ABSTRACT
Forty percent of the respondents explained that they use only the minimum steel section for bending whereas 60% adopt the minimum both for bending and for shrinkage control.
60% of the respondents either never design tunnels to be waterproof (15%) or they did it only few times (45%). The most favorite technique to water proof tunnel linings are impervious geomembranes, system (39% of the answers) that has been just introduced in the country. On the other hand this is seconded by a group of more traditional procedures in Brazil that aims the reduction of concrete permeability, by special mix design, special admixtures and controlled curing of the concrete (summing 32,3% of the answers). This group combined with the design of concrete with limited crack widths total 45% of the answers, while 5 to 10 years ago they would count for 100% of the answers.
4 GEOTECHNICAL DESIGN
