lacustrine clay | ScienceGate

AbstractWe present a sediment-mixing process model of till genesis based on data from surface tills of the Saginaw lobe terrain in lower Michigan. Our research uses a spatial approach to understanding glacial landsystems and till genesis. We sampled calcareous till at 336 upland sites and at 17 sites in lacustrine sediment of the Saginaw Lake plain. The loamy tills have bimodal grain-size curves, with a fine-texture mode near the silt–clay boundary and a sand mode. Spatial grouping analysis suggests that tills can be divided into six groups, each with different textures and clay mineral compositions that vary systematically down-ice. The similarity among groups with respect to the silt–clay mode and clay mineralogy argues for a common origin for the fines—illite-rich lacustrine sediment of the Saginaw Lake plain. Fine-textured sediments were probably entrained, transported, and deposited down-ice as till, which also becomes sandier and enriched in kaolinite, reflecting increasing mixing with shallow sandstone bedrock with distance from the lacustrine clay source. Clayey tills on the flanks of the Saginaw terrain may reflect proglacial ponding against nearby uplands. A process model of progressive down-ice mixing of preexisting fine lake sediments with crushed/abraded sandstone bedrock helps to better explain till textures compared with a purely crushing/abrasion process model.

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Behaviour of a cemented clay

Canadian Geotechnical Journal ◽

10.1139/t95-086 ◽

1995 ◽

Vol 32 (5) ◽

pp. 899-904 ◽

Cited By ~ 11

Author(s):

Jaroslav Feda

Keyword(s):

Shear Strength ◽

Pressure Measurement ◽

Pore Water Pressure ◽

Water Pressure ◽

Stress Strain ◽

Factors Affecting ◽

Undisturbed Samples ◽

Principal Factors ◽

Lacustrine Clay ◽

Sample Disturbance

A series of 18 triaxial CIUP (undrained isotropically consolidated with pore pressure measurement) tests of fissured cemented Neogene lacustrine clay from northern Bohemia is analyzed, with special reference to the shear strength. The effects of sample disturbance, swelling, and cementation are shown to be the principal factors affecting the shear envelope. During the prepeak stage of testing, destruction of the cementation of some specimens occurs, which is reflected in the wavy form of the stress–strain diagrams. The linear strength envelopes were found to be arranged according to the amount of disturbance (as expressed in the magnitude of swelling). Cemented and uncemented specimens differ when pore-water pressure and stress–strain diagrams are compared. Key words : Miocene clay, undisturbed samples, triaxial test, structural bonds, cementation, sample disturbance.

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Yielding and rupture in a lacustrine clay

Canadian Geotechnical Journal ◽

10.1139/t80-063 ◽

1980 ◽

Vol 17 (4) ◽

pp. 559-573 ◽

Cited By ~ 10

Author(s):

A. Baracos ◽

J. Graham ◽

L. Domaschuk

Keyword(s):

Shear Failure ◽

Friction Angle ◽

In Situ Stress ◽

Grain Structure ◽

Testing Procedures ◽

Straight Line ◽

Stress Levels ◽

Lacustrine Clay ◽

Field Behaviour

Recent tests have examined the properties of block samples and tube samples from depths to 12 m in Winnipeg clay. Careful trimming and a wide variety of testing procedures have permitted new insights into the behaviour of the clay that is markedly anisotropic and non-homogeneous. The effective strength envelope for "blue clay" from 6 to 12 m depth can be simplified into three straight-line sections. At low stresses, a section of the envelope has been identified having a low cohesion intercept and a high "friction" angle. This is thought to be caused by close Assuring in the clay, and controls the field behaviour in many small embankment, riverbank, and excavation problems. At in situ stress levels, the clay dilates markedly as failure is approached. Porewater pressures depend strongly on stress levels during laboratory reconsolidation. Residual strengths are low, and are influenced by the methods used during testing. Yielding has been clearly identified for shear failure of the grain structure, but is more poorly defined for increasing normal octahedral stresses. The work has emphasized the importance of selecting appropriate testing procedures and stresses for field applications.

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