File: 9049 Appendix - 7 Mar.docx Memorandum Ground settlement and tilt estimates for Wharekirauponga Vent Shafts, Mine and Tunnel. A1.0 INTRODUCTION This memorandum summarises the assumptions and results of two-dimensional (2D) seepage and deformation numerical modelling of Wharekirauponga Mine (WUG), Vent Shafts and Tunnel. The modelling was undertaken to enable estimates of settlements due to dewatering and depressurisation. The analyses have been undertaken using Geostudio 2D finite element analysis (FEA) programs, SEEP/W and SIGMA/W (Refs. 1 and 2). The SEEP/W model of the ground and groundwater parameters for the vent shafts and tunnel (at Willows Road Farm) were provided by GWS. A2.0 SCOPE OF WORK The scope of work has included: i. Deformation analyses using SIGMA/W with changes in stress due to the depressurisation of the tunnel at Willows Road Farm, estimated by the SEEP/W modelling. ii. Deformation analyses using SIGMA/W with changes in stress due to potential seapage of groundwater into the vent shafts, estimated by the SEEP/W modelling. iii. Deformation analyses (total settlement) using SIGMA/W with changes in stress due to dewatering from the Wharekirauponga mine. A3.0 SOIL PROFILE AND GROUND MODEL A3.1 Willows Farm Tunnel Section Figure A1a and Figure A1b provides the model geometry and the associated boundary conditions for the tunnel assessment base condition (i.e. before tunnelling). Figure A2a and A2b provides the model geometry and associated boundary conditions after tunnelling. The Willows Road Farm tunnel section replicates a general drawdown profile in a typical weathered andesite rock mass. The drawdown condition assumed one set of permeability condition for the full profile in SEEP/W. The SIGMA/W deformation model applied three different stiffness layers. From the surface these layers were: regolith, weathered andesite, and unweathered andesite. The model extends from RL370m down to a base level at RL10m. The parameters summarised in Table A1 have been adopted for SIGMA/W deformation analyses for the depressurisation around the tunnel (at Willows Road Farm).
RkJQdWJsaXNoZXIy MjE2NDg3