August 2020

• Improving Reliability in Slope Design Through Discrete Fracture Network (DFN) Modelling by Steve Rogers, Ph.D., P.Geo, Principal at Golder Associates Ltd. Canada

Steve talks about how DFN models can be used to provide a basis for improving reliability in slope designs. He discusses the issues associated with DFN modelling in general and slope engineering more specifically.

Then he looks at DFN models in bench design and finally some exciting work they’ve been doing integrating FracMan DFN models of inter ramp slopes and integrating these with a custom 3D limit equilibrium tool for improved inter-ramp design…

• A New Three-Dimensional Rockfall Trajectory Simulator for Open-Pit Mines by Bijan Peik, M.Sc., Modelling Specialist at Golder Associates Inc., US

Background. Rockfall hazards on open-pit highwalls are composed of two major associated risks, the chance of the rockfall itself and the area impacted by falling rock blocks or the runout zone. Rockfall trajectory assessment is essential for estimating the consequences of such incidents. Several simulation techniques in the form of computer programs have been developed for this purpose. They are used to obtain the required basis for protection designs and safety considerations in rockfall prone areas. Innovations. In this thesis, a new three-dimensional analytical program was developed for rockfall trajectory simulation and estimating runout zones. This program is designed to effectively read and visualize topographies composed of large numbers of mesh elements. It utilizes special algorithms to enable fast and effective simulations of high-resolution terrain models. The output generated by this program includes rockfall trajectories providing bounce heights, rockfall velocities and impact locations for safety designs and rock trace maps that identify hazardous zones. Both may be used by operations management to designate safe working stations in open-pit mines. Results. The developed program was calibrated using small-scale bounce tests where a detailed study was conducted on the efficiency of the program to accurately simulate bounce heights and lengths. Moreover, the performance of the program was examined in an actual open-pit mine to highlight specific capabilities of incorporated algorithms for trajectory modeling and processing high-resolution terrain models. Based on results from the case study, the program’s modeling showed acceptable correspondence to experimental results as well as reliable performance in trajectory simulation of rockfalls in terms of time-effective analysis and the reasonable outcome has given assumptions and input parameters.

• Case Study of TBM Obstruction by Boulders by Keivan Pak Iman, M. Eng, EIT, C.E.T, Tunnelling and Trenchless Technical Lead at GHD, Canada

Historically, boulders are a frequent source of problems in soft ground tunneling. Boulders can pose major problems for full face TBMs in terms of slowing or halting the tunnel advance, cutter damage, and abrasive wear. Although a proper selection of the TBM and the cutter head can manage the risk ground uncertainties still cannot be eliminated.

This presentation reviews the case study of a 3480 MM diameter EPB-TBM utilized for completion of 2.5 KM tunnel in Glacial Till and crossing the CP railway, HWY 401, creek and confined aquifer. Alignment consists of multiple horizontal curves including small radius curves of 210 m radii at shafts breakthrough. An unexpected boulder cluster leads the contractor to experience extreme damages to the screw conveyor, RFJ system and causing a crack in the main motor plate which results in losing one of the six main motors.