Moe Momayez

Crack Development and Acoustic Emission in Potash Rock

Abstract Acoustic emission (AE) techniques under laboratory testing conditions are used to understand the mechanical behavior and deformational processes of uniaxially compressed potash rock. Results obtained from the AE measurements are compared to deformational features identified using optical and electron microscopy. Although the potash rock from Saskatoon can be divided into four types based on the compositional ratio between sylvite, halite, clay, textural homogeneity and structural interlocking, it is shown that the analysis of the AE data collected during a complete load cycle can provide a general picture of the AE behavior. Detailed analysis of AE parameters such as b-value, amplitude and event-duration distribution can be used to monitor progressive changes in crack development.

Wave separation: Application for arrival time detection in ultrasonic signals

A method to detect and accurately measure the arrival time of wave packets in ultrasonic signals using a nonlinear decomposition technique is presented. We specifically address the problem of extracting events that are not well separated in the time, space and frequency domains. Analysis of complex ultrasonic signals, even those composed of poorly separated echoes, provided exceptional estimates of the desired time of arrival, from the media under investigation.

DETECTION OF INCLINED CRACKS INSIDE CONCRETE STRUCTURES BY ULTRASONIC SAFT

Detection of internal defects in concrete structures is a difficult task as these anomalies are not always observable at the surface, yet have the potential to expand and damage the structure. The focus of this work is to locate and characterize inclined cracks inside a concrete mass which is essential in monitoring the integrity of many civil structures. For this purpose, three concrete slabs were constructed each having a different sub‐horizontal crack. To obtain high resolution images of the concrete interior, an extension of the ultrasonic technique known as SAFT is used. SAFT has shown great potential to produce detailed 3D images of tendon ducts, holes and flaws inside concrete structures. The results of this study show that cracks with angles varying from 5 to 15 degrees can be accurately located inside a concrete slab having a thickness of up to 200 mm.

Development of the Road Aggregate Test Specifications for the Modified Ethylene Glycol Durability Index for Basic Crystalline Materials

AbstractMany basic igneous rocks contain smectite clays as a result of deuteric alteration during their formation or subsequent chemical decomposition. This has resulted in numerous failures when such materials are used in road construction due to inadequate durability. Various methods for assessing material durability have been developed and those using ethylene glycol (EG) to expand smectite clays appear to be the most effective. Protocols have been developed for a number of tests using EG, but it can be difficult to quantify the results in terms of unique values and develop specification limits for use in road construction. A simple new protocol for an EG soaking test, the modified ethylene glycol durability index (mEGDI), has been developed and the proposed interpretation of results is compared with existing specifications in this paper. The mEGDI is suitable for use as a screening test to identify poor-durability materials. However, inconsistent correlations with existing specifications exist for mat...

An investigation to use tailing ponds as solar photovoltaic farms

Fine-grinding of ores for the liberation of metal- or other valuable concentrates most often results in acreage dedicated to tailings impoundments. A determination of the post-mining land use of such acreage is then required. Tailings impoundments can be suitably utilized as sites for installation of solar photovoltaic (PV) panels. The electrical energy produced can be used initially for mining and concentrating operations, and subsequently for the utility grid after mine closure is complete. Since the extraction, processing and transport of minerals is energy-intensive, most mines already have a substantial electrical transmission-line infrastructure. This eliminates one of the major costs associated with PV energy farms. In this paper, we analyze the long-term economic benefit (i.e. payback period) of PV installation and energy production at mine sites. We also discuss integrating PV systems with erosion control and revegetation measures.

Using NDT for thickness measurement of shotcrete rock support systems in underground mines

Shotcrete is quickly becoming the economical material of choice for rock support systems in underground mines throughout Canada. Although shotcrete technology has gained acceptance in the mining industry, there are some problems which have emerged with respect to quality assessment and thickness measurement of the liner. This paper presents recent tests performed with a miniature seismic reflection device developed primarily for thickness measurement of this heterogeneous liner. Work was performed on site in an underground mine in Ontario, Canada. This paper also presents the results from laboratory tests performed on fiber reinforced an non reinforced shotcrete panels which were used to asses the P-wave velocity in both materials. The results of these tests were used in a second on site investigation. The NDT thickness measurements showed good agreement with the results obtained by mine personnel with conventional methods.

Smectite clay identification and quantification as an indicator of basic igneous rock durability

Abstract In terms of aerial extent, basic igneous rocks are one of the most used road building materials in South Africa. This is mainly due to the fact that approximately 57% of the surface lithology in South Africa is of poor road construction quality, rendering the localized Karoo dolerite intrusions the best construction material available for many road construction projects. Historically, examples of such non-durable materials have been reported and investigated by many authors and current South African specifications specifically require consideration of this potential phenomenon. There is, however, still the need for an accurate, reasonably quick and inexpensive method of determining material durability in order to identify variations within any one aggregate source. Smectite clay content has been proposed for this task but quantification of the clay mineral content of typical Karoo basic igneous rock aggregates has been problematic in recent studies. Published works have commonly discussed reasons why quantitative X-ray diffraction analysis of clays and some of the techniques developed to qualify and quantify clays using X-ray diffraction are problematic. Recent attempts to quantify clay mineralogy as an indication of basic igneous rock aggregate durability proved inconclusive and lead to a comparative study on X-ray diffraction results obtained using different techniques and by different laboratories. The findings confirmed what that literature suggested and also revealed that proposed specifications based on smectite content are not feasible due to quantification accuracy exceeding some of the proposed limits.

Geotechnical considerations for solar panel installation on mine tailings

Geotechnical stability considerations are important for the installation of solar panels on mine tailings areas. Active tailings deposition areas consist of coarse-grained, free-draining relatively stable particulate mass at the perimeter with fine-grained, low shear strength mass around the supernatant pond in the deposition area. An evaluation of the geotechnical stability of the supports for the solar panels constructed, which will have their foundations placed on mine tailings, is essential so that the orientation of the solar panels can be maintained within suitable limits. An assessment of the forces imposed on the solar panel supports, including the distributed weight of the solar panel arrays and effect of wind loading on the flat array surfaces, also need to be considered in the design of suitable foundations for these supports. This paper enumerates some of the geotechnical issues related to the installation of solar panel arrays on active and inactive mine tailings areas. _______________________________ 1 Paper was presented at the 2009 National Meeting of the American Society of Mining and Reclamation, Billings, MT, Revitalizing the Environment: Proven Solutions and Innovative Approaches May 30 – June 5, 2009. R.I. Barnhisel (Ed.) Published by ASMR, 3134 Montavesta Rd., Lexington, KY 40502. 2 Srikant Annavarapu is Graduate Associate, Department of Mining & Geological Engineering, University of Arizona, Tucson AZ, 85721, Terril Wilson is Adjunct Professor and Moe Momayez is Assistant Professor. Alex Cronin is Assistant Professor, Department of Physics, University of Arizona Proceedings America Society of Mining and Reclamation, 2009 pp 37-43 DOI: 10.21000/JASMR09010037

Machine Learning: A Novel Approach to Predicting Slope Instabilities

Geomechanical analysis plays a major role in providing a safe working environment in an active mine. Geomechanical analysis includes but is not limited to providing active monitoring of pit walls and predicting slope failures. During the analysis of a slope failure, it is essential to provide a safe prediction, that is, a predicted time of failure prior to the actual failure. Modern-day monitoring technology is a powerful tool used to obtain the time and deformation data used to predict the time of slope failure. This research aims to demonstrate the use of machine learning (ML) to predict the time of slope failures. Twenty-two datasets of past failures collected from radar monitoring systems were utilized in this study. A two-layer feed-forward prediction network was used to make multistep predictions into the future. The results show an 86% improvement in the predicted values compared to the inverse velocity (IV) method. Eighty-two percent of the failure predictions made using ML method fell in the safe zone. While 18% of the predictions were in the unsafe zone, all the unsafe predictions were within five minutes of the actual failure time, all practical purposes making the entire set of predictions safe and reliable.

The identification and treatment of poor durability Karoo dolerite base course aggregate - evidence from case studies (comment and response)

Table 1 (referencing COLTO 1998) of the above-mentioned technical paper incorrectly states that the PI shall be < 12 when the PI is determined on the -0.075 mm fraction because -0.425 mm fraction is non-plastic. COLTO requires that the PI of the -0.075 mm fraction shall not exceed 12 without any qualification. If the PI exceeds 12, the material shall be chemically modified. After chemical modification the PI of the -0.075 mm fraction shall not exceed 8. The Technical Committee involved in the COLTO 1998 edition based these criteria.