Fleur Loveridge, Mott MacDonald. This paper was first published in GE’s August 2001 edition.
Conventional design methods for braced excavations are commonly found to overestimate the prop loads measured during subsequent construction (Powrie & Batten, 2000, Twine 8r Roscoe, 1999). This may result in the over-design of support systems. The distributed prop load (DPL) method provides an alternative method of estimating temporary prop loads based on case histories.
This paper compares loads found using the DPL method and those given by conventional wall analysis with loads measured during the early stages of construction of the Channel Tunnel Rail Link (CTRL) Contract 430. It demonstrates that the DPL loads are greater than those measured, but significantly less than those found by analysis. The DPL method is then applied to forthcoming areas of construction. The subsequent reduction in prop load predictions allowed review of the method of propping and resulted in cost savings of approximately f.175,000.