Predicting the advance rate associated with the driving of any tunnel can obviously facilitate the planning and scheduling of maintenance, equipment, etc. The advance rate associated with the Straight Creek tunnel pilot bore was compared by a 'step-wise regression' analysis with engineering and geologic variables determined early in the course of tunnel driving. The variables significantly affecting advance rate and the number of observations necessary for predicting advance rate were determined.
The model developed was found to be quite satisfactory as a predictor of the mean advance rate; however, the variance indicates an increase in inaccuracy as the model is used. beyond the range for which it was developed. As developed, this model would be useful in predicting the completion dates for sections of the tunnel as well as the time required to complete the entire project.
Engineering
SlzE--The size of the steel sets used for supports, either 4 or 6 in. if used, and '0' if not used sTsM--Section modulus corresponding to the 4 or 6 in. steel set used sTsec--Spacing (ft) of steel supports at station vEnT--Invert either present or absent (1 or 0) eLAG--Per cent lagging (%) WiDTH--Tunnel width (ft) wvgcE--Peak water flow at face (GPM) WFLUME--Water flOW at portal flume (GPM) FEnHO---Number of feeler holes in tunnel face TDEPTH--Vertical distance to surface from center of tunnel (ft) TLENGTH--Distance from tunnel face to east portal (ft) TTEMP--Rock temperature at face (ยฐF) DAY--Day of the week (Sunday = 1, Saturday --7) RE--Advance rate (ft/shift) Geology OlST--Distance from tunnel face to east portal (it) DEPTH---Vertical distance to surface from center of tunnel (ft) FLTDP--Dip of nearest encountered fault (deg.) FLTDPAZ--Azimuth of dip of nearest encountered fault (deg.)--Tunnel CL = 0 ยฐ FLTCE--Angle the strike of the nearest encountered fault makes with the centerline of the tunnel (deg.) DlSTFE--Distance to the nearest encountered fault (ft) TriVET--Thickness of the nearest encountered fault (ft)--Shear and gouge zones combined GGTHK--Gouge thickness of nearest encountered fault (ft) SHINY--Intensity of shearing based on arbitrary scale (1-10); intense = 10, moderate = 5 (used by ROBINSON and LEE[2]) THSTR--Thickness of rock unit as measured from present tunnel face to initial contact (ft) nJxs--Average joint spacing (ft) AJDIPAZ--Azimuth of jointing dip (deg.) AJDIP--Jointing dip (deg.) AJCL--Angle the strike of the joints makes with the centerline of the tunnel (deg.) VGRAN--Per cent granite in rock (%) FEDIVA--Azimuth of foliation dip (deg.) FOLDIV--Dip of foliation (deg.) rANGE--Angle the strike of foliation makes with the centerline of the tunnel (deg.) D1PLINA--Azimuth of lineation (deg.)--Tunnel C L = 0 ยฐ DIVLIN--Dip of lineation (deg.) CELIN--Angle lineation makes with the centerline of the tunnel (deg.