Ferri P. Hassani

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.

Sustainable heat extraction from abandoned mine tunnels: A numerical model

Abandoned mines are often associated with enduring liabilities, which involve significant costs for decades after the decommissioning of the mine. Using a decommissioned mine as a geothermal resource can offset the environmental costs by supplying green heat to the communities living in and around the mine area. In this paper, a numerical assessment of geothermal heat extraction from underground mine workings using an open loop geothermal system is carried out. In this study, our focus is on fully flooded mines where the heat flow from the rock mass to the mine cavities is dominantly controlled by conduction in the rock mass. The sustainable heat flux into the mine workings is assessed using a transient two-dimensional axisymmetric heat transfer model. Finite volume method is applied to solve the model and simulate the transient temperature fields in the rock mass and within the water (flowing through cavities). The model is capable of controlling the rate of heat extraction through continuous adjustment ...

Land use-based landscape planning and restoration in mine closure areas.

Landscape planning and restoration in mine closure areas is not only an inevitable choice to sustain mining areas but also an important path to maximize landscape resources and to improve ecological function in mine closure areas. The analysis of the present mine development shows that many mines are unavoidably facing closures in China. This paper analyzes the periodic impact of mining activities on landscapes and then proposes planning concepts and principles. According to the landscape characteristics in mine closure areas, this paper classifies available landscape resources in mine closure areas into the landscape for restoration, for limited restoration and for protection, and then summarizes directions for their uses. This paper establishes the framework of spatial control planning and design of landscape elements from “macro control, medium allocation and micro optimization” for the purpose of managing and using this kind of special landscape resources. Finally, this paper applies the theories and methods to a case study in Wu’an from two aspects: the construction of a sustainable land-use pattern on a large scale and the optimized allocation of typical mine landscape resources on a small scale.

An Overview of Autonomous Loading of Bulk Material

Autonomous loading implies a fully automated scenario in which automated excavating machines, such as front-loaders, load themselves from a heap of bulk material and deliver to the dumping site. The process comprises all the functions of loading, navigating, obstacle detection and avoidance and unloading to be automated and controlled by a supervisory computer. Autonomous loading benefits a number of industries such as construction and mining, from economical view point as well as other concerns like operators safety when the workplace is not hazard free. Despite all the benefits and despite considerable amount of research on the subject, there are no commercially available systems that can be purchased and put to work. In addition to a breakdown of all the tasks that need to be automated and the difficulties involved, this paper reviews and reports the various research and/or development activities that have been carried out during the past two decades on the subject.

A transient natural convection heat transfer model for geothermal borehole heat exchangers

The effect of buoyancy-driven natural convection on the performance of ground-coupled heat exchangers of closed loop geothermal systems is investigated. The governing equations of continuity, momentum, and energy balance are derived, taking into account a porous ground medium fully saturated with liquid water. Boussinesq approximation is used to model the effect of buoyancy forces in water. A three-dimensional finite-volume discretization method over a structured mesh is used to solve the governing equations numerically. The performance of the ground-coupled heat exchanger system is assessed based on the rate of energy extraction and the outlet fluid temperature. The effects of hydraulic conductivity of the heat exchange medium and seasonal variations of heat load on the heat transfer phenomenon are studied. The results are evaluated by comparing them against the results of existing conduction-based heat transfer models. The influence of natural convection on the sustainable rate of heat extraction from a geothermal resource is underlined and interpreted.

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.

An Experimental Study on the Effective Parameters of Thermal Conductivity of Mine Backfill

This paper investigates the thermal conductivity of cemented backfill. Two major measurement methods, namely, steady state and unsteady state, are compared. Effect of backfill design parameters such as pulp density and binder content, along with sample homogeneity and sample size, are studied. Thermal conductivity of backfill with and without sodium silicate additive, as a new binder, is investigated. A novel method for interpreting thermal conductivity of backfill is presented by introducing backfill as a multiphase porous material for which the effects of physical parameters, such as degree of saturation, porosity, and thermal conductivity of solid particles, are studied. The results of this research help to better understand the thermal interaction of backfill with the surrounding rock mass and therefore contribute to progressive improvement of backfill technology.

The Development of Microwave Assisted Machineries to Break Hard Rocks

Novel rock breakage techniques are becoming more viable. According to a major research report on explosive free rock breakage (EFRB) completed by the authors and others, the use of microwave energy was highlighted as a high potential technique in assisting the breaking of hard rocks. Microwave energy, as a thermal energy which is capable of inducing micro cracks, is a technology that is growing fast in mineral processing and ore comminution applications. Recently, use of microwave has been evaluated as a possible avenue for spatial and terrestrial drilling applications and full face tunneling (TBM) or rock breaking machines. As part of an overall research on use of microwave in rock breaking systems, the influence of microwave energy on the mechanical properties of some common hard rock types is reported. Experimental and simulation results underline the potential impact of the use of microwave energy in underground or surface excavation. This will also contribute economically when mine-to-mill operation is fully considered. Furthermore, the microwave assisted drilling machine which was developed at McGill University and its possible drill bit design is discussed. It also outlines the potential impact of a future microwave assisted tunnel boring machine enhanced with microwave and its performance.

Microwave Assisted Rock Breakage for Space Mining

With the new advancements in space technology and also involvement of private sectors in space programs, space mining became an attractive subject either in In-Situ Recourse Utilization (ISRU) on the moon or mineral extraction from an asteroid. One can imagine that excavation and breakage technique that will be used will mainly be affected by the terrestrial methods which has been tested, tried and proved reliable. Drilling rocks is the first stage in order to extract the resources. It mainly relies on the mass of the drill and the reactive force that comes from the gravity. On the moon or an asteroid, where the gravitational force is one sixth or negligible, the drilling performance would not be equivalent to that on the earth. In this study, employment of microwave as a mean to reduce strength of the rocks before drilling is investigated. A magnetron can be installed on the drill and emit microwaves on the rock surface. Microwave penetrates into the rock and creates macro/micro fractures on the surface of the rocks due to thermal expansion ratio within grains, consequently easing the breakage process. Tests were performed on basalt, a common hard rock sample, when exposed to 3 kW electromagnetic waves at 2.54 GHz in a 60×60×60 cm confined oven. Temperature was measured at different depth of the rock as its distance varied from the waveguide. Numerical modeling was

A study into extraction of geothermal energy from tailings ponds

Assessing the performance of ground-coupled heat exchangers (GCHE) of closed-loop geothermal systems installed in tailings ponds is studied. A heat transfer model is constructed, taking into account heat conduction as well as groundwater advection. A three-dimensional finite volume discretisation method over a structured mesh with variable grid size is used to solve the governing equations. The performance of a GCHE system installed in tailings ponds is assessed based on the rate of energy extraction and the outlet fluid temperature. The geothermal capacity of mine tailings ponds and its sustainable rate of heat extraction are estimated. Effects of tube network configuration and horizontal and vertical underground advection on the performance of the system are investigated. It is found that two-dimensional heat transfer models may lead to over-designed systems and the effect of advection cannot be neglected in highly pervious tailings.