Doctoral Dissertations

Keywords and Phrases

Mechanical Excavation; Overbreak and Underbreak; PFC3D; Rock cutting; Specific energy; Surface hardness


"This research involved lab and numerical excavation of a clastic sedimentary rock (Roubidoux Sandstone) using a long-bladed disc cutter in a Linear Rock Cutting Machine (LCM) with the aim of establishing relationships between the cutting parameters, excavated surface parameters (underbreaks, overbreaks and hardness), and performance parameters (specific energy and cutting rate). Three-dimensional cutting forces were recorded during the linear cutting. A structured laser imaging system was used to image the excavated surfaces for the estimation of the irregularities (ridge volumes (RV) and overbreak volumes (OV)). The excavated surface hardness was measured using the N-type Schmidt hammer. The numerical simulation was conducted in Itasca’s Particle Flow Code 3D (PFC3D). It involved model calibration, a study of the effects of the cutting geometry and cutter scale on the cutting forces, validation of the models using the lab cutting data, and a study of the effects of cutter size on the cutting forces.

The results showed that the RV increased with increasing spacing-penetration (s-p) ratio for s-p ratios at which relieved cutting was achieved. However, the RV decreased with increasing s-p ratio under unrelieved cutting. The OV had a negative linear correlation with the s-p ratio under relieved cutting. In unrelieved cutting, the OV was independent of the s-p ratios. These findings can be used to determine the s-p ratio at which relieved cutting is first achieved. The specific energy decreased linearly with increasing surface hardness. The hardness was used together with the s-p ratio to develop a function for estimating SE. The numerical models yielded logarithmic functions for scaling forces from linear rock cutting simulations in PFC3D"--Abstract, page iii.


Gertsch, Leslie S.

Committee Member(s)

Rogers, J. David
Maerz, Norbert H.
Sherizadeh, Taghi
Samaranayake, V. A.


Geosciences and Geological and Petroleum Engineering

Degree Name

Ph. D. in Geological Engineering


Missouri University of Science and Technology

Publication Date

Spring 2021


xii, 223 pages

Note about bibliography

Includes bibliographic references (pages 211-222).


© 2021 Prosper Evaristus Akansah Ayawah, All rights reserved.

Document Type

Dissertation - Open Access

File Type




Thesis Number

T 11824

Electronic OCLC #