Predicting rates of shore platform downwearing from rock geotechnical properties and laboratory simulation of weathering and erosion processes

Laboratory simulations of inter-tidal weathering and erosion processes were conducted to examine the relative resistance of a range of shore platform rock types and to assess the potential for predicting platform downwearing rates. Wetting and drying, frost weathering and abrasion experiments were conducted using a standard sea water solution. Selective field and laboratory rock strength tests and laboratory measurement of sea water absorption were carried out. With a total of 40 cycles of wetting-drying, a Mallorcan sandy limestone and French chalk showed greatest weight loss. After 40 cycles of frost weathering, French and British chalks recorded most breakdown. In the abrasion experiment, these chalks showed greatest weight loss after a total of 10 hours of tumbling. They also recorded the lowest strength and rebound readings and the highest sea water absorption. Conversely, Swedish dolerite, gneiss and granite were least susceptible to weathering and abrasion, recorded the lowest water absorption and intermediate to high strength and rebound values. The laboratory-measured geotechnical properties and abrasion rates correlate with field-measured downwearing rates. It is proposed that, with further testing, laboratory measured parameters may be used to predict platform downwearing rates.