Cost Effective Mine Stabilization
Designing a cost effective mine stabilization program requires significant interaction between the risk manager and the Engineer who should be an expert in mine subsidence engineering. The remediation choice made by the risk manager based on options proposed by Engineer can mean easily $100,000’s to over a $1,000,000 reduction in project costs on a typical project.
When evaluating mine stabilization options, the risk manager decisions depend on the comfortability (i.e. reliability) on the Engineer’s opinions and thus their qualifications. This is important because the risk manager must rely on the asserted damage potential for the different grout options proposed by the Engineer for the lifespan of the project. Therefore, qualifications of the Engineer, risk acceptability of the risk manager and a good understanding of the damage potential all play a crucial role in determining the best decision for the project.
The process of designing the most cost effective mine stabilization plan involves a number of important steps and is summarized in the workflow chart shown in Table 1. It involves determining which mine areas under the structure are unstable and require stabilization. This typically includes subsurface mine investigation and mine stability analyses. In areas where the stability of the mine is an issue, a cost versus risk (damage) analysis is then performed considering various mine grouting options. The Engineer should provide the risk manager mine stabilization options with the relevant cost-benefit data. For example, two very important aspects of cost-benefit analysis are the grout methodology and the amount of subjacent buffer that should be grouted and stabilized around the protected structure. Different mine grouting methodologies are discussed in the article entitled Anatomy of Mine Grouting Voids. Establishing the buffer should be determined by comparing the grouted buffer width around the protected structure to the damage potential and associated costs. This is demonstrated in Figure 1 which illustrates the chance damage spectrum (CDS) and directly relates to the associated cost for a stabilization project.
After discussion with the Engineer, the risk manager then selects the cost-risk option which is most acceptable to them. Then, with the mine stabilization option selected, the Engineer optimizes the mine grouting approach and produces the plans and specifications for the project from their experience on the performance of previous mine grouting projects. Plans and specifications for mine grouting are written with a wide range of established performance-based[1] requirements.
FIGURE 1 ILLUSTRATION OF NECESSARY MINE STABILIZATION DATA TO PERFORM A COST-BENEFIT ANALYSIS
With copyrighted plan and specification which have been through over 30 years of mine grouting experience combined with MEA’s over 40 years experience with dispute resolution proceeding. From our experience, with these plans and specifications claims are difficult to obtain even when significant loses occur by the Contractor.
[1] Performance based specifications consist of naming the product requirements without identifying procedural requirements on how to get the product. Procedural requirements control how the product can be constructed.
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