Hillerslev outcrop chalk

A field trip was made to the Hillerslev outcrop chalk quarry located in the northern part of Jutland. Here, a (global) fracture description was carried out and twelve chalk block specimens were sampled. A (local) fracture description was carried out on eight Hillerslev outcrop chalk specimens.
The main orientation NNE-SSW and the secondary orientation NNW-SSE was found in all three fracture data sets in the Ph.D. project. A comparison of the measured Joint Roughness Coefficient (JRC) and fracture aperture for all Ph.D. fracture data shows that some of the fractures along the chalk wall were disturbed which apart from the influence of excavation may be due to weathering near the chalk wall.
Fracture description and sampling carried out in the Hillerslev chalk quarry during ”Fractures and Rock Mechanics”, phase 1 and 2 was compared to the work presented in this report (Ph.D. project). A comparison shows that the main orientation ENE-WSW is found in phase 1 and 2, and along the wall in the Ph.D. project. This orientation is also found as a secondary orientation behind the specimens. In all fracture data in the Ph.D. project and in phase 2, horizontal beds were observed, and horizontal bedding parallel fractures were common. The fracture density for all the measured fractures in the Hillerslev chalk quarry indicate almost random spacing of fractures, and the majority of all the fractures are steeply dipping with a dominance of almost vertical fractures.
All the specimens were fractured to a higher or lesser degree. In four of the specimens horizontal fracture planes were present. The most dominant fractures in the periphery of the specimens were very steeply dipping and seemed almost vertical. Zones with brittle chalk as seen in two of the specimens were also seen at the Hillerslev quarry.
Overall, the three fracture data sets in the Ph.D. project are evaluated to be similar. Further, it is evaluated that the fracture descriptions in the three research projects are similar. Finally, the local and the global fracture descriptions were in accordance, i.e. the fracture system in the specimens represents the major part of the Hillerslev chalk fracture pattern.