Development of a water‐permeable annular gap fill for single‐shell drained segmental linings

Abstract

Nowadays, tunnels with single‐shell segmental lining are often constructed pressure‐tight using gaskets. The economic application limit of this construction type is about 50 metres head of water. If the water pressure exceeds this value, considerably more complex – and thus more expensive – two‐shell construction with an additional drainage layer between the inner and the outer lining is required. To extend the field of application of mechanized tunnelling with single shell lining in mid‐mountain formations, an innovative approach was developed based on the application of a drainage layer in the annular gap fill with a water permeability kF >10–4 m/s. The basic idea of the newly developed water‐permeable material for annular gap grouting is the use of a foam generator without a disturbing body, which foams the cement suspension in a defined way with sufficient compressive strength. Complex interrelations of material, process engineering and construction had to be considered comprehensively. The overall suitability of the developed process has been demonstrated in an extensive experimental program including field tests. The present paper focuses on the development of the construction material.