The use of TBM process data as a normative basis of the contractual advance classification for TBM advances in hard rock

In April 2016 a newly formed working group began with the revision of the Austrian standard ÖNORM B 2203‐2. The goal of the group was the establishment of a practicable advance classification scheme, which would be applicable both for the design and for the construction phase. In addition, a clear separation should be established between a regular advance, which is clearly described and can be calculated by the bidding contractor, and a ”hindered advance“, which cannot clearly be described and calculated. The contractual framework is used to compensate for the regular advance, and hindering occurrences such as water ingress or increased wear are compensated by additional contractual time‐dependent costs. Fair compensation regulations for hindered advance (such as an advance through blocky rock mass, mixed face conditions, swelling, squeezing ground, major face instabilities, increased adhesion and stickiness of muck, obstacles and suspension losses) are to be defined as well. The method presented in this paper and based on systematic TBM data evaluation achieves both the goal of contractual advance classification and the goal of establishing a simple threshold differentiating regular advance and hindered advance.