Sample disturbance effects on medium plasticity clay/silt

The dissipated strain energy method (DSEM), a new method for determining the preconsolidation pressure, is presented in this paper. Compared with the energy method, the DSEM uses dissipated strain energy and the slope of the unloadingreloading cycle (in the strain energy effective consolidation stress space) for the plot to minimize the sample disturbance effects and eliminate the effect of elastic deformation. Dissipated strain energy, in terms of micro mechanics, is directly related to the irreversible process of consolidation and can be supported by theories dealing with consolidation and compaction. The use of the unloadingreloading slope to simulate the elastic reloading for the recompression stage can minimize sample disturbance effects. Examples presented indicate that the proposed new method is less operator dependent than most of the existing methods.Key words: dissipated strain energy, preconsolidation pressure, consolidation, energy method, dissipated strain energy method.

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1623 - Environmental disturbance effects on community structure and function of microbial mats from hypersaline lakes on Rottnest Island (Western Australia)

10.26226/morressier.5b5199c4b1b87b000eceefb6 ◽

2018 ◽

Author(s):

Juliana Mendes Monteiro

Keyword(s):

Community Structure ◽

Western Australia ◽

Microbial Mats ◽

Structure And Function ◽

Environmental Disturbance ◽

Hypersaline Lakes ◽

Disturbance Effects ◽

And Function

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An X-ray CT study of miniature clay sample preparation techniques

E3S Web of Conferences ◽

10.1051/e3sconf/20199201004 ◽

2019 ◽

Vol 92 ◽

pp. 01004

Author(s):

Christopher Ibeh ◽

Matteo Pedrotti ◽

Alessandro Tarantino ◽

Rebecca Lunn

Keyword(s):

Sample Preparation ◽

Shear Plane ◽

Cohesive Soil ◽

Image Resolution ◽

Particle Orientation ◽

X Ray ◽

High Resolution Images ◽

X Ray Computed ◽

Sample Disturbance ◽

Relationship Of

The quality and reliability of cohesive soil laboratory test data can be significantlyaffected by sample disturbance during sampling or sample preparation. Sample disturbance may affect key design and modelling parameters such as stiffness, preconsolidation stress, compressibility and undrained shear strength, and ultimately determine particle mobilization and shear plane development. The use of X-ray computed tomography (X-CT) in the study of soil is restricted by the inverse relationship of specimen size and obtainable image resolution. This has led to the testing of miniature specimen sizes which are far less than conventional laboratory sample size in a bid to obtain high resolution images and detailed particle-scale soil properties; however, these miniature soil specimens are more prone to sample disturbance. In this work 2% muscovite was mixed with speswhite kaolin clay as a strain marker for use in X-CT. The clay soil sample was prepared from slurry and either consolidated using an oedometer or a gypsum mould. Specimens obtained from a 7 mm tube sampler were compared to lathe trimmed specimens with a diameter (Ø) of 7 mm. Results from X-CT imaging were used to study the influence of sampler type on specimen disturbance, by analysing the muscovite particle orientation of the obtained 3D images. The results show that; for samples subjected to large consolidation stress (>200kpa) lathe trimmed specimens may be subject to lesser disturbance compared to tube sampled specimens.

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Laboratory and In Situ Determination of Hydraulic Conductivity and Their Validity in Transient Seepage Analysis

Water ◽

10.3390/w13081131 ◽

2021 ◽

Vol 13 (8) ◽

pp. 1131

Author(s):

Soonkie Nam ◽

Marte Gutierrez ◽

Panayiotis Diplas ◽

John Petrie

Keyword(s):

Hydraulic Conductivity ◽

Field Measurements ◽

Natural Soil ◽

In Situ Tests ◽

Seepage Analysis ◽

Soil Deposits ◽

Seepage Modeling ◽

Sample Disturbance

This paper critically compares the use of laboratory tests against in situ tests combined with numerical seepage modeling to determine the hydraulic conductivity of natural soil deposits. Laboratory determination of hydraulic conductivity used the constant head permeability and oedometer tests on undisturbed Shelby tube and block soil samples. The auger hole method and Guelph permeameter tests were performed in the field. Groundwater table elevations in natural soil deposits with different hydraulic conductivity values were predicted using finite element seepage modeling and compared with field measurements to assess the various test results. Hydraulic conductivity values obtained by the auger hole method provide predictions that best match the groundwater table’s observed location at the field site. This observation indicates that hydraulic conductivity determined by the in situ test represents the actual conditions in the field better than that determined in a laboratory setting. The differences between the laboratory and in situ hydraulic conductivity values can be attributed to factors such as sample disturbance, soil anisotropy, fissures and cracks, and soil structure in addition to the conceptual and procedural differences in testing methods and effects of sample size.

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