TRANSMISSION TOWER SUPPORT
The excavation for this new stretch of SH1 along the Kapiti Coast, NZ required the underpinning and strengthening of the Transpower tower and new cut.
The Transmission Gully State Highway 1 alignment required excavation close to the existing Transpower transmission tower. As a result the foundations of the tower which was perched on top of a steep crest required ground anchors and shotcrete to underpin the tower and cut slope.
The slope was designed for 100 years with the pre-grouted double corrosion protected ground anchors using high tensile bar specified to BS8081:2015.
We installed over 100No. 15m long DCP ground anchors that wererequired to be constructed onsite to ensure the critical path program could be achieved for the client. This involved the set up of a scaffold structure to allow pre-grouting, curing and lifting to ensure the cracking tolerances were achieved. Testing the integrity of the grouting process was undertaken by cutting anchors throughout the process for visual inspection by the engineer.
Due to the significance of the transmission tower above, staged construction was carefully managed to ensure the ground anchors were tested on each cut and curing times were sufficient for the grout and shotcrete to stabilise the cut before excavation.
The ground anchors were transported and inserted into the bore holes in a scaffold frame under a crane to ensure the pre-grouted products didn't bend and cause cracking.