The Clyde Dam in the South island of New Zealand is located in an area more unstable than was thought when it was designed. It took more than 10 years to build and is the largest concrete dam in New Zealand. Therefore the Electricity Corporation of New Zealand has taken additional precautions to ensure the stability of the hillsides surrounding it by constructing an underground curtain of 1,362 meters along the Clutha River. Such a curtain is constructed by drilling holes in the rock and injecting concrete into them. This required hiring drilling rigs and the construction company wanted to minimize the drilling time of the drilling rigs to finish the project quickly. From the few holes the company had already drilled, the company found that the drilling rigs were often idle while it pursued interrelated activities. Since these rigs were hired from an outside company at a cost of NZ$227/hour, this idling time was a major concern. It also meant that project completion would be delayed. There were five steps to creating the grout curtain: (1) drilling the holes, (2) washing out the holes, (3) performing a water test, (4) grouting the holes, and (5) allowing the grout to set. There were five different types of holes to drill along the 1,362 meter stretch (the number of each is indicated in parentheses) – primary (228), secondary (227), tertiary (454), quaternary (908), and quinary (1816). The drilling rate at each stage varied according to the rock conditions at different depths. Each of the steps had random times associated with them. For example, step four had grouting times at the different stages with right-skewed distributions. After the fifth step, there was always some probability the hole would collapse and the process would have to be repeated. Depending on the type of hole, this probability varied from 2.3% to 18.4%. In addition to the random variables mentioned earlier, there were many decisions to analyze- the number of drilling rigs, the number of grouting machines, the distance between hole types, the number of stages and their depths for each hole type. You have been asked to supervise the development of this new project for the Electricity Corporation of New Zealand. They look to you for advice regarding the analytical tool(s) to be used for this study. You consider using decision analysis, and implementing Precision Tree, and the unique insights regarding this construction process you would hope to obtain based on the use of this modeling approach. You consider using simulation, and developing an @Risk model to evaluate this project, and the unique insights regarding the problem you would hope to obtain based on the use of this modeling approach. Finally, you consider using linear programming, or perhaps integer programming, using the professional large-scale version of the Excel Solver and the unique insights regarding the Clyde Dam construction project you would hope to obtain based on the use of this modeling approach. Suppose you can recommend the use of only one of the three approaches to analyzing this problem that you have considered above. Which one would it be? Why?
The Clyde Dam in the South island of New Zealand is located in an area more unstable than was thought when it was designed. It took more than 10 years to build and is the largest concrete dam in New Zealand. Therefore the Electricity Corporation of New Zealand has taken additional precautions to ensure the stability of the hillsides surrounding it by constructing an underground curtain of 1,362 meters along the Clutha River. Such a curtain is constructed by drilling holes in the rock and injecting concrete into them. This required hiring drilling rigs and the construction company wanted to minimize the drilling time of the drilling rigs to finish the project quickly.
From the few holes the company had already drilled, the company found that the drilling rigs were often idle while it pursued interrelated activities. Since these rigs were hired from an outside company at a cost of NZ$227/hour, this idling time was a major concern. It also meant that project completion would be delayed. There were five steps to creating the grout curtain: (1) drilling the holes, (2) washing out the holes, (3) performing a water test, (4) grouting the holes, and (5) allowing the grout to set. There were five different types of holes to drill along the 1,362 meter stretch (the number of each is indicated in parentheses) – primary (228), secondary (227), tertiary (454), quaternary (908), and quinary (1816). The drilling rate at each stage varied according to the rock conditions at different depths.
Each of the steps had random times associated with them. For example, step four had grouting times at the different stages with right-skewed distributions. After the fifth step, there was always some probability the hole would collapse and the process would have to be repeated. Depending on the type of hole, this probability varied from 2.3% to 18.4%. In addition to the random variables mentioned earlier, there were many decisions to analyze- the number of drilling rigs, the number of grouting machines, the distance between hole types, the number of stages and their depths for each hole type.
You have been asked to supervise the development of this new project for the Electricity Corporation of New Zealand. They look to you for advice regarding the analytical tool(s) to be used for this study. You consider using decision analysis, and implementing Precision Tree, and the unique insights regarding this construction process you would hope to obtain based on the use of this modeling approach. You consider using simulation, and developing an @Risk model to evaluate this project, and the unique insights regarding the problem you would hope to obtain based on the use of this modeling approach. Finally, you consider using linear programming, or perhaps integer programming, using the professional large-scale version of the Excel Solver and the unique insights regarding the Clyde Dam construction project you would hope to obtain based on the use of this modeling approach. Suppose you can recommend the use of only one of the three approaches to analyzing this problem that you have considered above. Which one would it be? Why?
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