Constant rate of strain consolidation testing of soft clays and fibrous peats

2019 ◽  
Vol 56 (10) ◽  
pp. 1526-1533
Author(s):  
Gholamreza Mesri ◽  
Tao-Wei Feng
Keyword(s):  
Strain Rate ◽  
Flow Equation ◽  
Test Duration ◽  
Soft Clays ◽  
Vertical Strain ◽  
Empirical Correction ◽  
Preconsolidation Pressure ◽  
Constant Rate ◽  
Specimen Quality ◽  
Incremental Loading

The constant rate of strain (CRS) oedometer test, using an imposed vertical strain rate [Formula: see text] equal to 10 times the end-of-primary (EOP) vertical strain rate [Formula: see text], requiring a test duration of about 2 days produces reliable information on both the e versus log[Formula: see text] relation and e versus logkv relation of soft clays and fibrous peats. An empirical correction for the strain rate effect on preconsolidation pressure leads to the EOP e versus log[Formula: see text] relation and EOP [Formula: see text]. The imposed vertical strain rate [Formula: see text] produces excess pore-water pressures at the impervious bottom of the specimen, corresponding to [Formula: see text] values in the range of 3%–15% and allows, use of the Darcy flow equation, a reliable calculation of the coefficient of permeability. Compressibility and permeability data are from CRS and incremental loading (IL) oedometer tests on specimen quality designation (SQD) A samples of seven soft clays and two fibrous peats are presented in this paper.

New method to determine proper strain rate for constant rate-of-strain consolidation tests

2012 ◽  
Vol 49 (1) ◽  
pp. 18-26 ◽  
Author(s):  
A. Tolga Ozer ◽  
Evert C. Lawton ◽  
Steven F. Bartlett
Keyword(s):  
Strain Rate ◽  
Linear Equation ◽  
Pore Pressure ◽  
Void Ratio ◽  
Semiempirical Method ◽  
The Other ◽  
Initial Void Ratio ◽  
Constant Rate ◽  
Loading Tests ◽  
Incremental Loading

The development of a new semiempirical method to predict the proper strain rate for constant rate-of-strain (CRS) consolidation tests is described herein. The validity of the proposed method is analyzed using experimental results from CRS and incremental loading tests on four types of soil: Lake Bonneville clay, Massena clay, kaolinite, and montmorillonite. It is found that the maximum allowable strain rate depends on the initial void ratio of the soil and thus is related to the compressibility of the soil. The effect of the strain rate on the distribution of the pore pressure within the sample is investigated by comparing values of effective vertical stress calculated using a linear equation published by Wissa et al. in 1971 with values of effective stress at the base of the specimen determined from measured values of pore pressure. Overall, the proposed method predicts the maximum allowable strain rate very well for three of the four soils and moderately well for the other soil.

Profiling of overconsolidation ratio in clays by field vane

1988 ◽  
Vol 25 (1) ◽  
pp. 150-157 ◽  
Author(s):  
Paul W. Mayne ◽  
James K. Mitchell
Keyword(s):  
Shear Strength ◽  
Strain Rate ◽  
Undrained Shear Strength ◽  
Correction Factors ◽  
Test Results ◽  
Overconsolidation Ratio ◽  
Empirical Correction ◽  
Preconsolidation Pressure ◽  
Undrained Strength ◽  
Undrained Shear

The field vane (FV) has traditionally been utilized to obtain profiles of undrained shear strength in soft to medium clays. After some 40 years of experience with FV results, it has been suggested that empirical correction factors be applied to the FV data to account for the effects of strain rate, anisotropy, and disturbance on measured shear strengths. As an additional use of the device, the FV may be calibrated at each site to develop profiles of overconsolidation ratio (OCR) with depth. A data base of oedometer test results and FV strengths from 96 different clays has been compiled to use as a basis for this calibration. Key words: field vane, undrained strength, clay, overconsolidation ratio, preconsolidation pressure, shear strength, vane shear.

Mode based characterisation of swell deformations in a high plasticity Paleogene clay

2021 ◽  
Author(s):  
Emil Mejlhede Kinslev ◽  
Ole Hededal ◽  
Irene Rocchi ◽  
Varvara Zania
Keyword(s):  
Deformation Behaviour ◽  
Accurate Prediction ◽  
High Plasticity ◽  
Complex Deformation ◽  
Constant Rate ◽  
Incremental Loading

Accurate prediction of soil deformations is important in unloading as well as loading. Historically, however, the loading scenario has been the most common and thus the most extensively studied phenomenon, leaving unloading less well described. Overconsolidated high plasticity clays are particularly challenging in this regard due to their complex deformation behaviour that has previously shown two conceptually different unloading behaviours. Based on a series of incremental loading and constant rate of strain compression and swelling tests on folded Røsnæs Clay, these unloading behaviours are unified in a framework as different swell modes, and an additional swell mode is identified. These different modes represent a variation in swell inhibiting structure, seemingly unrelated to the structure in compression. The use of constant rate of strain tests greatly enhanced the detailed description of stiffness development in each mode, which may be characterised by up to three swell phases. The parameters governing the occurrence of the swell modes are identified along with the variables that define the transition between the swell phases and their detailed development.

scholarly journals Time-dependent behaviour of sand with different fine contents under oedometric loading

2019 ◽  
Vol 56 (1) ◽  
pp. 102-115 ◽  
Author(s):  
Friedrich Levin ◽  
Stefan Vogt ◽  
Roberto Cudmani
Keyword(s):  
Strain Rate ◽  
Creep Behaviour ◽  
Silty Sand ◽  
Granular Soils ◽  
Rate Dependency ◽  
Viscous Effects ◽  
Fine Content ◽  
Constant Rate ◽  
Rate Controlled ◽  
Strain Rate Dependency

To characterize the effects of creep, strain rate, and relaxation in granular soils, different sands have been studied under oedometric loading. The tests were analysed in the framework of the isotache concept. The results show increasing creep rates with increasing vertical stresses and a strong reduction of the creep rate upon unloading. A lower void ratio leads to less creep. Evaluation of the ratio Cα/Cc, where Cα is the creep coefficient and Cc is the compression index, demonstrates considerable deviation from a constant soil-specific value for the sands. With increasing fine content, however, a constant soil-specific ratio has been found for a silty sand. In strain rate–controlled tests, a sand with low and a sand with significant content of nonplastic fines were compared. Constant rate of strain tests displayed practically no strain rate dependency for the sand with little fines and a well visible strain rate dependency for the very silty sand. Tests with stepwise change of strain rate showed non-isotache behaviour for the sand with little fines and isotache behaviour for the other. Stress-relaxation tests displayed an isochronous behaviour. The analysis of the three viscous effects in sands showed they cannot altogether be mathematically described in the framework of the isotache concept. A new compression model for the creep behaviour of sands is presented.

scholarly journals Short-period observations of speed, strain and seismicity on Ice Stream B, Antarctica

1993 ◽  
Vol 39 (133) ◽  
pp. 463-470 ◽  
Author(s):  
W. D. Harrison ◽  
K. A. Echelmeyer ◽  
H. Engelhardt
Keyword(s):  
Strain Rate ◽  
High Strain ◽  
Ross Sea ◽  
Diurnal Variations ◽  
Atmospheric Effects ◽  
Vertical Strain ◽  
Ice Stream ◽  
Short Period ◽  
Local Modification ◽  
Ice Stream B

AbstractThe speed of Ice Stream B, Antarctica, was measured twice a day-over a 1 month study period, and found to be steady at about the ±3½% level, the sensitivity of the measurements. The vertical strain was measured at three sites over a 1 year period at 1 h intervals with sensitivities of 2 or 0.2 ppm. The strain rate varied on all time-scales. Events of high strain rate were observed, but never at more than one site at a time. They can probably be understood in terms of local modification of the strain field associated with crevassing. Diurnal variation in strain rate was observed at one and possibly two sites during two summers. The seismicity was measured at all three sites, and diurnal and seasonal variations were prominent at all, the seismicity being much more intense in winter. Several possible causes of the diurnal variations in strain and seismicity are considered: thermal and atmospheric effects, and the effects of tides in the Ross Sea.

scholarly journals Depth- and time-dependent vertical strain rates at Siple Dome, Antarctica

2004 ◽  
Vol 50 (171) ◽  
pp. 511-521 ◽  
Author(s):  
Daniel H. Elsberg ◽  
William D. Harrison ◽  
Mark A. Zumberge ◽  
John L. Morack ◽  
Erin C. Pettit ◽  
...  
Keyword(s):  
Strain Rate ◽  
Time Dependence ◽  
Strain Gauge ◽  
Water Pressure ◽  
Time Dependent ◽  
Strain Rates ◽  
Ice Streams ◽  
Vertical Strain ◽  
Siple Dome ◽  
A Site

AbstractAs part of a project to investigate the flow of ice at low effective stress, two independent strain-gauge systems were used to measure vertical strain rate as a function of depth and time at Siple Dome, Antarctica. The measurements were made from January 1998 until January 2002 at the ice divide and a site 7km to the northeast on the flank. The strain-rate profiles place constraints on the rheology of ice at low stress, show the expected differences between divide and flank flow (with some structure due to firn compaction and probably ice stratigraphy), and suggest that the flow of the ice sheet has not changed much in the last 8.6 kyr. The strain rates show an unexpected time dependence on scales ranging from several months to hours, including discrete summer events at the divide. Time dependence in strain rate, water pressure, seismicity, velocity and possibly basal motion has been seen previously on the Siple Coast ice streams, but it is especially surprising on Siple Dome because the bed is cold.

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