Engineering classification of pedologic soil groups in Knox County, Tennessee, for residential housing

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Virginia Polytechnic Institute

The proper location of residential housing sites within large areas requires preliminary investigations of soil conditions. It is possible to process for engineering purposes the information contained in geologic and pedologic maps and reports. In this way, adverse site conditions, such as flooding, frost action, expansion and shrinkage of soils, which are currently causing widespread failures in residential developments, might often be avoided.

This study is concerned with the rating of the soils in Knox County, Tennessee, as to their suitability for residential locations based on information contained in a Soil Survey Report of Knox County, field investigations, and laboratory testing. For this, the soils of Knox County are grouped into eight groups; namely, recent alluvial soils, old alluvial soils, recent local fluvial soils, old local fluvial soils, soils in sinkholes, soils shallow to bedrock, soils deep to bedrock, and unclassified soils. Each of these groups possesses characteristic engineering features. The poor hydrologic position of alluvial soils, recent local fluvium, and soils in sinkholes renders them unsuitable for residential housing. In addition, the soils shallow to bedrock and the unclassified soils are considered as being of limited suitability. Other groups are generally favorable for the location of residential housing. Each of the soils in each of the groups is rated as to its suitability with respect to foundations, access roads, and individual absorption field sewage disposal systems. This rating is based on soil properties and test results. Suitability ratings of “favorable”, “conditional”, and “unsuitable” are adopted for rating the Knox County soils, but the pedologic names and map symbols are retained for the identification of each soil unit. This enables the engineer to interpret the Soil Survey Reports and Maps for engineering purposes, to locate engineering soil boundaries from those on pedologic maps, and to prepare engineering soil maps.