Hydrogeological instrumentation, ANDRA Rock Laboratory CMHM

The hydrogeological characterisation of the host rock plays an important role in the investigation programme of the ANDRA CMHM Rock Laboratory. To monitor pore water pressures, permeabilities or temperatures of the rock over many years in connection with excavations of new galleries and their ventilation, observation wells equipped with packer systems are needed.

Multi-packer systems

Instrumentation of boreholes with multi-packer systems is part of Solexperts' core competence. Since the foundation of Nagra's Grimsel rock laboratory in 1982, we have equipped countless boreholes for a wide range of rock laboratory experiments. With our 40 years of expertise, we can now offer packer systems for a very wide range of applications and boundary conditions; be it high temperatures or high pressures, inert surfaces or minimised interval volumes, or integration of fibre optic cables for temperature or strain measurements. We are pleased that with the fifth framework order in a row, the success story continues for 4 years.

Challenges

The host rock Callovo-Oxfordian places high demands on the instrumentation. Since the hydraulic permeability of the clay rock is extremely low, the systems must be very stiff and the volumes of the observation intervals must be very small to reduce the influence of the packer systems on pore water pressure measurements and permeability tests. In addition, the systems must be quickly installed because the boreholes are only stable for a short period, depending on the orientation in the stress field of the rock .