Cave volume computed on the behaviour of a blowing well (Tournai basin, W. Belgium)

Abstract

It is difficult to measure karst volume but important to do so to assess risk of sinkhole formation. Measurements of airflow and atmospheric pressure pattern on a water well in buried karst of the overexploited Tournai hydrogeological basin (Belgium) show that inflow and outflow are highly correlated to atmospheric pressure and the differences of external and internal air densities. The volume of natural voids in connection with the well within the vadose zone can best be estimated by a calculation based on outflow under constant atmospheric pressure, which suggests a possible cavity volume of 700 000 m3 indicating likelihood of sinkhole formation.

Air circulation and its impact on microclimatic variables in the Císařská Cave (Moravian Karst, Czech Republic)

“…A consensus exists that driving forces of airflow are proportional to the differences in air densities (Cigna 1968; de Freitas et al , 1982; Christoforou et al , 1996; Massen et al , 1998; Spötl et al , 2005; Fernandez‐Cortes et al , 2009b; Kowalczk and Froelich 2010). For the density of a binary mixture of dry air (a‐subscript) and water vapour (w‐subscript), the ideal gas equation gives where ρ is the mixture density [kg m −3 ], M i is molar mass of i‐gas [kg mol −1 ], P is total pressure of gas mixture [Pa], p w is partial pressure of water vapour (Pa), R is the universal gas constant [m 3 Pa K −1 mol −1 ], and T is absolute temperature [K].…”

Temperature distribution in karst systems: the role of air and water fluxes

“…It must be emphasized that further processes, such as barometric fluctuations, might lead to significant air flows in larger systems (e.g. Conn, 1966; Massen et al ., 1998). These will, however, increase the influence of air flow, as suggested by our model.…”

Annual and transient signatures of gas exchange and transport in the Castañar de Ibor cave (Spain)

“…Unlike humidity, a significant increase in the proportion of CO 2 , whose molecular weight is 44.01 g/mol, would lead to an increase in the density of air under equal conditions of pressure and temperature. A general expression for calculating the density of humid air is based on the equation of state of a mixture of dry air and water vapor (equivalent equations were implemented by Badino, 1995 andMassen et al, 1998):…”

“…222 Rn gas, Perrier et al, 2004), or also estimating the volume of natural voids by a calculation based on outflow of air from a well connected to the void under constant atmospheric pressure (Massen et al, 1998).…”