Engineering and Construction

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Selecting the general contractor is a crucial part of a project. A number of selection methods exist. The method used in selecting the general contractor, its timing, and the contractor’s obligations under the contract distinguishes one project delivery method from the other. Some of the most commonly used delivery methods are:

•    Design-bid-build  method
•    Design-negotiate-build  method
•    Construction manager as agent method
•     Construction  manager  at  risk   method
•    Design-build  method
•    Integrated  project  delivery  method

The design-bid-build method is the oldest and most familiar method of project delivery. This method is covered first. Because the essential features of construction and postconstruction phases are almost identical in all delivery methods, a discussion of what is included in these two phases is presented next. Subsequently, other methods are discussed in terms of how they differ from the design-bid-build method. The table “Project Delivery Methods at a Glance” provides a synopsis of these methods.

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The first step in a foundation investigation is to obtain preliminary information, such as the following:

1. Project location. Basic information on the location of the project is required. The location of the project can be compared with known geologic hazards, such as active faults, landslides, or deposits of liquefaction prone sand.

2. Type of project. The geotechnical engineer could be involved with all types of foundation engineering construction projects, such as residential, commercial, or public works projects. It is important to obtain as much preliminary information about the project as possible. Such information could include the type of structure and use, size of the structure including the number of stories, type of construction and floor systems, preliminary foundation type (if known), and estimated structural loadings. Preliminary plans may even have been developed that show the proposed construction.

3. Scope of work. At the beginning of the foundation investigation, the scope of work must be determined. For example, the scope of work could include subsurface exploration and laboratory testing to determine the feasibility of the project, the preparation of foundation design parameters, and compaction testing during the grading of the site in order to prepare the building pad for foundation construction.

After the preliminary information is obtained, the next step is to plan the foundation investigation work. For a minor project, the planning effort may be minimal. But for large-scale projects, the plan can be quite extensive and could change as the design and construction progresses. The planning effort could include the following:

• Budget and scheduling considerations
• Selection of the interdisciplinary team (such as geotechnical engineer, engineering geologist, structural engineer, hydrogeologist and the like) that will work on the project
• Preliminary subsurface exploration plan, such as the number, location, and depth of borings
• Document collection
• Laboratory testing requirements
• Types of engineering analyses that will be required for the design of the foundation

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For some projects, the foundation design requirements will be quite specific and may even be in writing. For example, a public works project may require a geotechnical investigation consisting of a certain number, type, and depth of borings, and may also specify the types of laboratory tests to be performed. The more common situation is where the client is relying on the geotechnical engineer to prepare a proposal, perform an investigation, and provide foundation design parameters that satisfy the needs of the project engineers and requirements of the local building officials or governing authority.

The general requirements for foundation engineering projects are as follows (Tomlinson, 1986):

1. Knowledge of the general topography of the site as it affects foundation design and construction, e.g., surface configuration, adjacent property, the presence of watercourses, ponds, hedges, trees, rock outcrops, and the available access for construction vehicles and materials

2. The location of buried utilities such as electric power and telephone cables, water mains, and sewers

3. The general geology of the area with particular reference to the main geologic formations underlying the site and the possibility of subsidence from mineral extraction or other causes

4. The previous history and use of the site including information on any defects or failures of existing or former buildings attributable to foundation conditions

5. Any special features such as the possibility of earthquakes or climate factors such as flooding, seasonal swelling and shrinkage, permafrost, or soil erosion

6. The availability and quality of local construction materials such as concrete aggregates, building and road stone, and water for construction purposes

7. For maritime or river structures, information on tidal ranges and river levels, velocity of tidal and river currents, and other hydrographic and meteorological data

8. A detailed record of the soil and rock strata and groundwater conditions within the zones affected by foundation bearing pressures and construction operations, or of any deeper strata affecting the site conditions in any way

9. Results of laboratory tests on soil and rock samples appropriate to the particular foundation design or construction problems

10. Results of chemical analyses on soil or groundwater to determine possible deleterious effects of foundation structures

Often the client lacks knowledge of the exact requirements of the geotechnical aspects of the pro- ject. For example, the client may only have a vague idea that the building needs a foundation, and therefore a geotechnical engineer must be hired. The owner assumes that you will perform an investigation and prepare a report that satisfies all of the foundation requirements of the project. Knowing the requirements of the local building department or governing authority is essential.

For example, the building department may require that specific items be addressed by the geotechnical engineer, such as settlement potential of the structure, grading recommendations, geologic aspects, and for hillside projects, slope stability analyses. Examples of problem conditions requiring special consideration are presented in Table 1.2. Even if these items will not directly impact the project, they may nevertheless need to be investigated and discussed in the geotechnical report.

There may be other important project requirements that the client is unaware of and is relying on the geotechnical engineer to furnish. For example, the foundation could be impacted by geologic hazards, such as faults and deposits of liquefaction prone soil. The geotechnical engineer will need to address these types of geologic hazards that could impact the site.

In summary, it is essential that the geotechnical engineer know the general requirements for the project (such as the 10 items listed earlier) as well as local building department or other regulatory requirements. If all required items are not investigated or addressed in the foundation engineering report, then the building department or regulatory authority may refuse to issue a building permit.

This will naturally result in an upset client because of the additional work that is required, delays in construction, and possible unanticipated design and construction expenses.