Norbert H. Maerz

JOINT ROUGHNESS MEASUREMENT USING SHADOW PROFILOMETRY

Abstract The shadow cast by a ruler or string reveals a roughness profile across a joint surface. If the rock is smooth, the edge of the shadow is straight, and if rough, the shadow is irregular. The image can be recorded on video tape, digitized by an image analyzing microcomputer, then processed to isolate the shadow edge. Parameters of roughness can then be calculated and displayed. This photoanalysis method compares favourably with the often awkward and impractical mechanical and optical techniques of roughness measurement. In a series of laboratory and field experiments, the authors have investigated errors resulting from variations of illumination and image processing. Results demonstrate that with reasonable precautions, the results can be reproduced to within about 5% of the full roughness range. Roughness parameters convey in a quantitative manner the meaning of “smooth” and “rough”, and are needed as a basis for prediction of shear strength and other properties. The many available alternative parameters, borrowed from fields of electronics, acoustics and mechanical engineering, range from simple measures of amplitude, wavelength and slope, to more complex stochastic, frequency domain and fractal analyses. These are reviewed, and criteria for selection discussed. Shear strength models based on roughness include those of Patton, Ladanyi and Archambault, and Barton. Bartons JRC is not a geometric property: it must be estimated either from shear tests or by comparing a rough joint with the published standard set of comparator profiles. Visual comparison is found to be unreliable. Better results can be obtained by digitizing the standard profiles using the method described in this paper, and relating JRC to a measurable quantity, the roughness profile index, Rp. The regression equation relating JRC to Rp compares closely with the same form of equation determined by direct correlation of the results of shear testing and roughness measurement.

Rock mass characterization using photoanalysis

SummaryRock formations are distinguished from each other by measuring first the properties of the intact rock, and second those of the jointing. Whereas simple methods are available for measuring intact rock properties, those available for measuring jointing remain slow, expensive, and sometimes dangerous. Digitized photographs (‘photoanalysis’) may provide a solution. In this paper, the new techniques of photoanalysis are reviewed together with applications, promising areas for research, and also some obstacles that remain to be overcome. Aspects of the rock mass that lend themselves to photoanalytical measurement include those of individual joints, such as persistence, orientation and roughness, and those relating to the mass as a whole, such as block size and the spacing or intensity of jointing. Photoanalysis can also be applied to measurement of blasting. It allows characterization of the rock about to be blasted, helping the engineer to predict fragmentation and to design an appropriate blasting pattern. Afterwards, the same methods can be used to measure fragmentation, overbreak and backbreak, for quality control and for diagnosis of problems.

Optical digital fragmentation measuring systems - inherent sources of error

Abstract Automated optical imaging systems of measuring fragmentation are increasingly being used in the mining, comminution, and materials handling industries. These methods have been well received in many of the industries involved. Considering that in many of these applications there are no alternative ways of sizing material, having even a rudimentary measurement of size distributions allows evaluations of explosive, blast design, detonator performance, crusher and milling performance, and material degradation due to transport. Optical methods have inherent limitations, which reflect on accuracy, precision, and reproducibility of measurement results. This stems from the fact that there are myriads of variables, which affect the outcome of the measurements. Errors start with the imaging process, which may distort the reality because of the scale of observation, may induce sampling bias, and may simply not return a good representation of the reality. More errors are introduced in the digital processing ...

New Risk–Consequence Rockfall Hazard Rating System for Missouri Highways Using Digital Image Analysis

The Missouri Rockfall Hazard Rating System (MORFH RS) is a new scheme for rating rockfall hazards along the roads of the Missouri State highway system. Existing rating systems used in other jurisdictions focus on the risk of failure and ignore the consequence of failure, or they lump the ratings for risk and consequence together. Missouri highway rock cuts tend to have low heights but are typically highly weathered, with special problems from karst and paleokarst. In MORFH RS, risk and consequence factors are given equal weight but isolated from each other. MORFH RS utilizes two phases: 1) identification of the most potentially problematic rock cuts using mobile digital video logging; 2) characterization and prioritization of remediation for the potentially problematic rock cuts identified in phase 1, using MORFH RS. In phase 2 four types of parameters are evaluated: 1) parameters that can be measured on computer scaled video images; 2) parameters which are descriptive, and need field evaluation; 3) parameters which are obtained from MODOT records; 4) conditional parameters which are evaluated under specific conditions. Only those parameters were selected that were deemed meaningful and/or relatively easy to measure or estimate. Parameters were assigned to either a risk or consequence category or both. MORFH RS has been tested on sections of Missouri highways. About 300 rock cuts were evaluated and used to prepare, modify, test, and verify the system. Sensitivity analysis of the system was done by quantifying potential errors in the video measurements and by a rating comparison of 12 MODOT and University of Missouri-Rolla (UMR) personnel on 10 rock cuts along Highway 63.

Implementation of multivariate clustering methods for characterizing discontinuities data from scanlines and oriented boreholes

In geological engineering, discontinuities are typically analyzed by grouping (clustering) them into subsets based on similar orientations, and then characterizing each set in terms of position, spacing, persistence, roughness and other parameters. Multivariate analysis can be used to incorporate some of these other parameters directly into the cluster analysis. The implementation of four methods of cluster analysis that consider orientation, spacing and roughness are described here: nearest neighbor, k-means, fuzzy c-means, and vector quantization. The net result is a better grouping of discontinuities, so that members of a subset might be more uniform in terms of mechanical or hydrological properties. This paper presents the implementation of this analysis in a Windows® based program CYL that also serves as a graphical visualization tool.

OVERBREAK AND UNDERBREAK IN UNDERGROUND OPENINGS PART 2: CAUSES AND IMPLICATIONS

SummaryThe newly developed light sectioning method has been used to investigate some of the causes and costs of overbreak and underbreak. Investigations at the Aquamilpa Hydroelectric Project in Mexico have shown decreased overbreak and increased underbreak as a result of increased rock quality and decreased explosive energy. A new measure of explosive energy, the ‘perimeter powder factor’ (PPF), has been defined and shown to be useful in the context of tunnel-wall rock damage. Tentative results indicate that explosive energy (PPF) may be a more important factor in producing underbreak, whereas rock quality may be a greater factor in producing overbreak. A site-specific equation is given for predicting overbreak or underbreak as a function of rock quality and explosive energy, with an evaluation of the cost of underbreak and overbreak.

Overview of some geological hazards in the Saudi Arabia

The Saudi Arabia has harsh environmental conditions which enhance some geomorphologic/geological processes more than in other areas. These processes create different geological hazards. The general physiography of the Saudi Arabia is characterized by the Red Sea coastal plains and the escarpment foothills called Tihama, followed by the Arabian Shield Mountains, the Arabian Shelf plateau and finally the Arabian Gulf coastal plains. These types of geological hazards can be categorized into sand accumulations, earth subsidence and fissures, flash floods, problematic soils, slope stability problems, and karst problems. The current study gives an overview of all these hazards with examples, as well as develops a geo-hazard map for the Saudi Arabia. Our findings indicate that the desert environment needs much concern and care. National and international agencies have to join together with other people to keep the system balanced and to reduce the resulting geological hazards. Also, remedial measures should be proposed to avoid and reduce these natural hazards.

Post-Muckpile, Pre-Primary Crusher, Automated Optical Blast Fragmentation Sizing

Automated rock sizing using digital image analysis has been well established. The methods work best under the controlled conditions of a conveyor belt, where camera angles and distances are constant, lighting is controlled, and sampling errors are at a minimum. Unfortunately, in most operations by the time rock is loaded onto a conveyor belt, it has passed through a primary crusher, and the size distribution no longer reflects only the blasting process. On the other hand, imaging and measuring the size of fragmentation on muck piles, while still useful, is problematic. Results can vary because of camera distances and angles, different lighting conditions can change measurements, and most importantly, because only the surface of the muck piles can be measured, tremendous sample bias can result in large measurement errors. The solution is to image the rock while in transit between the muck pile and the primary crushing station. This includes surface and underground HD (Haul Dump) and LHD (Load Haul Dump) type vehicles, using this method results in significantly decreased sampling errors. However new technical difficulties enter into the picture, including the need for advanced triggering and vehicle tracking mechanisms.

Mobile Highway Inventory and Measurement System

Surveyor is a mobile highway data collection system designed to collect measurement data about objects, features, structures, and landmarks located along highways and roadways for highway planning, management, and maintenance. It creates classified inventories annotated with object dimensions, object position relative to the road, and global position reference. The mobile data collection part of the system consists of a high-speed multifunction vehicle with minimum complement of a right-of-way video system with a precisely calibrated high-resolution video camera, a distance-measuring instrument for spatial positioning, a gyroscopic geometries system, and an ultrasonic grade system for precise measurement of vehicle attitude. Data acquisition is facilitated by multiple on-board computers, and the right-of-way video uses a time code for synchronization to the geometric and position databases. The interactive (postprocessing) part of the system uses a workstation to retrieve and buffer the video for the user to identify targets by using point and click with a mouse, to classify them, and to request position or size measurements. The software can make measurements on multiple images by using triangulation or on single images by using the idealized plane of the highway as a reference.

CONCRETE ROUGHNESS CHARACTERIZATION USING LASER PROFILOMETRY FOR FIBER-REINFORCED POLYMER SHEET APPLICATION

The failure of a reinforced concrete member strengthened with fiberreinforced polymer (FRP) laminates may be caused by crushing of concrete, rupture of FRP laminates, or delamination of the FRP sheet. Therefore, the effectiveness and failure mode of FRP sheets applied to beams and columns is related to the degree of adhesion of the epoxy to the concrete surface. When a peeling or delamination failure can be avoided, a more effective engagement of the FRP sheet occurs, which results in more efficient use of the material. One of the principal factors affecting the bond behavior between the concrete and epoxy is the roughness of the concrete substrate. To prepare the bond surface, sand blasting or grinding is typically used to roughen the concrete. To that end, a portable device has been developed to measure the roughness of concrete surfaces. This device can be used as a quality-control tool to characterize surface roughness and identify when an adequate surface preparation has been attained. The method uses laser striping and image analysis. The method was tested on six slabs of sandblasted concrete, which were sandblasted to varying degrees of surface roughness, and a series of nine plastic model concrete surface profiles.