{'fraction_non_alphanumeric': 0.019193857965451054, 'fraction_numerical': 0.01199616122840691, 'mean_word_length': 4.991379310344827, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Thermal Infrared survey of mineshafts at Pewfall, St. Helens

Abandoned mineshafts are ground disturbances that have very localised effects on the morphology, physical, chemical, drainage and moisture properties of the surface geological materials and thus thermo- physical properties. Hence, localised differences in the temperature of the ground surface about a mineshaft occur that can be detected by thermal infrared (IR) surveys. Using a handheld thermal infrared imaging camera pixel-averaged measurements of temperature were taken at 2m intervals over a 50m by 50m grid at the former colliery of Pewfall, St. Helens. Measurements were contoured to provide a temperature image of the ground within the grid surrounding a mineshaft whose exact position was unknown. The week before the survey was characterised by very clear, sunny days with freezing temperatures in the evening. Prior to and during the survey air temperature, ground temperature at 0.1m, ground temperature at 1.0m and barometric pressures were logged (every 30 minutes) at various locations at the site. Effects on potential ground heating of wind exposure and sun-trapping caused differences in measured air temperatures of up to 5 o C. Diurnal fluctuations are readily observed on ground temperature measurements at 0.1m depth, but measurements at 1m depth only show an overall temperature reduction of 0.5 o C due to longer term mean air temperature changes. IR measurements indicated differences in temperature that correlated well with different ground conditions such as areas of long, tufty grass, very wet ground with standing water and ice, made ground with coarse gravel and brick rubble and very disturbed ground that was either tamped, highly vehicle rutted or highly cut up. A thermal anomaly of about 6m 2 above a known mineshaft was characterised by increased temperatures of between 0.5 to 1 o C in comparison to the adjacent ground surface. The anomalous ground contained traces of methane gas and the total O 2 + CO 2 content only comprised the CO 2 component indicating oxidation of methane.