Our Ref:9049 13 June 2022 Page 1 File: 9049 Appendix.docx The parameters summarised in Table A1 have been adopted for SIGMA/W deformation analyses for both the depressurisation around the Wharekirauponga Access Tunnel and the Gladstone Open Pit vein dewatering. TABLE A1 Material Deformation Parameters Unit Unit Weight (kN/m3) Young's Modulus (MPa) Poisson's Ratio Younger Volcanics 25 1,000 0.2 Weathered Andesite 22 1,000 0.2 Andesite -Undisturbed (both Higher K and Lower K) 27 8,700 0.2 A4.0 MODELLING AND RESULTS Decoupled seepage and deformation analyses using SEEP/W and SIGMA/W have been undertaken for both the Gladstone Open Pit vein dewatering and the Wharekirauponga Access Tunnel. The SEEP/W model calculates the change in pressure associated with dewatering and depressurisation. The SIGMA/W model then calculates the ground deformation that is caused by the change in pressure. Two separate geometries were used to model ground deformations, one for the Gladstone Open Pit and one for the Wharekirauponga Access Tunnel. The tunnel geometry was modelled for two different scenarios. The first scenario is the case where the tunnel intersects veins which may cause dewatering shown in Figure A2, and the second scenario is modelled for where the tunnel intersects no veins and local depressurisation occurs shown in Figure A3. The Gladstone Open Pit geometry was only modelled for vein dewatering shown in Figure A4. A4.1. Settlement Modelling The SIGMA/W modelling has been undertaken to calculate the settlement and tilt induced by the pressure change. Figure A2b shows the settlement from the potential groundwater drawdown in veins intersecting the tunnel. Figure A3b shows the settlement for groundwater depressurisation around the tunnel where no veins are interected. The settlements for the potential drawdown in the modelled intersecting veins for Gladstone Open Pit are shown in Figure A5. The estimated average settlements are summarised in Table A2 and A3. These values are the average of the settlements across the whole profile modelled. TABLE A2 Estimated Settlements from the Wharekirauponga Access Tunnel Analysis Average Settlements (mm) Depressurisation around Tunnel 8 Tunnel Vein Drawdown 85
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