FOUNDATION ANCHOR PILES IN CLAY - SHALES

Earth dams and appurtenant structures in the Prairie Provinces are often constructed on a clay-shale foundation. Concrete structures such as spillways may be damaged due to swelling of the foundation or to differential movements. Various protective devices have been installed to reduce and control the amount of swelling and differential heave beneath structures. Hold down piles have been used, which were mainly reinforced concrete with the bottom flared out. This type, which could take little strain, often became ineffective either through breakage or slippage. To overcome this problem, anchor piles were designed to stretch a certain extent without failure due to load applied through swelling of the shale. It was not intended that this type of pile would eliminate swelling, but that it would reduce the rate and amount of swelling or differential movement. The design includes recommendations regarding depth of anchoring, pile spacing, and size of anchor rod for various bell sizes.