A Case Study on Lateral Ground Movements Due to Piling Driving in Soft Clay Near an Existing Elevated Roadway

As the populations of many major cities in Australia continue to grow, the availability of land to construct new road infrastructure is becoming scarce. As a consequence, existing roadways are being augmented or brownfield sites are being utilised for future development. One cost-effective way to increase the capacity of existing roadways in densely populated and congested areas is to use elevated roadways or even widen the existing ones. However, as a consequence, there is usually a need to construct new footings in close proximity to existing footings supporting other structures. This paper presents some results of field monitoring trials during the installation of precast concrete-driven piles in deep soft clay. The pile driving trials were undertaken to assess the potential effects on an existing elevated roadway founded on pile groups. Lateral ground movements in the order of 9-90 mm were observed and varied according to the ground conditions, number of piles installed, and position of the inclinometers used to measure ground movement. The field data is compared to three-dimensional finite element analysis and the shallow strain path method, and overall good agreement is observed. Adiscussion on how these free field movements may be used to assess the behaviour of an existing pile is also provided. It is shown that the impact on an existing pile can be readily assessed using simple published chart solutions and/or finite element analysis.