Work as a criterion for determining in situ and yield stresses in clays

1987 ◽  
Vol 24 (4) ◽  
pp. 549-564 ◽  
Author(s):  
D. E. Becker ◽  
J. H. A. Crooks ◽  
K Been ◽  
M. G. Jefferies
Keyword(s):  
Effective Stress ◽  
Unit Volume ◽  
In Situ Stress ◽  
Natural Clay ◽  
Linear Relationships ◽  
Clay Deposits ◽  
Preconsolidation Pressure ◽  
Significant Divergence ◽  
Oedometer Tests

A method of interpreting conventional oedometer test data using work per unit volume as a criterion for determining both in situ effective and yield stresses in clay is presented. This technique was applied to the results of oedometer tests carried out on samples of natural clay deposits and on specimens consolidated anisotropically from a slurry to a known effective stress state. The work per unit volume – effective stress relationship, using arithmetic scales, can be approximated or fitted using linear relationships. The intersections of these fitted lines are demonstrated to provide accurate values for in situ current and yield (preconsolidation) stresses. The yield stress is defined as the intersection of the initial fitted line and the linear relationship observed at higher stresses. The current effective stress is indicated by the first significant divergence of the data from the initial fitted line. These relationships apply to both conventionally (horizontally) trimmed specimens and to vertically trimmed oedometer samples. It is hypothesized that the in situ effective and yield stresses (in both the vertical and horizontal directions) in a natural clay can be determined by the work per unit volume interpretation of oedometer tests carried out on horizontally and vertically trimmed specimens. Key words: in situ, stress, yield, oedometer, interpretation, clays, work, state, K0, preconsolidation pressure.

Interpretation of overconsolidation ratio from in situ tests in Recent clay deposits in Singapore and Malaysia

1991 ◽  
Vol 28 (2) ◽  
pp. 210-225 ◽  
Author(s):  
M. F. Chang
Keyword(s):  
Site Investigation ◽  
Test Methods ◽  
In Situ Tests ◽  
Stress History ◽  
Overconsolidation Ratio ◽  
Clay Deposits ◽  
Preconsolidation Pressure ◽  
Pressure Stress ◽  
Sample Disturbance

The stress history as indicated by the profile of overconsolidation ratio (OCR) of a soil deposit is one of the most dominant factors that influence the engineering behaviour of the soil. Its assessment, which is traditionally based on the laboratory oedometer test, is not often satisfactory. The problem arises from inevitable sample disturbance and the high cost of a detailed investigation. These difficulties can be overcome by the use of in situ tests. The field vane test, the piezocone test, and the dilatometer test are three such methods that provide indirect means for the estimation of the OCR for clay deposits. A number of empirical correlations are available for this purpose. Calibration of these correlations against results of site investigation in Singapore and Malaysian marine clays reveals the usefulness of these test methods in profiling the OCR for Recent clay deposits. Key words: clay, in situ test, overconsolidation ratio, preconsolidation pressure, stress history.

Preconsolidation pressure of Champlain clays. Part I. In-situ determination

1983 ◽  
Vol 20 (4) ◽  
pp. 782-802 ◽  
Author(s):  
P. Morin ◽  
S. Leroueil ◽  
L. Samson
Keyword(s):  
Laboratory Tests ◽  
Research Study ◽  
Simple Correlation ◽  
Eastern Canada ◽  
Existing Structures ◽  
Undisturbed Samples ◽  
Preconsolidation Pressure ◽  
Oedometer Tests

The preconsolidation pressure of sensitive clays is an important parameter for the design of foundations on these soils, which are widespread in Eastern Canada and above all in the St. Lawrence and Ottawa Valleys where Champlain clays are found. A research study was initiated in 1979 to assess whether the preconsolidation pressure values derived from laboratory tests are representative of the preconsolidation pressure effectively mobilized in situ.Several existing structures were investigated and five of them are presented with performance records taken during and after construction together with data obtained from recent soil investigations. For each case study, the in-situ preconsolidation pressure is determined from the analysis of settlement and/or pore pressure records.The preconsolidation pressure values derived from conventional oedometer tests on good quality undisturbed samples are compared with the in-situ values and a simple correlation taking into account the overconsolidation ratio of the clay is proposed. Keywords: preconsolidation pressure, in-situ, laboratory, Champlain sea clays.

Statistical relationships between piezocone measurements and stress history of clays

1996 ◽  
Vol 33 (3) ◽  
pp. 488-498 ◽  
Author(s):  
B SY Chen ◽  
P W Mayne
Keyword(s):  
Cone Penetration ◽  
Stress History ◽  
Statistical Correlations ◽  
Cone Tip Resistance ◽  
Clay Deposits ◽  
Preconsolidation Pressure ◽  
Tip Resistance ◽  
History Of ◽  
Statistical Relationships ◽  
Oedometer Tests

A database containing piezocone soundings from 205 clay sites around the world has been compiled for the calibration of an analytical cone penetration model and the development of statistical correlations. Yield stresses from laboratory oedometer tests were used as reference values for determining the stress history of natural clay deposits. Both simple and multiple regression analyses were performed on these data to evaluate correlative trends. Several simplified empirical relationships were identified for use in practice with the most reliable in relating preconsolidation stress to net cone tip resistance. Key words: cone tip resistance, overconsolidation ratio (OCR), preconsolidation pressure, piezocone, statistical relationships, stress history.

scholarly journals Effect of sample disturbance on triaxial and oedometer behaviour of a stiff and heavily overconsolidated clay

2014 ◽  
Vol 51 (8) ◽  
pp. 896-910 ◽  
Author(s):  
Toralv Berre
Keyword(s):  
Shear Strength ◽  
Water Content ◽  
In Situ Stress ◽  
Undrained Shear Strength ◽  
Stress Strain ◽  
Effective Stresses ◽  
Sample Disturbance ◽  
Oedometer Tests ◽  
Undrained Shear

The tests in this investigation were performed on a natural soft clay with plasticity index around 32%, which was K0 consolidated to a vertical stress of 2942 kPa and then K0 unloaded to a vertical stress of 74 kPa (i.e., to the “in situ” stress). The specimens so created were disturbed in various ways to study the effect of sample disturbance on the stress–strain relationships during undrained shearing and during drained K0 loading (i.e., K0 triaxial and oedometer tests). The results for two testing alternatives may be summarized as follows. Alternative 1: Allow the specimen to swell at the correct in situ effective stresses, but accept an initial water content that is higher than the in situ value. This alternative was found to give the best stress–strain relationships around the in situ effective stresses for undrained triaxial tests, but with undrained shear strength values up to about 20% too low, due to the swelling taking place during consolidation to the in situ effective stresses. Alternative 2: Prevent swelling by starting the test at effective stresses that are higher than the in situ stresses, but with a water content that is closer to the in situ value than if alternative 1 is chosen. Using only isotropic stresses prior to shearing, this alternative was found to give better undrained shear strength values (although up to about 14% too high) but strain values much too small around the in situ effective stresses. For oedometer tests, only alternative 2 was investigated. Also, for these tests, the strains around the in situ stress were too small, but preconsolidation stresses estimated from stress–strain curves were typically only around 60% of the true value.

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