ANCOLD Conference 2022 Masterclass
The question I most get asked, when discussing spillway erosion, is what method can I use to examine spillway erosion, and is it any good? I was asked to present a masterclass on rock erosion at the ANCOLD conference in Sydney in October 2022, and used the opportunity to provide a long-winded answer to that […]
Slug test interpretation using Hvorslev
A “slug test” is a quick procedure you can do to open wells (“standpipes”) to get an estimate of the hydraulic conductivity of the ground. It involves applying a small pertubation to the standing groundwater level in a well, and monitoring its recovery back to pre-test conditions. The picture shown above is of a air-displacement […]
A history of the construction of the Pells Hut
I never met my grandfather Eddie, but the accounts I have gleaned paint a picture of a man full of adventure and enthusiasm. The story goes that he was impressed by the sport of skiing that he experienced in the early 1920’s during a period of study in Europe. On his return to South Africa […]
Erosion of rock in spillways
I finished my PhD on “Erosion of Rock in Spillways” in 2016. UNSW posts a version of the PhD here: PhD – 200MB low -res – this one is lower resolution and around 200MB. Understandable, as the full resolution one is 800MB, but if you prefer you can get it from here (PhD – 800MB hi-res).
seep/w parameters
I’m always looking for this piece of paper, so I posted it here for easy access. seep/w is a groundwater flow model – its 2D (although can be axisymmetric and there is a 3D version these days) but its very quick to solve and reliable, and a useful tool. Unlike many other groundwater models, it […]
Design of apron slabs
It is common to place a concrete slab (i.e. an ‘apron’) below a dam structure to protect against scour or to form a basin to control flows. Design of this apron has to account for various hydraulic pressures, which I consider below in three categories: 1. static 2. kinetic and 3. kinetic-dynamic. Consider the case […]
New home for Pells Consulting
Pells Consulting moved back to Sydney – new address at 12/6 Tilley Lane, Frenchs Forest. Come and say hello 🙂
Tunnel inflows
The Oct 2025 issue of the ANZ Tunnelling Journal included a paper by Steven Pells on tools to estimate inflows to tunnels. There are various analytical equations that are used to estimate inflows, but the paper shows that the available equations all boil down to a single linear factor – the “Shape Factor”. Analytical equations typically represent […]
Solving Shield’s diagram for the diameter to be mobilised
I once fitted a curve to the Shield’s diagram. I’m sure this must have been done before, but anyway my version is: Where the subscript ‘c’ refers the the critical condition – i.e. the line on the Shields diagram above. This line indicates that combination of average bed shear stress and sediment diameter in which […]
CRC-P PROJECT “SMART TECH FOR SAFER DAMS: TACKLING EROSION WITH INNOVATION”
Our application for a CRC-P funded research project has been successfully funded. This exciting collaboration between UNSW, Pells Consulting, and Sunwater aims to develop next-generation tools to address one of the most challenging problems in dam engineering: rock erosion in spillways, with the following topic areas to be addressed: Undertaking UAV (terrestrial) and USV (bathymetric) surveys of various dam spillways, with […]