Theoretical and experimental study of external water pressure on tunnel lining in controlled drainage under high water level

To reduce environmental effects due to free tunnel drainage, a controlled drainage scheme is proposed for tunnels under high water level, for which there is no code provision for tunnel design. A suitable structure form is suggested and the distribution of water pressure on tunnel lining is studied by theoretical analysis, indoor test and field measurement. The study indicates that the grouting zone cannot reduce water pressure on lining with complete waterproofing, only when drainage measure is taken can the grouting zone be effective in reducing water pressure on lining. It is also shown that there exists an optimum size for grouting zone, increase of the size of grouting zone may not unlimitedly reduce the water pressure on lining. (C) 2007 Elsevier Ltd. All rights reserved.