Activity 4.5.1:  Almost any structure we build rests on the ground. Before we can design the structure or determine a site grading plan, we must understand the soil conditions. Soil is made up of many different size grains of broken-down rock (sand, silt, and clay). How much water a soil will hold, how easily water passes through the soil, and what happens to the soil as it dries depend on the combination of these materials in your particular soil. The regions climate and weather conditions and their affect on the soil must be considered.

Before the design of a major project, such as a highway, building, bridge or dam, can begin, the ground underneath the proposed construction site must be tested to determine composition and other factors affecting its load-bearing capacity. On large projects, core samples are used. Engineers use a drill to remove samples of earth at prescribed intervals. Sometimes core samples are taken from a depth of one hundred feet or more. The samples are then brought to the surface for study.

A geotechnical engineer, which is a type of civil engineer, collaborates with a surveyor to map grades, slopes and any modifications that may have been made to the site. The engineers will determine appropriate sites and depths for taking soil samples. Boring sites will include areas where filling and cutting may occur during construction. In addition, engineers will develop preliminary concepts for drainage structures that may be needed to direct water away.

Not every project needs test borings. However, you must know the basic soil type before you can proceed. In this activity, you will be using some tests to quickly determine a soil type. By identifying the soil type and properties using a chart, you will be able to make some preliminary decisions regarding grading and load bearing characteristics.

Activity 4.5.2:  Construction of any kind of a structure requires preparation of the site. Foundations, abutments, or roadbeds require the removal of the top layer of soil that contains organic matter. Once that layer is removed, we might have to dig deeper or add soil material to level a spot. Soil is expensive to move so extensive planning is done. Soil is also expensive to purchase; therefore, existing topsoil is set aside for future use in the final stages of grading and landscaping. The plot is studied, and the site plan is adjusted many times to balance the amount of soil to be removed with the amount needed to level the site. In addition, plans must be made for the angle of repose, or desired slope of the area around the structure. The process is called cut and fill.

There are times the soil that is removed or “cut” can be reused for fill. Other times, because of drainage, load bearing, or organic characteristics, the soil is not suitable and must be disposed of, which adds to the cost of the project. Knowledge of the type of soil is important in making decisions. Once final decisions are made, the site-grading plan is created. Engineers working with modern software can query the software to find the total cut and fill and make projections on cost.

Cut and fill can be planned and simulated with computer software which breaks the surface down into triangular shapes which are a more accurate way of calculation. In this activity, you will explore the concepts behind cut and fill by examining a simple excavation.

Activity 4.5.4:  A survey is a map (drawing) that shows the exact size, shape, and level of a lot. When prepared by a licensed surveyor, the survey is a legal document and filed with the deed to the property, generally at the local courthouse.

When a building cannot be laid out by working from reference lines, the builder or surveyor is able to use several kinds of surveying instruments. These instruments work with either optical or laser technology. Some surveying activities are based on Global Positioning System (GPS) technology. GPS works very well for topographic mapping, wetland delineation, and such; however, most property surveys are performed using optical or laser equipment.

Surveyors who use optical instruments rely on line-of-site observations to determine position. The user looks through the instrument to spot a target or leveling rod held by an assistant. The leveling rod is a slender, straight rod marked with graduations in feet and fractions of a foot. It is held in a vertical position during use. Leveling rods come in different varieties; one of the most common is the Philadelphia rod.

The two basic types of surveying instruments used in construction are levels and transits. Both are used atop a tripod for ensuring steadiness and accuracy.

The telescope of a level is fixed in a horizontal plane. It can be used for measuring horizontal angles because it cannot tilt up or tilt down. The level can also be used to accurately measure changes in elevations (vertical difference) and estimate horizontal distances (stadia calculations). The level is a standard piece of equipment for most construction outfits.