The FEBEX benchmark test: case definition and comparison of modelling approaches

Abstract

The FEBEX (Full-scale Engineered Barriers Experiment in Crystalline Host Rock) ''in situ'' test was installed at the Grimsel Test Site underground laboratory (Switzerland) and is a near-to-real scale simulation of the Spanish reference concept of deep geological storage in crystalline host rock. A modelling exercise, aimed at predicting field behaviour, was divided in three parts. In Part A, predictions for both the total water inflow to the tunnel as well as the water pressure changes induced by the boring of the tunnel were required. In Part B, predictions for local field variables, such as temperature, relative humidity, stresses and displacements at selected points in the bentonite barrier, and global variables, such as the total input power to the heaters were required. In Part C, predictions for temperature, stresses, water pressures and displacements in selected points of the host rock were required. Ten Modelling Teams from Europe, North America and Japan were involved in the analysis of the test. Differences among approaches may be found in the constitutive models used, in the simplifications made to the balance equations and in the geometric symmetries considered. Several aspects are addressed in the paper: the basic THM physical phenomena which dominate the test response are ARTICLE IN PRESS www.elsevier.com/locate/ijrmms 1365-1609/$ -see front matter r

Exploring the concept of compressed air energy storage (CAES) in lined rock caverns at shallow depth: A modeling study of air tightness and energy balance

“…The permeability of the concrete lining is significantly smaller than that of the rock mass, which is also reasonable considering the presence of natural fractures in the rock mass. Using the van-Genuchten model [19], the water-retention and relative permeability curves are taken from a previous study of water retention properties around a tunnel in fractured crystalline rock [20,21]. In the base-case simulation, the retention properties of the concrete are here set to be equivalent to that of the rock.…”

Thermo-hydro-mechanical processes in fractured rock formations during a glacial advance

“…The longevity constraints with regard to the safety of deep geologic sequestration of high level radioactive waste suggest that the conventional scientific approaches to the investigations that involve laboratory and field studies must be complemented by approaches that will allow for predictions on timescales that are beyond conventional geological engineering activities involving underground facilities (Laughton et al, 1986;Chapman and McKinley, 1987;Selvadurai and Nguyen, 1997;Rutqvist et al, 2005;Alonso et al, 2005). Current concepts for deep geologic storage require an assessment of the geological setting containing a repository to account for geomorphological processes that can occur over timescales of several thousands of years.…”

Characterizing Excavation Damaged Zone and Stability of Pressurized Lined Rock Caverns for Underground Compressed Air Energy Storage

“…In Table 2, we also include values (within parenthesis) that indicate properties for less compliant EDZ conditions that we used for model comparison. Values for water retention and the relative permeability curve in the van Genuchten model (van Genuchten, 1980) as well as the gas relative permeability governed by Corey's model (Corey, 1954), were referred to previous studies of a tunnel in fractured rock (Finsterle and Pruess, 1995;Alonso et al, 2005). In theory, thermal properties of EDZ could affect the results of thermodynamic analysis especially when wide range of temperature is concerned.…”

“…In theory, thermal properties of EDZ could affect the results of thermodynamic analysis especially when wide range of temperature is concerned. However, numerous in situ heater experiments in fractured rock masses such as the Kamaishi mine heater experiment in Japan (Rutqvist et al, 2001), the FEBEX in situ test at Grimsel test site in Switzerland (Alonso et al, 2005) and the Yucca Mountain drift scale test, in Nevada, U.S. (Rutqvist et al, 2008) have shown a that precise temperature evolution could be predicted by numerical modeling without using different thermal properties in the EDZ. This can be explained by thermal conduction and storage being controlled by matrix thermal properties, whereas fracture porosity is usually very low.…”