: The mechanical behaviour and conductivity of intact and fractured chalk have been studied in laboratory tests. The objectives of the tests were: to investigate the effects of fractures on deformation due to pore collapse; and to investigate the effects of shearing and normal load on fracture conductivity and matrix permeability. Cylindrical specimens of Lägerdorf Chalk, approximately 100 mm diameter by 200 mm length, were made, some of which included a natural fracture. The specimens were tested in a triaxial cell with the capability of measuring fracture conductivity, matrix (bulk) permeability, vertical and horizontal deformation.
The results indicated that: changes in the conductivity of a fracture are dependant on the normal stress during fracture shear displacement; the pore collapse mechanism may begin at lower stresses in fractured chalk due to stress concentrations caused by the fractures; and that fracture conductivity may be significantly reduced under high normal stresses and may not recover when stresses are relaxed.
