Optimal mining rates revisited: Managing mining equipment and geological risk at a given mine setup

This paper presents a mixed integer programming formulation dealing with the effective minimisation of risk incurred when optimizing mining production rates in such a way that production targets are met in the presence of geological uncertainty. This is developed through the concept of a “stable solution domain” that provides all feasible combinations of ore and waste extraction for the ultimate pit limit of a given deposit, independent of the geological risk. The proposed formulation provides an optimal annual extraction rate, together with the optimal utilization of a mining fleet and an equipment acquisition program. This solution eliminates unnecessary capital expenses and is feasible under all geological scenarios. The mathematical programming model is detailed and tested at a gold deposit. The results are used as input to a production schedule design and are compared to the schedule generated using a constant mining rate; the comparison shows that about 40% of equipment acquisition can be delayed for 7 years and mill demand still be met, thus maximizing profit and minimizing costs.     

Concepts of Wildland Fire Protection of Cultural Monuments and National Parks in Greece. Case Study: Digital Telemetry Networks at the Forest of Ancient Olympia

The concepts and particularities of fire protection planning for monuments of cultural heritage that are surrounded by national parks and other public wildlands are outlined, in the context of the general wildland fire problem of Greece. Typical examples of cultural monuments that were threatened by wildland fires in Greece are reported. A conceptual flowchart that combines optimal fire protection objectives with the protected values and functions of the national parks and cultural monuments is analyzed. A case-study presents the development of an electronic forest fire protection support system in the forest around the Ancient Olympia site in Greece, as an example of the potential deployment of innovative technologies in wildland fire protection. The aim of the system is twofold. First, the system supports remote monitoring of an extensive hydraulic network of pipelines, pumps and water-storage tanks build in the vicinity of the site. Second, the system provides means for remote operation of numerous revolving water-jets installed on top of heavy-duty tree-high metal towers, spread at key-locations inside the surrounding forest. All system telemetry data and command signals are transmitted through a single underground wire link requiring no external electric power at sensor/actuator locations inside the forest. Special user interfaces allow immediate system deployment either from a central graphics-based console screen or from purpose-build remote consoles installed at selected locations in the forest, thus achieving a high degree of readiness.     

Seismic response analysis of skew bridges with pounding deck-abutment joints

In this paper the seismic response of short skew bridges with deck-abutment pounding joints is revisited. The permanent deck rotations and transverse displacements of such bridges after the recent earthquake in Chile created an incentive to revisit their non-conventional behaviour. A novel non-smooth rigid body approach is proposed to analyze the seismic response of pounding skew bridges which involves oblique frictional multi-contact phenomena. The coupling of the response, due to contact, is analysed in depth. It is shown that the tendency of skew bridges to exhibit transverse displacements and/or rotate (and hence unseat) after deck-abutment collisions is not a factor of the skew angle alone, but rather of the plan geometry plus friction. This is expressed with proposed dimensionless criteria. The study also unveils that the coupling is more pronounced in the low range of the frequency spectrum (short-period excitations/flexible structures) and presents novel dimensionless response spectra for the transverse displacements and rotations, triggered by oblique contact in a skew bridge subsystem. Despite the complexity of the response, the proposed spectra highlight a clear pattern. The dimensionless rotations, arising from contact, decline as the ratio of the structural versus excitation frequency increases and become practically negligible in the upper range of the frequency spectrum. Finally, a pilot application to a typical skew bridge is presented.     

Deformation of an elastic capsule in a microfluidic T-junction: settling shape and moduli determination

Microdevices involving a stagnation-point flow, such as cross- and T-junctions, are useful for particle manipulation and characterization. In contrast to the wide use of cross-junctions, T-junctions have received limited attention as a medium for capsule deformation and characterization. In the present study, we investigate computationally the settling shape of an elastic capsule in a T-junction microchannel for a wide range of flow rates. Our work reveals that the capsules show a rich deformation behavior including (inverse) swallow-cap, sit-on and whitewater kayak shapes. We also propose a new methodology for the simultaneous and accurate determination of the shear and area-dilatation moduli of the membrane of artificial capsules via a single experimental technique by utilizing the dependence of the settling capsule’s dimensions on the capillary number and the membrane hardness identified in our investigation. Our moduli methodology utilizes high flow rates (i.e., large capsule deformations) where the effects of the membrane hardness become prominent and thus capsules with different area-dilatation modulus can be identified. Our procedure has the additional advantage of not being influenced by the fluids’ viscosity ratio or the membrane viscosity.     

A matheuristic approach for optimizing mineral value chains under uncertainty

Optimization and Engineering - Mineral value chains, also known as mining complexes, involve mining, processing, stockpiling, waste management and transportation activities. Their optimization is...     

Production scheduling with uncertain supply: a new solution to the open pit mining problem

The annual production scheduling of open pit mines determines an optimal sequence for annually extracting the mineralized material from the ground. The objective of the optimization process is usually to maximize the total Net Present Value (NPV) of the operation. Production scheduling is typically a Mixed Integer Programming (MIP) type problem containing uncertainty in the geologic input data and economic parameters involved. Major uncertainty affecting optimization is uncertainty in the mineralized materials (resource) available in the ground which constitutes an uncertain supply for mine production scheduling. A new optimization model is developed herein based on two-stage Stochastic Integer Programming (SIP) to integrate uncertain supply to optimization; past optimization methods assume certainty in the supply from the mineral resource. As input, the SIP model utilizes a set of multiple, stochastically simulated scenarios of the mineralized materials in the ground. This set of multiple, equally probable scenarios describes the uncertainty in the mineral resource available in the ground, and allows the proposed model to generate a single optimum production schedule. The method is applied for optimizing the annual production scheduling at a gold mine in Australia and benchmarked against a traditional scheduling method using the traditional single “average type” assessment of the mineral resource in the ground. In the case study presented herein, the schedule generated using the proposed SIP model resulted in approximately 10% higher NPV than the schedule derived from the traditional approach.