This diploma thesis is part of the research activities for the development of an innovative contract and compensation model for mechanized tunnelling at the Institute of Interdisciplinary Construction Process Management Research Unit of Construction Process and Methods. Various possibilities for the evaluation of the scope of changed construction conditions will be shown and one of those the reference section modelling is examined in detail. At the beginning the consequences and the handling of changed construction conditions are explained, based on a comprehensive literature review. A consistently definition of various important terms, regarding the determination of the scope of non-contractual services, is established. Some methods to calculate this scope are listed. Furthermore, the current regulations for compensation and separation of risks in mechanized tunnelling are shown in order to establish a connection and to create a better understanding of the difficulties in calculation and compensation. This diploma thesis refers only to the conditions in Austria. Therefore, an analysis of the Austrian code ÖNORM B 2203-2 and the Guideline for the Geotechnical Design of Underground Structures with Mechanized Excavation of the Austrian Society for Geomechanics (ÖGG) is done. By considering the standard service items of Standardisierte Leistungsbeschreibung Verkehr und Infrastruktur (LB-VI) of the Austrian Research Association for Roads, Railways and Transport (FSV) the possibility to integrate the alternative compensation model into tenders and to compensate it according to current contractual standards is to be examined. In a further step, a detailed analysis of the reference section model will be carried out as an approach to alternative compensation. The model already has been used in a modified form in a project in Austria. An understanding of the functionality of the model and its role to compensate non-contractual circumstances and separate the risks between the contracting parties shall be created and limits for its application shall be established. The classification of the reference section model into the data flow of a mechanized tunnelling job-site will be considered in order to demonstrate the potential of digital data acquisition and automatic data processing. In addition to the evaluation of the model, a number of experts from the fields of tunnelling, contract and claim management will be interviewed on the subject in order to determine the expertise currently available in the circle of experts.