A study for enabling uncertainty evaluation of geological/geotechnical three-dimensional model in construction projects

抄録

Applications of the BIM (Building Information Modeling) to civil engineering and construction industries have been started in Japan, under the initiative of Ministry of Land, Infrastructure and Transport of Japan. In the BIM for infrastructure, geological/geotechnical investigation results are transformed into a 3-D model and are consistently managed as public project information throughout the entire life cycle of an infrastructure to be shared and used among relevant parties. However, it should be noted that geological/geotechnical model is an inferred model with uncertainty, unlike product model for building structure that expresses a visible object based on a design drawing. In order to reduce such risks of improper designing that the accuracy of geological/geotechnical model is overestimated or misused in the downstream operations, it is important to maintain the records that specify the uncertainty of inferred model along with underlying actual data. We, members of a working group under the ISSMGE ATC10, are working on the following two issues currently; 1) identification of the factors that affect model uncertainty and 2) review of Japanese and international standards on the 3-D modeling. In first issue, based on some examples of construction projects, the factors that affect the model uncertainty and the information to be maintained for downstream processes have been identified. For example, modeling area and the validity for its setting, modeling process, type and position of input data, geologic stratigraphy applied to the model, and rationale for stratigraphic identification are recognized as such factors. In the standard review, a total of 51 Japanese and international standards related to geological/geotechnical survey have been reviewed and we recognize that there are descriptions of requirements for the reliability of the 3-D model. Some terms such as 'geological model' and 'geotechnical model' are found to have been used in different meanings and causes confusions among stakeholders, so we are defining and categorizing some important terms such as geological model, geotechnical model, geotechnical information, uncertainty and reliability. We continue to examine the actual description methods and formats that allow the information related to uncertainty is handed over to the downstream processes so that the uncertainty can be re-evaluated afterward. We plan to include the final outcomes of this study in "JAPANESE GEOTECHNICAL SOCIETY STANDARDS: Geotechnical and Geo-environmental Investigation Methods”.