ESF SOUTH PORTAL BOX-CUT/HIGHWALL STABILITY ANALYSIS (SCPB:N/A)
PURPOSE The main purpose and objective of this analysis is to design a Box-Cut at the ESF South Portal to accommodate the Tunnel Boring Machine's (TBM) exit at the conclusion of the ESF Main Loop construction. The stability of the Highwall and the sidewalls at the Box-Cut are assessed using analytical methods by numerical modeling techniques. A ground reinforcement system for the South Ramp Box-Cut slopes will be recommended. This report summarizes the results of the analyses and provides the
... tails of the recommended ground reinforcement system for the Box-Cut slopes at the South Portal. The reinforcement design details are then incorporated into design output documents for implementation in the field. Method of excavation for the Box-Cut is also discussed and a recommendation is provided in this analysis. QUALITY ASSURANCE The quality assurance classification for ground support items discussed in this analysis are presented in Reference 5.4. The ground support will be installed in Box-Cut slopes (Highwall and both sidewalls). The work control evaluation for ESF design (Reference 5.2) has determined that the QA program applies to this analysis. The permanent function ground support installed at the ESF South Portal Highwall is classified as QA-I and QA-5 in Reference 5.4 and is therefore subject to QA controls. The Highwall is defined as the rock cut surface at the back of the Box-Cut bounded by both sidewalls (Figure 26) . The Highwall is referred to as Headwall in Reference 5.4. The sidewalls at the Box-Cut are not considered permanent and therefore do not require classification in Reference 5.4. Any temporary function ground support installed by the constructor for reasons of personnel safety does not require classification (Reference 5.4). METHOD Analytical methods, are used to evaluate the stability of the Box-Cut slopes under in situ and seismic loading conditions. The analytical methods and computational details are presented in Section 7.