Abstract
Volcanic ash deposited on paved surfaces during volcanic eruptions often compromises skid resistance, which is a major component of safety. We adopt the British pendulum test method in laboratory conditions to investigate the skid resistance of road asphalt and airfield concrete surfaces covered by volcanic ash sourced from various locations in New Zealand. Controlled variations in ash characteristics include type, depth, wetness, particle size and soluble components. We use Stone Mastic Asphalt (SMA) for most road surface experiments but also test porous asphalt, line-painted road surfaces, and a roller screed concrete mix used for airfields. Due to their importance for skid resistance, SMA surface macrotexture and microtexture are analysed with semi-quantitative image analysis, microscopy and a standardised sand patch volumetric test, which enables determination of the relative effectiveness of different cleaning techniques. We find that SMA surfaces covered by thin deposits (~1 mm) of ash result in skid resistance values slightly lower than those observed on wet uncontaminated surfaces. At these depths, a higher relative soluble content for low-crystalline ash and a coarser particle size results in lower skid resistance. Skid resistance results for relatively thicker deposits (3–5 mm) of non-vesiculated basaltic ash are similar to those for thin deposits. There are similarities between road asphalt and airfield concrete, although there is little difference in skid resistance between bare airfield surfaces and airfield surfaces covered by 1 mm of ash. Based on our findings, we provide recommendations for maintaining road safety and effective cleaning techniques in volcanic ash environments.
Highlights
When ash was replenished between each swing, the skid resistance remained relatively constant with time, permitting calculation of a mean SRV for each condition
Our experiments suggest that the following lead to reduced skid resistance on asphalt road surfaces and may lead to slippery surfaces following volcanic ashfall:
The largest change in skid resistance for surfaces that became covered by ash occurs during dry conditions, where SRVs fall to levels just below those for wet non-contaminated surfaces, with similar SRVs as the wet contaminated surfaces
Summary
Functional transport networks are critical for society both under normal operating conditions and in emergencies. Transport networks may be required for the evacuation of residents, to allow sufficient access for emergency services or military personnel to enter affected areas and for regular societal activities. Once direct threats have subsided, transport networks are crucial for both immediate and long-term recovery, including the clean-up and disposal of material, and restoration of services and commerce. Damage to transport from proximal hazards such as lava flows, pyroclastic density currents and lahars is often severe, leaving ground routes impassable and facilities such as airports closed or inoperable. Even relatively small eruptions are capable of widespread disruption on ground transport and aviation, which may continue for months due to the remobilisation and secondary deposition of ash by wind, traffic or other human activities, even after an eruption has subsided
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