Transpower 400kV Line Trials

During the initial stages of construction of the new power line link from Whakamaru to Auckland, tomos were identified in the vicinity of the tower foundation and this presented a significant risk to the integrity of the foundations. Remedial options were limited due to the raked piles, very high permeability of the materials and the size of the tomos. Injection grouting was identified as the best option to remediate the tomo that have formed within the block of foundation soils and to prevent the possibility of new tomo forming in the future. Site trials were required for validation and Grouting Services was engaged to carry out a trial injection grouting and testing works programme that included:

• development of grout mix design to suit local conditions
• development of grout injection system and impact of pressure (low versus high)
• test pile installation, remediation and subsequent pull-out testing
• drilling and injection grouting works around 2 tower site