next blast round. When spiling bolts are used, the danger of any fall-outs is reduced so that it is much easier to maintain the correct profile until rock support after bla
