==>>SOIL SURVEYS FOR HIGHWAY CONSTRUCTION<<==

                   ==>>SOIL SURVEYS FOR HIGHWAY CONSTRUCTION<<==
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Soil surveys for highway construction entail the investigation of the soil characteristics on the highway route and the identification of suitable soils for use as sub base and fill materials. Soil surveys are therefore normally an integral part of preliminary location surveys, since the soil conditions may significantly affect the location of the highway. A detailed soil survey is always carried out on the final highway location. The first step in any soil survey is in the collection of existing information on the soil characteristics of the area in which the highway is to be located. Such information can be obtained from geological and agricultural soil maps, existing aerial photographs,and an examination of excavations and existing roadway cuts. It is also usually
helpful to review the design and construction of other roads in the area. The information obtained from these sources can be used to develop a general understanding of the soil conditions in the area and to identify any unique problems that may exist.The extent of additional investigation usually depends on the amount of existing information that can be obtained. The next step is to obtain and investigate enough soil samples along the highway route to identify the boundaries of the different types of soils so that a soil profile can
be drawn. Samples of each type of soil along the route location are obtained by auger boring or from test pits for laboratory testing. Samples are usually taken at different depths down to about five feet. In cases where rock locations are required, depths may be increased. The engineering properties of the samples are then determined and used to classify the soils. It is important that the characteristics of the soils in each hole
be systematically recorded, including the depth, location, thickness, texture, and so forth. It is also important that the location of the water level be noted. These data are then used to plot a detailed soil profile along the highway

==>>Geophysical Methods of Soil Exploration

Soil profiles can also be obtained from one of two geophysical methods of soil exploration known as the resistivity and seismic methods.

              1==>>Resistivity Method


The resistivity method is based on the difference in electrical conductivity or resistivity
of different types of soils.


              2==>>Seismic Method

The seismic method is used to identify the location of rock profiles or dense strata

underlying softer materials..

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