Date of Award

2023

Document Type

Open Access Master's Thesis

Degree Name

Master of Science in Geological Engineering (MS)

Administrative Home Department

Department of Geological and Mining Engineering and Sciences

Advisor 1

Snehamoy Chatterjee

Committee Member 1

Luke Bowman

Committee Member 2

Mohammadhossein Sadeghiamirshahidi

Abstract

Open pit mine planning encompasses a variety of uncertainties. Uncertainty due to geomechanics is most critical for a safe operation in an open pit mine. Without sufficient knowledge of the geomechanical properties of the subsurface, a reliability analysis of the slope stability could be challenging. Slope stability is a crucial step in pit optimization since the cash flow analysis of a mine is constrained by a stable slope angle. However, obtaining a stable slope angle with certainty is difficult to achieve as geomechanical parameters are modeled using a very limited number of samples. This thesis proposes a method to integrate geomechanical uncertainty, specifically uncertainty regarding slope stability, in pit optimization through reliability-based analysis. This research explores gold deposit data received from exploration drilling in Alaska, with potential to build an open pit mine. The gold grade was estimated by ordinary kriging (OK) using exploration drilling data. Rock Quality Designation (RQD) is the only geomechanical data available from this deposit, and it was used to calculate cohesion, angle of internal friction, and unit weights of the rock. The uncertainty of the RQD was quantified for each rock type of the deposit. The probability density function (PDF) of RQD for each rock type was fitted using log-normal distribution. The uncertainty-based slope stability analysis was carried out using the limit equilibrium method. The reliability and failure probability of the different slope angles were calculated, and the maximum slope angle with 100% reliability is 50°. The cash flow for each slope angle was identified and assessed along with the probability of failure for three different factor of safety values. The results showed that the steeper the slope angle used, the more profit would be generated, but the probability of failure increased. In contrast, using shallower slopes did not generate as much profit, but the probability of failure was lower. A threshold slope angle of 51.5° was determined to be the highest angle that can be utilized without the probability of failure outweighing the profit generated.

Download

Share

COinS