FRACTURE APERTURE EFFECT ON THE DYNAMIC THERMAL GRADIENT REGIME IN FRACTURED SEDIMENTARY ROCKWALL

Minimal research has been conducted in vivo to examine thermal weathering processes in temperate climates, specifically along the Niagara Escarpment. The highly fractured sedimentary cuesta in Hamilton, Ontario is rapidly eroding, posing threats to proximal urban infrastructure. The objective of this study is to determine the effect of fracture aperture in sub-vertical fractures on the rockwall thermal regime and weathering processes. To investigate this, thermistors were inserted at a depth of 12 cm into four fractures varying in aperture from 6–32mm. Additionally, each fracture thermistor was equipped with a corresponding surface thermistor affixed to the rockwall surface near to each fracture. Data was collected between June 2022 and December 2022 and analyzed in one-minute increments to capture rapid thermal shock processes. The data collected suggests that on a diurnal basis, a more drastic inversion of the surface-fracture temperature gradient occurs for apertures of a greater width. With an expansion on the number of thermistors employed in the study, a threshold aperture may be identified between apertures ranging from 6 mm to 15 mm. Differing fracture apertures do not considerably alter the surface-fracture temperature gradient. Other factors that may have a more considerable contribution to the thermal gradient experienced in the sub-vertical fractures may include roughness, moisture, intersection of fractures, and the surface area volume ratio.