Boundary Conditions The model was assigned free drainage conditions on the inside of the shaft on the model left hand side. The right-hand model boundary condition was assigned as a constant head set at ground elevation. Model Results The model predicted inflows for each of the vent shafts is presented in Table D2. These inflows were aggregated into the tunnel inflow model (Attachment B) at the relevant chainage intervals. Table D2 Ventilation Shaft Inflows The ventilation shaft models were used to generate potential drawdown profiles surrounding the shaft during construction in order to allow calculation of settlement potential. The profiles have been generated assuming the shaft is allowed to freely drain for the duration of its construction. Figure D2 Vent Shaft Drawdown Profiles Shaft Location Inflow Days Total Inflow m3/d m3 Shaft 1 Willow Farm 12.5 40 500 Shaft 2 DoC Land 23.5 60 1410 Shaft 3 WKP (Egress) 13.0 40 520 Shaft 4 WKP (RAR) 6.2 40 248 Shaft 5 WKP (FAR) 9.8 50 490
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