Rock Engineering Design of Splay and Anchor Chambers at Langenuen, Norway

ABSTRACT: Underground space development through hard, blocky rock in Norway is a mature industry, however developing a sustainable engineering foundation design suitable to support the longest suspended aluminium bridge deck in the world is a unique challenge. As part of the E39 highway upgrade programme, the foundation design of the proposed Langenuen Bridge, which is an aluminium suspension bridge which will span 1200 m from Jektavik in the west to Grovaneset in the east, was successfully delivered. This is achieved via cable anchors, and related underground works for their installation, which provide resistance against the uplift force from the main bridge cables. Adequate representation of the ground resistance is provided through rigorous rock mass characterisation and classification based on a preliminary suite of laboratory and in situ test data developed over multiple phases of ground investigation and geological fieldwork. Advanced numerical modelling was employed to capture complex ground behaviour at the foundation. The results demonstrate that the rock mass provides adequate resistance against the bridge cable loads. Furthermore, the undertaken analysis will assist in the design of appropriate support measures for the mined rock chambers as part of the required works for the cable installation. This paper provides an insight into the collaborative partnership between Statens Vegvesen (SVV), Aas-Jakobsen (AAJ) and Arup, which delivered verification of the concept design of the bridge cable anchorage system provided by Multiconsult and their sub-consultants.