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Van Tuyl Lecture: Isabella West, CSM GE/ GP Department 2022 Student Research Fair Winner
October 20, 2022 @ 4:00 pm - 5:00 pm
Isabella West, CSM ConocoPhillips GE/ GP Department Student Research Fair Winner
Berthoud 241/ Zoom, Thursday, October 20, 2022
Topic: Analysis of the Effects of Jointing on Rockmass Mechanical Behavior Using Rockmass Analog Numerical Models and Laboratory Specimens
Abstract: All civil and mining engineering structures are built on or in soil and rock. Particularly for infrastructure requiring excavation – such as tunnels, road cuts, and deep foundations – rock is an important construction medium. For engineering purposes, large-scale rock formations in the Earth’s crust are referred to as “rockmasses,” which contain sections of intact rock separated by a network of preexisting structures (e.g. joints). Since the elementary representative volume of a rockmass is typically on the scale of meters, it is almost always impossible to perform laboratory tests on a representative specimen of a rockmass. Thus, direct experimental research on rockmass behavior at engineering scales is limited. Currently, engineers frequently rely on empirical classifications to predict the behavior of rockmasses, since representative laboratory studies are not usually possible. However, these systems are prone to error, as they were developed using limited datasets that explicitly or implicitly incorporated certain assumptions about the rockmass.
In recent years, laboratory tests have been performed on artificially-jointed small-scale cylindrical rock specimens, which act as an analog for large-scale rockmasses. These tests allow for the quantification of rockmass behavior without the need for large-scale rockmass specimens or rockmass classification systems. However, only a small variety of jointed specimens have been considered thus far using this type of approach, so generalized conclusions about rockmass behavior cannot yet be made. Specimen preparation for such tests is difficult to perform in the laboratory, so studies using rockmass analog specimens with more complex jointing are largely absent from the literature. This research specifically investigates the brittleness of intact rock and its effects on the mechanical behavior of jointed rockmass analog laboratory specimens. More brittle rocks (i.e. granite) were found to be affected more by preexisting joints than by more ductile rocks (i.e. marble).
Another method to evaluate the mechanical behavior of jointed rock specimens under load is using numerical models, where the artificial joints can be easily generated with any geometry. Specifically, Bonded Block Models (BBMs) have been demonstrated to be an effective approach for modeling the full range of intact rock mechanical behavior, and it has been hypothesized that incorporating fractures into these models will allow for accurate simulation of rockmass mechanical behavior. In contrast to previous work which has focused on backward-looking model calibration, this research presents an evaluation of the predictive capabilities of BBMs for simulation of rockmass analog specimens when joints are added to previously calibrated intact rock models. The results of this work show that different types of BBMs have predictive accuracy as good as +/- 10% under the conditions tested. As a result, BBMs have the potential to be used as a predictive tool to evaluate various rockmass condition that cannot easily be replicated in a laboratory setting.
This lecture is scheduled in a hybrid format. If you would like to join the meeting please:
Join from PC, Mac, Linux, iOS or Android: https://mines.zoom.us/j/92628028658?pwd=NWIwVytBb1hiRjNjUTZqQmVTTVE2QT09
The Van Tuyl lectures are scheduled at 4-5pm in BE 241/ Zoom (hybrid format), and after the lecture there will be a get-together from 5-6pm in BE 243 with pizza and sodas.