Following a series of sub-tropical rainstorm events, Kawakawa and the wider Auckland region suffered extensive landslip issues. Many roads in the region developed both underslips and overslips, severely affecting the flow of traffic. On some roads, full closures were required. Due to their longstanding relationship with our company, Broadspectrum contacted us to provide a competitive design/build solution for the underslips on Clevedon Kawakawa Road.
GSI successfully negotiated design/build solutions for a total package of eight slip sites. We developed solutions that minimised costs to the client through innovation and experience, having remediated many hundreds of similar underslip issues. Working under an emergency timeframe, our in-house engineers carried out site investigations and mapping to complement the available geotechnical information. To provide a rapid turnaround, a number of assumptions were made during the design stage, which were then confirmed with sacrificial soil nails tested to failure.
Two sites in close proximity were remediated with different systems. One was a simple soil nail and shotcrete solution where no shoulder build-out was required. The other involved soil nails and a Geosynthetically Confined Soil® (GCS®) wall to re-establish the road’s width compromised by the landslide. The GCS® system is a comparatively very low-cost solution, and this innovative design/build solution provided savings to the client in the order of 20% over traditional retaining methods.
Following a series of sub-tropical rainstorm events, Waiheke and the wider Auckland region suffered extensive landslip issues. Many roads in the region developed both underslips and overslips, severely affecting the flow of traffic.