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The Misbehavior of the Laramie Formation Claystones
The Laramie Formation is the near-surface bedrock over much of the northern Front Range of Colorado. The Late Cretaceous bedrock is characterized by complexly interbedded sandstones and claystones with numerous vertical and lateral facies changes. The Lower Laramie also has coal beds that were mined in the areas near Marshall, Louisville, Lafayette, and the Tri-Towns. However, the main Laramie Formation lithology is claystones. In general, claystones are in the "gray" area between soil and rock and can be described as highly over-consolidated, very stiff, fissured clays. Claystones generally have the following properties: 1. low strength and are prone to landsliding; 2. are compressible under high structure loads; 3. are expansive and swell and shrink with changes in moisture content; 4. are prone to slaking and break down readily when exposed to air and water; and 5. are erodible when exposed to water. The Laramie claystones have caused numerous problems for civil structures and much of the construction in the northern Front Range area encounters this formation. The behavior, or rather the misbehavior, of the Laramie claystones largely results from their mineralogy. Laramie claystones are a smectite-rich (bentonite) mixed-layer clay of illite/smectite with lesser amounts of kaolinite and illite. The Laramie claystones are a very low-strength bedrock with low to very high swell potential. Plasticity Indices typically range from mid-20 percent to 50 percent and higher. The stress history of the claystones also has contributed to the properties and behavior of the Laramie claystones. This paper presents short examples and case histories that illustrate the properties of the Laramie claystones as encountered in civil projects.
The Misbehavior of the Laramie Formation Claystones
The Laramie Formation is the near-surface bedrock over much of the northern Front Range of Colorado. The Late Cretaceous bedrock is characterized by complexly interbedded sandstones and claystones with numerous vertical and lateral facies changes. The Lower Laramie also has coal beds that were mined in the areas near Marshall, Louisville, Lafayette, and the Tri-Towns. However, the main Laramie Formation lithology is claystones. In general, claystones are in the "gray" area between soil and rock and can be described as highly over-consolidated, very stiff, fissured clays. Claystones generally have the following properties: 1. low strength and are prone to landsliding; 2. are compressible under high structure loads; 3. are expansive and swell and shrink with changes in moisture content; 4. are prone to slaking and break down readily when exposed to air and water; and 5. are erodible when exposed to water. The Laramie claystones have caused numerous problems for civil structures and much of the construction in the northern Front Range area encounters this formation. The behavior, or rather the misbehavior, of the Laramie claystones largely results from their mineralogy. Laramie claystones are a smectite-rich (bentonite) mixed-layer clay of illite/smectite with lesser amounts of kaolinite and illite. The Laramie claystones are a very low-strength bedrock with low to very high swell potential. Plasticity Indices typically range from mid-20 percent to 50 percent and higher. The stress history of the claystones also has contributed to the properties and behavior of the Laramie claystones. This paper presents short examples and case histories that illustrate the properties of the Laramie claystones as encountered in civil projects.
The Misbehavior of the Laramie Formation Claystones
Spitzer, Roy H. (author) / Deere, Don W. (author)
Biennial Geotechical Seminar 2012 ; 2012 ; Denver, Colorado, United States
GeoChallenges ; 148-163
2012-11-09
Conference paper
Electronic Resource
English
Landslides , Hazards , Stones , Debris , Bedrock , Colorado , Tunnels , Clays , Rocky Mountains , Geotechnical engineering , Seismic effects , Soil mechanics , Foundations , Soil properties , Geology
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