Field test of thermal environment and thermal adaptation of workers in high geothermal tunnel

Abstract

During the process of constructing high geothermal tunnels on plateaus, people easily feel uncomfortable in the extremely hot (>45 °C), humid(>70%), and low-oxygen(19.6%) environments. In addition, the increase in work intensity further exacerbates this effect. In order to ensure productivity and health of workers, it is necessary to evaluate the influence of temperature, relative humidity, and work intensity on the workers’ physiology and psychology under these kind of extreme conditions. At a construction site, workers doing different jobs (such as installing explosives (LW), setting arches (MW), and drilling (HW)) were exposed to different combinations of air temperature (Ta = 35 °C, 40 °C, or 45 °C) and relative humidity (RH = 50% or 70%); their physiological and psychological responses to the environment were then investigated. Based on the field test results, a new thermal damage classification has been proposed, which shows that work intensity greatly influences heart-rate, especially when the temperature exceeds 40 °C. Under the conditions of Ta40°CRH70% and Ta45°CRH70%, high work intensity can cause a significant increase in thermal sensation. Heart-rate, skin temperature, and thermal acceptability are second-order polynomial functions of the wet-bulb globe temperature (WBGT), while thermal sensation is a linear function of it. There are four grades of thermal working levels in high-temperature operations; the upper limits of the WBGT for LW, MW, and HW are 40.4 °C, 38.4 °C, and 37.3 °C, respectively. Environmental conditions have a more prominent influence on people as compared to work intensity when the heat damage level is above III.