Reclaiming The Underground Space - Volume 1

Proceedings of the ITA World Tunneling Congress, Amsterdam 2003.

International Tunnelling Association, J. Saveur

• Publisher: Routledge
• Year: 2022
• Print ISBN: 9789058095435
• eBook ISBN: 9781351419536
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Civil Engineering
• Index: Technology & Engineering

This book contains papers, presented at the ITA World Tunnelling Congress 2003 held in Amsterdam, which reflects the state of the art with regard to research, analysis, design and practical experience in almost all fields of tunnelling and underground space construction.

Rock tunnelling

Motorway tunnelling through the karstic rocks and active seismic faults of Kakia Skala

V. Avramea, A. Kalkantzi, I. Sakkas, E. Sarantopoulou

PATHE Motorway, Athens, Greece

A.I. Sofianos

School of Mining and Metallurgy, NTUA, Athens, Greece

ABSTRACT: The Kakia Skala motorway project includes tunnels with very large cross sections 200m². These are passing through limestone rocks that are tectonically faulted and brecciated. The faults are considered as active. Further, the rock formations are heavily karstified, and in some cases the karst voids fill a large portion of the tunnel section. The use of appropriate support measures, careful drilling and probing, allowed for the successful construction of the project. Finally, the cross section of the tunnels close to the active faults was further enlarged in order to accommodate any offset due to a serious seismic event.

1 THE PROJECT

The Athina–Korinthos highway (Figure 1) is one of the two main portals connecting the capital with the rest of Greece. It consists of two lanes in each direction, that are loaded with heavy traffic, especially at the weekends; this load is expected, according to last estimates, to increase further. In order to accommodate it, the existing national road is to be transformed into a three lane, in each direction, high-speed motorway.

Kakia Skala is situated in this highway about 50 km west of Athina, at the northern coast of Saronikos bay. The relief of the area is intense as a result of tectonic events that have taken place during the alpine orogenesis and neotectonic movements. The existing national road includes parts that follow the contour lines, forming thus large curvatures. Realignment was therefore considered necessary to satisfy the motorway standards; this necessitated the reconstruction of an 8 km long part of the highway (Figure 1).

In order to pass under the successive saddles along the improved alignment, two twin tunnels (AΣ1–AΣ2), and a single branch tunnel (AΣ3) are constructed, the total length of which is 3806 m. The width of the motorway there will be uniform with no narrowing parts in the tunnels. These tunnel sections thus comprise of three lanes, an emergency lane and pavements. They are the largest tunnels constructed in Greece and Europe; their excavation width reaches 19 m and their excavation height 12 m.

Figure 1. Map of PATHE highway.

Construction started in 2000, and completion of the project is anticipated by the year 2003. Three of the tunnels are already completed, while a twin tunnel is still under construction. While the whole project is under construction, the existing national road and the nearby passing railway continue their operation.

2 LOCAL GEOLOGY

The area of Kakia Skala belongs to the Ypopelagoniki geotectonic zone. The geological structure of the area comprises the following formations:

• • Middle – Upper Triassic limestones, dolomitic limestones and dolomites, white, yellow and grey, thick bedded to massive, biomicrites. Thin dolomitized intercalations locally occur. They are karstified mainly along discontinuities.
• • The sedimentation of Triassic limestones stopped during Jurasssic-Lower Cretaceous due to retraction of the sea. During this period boxitic deposition occurs of brownish, red colour and pisolithic texture, which fills up limestone cavities of Triassic age.
• • Upper Cretaceous limestones, marly limestones, marls which overlay transgressively the Triassic beds. These formations in the upper members are thick bedded to massive, grey to black-grey, biomicrites to sparites alternating with yellow to yellowbrown marls and marly limestones. In the area of the Kavallaris Mountain they cover small boxitic occurrences.
• • The recent formations of the area are mainly recent to old scree and talus cones, which are lightly to heavily cemented and form steep slopes. These formations consist of angular limestone fragments, enclosing limestone blocks. The cement is reddish, clayey to marly.

Triassic limestones are met at the western and central part of Kakia Skala project and tunnels A Σ 2 and A Σ 3 are excavated in these formations. They are karstified to the surface of the area (Figure 2) as well as to the depth of the tunnels. The karstic formations are developed along faults and joints, and are either open or filled with fine material, boulders or both. No water is encountered either as water bearing strata or as karstic contacts filled with water. Generally, these limestones are massive at the project area, but they are heavily fractured near fault zones.

At the eastern part of the project area Cretaceous limestones are met. At these formations karstification is much less developed or even absent. They are fractured to heavily fractured, especially near fault areas. In places they are brecciated and incoherent, and can be mistakenly considered as scree.

Figure 2. Surface karstification.

Figure 3. Cover and cut construction in the scree area.

Talus cones and scree were met at the western portal (Figure 3) of AΣ3 tunnel, which was constructed with the cover and cut method.

3 TECTONICS

The intense relief of Kakia Skala area is characteristic and is the result of tectonic actions that have taken place during alpine orogenesis as well as neotectonic movements. This zone is part of the northern margin of the tectonic basin of Saronic Bay (Mariolakos and Papanikolaou, 1982). Many faults are present with characteristic smooth fault surfaces of great extent. This fault zone extends from the top of the Kavallaris Mountain down to the sea mainly by a set of sub – parallel normal faults that have a general direction E–W while a numbe...

Table of contents

• Cover
• Half Title
• Title Page
• Copyright Page
• Table of Contents
• Preface
• Organisation
• Opening address
• Keynote lectures
• Underground space use
• Underground space construction
• Sustainability of underground space
• Safety
• Immersed tunnels and submerged floating tunnels (SFT)
• - Presentation in the ITA open session
• Cut-and-cover tunnelling
• Rock tunnelling
• Author index