Trevor G. Carter

Golder Associates · Rock Engineering

Worldwide, degradable, poor quality rock units frequently exist within the final perimeter walls of large open pits, sometimes en-masse and sometimes intercalated within otherwise competent rocktypes. Almost irrespective of location and origin, degradable zones pose a longevity instability problem and need to be dealt with as part of open pit mine...

Typically, significant effort is expended by Mining Companies to optimize final designs of highwall slopes to ensure sufficient stability to achieve mining goals through to the end of planned pit life. Slope instability risk during operations is well managed through performance monitoring, trigger action response plans (TARPs) and corporate risk ma...

Most existing and planned mining operations require a closure pathway towards a self-sustaining post mining land use (PMLU). Historically very few mines have been successfully relinquished. Many mines sit in a state of ongoing litigation (with a substantial 'gap' between stakeholder objectives) and others with inadequate (poorly conceived, planned,...

Design Acceptance Criteria (DAC) for physical waste dump stability in an operational context was discussed in Chapter 8 of Guidelines for Mine Waste Dump and Stockpile Design (Hawley and Cunning, 2017). Guidance was provided for both deterministic and probabilistic analyses for static and seismic stability, and for allowable deformation/strain unde...

Closure implementation typically consists of two main stages. In the Active Closure (pre-stabilization) stage, geotechnical and hydrogeological conditions may change rapidly, so it is important the closure plan is sufficiently flexible to interactively adjust to the monitoring results, and to trigger any required mitigation measures. In the Passive...

Currently precious few guidelines exist for how a practitioner should tackle the quantitative assessment of long-term slope performance for open pit mine closure design. Material degradation, resulting from cumulative incremental time dependent deterioration processes, and propagation of episodic damaging events (eg., precipitation and seismicity)...

This paper showcases a practical application case study of identifying and describing open pit and pit lake closure hazards and managing the subsequent risks. Post-closure many open pit and waste dump slopes require ongoing geotechnical hazard identification. Changing physical conditions, such as slope degradation and rising pit lake levels need to...

Despite major improvements over the past several decades in computer methods for analyzing and synthesizing exploration and site investigation geological data for engineering purposes, which should have decreased project risk, unexpected failures and construction problems still occur. Often, this unexpectedness can be tied back to inadequate struct...

For open pit mining, understanding and managing slope performance is critical for both operations and closure. Towards the end of mine life, achieving reliability of slope performance in operations often necessitates real-time implementation of active slope stabilisation controls. This situation changes significantly towards closure, when productio...

Closure planning is a fundamental requirement for all existing and planned future mines. However, there are no accepted industry guidelines for how to assess options for open pit closure or for advancement of the closure plan in parallel stages with overall project development and operation. Ideally, closure planning needs to consider the site sett...

The trend today to ever increasing modelling sophistication demands that much more attention be paid by practitioners to achieving better appreciation and characterization of geology and rockmass variability, so that rock–structure interaction effects can be analysed more realistically in better calibrated models. This paper is thus directed toward...

Weak rocks can be found in many mines around the world with strengths varying from extremely weak (R0) to very weak (R1) and to weak (R2). R0 materials are usually treated as soils, whereas materials from the middle to upper R2 strength range can be assumed to behave as a rock mass. The problem is therefore the handling of so-called R1 to R2 materi...

Evaluating the condition and stability of coastal cliffs and assessing longevity of significant overhangs and undercuts in an active marine environment is a challenge. As part of cliff management studies undertaken for the Coastal Zone Management Unit of the government of Barbados, a programme of innovative cliff profile mapping was conducted aroun...

Several investigators have attempted to quantify the Geological Strength Index (GSI) chart, with the latest modification of the chart (2013) utilizing RQD as a measure of blockiness. This approach has limitations where discontinuity spacing is wide (typically greater than 0.3 m) and RQD alone cannot adequately characterize the degree of blockiness,...

In rock engineering design, significant advances have occurred in recent years in numerical modelling capability with increasing trends to ever greater use of synthetic rock mass models and discrete fracture network (DFN) modelling, but all too often with little comparative improvement in geologic base data. As a consequence, there is even more nee...

This case study describes the grouting aspects of the foundation improvements carried out to remediate the settlement distress of a partially constructed new building located on the west coast of the Caribbean island of Barbados. The foundation remediation ultimately included the construction of a 280-foot-long sub-surface ‘sea-wall’, the installat...

Real time electronic monitoring has become standard for rock grouting. By the early 1980s, its use had already become a reality, but in only a few places worldwide. From the earliest work using paper chart recorders, to the introduction of the personal computer, through to use of the present, sophisticated, parallel multi-hole computer recording so...

Fractured rocks, specifically sedimentary sequences, present a particular challenge for grouting, as major connected fractures that must be sealed will rarely be intersected by vertical groutholes. The aperture controlled grouting (ACG) method can be readily applied using discrete fracture network (DFN) analysis approaches to understand the pattern...

The original Geological Strength Index chart was developed on the assumption that observations of the rock mass would be made by qualified and experienced geologists or engineering geologists. With the ever increasing use of the GSI chart as the basis for the selection of input parameters for numerical analysis, often by individuals without the str...

Because of the potentially problematic conditions created to deep mining or civil projects by adverse fault slip behaviour, assessing what geological structures are under a critical stress state is becoming an increasingly important endeavour. This paper presents common structural geology techniques that are not widely known or regularly applied ei...

The effectiveness of grouting fractured rock depends on the distance that grout penetrates into individual fractures and spreads into connected fracture networks. Assessing grout spread, and the consequent effect on groundwater flow, requires consideration of the 3-D geometry and hydraulic properties of the natural fracture network. Discrete fractu...

Traditionally, closure criteria and control of grouting effectiveness for bedrock permeation grouting has always relied on "final stage" confirmatory water pressure testing of the grouted rock mass using classic Lugeon-style testing. However, increasing industry-wide acceptance of real-time grout monitoring using electronic data acquisition can all...

As Canadian hard-rock mines go deeper, they are experiencing greater stress-induced rock burst problems, which on occasion have seriously complicated effective and efficient mining. The mine in-dustry is actively addressing these problems by using the deep mines as large in situ laboratories for improv-ing the understanding of controlling rock mass...

A multi-disciplinary Deep Underground Science and Engineering Laboratory (DUSEL) is being planned at the site of the former Homestake Gold Mine in Lead, South Dakota. Current plans include development of large excavations at the 4850 (1480 m depth) and 7400 (2260 m depth) Levels. Proposed excavations at the 7400 Level include large excavations (15...

A multi-disciplinary Deep Underground Science and Engineering Laboratory (DUSEL) is being planned at the site of the former Homestake Gold Mine in Lead, South Dakota. The proposed underground facilities for the mid-level campus (4850 Level [1480 m depth]) will utilize parts of the original mine infrastructure and several new large excavations. This...

Sheeting joints are extensive fractures that typically develop parallel to natural slopes. Embryonic sheeting joints initially constitute channels for water flow and then become the focus for weathering and sediment infill accompanied by progressive deterioration and dilation. Slabs of rock fail along them periodically because of their adverse orie...

Increasingly mining operations are looking at developing large open pits down through old underground workings in order to extract remnant ore left within pillar zones. Maintaining pit wall stability while mining a large open pit through major scale underground stoping zones presents both a risk and challenge that can have significant impact on ove...

Support system design for tunnels and underground excavations has for many years relied heavily on the use of rock mass classification systems and the Hoek-Brown failure criterion as a means for characterizing rock mass behaviour. Because of their development, both the GSI system and the Hoek-Brown criterion admirably characterize most 'normal' roc...

Assessing collapse risk for any near surface mine opening or for a civil tunnel is challenging, while defining an appropriate minimum rock cover thickness that should be left above the crown is a particularly difficult design task. The difficulties of predicting behaviour and of correctly dimensioning crowns is borne out by the fact that in recent...

The GSI system for rockmass strength estimation based on the Hoek-Brown criterion has become the industry standard for international tunnelling and is becoming popular in slope applications. This system is based on the principle that structure within a rockmass (joints, fractures, joint surface alteration and degradation) acts to reduce both the co...

In the design of open pits and shallow foundations engineers are often faced with materials that can be classified as rock but do not fit the current set of criteria used to assess their field strength (saprolites, regoliths, duricrusts (ironstones and carbonate caps), coralline limestones, etc.). These materials can be thought of as transition mat...

The need to deal with mine hazards and developing accurate costs for closure and monitoring is creating an increased demand for the estimation of collapse risks from mine workings. The estimation will help in the development of better risk management plans that are more cost effective as these plans satisfy government legislators and is also accord...

The engineering and construction of an almost 10 metre deep, 20 metre diameter basement excavation, along with ancillary underpinning, tunnels, shafts, and raises to provide new underground space in the limestone bedrock forming the foundations of the Library of Parliament in Ottawa, Canada, without damage to the existing heritage building or disru...

A deep grouted cut-off was constructed as part of the 140 m high, concrete-faced rockfill dam at Antamina in the high Andes of Peru. Foundation conditions comprised upstream-dipping, contorted argillaceous rocks in the left abutment, varying to limestone with karstic solutioning in the right abutment. This potential for karst was of concern for ens...

Construction of a novel retaining wall and implementation, for the first time in Hong Kong, of high energy rock fall protection fences contributed to the successful completion of one of the most difficult highway realignment and widening programs ever undertaken in the Territory. The Tuen Mun Highway is one of the major arterial roads linking Hong...

The widening of the Tuen Mun Highway involved demanding aspects of site investigation, design and construction due to the combination of existing steep cut slopes, an extensive weak zone and heavy adjacent traffic. The application, for the first time in Hong Kong, of high energy rockfall protection fences and novel tie-back retaining wall design ar...

Owing to increasing traffic flows, many highways in Hong Kong require widening, improvement or parallel development. This paper describes the site investigations undertaken for a particularly difficult highway widening project, where dual 3-lane traffic flows of typically 9000 vehicles per hour had to be maintained throughout the investigation peri...

In many countries mines are now required to file closure plans and post bonds for decommissioning. Establishing whether the remediation of specific surface hazards arising from mining activity is necessary in a given situation is not always straightforward. In consequence, considerable interest is being focused on improving methods of assessing the...

Blasting near the access road to a new airport for the Town of St. Anthony, Newfoundland exposed a large open cavity. Although a site investigation had been previously carried out for the proposed airport development, its scope had been limited to investigation of overburden soils. Since the new airport was already partially completed it became cri...

Mass transport inside the oscillatory bottom layer near the sea bottom is studied for three-dimensional wave motion. Influence on the transport of fine and coarse sand and significance to the sea bottom morphology are presented.

Mass transport inside the oscillatory bottom layer near the sea bottom is studied for three-dimensional wave motion. Influence on the transport of fine and coarse sand and significance to the sea bottom morphology are presented

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