Our Ref:9049 7 March 2022 Page 3 File: 9049 Appendix - 7 Mar.docx A4.1. Settlement Modelling The SIGMA/W modelling has been undertaken to calculate the potential settlement and tilt induced by the pressure change. Figure A2b shows the settlement for groundwater depressurisation around the tunnel at Willows Road Farm. Figure A4b and A6b shows the settlement from the potential groundwater drawdown caused from potential seapage into Vent Shafts 1 and 2. The estimated settlement for the potential full drawdown caused by dewatering of the WUG mine is shown in Figure A8. The estimated maximum settlements are summarised in Table A6, A7 and A8. These values are the maximum settlements across the whole profile modelled. TABLE A6 Estimated maximum settlements from the tunnel at Willows Road Farm Analysis Maximum Settlements (mm) Depressurisation around Tunnel 10 TABLE A7 Estimated maximum settlements from the vent shafts Analysis Maximum Settlements (mm) Vent Shaft 1 – Willows Farm Road 75 Vent Shaft 2 - WUG 140 TABLE A8 Estimated settlements from the WUG Mine. Analysis Maximum Settlements (mm) WUG Mine Drawdown 700 The maximum modelled settlements for the depressurisation around the tunnel is 10 mm. The maximum modelled settlement from potential drawdown due to seepage into the vent shaft at Willows Road Farm and WUG is 75mm and 140mm, respectively. For the drawdown associated with WUG mine dewatering, the maximum modelled settlement is 700 mm. The modelling allow an estimation of ground surface tilts caused by the additional effects from the tunnel or vent shafts. They are summarised in Table A9 for the tunnel at Willows Road Farm tunnel section and Table A10 for the vent shafts at Willows Road Farm and WUG. They have been obtained by selecting the maximum tilt from the surface settlement profiles shown in Figure A2b, A4b and A6b.
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