Evaluation of excess pore pressures and drainage conditions around driven piles using the cone penetration test with pore pressure measurements

1990 ◽  
Vol 27 (2) ◽  
pp. 249-254 ◽  
Author(s):  
P. K. Robertson ◽  
D. J. Woeller ◽  
D. Gillespie
Keyword(s):  
Pore Pressure ◽  
Large Diameter ◽  
Cone Penetration Test ◽  
Pressure Measurements ◽  
Penetration Test ◽  
Cone Penetration ◽  
Pore Pressures ◽  
Clayey Silt ◽  
Excess Pore Pressures ◽  
Excess Pore

Large-diameter steel pipe piles were driven as part of the foundations for the Alex Fraser Bridge near Vancouver, British Columbia. The piles penetrated through a normally consolidated marine clayey silt. As part of the geotechnical studies a multipoint piezometer was installed close to the pile group. A cone penetration test with pore pressure measurements (CPTU) was performed adjacent to one of the piles shortly after driving. During the CPTU through the clayey silt deposit, dissipation tests were performed to evaluate the pore pressures around the nearby pile. The CPTU results are compared with the pore pressures recorded at the multipoint piezometer, allowing for differences in radial distance from the piles. Excellent agreement was obtained between the CPTU and multipoint piezometer data, both showing large excess pore pressures around the piles. The CPTU dissipation data were also analyzed to evaluate the time required for dissipation of excess pore pressures around the piles. The upper half of the clayey silt deposit was inter bedded with thin sand and silt layers. The CPTU data showed that the thin sand layers were sufficiently large in extent to allow rapid dissipation of the pore pressures due to cone penetration but were not of sufficient extent to allow dissipation of the excess pore pressures from the much larger diameter piles. Key words: in situ, piles, pore pressures, CPT.

Analysis of the Pore Pressure Changes Following the Excavation of a Slope

1975 ◽  
Vol 12 (3) ◽  
pp. 429-440 ◽  
Author(s):  
Kurt D. Eigenbrod
Keyword(s):  
Pore Pressure ◽  
Field Data ◽  
Pressure Measurements ◽  
Pore Pressures ◽  
Field Evidence ◽  
Slope Excavation ◽  
Order Of Magnitude ◽  
Excess Pore Pressures ◽  
Pressure Changes ◽  
Excess Pore

In a numerical analysis the pore pressure changes due to excavation of a slope and the subsequent dissipation of excess pore pressures were calculated. The analytical results of the pore pressure changes due to unloading of a slope agree reasonably well with pore pressure measurements in comparable embankments. This suggests that pore pressures immediately after slope excavation can be predicted analytically in homogeneous materials.The results of an analysis dealing with the dissipation of excess pore pressures due to unloading can also be substantiated by field evidence; however, only few comparable field data are available. For many slopes it can be noted that the time for full dissipation is of the same order of magnitude as the time between excavation and failure. This suggests that many failures might be caused by the delayed equalization of pore pressures.

Effects of test procedure on flat dilatometer test (DMT) results in intermediate soils

2016 ◽  
Vol 53 (8) ◽  
pp. 1270-1280 ◽  
Author(s):  
F. Schnaid ◽  
E. Odebrecht ◽  
J. Sosnoski ◽  
P.K. Robertson
Keyword(s):  
Pore Pressure ◽  
Soft Clay ◽  
Test Procedure ◽  
Pressure Measurements ◽  
Dimensionless Velocity ◽  
Pore Pressures ◽  
Rate Effects ◽  
Excess Pore Pressures ◽  
Excess Pore ◽  
Flat Dilatometer Test

The evaluation of rate effects on the flat dilatometer test (DMT) can best be developed with some knowledge of the excess pore pressures generated during penetration, dissipation, and subsequent membrane expansion. While research that includes pore pressure measurements in the DMT has documented drainage conditions in clean sand and soft clay, further studies are required to determine the drainage conditions during the DMT in intermediate permeability soils, such as silts. For that purpose, a simple and inexpensive research device has been developed for monitoring pore pressures at the center of the DMT blade. Data using both a standard DMT and the modified research DMT from various tests in sand, silt, and clay have been compared in a space that correlates dimensionless velocity to degree of drainage. In this space, it is possible to evaluate whether partial drainage is taking place. Measurements indicate that the DMT is essentially undrained in soft clay and dominated by penetration pore pressures, is drained in clean sand and is partially drained in intermediate permeability soils, such as silt. A method is suggested to identify soils where partial drainage may influence the standard DMT results.

Interpretation of cone penetration tests. Part I: Sand

1983 ◽  
Vol 20 (4) ◽  
pp. 718-733 ◽  
Author(s):  
P. K. Robertson ◽  
R. G. Campanella
Keyword(s):  
Shear Strength ◽  
Pore Pressure ◽  
Cone Penetration Test ◽  
Deformation Characteristics ◽  
Penetration Test ◽  
Cone Penetration ◽  
Stress History ◽  
Penetration Testing ◽  
Cone Penetration Testing ◽  
Recent Developments

Significant advances have been made in recent years in research, development, interpretation, and application of cone penetration testing. The addition of pore pressure measurements during cone penetration testing has added a new dimension to the interpretation of geotechnical parameters.The cone penetration test induces complex changes in stresses and strains around the cone tip. No one has yet developed a comprehensive theoretical solution to this problem. Hence, the cone penetration test provides indices which can be correlated to soil behaviour. Therefore, the interpretation of cone penetration data is made with empirical correlations to obtain required geotechnical parameters.This paper discusses the significant recent developments in cone penetration testing and presents a summarized work guide for practicing engineers for interpretation for soil classification, and parameters for drained conditions during the test such as relative density, drained shear strength, and deformation characteristics of sand. Factors that influence the interpretation are discussed and guidelines provided. The companion paper, Part II: Clay, considers undrained conditions during the test and summarizes recent developments to interpret parameters for clay soils, such as undrained shear strength, deformation characteristics of clay, stress history, consolidation characteristics, permeability, and pore pressure. The advantages and use of the piezometer cone are discussed as a separate topic in Part II: Clay. The authors' personal experiences and current recommendations are included. Keywords: static cone penetration testing, in situ, interpretation, shear strength, modulus, density, stress history, pore pressures.

Tassement et consolidation au dégel d'un silt argileux à Kangiqsualujjuaq

1991 ◽  
Vol 28 (5) ◽  
pp. 678-689
Author(s):  
Serge Leroueil ◽  
Guy Dionne ◽  
Michel Allard
Keyword(s):  
Key Words ◽  
Physical Characteristics ◽  
Pore Pressures ◽  
Clayey Silt ◽  
Excess Pore Pressures ◽  
Excess Pore

The physical characteristics, the compressibility, and the consolidation of a permafrost clayey silt of Kangiqsualujjuaq, Quebec, have been studied, in the laboratory and in the field, by melting the permafrost in the foundation of an excavation. It appears that the values of the thawing settlement parameter (A0) obtained in the laboratory and in the field coincide perfectly with one another, and with those found in the literature for the same type of soil. It has also been observed, on that site, that the thawing of the permafrost, even though ice-rich, does not generate excess pore pressures. Key words: permafrost, compressibility, consolidation, laboratory, in situ. [Journal translation]

Development of pore pressures in quasi-static penetration tests in sensitive clay

1982 ◽  
Vol 19 (2) ◽  
pp. 124-138 ◽  
Author(s):  
Marius Roy ◽  
Michel Tremblay ◽  
François Tavenas ◽  
Pierre La Rochelle
Keyword(s):  
Penetration Test ◽  
Sensing Element ◽  
Cone Penetration ◽  
Pore Pressures ◽  
Soil Deposits ◽  
Sensitive Clay ◽  
Rate Of Dissipation ◽  
Excess Pore Pressures ◽  
Penetration Tests ◽  
Static Cone Penetration Test

The static cone penetration test is a valuable tool for the investigation of soil deposits but its potential may be further improved in the future if the pore pressures generated around the cone tip during the penetration are measured.A new sounding instrument called a piezocone was built at Université Laval to investigate the magnitude, effects of rates of penetration, and rate of dissipation of the excess pore pressures according to the location of the porous stone on the apparatus.The magnitude of the pore pressures induced during driving is a maximum at the cone tip and then decreases along the shaft as measured by porous stones located behind the cone tip. Induced pore pressures at the tip are independent of the rate of penetration, but a very small rate effect may influence the pore pressures measured behind the cone tip. The results show that the use of the ratio u/qc for soil characterisation may be considered only after adoption of standards regarding the location of the sensing element and the rate of penetration.The new sounding tool models the penetration of a single pile relatively well and its use is suggested for the study of pore pressures during the penetration of piles and their dissipation with time.

HHT Analysis on Pore Pressure Dissipation of Wave-Induced Fluidization in a Sandy Bed

2011 ◽  
Author(s):  
Shiaw-Yih Tzang ◽  
Yung-Lung Chen ◽  
Shan-Hwei Ou
Keyword(s):  
Pore Pressure ◽  
Soil Layer ◽  
Excess Pore Pressure ◽  
Pressure Measurements ◽  
Flume Tests ◽  
Dissipation Mechanism ◽  
Frequency Components ◽  
Excess Pore Pressures ◽  
Wave Induced ◽  
Excess Pore

Wave-induced pore pressure variations during the stage of increasing excess pore pressure consist of the mechanism of generation of fluidization. Moreover, in post-fluidization stage, pore pressure variations not only reveal the dissipation mechanism of fluidization but also the wave-fluidized bed interactions. Past results from a series of lab flume tests have further illustrated that pore pressure variations in a fluidized response are nonlinear and nonsataionary. Hence, the HHT method was further applied to analyze the pore pressure measurements in this study. The results demonstrate that after the dissipation of excess pore pressures the amplitudes of fundamental and higher-frequency components begin to decay. Meanwhile, the amplified amplitudes of fundamental and higher-frequency components during fluidization response would decrease with decreasing thickness of fluidized soil-layer in consecutive tests.

Surpressions interstitielles développées par le fonçage dans les sols cohérents

1979 ◽  
Vol 16 (4) ◽  
pp. 814-827
Author(s):  
M. Peignaud
Keyword(s):  
Pore Pressure ◽  
Excess Pore Pressure ◽  
Overburden Pressure ◽  
Pore Pressures ◽  
Excess Pore Pressures ◽  
Plastic Clays ◽  
Excess Pore

The Laboratoire Régional des Ponts et Chaussées, Angers (France) has investigated the excess pore pressures developed during the driving of a piezometer probe at different rates on four sites. Attention is drawn to the important differences between the pore pressures measured during penetration and at rest.During driving, negative excess pore pressures are measured. When the piezometer is stopped the pore pressures become large and positive. For the soils tested, i.e., plastic to highly plastic clays, the maximum excess pore pressure at rest may be estimated from the total overburden pressure. [Journal translation]

Development of a quasi-static piezocone apparatus

1982 ◽  
Vol 19 (2) ◽  
pp. 180-188 ◽  
Author(s):  
Marius Roy ◽  
Michel Tremblay ◽  
François Tavenas ◽  
Pierre La Rochelle
Keyword(s):  
Pore Pressure ◽  
Excess Pore Pressure ◽  
European Symposium ◽  
Failure Zone ◽  
Conical Part ◽  
Penetration Test ◽  
Cone Penetration ◽  
Penetration Testing ◽  
Pore Pressures ◽  
Filter Arrangement

The European Symposium on Penetration Testing (ESOPT) held in Stockholm in 1974 has contributed to the improvement of interpretation methods and also to the standardization of the cone penetration test (CPT). In recent years, the importance of the pore pressures generated during cone penetration has led to the development of new sounding equipment to measure this parameter in addition to the usual cone penetration parameters.The apparatus developed at Université Laval consists of a conical tip equipped with a filter in order to measure pore pressure and cone resistance simultaneously during the penetration. In addition, since the conical tip is detachable, five types of tips were used in the study in order to vary easily the position of the pore pressure pick-up and to study the pattern of pore pressures generated at or behind the cone tip.The results show that the filter arrangement has a significant effect on the registered magnitude of excess pore pressure. The generated pore pressures are highest when they are measured in the failure zone of the intact clay, i.e., when the filter arrangement is located on the conical part of the tip.

A New Technique for Reduction of Excess Pore Pressures During Pile Driving

1974 ◽  
Vol 11 (3) ◽  
pp. 423-430 ◽  
Author(s):  
Robert D. Holtz ◽  
Per Boman
Keyword(s):  
Pore Pressure ◽  
Alternative Methods ◽  
New Technique ◽  
Excess Pore Pressure ◽  
Relative Reduction ◽  
Pile Driving ◽  
Pore Pressures ◽  
A New Technique ◽  
Excess Pore Pressures ◽  
Excess Pore

A new technique is described whereby excess pore pressures induced during pile driving in soft, varved silts and clays were economically reduced to a safe level. The technique was applied to piles at a bridge site south of Stockholm, Sweden, where a small slide had occurred during pile driving. A new paper–plastic drain was attached to the wood piles during driving, and two pulling tests indicated that the drain was undamaged under normal driving conditions. The excess pore pressure generated during the driving of some 13 test piles without drains and 48 piles with drains was measured. The data indicated at least a 50% relative reduction in excess pore pressure when the drain was used. In addition, the cost of the technique was considerably less than alternative methods for dealing with dangerous excess pore water pressures resulting from piling in similar soils. The technique has been successfully applied at two other piling sites in Sweden.

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