scholarly journals Improved Determination of Preconsolidation Pressure of a Sensitive Clay

2009 ◽  
pp. 254-254-18 ◽  
Author(s):  
J. J. Hamilton ◽  
C. B. Crawford
Keyword(s):  
Preconsolidation Pressure ◽  
Sensitive Clay

Electroosmotic strengthening of soft sensitive clays

1991 ◽  
Vol 28 (1) ◽  
pp. 62-73 ◽  
Author(s):  
K. Y. Lo ◽  
I. I. Inculet ◽  
K. S. Ho
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Strength Increase ◽  
Sample Length ◽  
Voltage Distribution ◽  
Steady Current ◽  
Preconsolidation Pressure ◽  
Sensitive Clay ◽  
Pressure Stress

A comprehensive experimental investigation on the electroosmotic strengthening of soft sensitive clay was performed to assess the effectiveness of the treatment and to study the mechanism of the process. A specially designed electroosmotic cell was developed to prevent gas accumulation near the electrodes, to allow better electrode-soil contact, and to improve the treatment efficiency. This apparatus also enables the monitoring of the generated negative pore-water pressure along the sample length, settlement, voltage distribution, and current variation during treatment. The investigation covered two different types of soil trimmed at different orientations: the vertically and horizontally trimmed overconsolidated Wallaceburg clay and the vertically trimmed slightly overconsolidated soft sensitive Gloucester (Leda) clay. Results of this study showed that the voltage distribution and induced negative pore pressure at equilibrium along the sample are linear with steady current flow across the sample, indicating that the electrode design in the electroosmosis test apparatus is efficient. The electroosmotic consolidation curve is similar to that of the conventional consolidation curve, and the preconsolidation pressure was increased by 51–88% with an applied voltage up to 6 V. The undrained shear strength increased to a maximum of 172%, and the moisture content decreased by 30%. The technique of electrode reversal is employed, and a relatively uniform strength increase between the electrodes is observed. Key words: electroosmosis, electroosmotic cell, soft sensitive clay, negative pore-water pressure, preconsolidation pressure, stress–strain behaviour.

A novel technique of electrical strengthening of soft sensitive clays by dielectrophoresis

1992 ◽  
Vol 29 (4) ◽  
pp. 599-608 ◽  
Author(s):  
K. Y. Lo ◽  
K. S. Ho ◽  
I. I. Inculet
Keyword(s):  
Shear Strength ◽  
Electric Field ◽  
High Voltage ◽  
Alternating Current ◽  
Novel Technique ◽  
Strain Behaviour ◽  
Preconsolidation Pressure ◽  
Electro Osmosis ◽  
Sensitive Clay ◽  
Applied Electric Potential

A novel technique of electrical strengthening of soil by dielectrophoresis was developed. The process employs an alternating current at high voltage, generating a converging electric field towards the electrode by which a net resultant movement of water in the clay mass is produced towards the direction of stronger electric field intensity. Laboratory tests were developed to investigate the mechanism of this process and to explore the possibility of its application in electrical strengthening of soft sensitive clays. The preliminary results of this study showed that the process is effective, and the shear strength of the treated clay (Wallaceburg clay) increased drastically by several times with a reduction of moisture content of approximately 25% at an applied electric potential of 20 kV for 28 days. When compared with electro-osmosis, similar results are obtained in dielectrophoresis, such as the increase in preconsolidation pressure, decrease in sensitivity, and improvement of stress–strain behaviour. It is also shown that the improvement of soil properties can be greatly enhanced by increasing the applied voltage and electrode depth. Key words : dielectrophoresis, alternating current, converging electric field, high-voltage electrode, dielectric constant, electro-osmosis, soft sensitive clay, shear strength, consolidation.

Estimation of some properties of Champlain clays with the Swedish fall cone

1977 ◽  
Vol 14 (4) ◽  
pp. 571-581 ◽  
Author(s):  
R. Garneau ◽  
J. P. LeBihan
Keyword(s):  
Void Ratio ◽  
Liquid Limit ◽  
Physical Characteristics ◽  
Unit Weight ◽  
Compression Index ◽  
Cone Penetration ◽  
Testing Procedures ◽  
Preconsolidation Pressure ◽  
Marine Clays

A large number of laboratory tests, carried out to determine index and physical characteristics of Champlain marine clays, using conventional testing procedures and the Swedish fall cone tests, have led to reliable relationships between the cone penetration and certain characteristics.The purpose of this study has been to establish a rapid method of estimating some index and physical characteristics of this clay. The method described in this paper allows the estimation of clay properties, such as liquid limit, compression index, preconsolidation pressure, undisturbed and remolded shear strength, sensitivity, water content, void ratio, and unit weight, within as little as half an hour and using a single undisturbed specimen. When testing according to conventional procedures, the determination of these characteristics takes several days or even weeks.This paper presents the method of estimation and the procedure used to establish the relationships between the results obtained by conventional methods and those derived using the Swedish fall cone.

Electrical strengthening of clays by dielectrophoresis

1994 ◽  
Vol 31 (2) ◽  
pp. 192-203 ◽  
Author(s):  
K.Y. Lo ◽  
J.Q. Shang ◽  
I.I. Inculet
Keyword(s):  
Shear Strength ◽  
Electric Field ◽  
Soil Improvement ◽  
Nonuniform Electric Field ◽  
Experimental Program ◽  
Effective Polarizability ◽  
Clay Particles ◽  
Shearing Resistance ◽  
Preconsolidation Pressure ◽  
Sensitive Clay

The theory of dielectrophoresis in clay–water–electrolyte systems is developed in this paper. Dielectrophoresis is the motion of particles generated by a nonuniform electric field. The dielectrophoretic forces on clay particles are determined by the effective polarizability and configuration of the nonuniform electric field. In most clay–water–electrolyte systems, including natural clays, the dielectrophoretic forces are directed towards the lower field intensity, determined by the negative polarizability. In the experimental program, an ac voltage of 60 Hz and 15 kV was applied through insulated electrodes on block samples of Leda clay for 28 days. The relationship between the soil undrained shear strength after treatment and the distribution of electric field provides direct experimental support for the theory developed. Under three electrical-field configurations, the overall shear strengths increased up to 44.0%, concurrent with significant reduction of sensitivity. The improvement of soil properties was also reflected as increases of preconsolidation pressure and shearing resistance in terms of effective stresses. The electrochemical reactions associated with electric current were minimized by insulation to the electrodes. Key words : dielectrophoresis, electrokinetics, soil improvement, sensitive clay, shear strength.

An approach for the determination of the preconsolidation pressure in sensitive clays

1980 ◽  
Vol 17 (3) ◽  
pp. 446-453 ◽  
Author(s):  
S. Leroueil ◽  
J. P. LeBihan ◽  
F. Tavenas
Keyword(s):  
Pore Pressure ◽  
Theoretical Basis ◽  
Axial Stress ◽  
New Method ◽  
One Stage ◽  
Preconsolidation Pressure ◽  
Constant Rate ◽  
Constant Gradient ◽  
Oedometer Tests

The present methods for the determination of the preconsolidation pressure of clays are time consuming and expensive. A new method is proposed in which the clay is loaded in a "one-stage loading" to an axial stress in excess of the estimated preconsolidation pressure. The preconsolidation pressure is determined from the observation of the pore pressure dissipation within a few hours. The theoretical basis of this method is also used to discuss the method of interpreting constant rate of strain and constant gradient oedometer tests.

Evaluation of preconsolidation pressure and the overconsolidation ratio from piezocone tests of clay deposits in Quebec

2002 ◽  
Vol 39 (1) ◽  
pp. 174-192 ◽  
Author(s):  
Denis Demers ◽  
Serge Leroueil
Keyword(s):  
Mechanical Behaviour ◽  
Laboratory Tests ◽  
Local Data ◽  
Overconsolidation Ratio ◽  
Clay Deposits ◽  
Pressure Profiles ◽  
Preconsolidation Pressure ◽  
Tip Resistance ◽  
Sensitive Clay

The preconsolidation pressure and overconsolidation ratio profiles are the most important factors related to the mechanical behaviour of clay deposits. They are interpreted on the basis of a limited number of laboratory tests, but the near-continuous information provided by the piezocone can allow local data to be extrapolated to an entire site. Numerous methods have been proposed for relating piezocone data to preconsolidation pressure and the overconsolidation ratio, but their validity is still uncertain. In this paper, nine methods are compared on the basis of data collected on 31 sensitive clay sites in Quebec whose preconsolidation pressure profiles are well known. Each method is briefly presented and the most promising are identified. The simplest method, which directly relates preconsolidation pressure to net tip resistance, also appears to be the most effective.Key words: clay, preconsolidation pressure, overconsolidation ratio, piezocone, correlations.

Log-Log Method for Determination of Preconsolidation Pressure

1989 ◽  
Vol 12 (3) ◽  
pp. 230 ◽  
Author(s):  
VP Drnevich ◽  
BT Jose ◽  
A Sridharan ◽  
BM Abraham
Keyword(s):  
Preconsolidation Pressure
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