14th Australia New Zealand Conference on Geomechanics, Cairns, 2023
Geopier Rammed Aggregate Piers® (RAPs) are a ground improvement technology that creates a densified column of aggregate surrounded by a stiffened matrix soil. This paper describes the design and construction of RAPs at Te Kaha, a $683- million Multi-Use Arena under construction in Christchurch, New Zealand. Show more…CLL Projects are constructing 8331 RAPs including 1092 tension RAPs to depths between 5.5 to 12m to provide a ground improvement system supporting the arena. Design considerations include estimation of soil densification in a wide range of soil conditions (sand, silty sand, silt and gravel), analysis of liquefaction triggering before and after ground improvement, numerical analysis to predict the bearing capacity and settlement of the foundations, and prediction of uplift capacity for tension RAPs. The design predictions and the actual results from verification testing are compared, including pre- and post- improvement CPTs and tension load tests. At Te Kaha the RAP installation resulted in a significant increase in sandy soils between the RAP elements. The CPT results consistently underestimated the fines content of the soil. The tension load test results showed that the uplift capacity is dependent on the soil conditions at the tip of the tension RAP. If adequate confinement cannot be achieved at the base the tension RAP ‘unravels’ and the capacity is much lower than typical design methods would predict.Show less…
