Prediction of Engineering Properties and Construction Conditions from Geomorphic Mapping in Regional Siting Studies
Siting studies for the MX advanced ICBM program require a rapid and inexpensive method of evaluating construction conditions over large areas. The engineering evaluations important to MX siting are for road construction, excavation, and aggregate resources. Generalized evaluations of these parameters are greatly facilitated by geomorphic studies of terrain conditions, soil types, and induration of basin-fill deposits.
In the alluvial valleys of the Great Basin considered for MX siting, fluvial, eolian, lacustrine, and alluvial fan deposits have been differentiated according to grain size, relative age, and/or morphology. Map units thus directly address terrain conditions, soil type, and induration. Eolian and modern lacustrine (playa) deposits denote areas of predictable soil type and terrain. Fluvial, pluvial lacustrine, and alluvial fan deposits are highly variable in terms of soil type, induration, and terrain.
Sandy and gravelly alluvial fan and lacustrine deposits are most suitable for road construction from all standpoints except terrain, whereas eolian sands and fine-grained deposits are least suitable. Fine-grained lacustrine and alluvial fan deposits present fewest excavation difficulties, and cemented gravelly alluvial fan and lacustrine deposits present greatest difficulties. Sandy and gravelly lacustrine shoreline and alluvial fan deposits are most suitable for use in concrete aggregate but still require processing. Eolian sand and all fine-grained deposits are unsuitable as aggregate sources.