Bi-Directional Static Load Testing Using Super Cells for the Hong Kong–Zhuhai–Macao Bridge

This paper describes the bi-directional static load testing (BDSLT) performed using Super Cells on four sacrificial bored piles and select results obtained therefrom for the Hong Kong–Zhuhai–Macao Bridge project on the Pearl River Delta. The BDSLT device consists of multiple units of pressure cells assembled to conform to the diameter of pile and transfers the force of each cell directly to the shaft without the use of large steel bearing plates. The general subsurface profile where the sacrificial piles were installed, two piles each at two locations, consists of marine silts, alluvial clays and sands, and residual soils, which are underlain by granite. The test piles were tipped into the weathered granite layer, where the BDSLT devices were located about 3.5–5.2 m (11.5–17 ft) above the bottom of each pile. The test piles were instrumented with embedded strain gauges and telltale extensometers along with surface mounted displacement transducers. The results of the static axial load testing were intended to confirm the design assumptions of axial resistance and to evaluate the contractor’s means-and-methods. However, the maximum anticipated test load could not be achieved due to the low side resistance along the pile length above the testing device, especially within the upper layers.