The following inflow assessment has been applied to the two proposed tunnel sections; the dual access tunnels from Willow Farm to WUG and the WUG access tunnel from Waihi to Willow Farm. The models meet at the vent shaft at Willow Farm. B.1 Calculation Methodology Rock Mass Inflow in Advancing Tunnels The exploration tunnel groundwater inflows have been calculated for both steady state and transient conditions. For steady state estimates, a number of methods based on the Goodman et al (1965) equation were evaluated and the method of Karlsrud (2001) used to make an initial estimate of inflows. The equation is as follows: Where: Q inflow unit tunnel length (m3/d/m) r Tunnel radius (m) K Hydraulic Conductivity (m/d) h Water head above tunnel centreline (m). These calculations yield estimates of inflows per metre length of tunnel. For calculation efficiency, the tunnel length was discretised into units based on geology; hydraulic conductivity; tunnel diameter; and water head above the tunnel. Total inflow was then assessed by integrating flows for each discretised unit. Transient inflow estimates were undertaken using the method of Perrocet (2005). Inflows were calculated for discretised zones and integrated to provide the inflow as the tunnel advanced. The equation used to calculate inflow over time was; Where: q Tunnel inflow at distance x at time t (m3/d) Ss Specific Storage coefficient So Groundwater Head (m) v Tunnel advance rate (m/d) t Time (days) x Distance advanced (m) Shaft Inflows In conjunction with the analytical method of determining rock mass inflow, discrete locations have been considered at the shaft positions. Inflows during construction of the vent raises prior to grout sealing have been determined using axis-symmetric SEEP/W numerical models (refer Attachment D). These models are setup under transient conditions that allow inflow over a period of time relevant
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