Factors influencing and methods of predicting greenhouse gas emissions from highway tunnel construction in southwestern China

Abstract

The rapid development of China's highway tunnels consumes great amounts of energy and materials and emits large volumes of greenhouse gases (GHGs). The design and construction of tunnels are susceptible to the geological environments, but few existing studies considered the roles of the geological environments and construction parameters in the GHG emissions of tunnels. To elucidate the mechanism of GHG emissions during the construction of highway tunnels, this study expanded the relationship of the geological conditions and construction parameters with GHG emissions. Forty-nine lining designs and geological conditions for eight real tunnels in southwestern China were studied. The life-cycle assessment (LCA) method was used to calculate the emissions from 49 tunnels, which ranged from 5.08 × 103 t to 52.63 × 103 t CO2eq. Relevant analyses were conducted to identify the key indicators affecting tunnel construction emissions. The influencing factors, according to the correlation with GHG emissions from high to low, are the total mass of materials, excavation area, excavation method, rock mass grade, and buried depth. Another finding was that excavation methods are significantly correlated with the rock mass grades. For the first time, two linear regression models for GHG emissions from tunnel construction were established. The excavation area and the rock mass grades can predict the approximate GHG emissions during tunnel construction, while the total mass of materials is a better predicting variable when the material input data are available.