External Factors and Constraints
The major external factors of the Big Dig include weather, soil condition, union rules, lobbyists, gas prices, and raw materials prices. Weather conditions can affect many aspects of any construction project from site work to worker comfort. Soil structure is a particularly unique factor to a tunnel project. Unlike other transportation infrastructure parts, the ground surrounding a tunnel can act as a supporting mechanism, or loading mechanism, or both, depending on the nature of the ground, the tunnel size, and the method and sequence of constructing the tunnel. Thus, for tunnel designers, the rock or soil surrounding a tunnel is a construction material, just as important as the concrete and steel used on the job. Unions and lobbying from local residents and merchants contributed to many of the delays. Gas a raw material prices affect any large scale construction project. The major constraints are infrastructure constraints, safety standards, building codes, environmental constraints, and federal and local laws and regulations. The external factors and constraints are best illustrated in the following diagram:
The Big Dig construction project was comprised of dedicated systems that together to created a more complex system which had more functionality and performance than the combined functionality and performance of the constituent systems. As the popular saying goes: “The whole is greater than the sum of its parts”. The contractors and sub-contractors (including the Joint Venture of Bechtel and Parsons managing the overall construction) combined various legacy construction techniques to accomplish unprecedented construction feats, such as building a tunnel under railroad infrastructure without interrupting rail service, and building major new foundations around 150 year old utility lines without interrupting service to residents and businesses. We can also look at the planning stages from...
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