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.

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.

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.

Dissipation Pattern of Excess Pore Pressure After Liquefaction in Saturated Sand Deposits

2003 ◽  
Vol 1821 (1) ◽  
pp. 59-67 ◽  
Author(s):  
Ik Soo Ha ◽  
Young Ho Park ◽  
Myoung Mo Kim
Keyword(s):  
Grain Size ◽  
Pore Pressure ◽  
Dynamic Loading ◽  
Time History ◽  
Excess Pore Pressure ◽  
Pore Pressures ◽  
Dissipation Pattern ◽  
Effective Grain Size ◽  
Coefficient Of Uniformity ◽  
Excess Pore

In liquefied areas, the amount of damage to a structure is mainly affected by the postliquefaction behavior of the liquefied ground. Understanding postliquefaction behavior requires understanding the dissipation pattern of excess pore pressure after liquefaction. It is difficult to measure pore pressures generated and dissipated during an earthquake because of the more-or-less randomness of earthquake events. Researchers have artificially generated liquefaction with sand samples in the laboratory and have simulated curves for the time history dissipation of excess pore pressure. To estimate variation in permeability during dynamic loading, which should be known for settlement predictions of the ground undergoing liquefaction, 1-g shaking table tests were carried out on five kinds of sands, all with high liquefaction potentials. During tests, excess pore pressures at various depths and surface settlements were measured. The measured curve of the excess pore pressure dissipation was simulated using the solidification theory. From analysis of the velocity of dissipation, the dissipation pattern of excess pore pressure after liquefaction was examined. Permeability during dissipation was calculated using the measured settlement and dissipation velocity, also used for estimating permeability during dynamic loading. The dissipation velocity of excess pore pressure after liquefaction had a linear correlation with the effective grain size divided by the coefficient of uniformity. The increase in the ground’s initial relative density played a role in shifting this correlation curve toward increased dissipation velocity. Permeability during liquefaction increased 1.4 to 5 times compared with the permeability of the original ground, the increase becoming greater as the effective grain size of the test sand increased and the coefficient of uniformity decreased.

scholarly journals In-situ measurement of the strength of deforming subglacial till

1994 ◽  
Vol 40 (136) ◽  
pp. 497-503 ◽  
Author(s):  
Neal R. Iverson ◽  
Peter Jansson ◽  
Roger Leb. Hooke
Keyword(s):  
Pore Pressure ◽  
Residual Strength ◽  
Plastic Material ◽  
Excess Pore Pressure ◽  
Cone Penetration ◽  
New Instrument ◽  
Average Residual ◽  
Basal Till ◽  
Source Of Error

AbstractThe shear strength of deforming till beneath Storglaciären, Sweden, was continuously measured with a new instrument, a “dragometer”. A cylinder with conical ends, roughened with till from the glacier bed, was dragged through the till, and the force on the cylinder was recorded. Consistent with studies of cone penetration in soils, it was assumed that the till behaves as a Coulomb plastic material. This allows the residual strength of the till to be calculated from the measured force. Results from laboratory experiments confirm the validity of the analytical procedure.The average residual strength of the till was ∼55 kPa. A source of error is the potential generation of pore pressure in excess of hydrostatic ahead of the cylinder, which could significantly weaken the till. Calculations indicate that excess pore pressure did not develop during the experiment, but could develop during similar experiments beneath rapidly sliding glaciers with less permeable basal till layers.

Cone penetration testing in snow

1987 ◽  
Vol 24 (3) ◽  
pp. 335-341 ◽  
Author(s):  
Leo H. J. Schaap ◽  
Paul M. B. Föhn
Keyword(s):  
Swiss Alps ◽  
Cone Penetrometer ◽  
Test Results ◽  
Penetration Test ◽  
Cone Penetration ◽  
Penetration Testing ◽  
Cone Resistance ◽  
Cone Penetration Testing ◽  
Chart Recorder ◽  
Special Cone

The application of the electric cone penetrometer test in snow has been investigated and compared with results from the ram penetrometer test, which is normally used for snow profiling and slope stability analysis. A special cone penetrometer system was built consisting of a sensitive 1 cm2 electric cone, depth transducer, and battery-operated chart recorder. The instruments were tested in April 1985 at three different locations in the Swiss Alps and the test results were compared with those of the ram penetrometer tests.The tests yielded repeatable results up to a depth of 4 m with a high resolution of different snow layers. The electric cone tests show more layers than found in the ram profile and snow pit analyses. In soft snow the ram resistances appear to be, on average, about 30% lower than cone resistance values. Recommendations are given for the future use of electric cone penetration testing in snow. Key words: snow, snowpack analysis, cone penetration test, ram penetrometer, cone resistance, ram resistance, ram number.

A numerical investigation of excess pore pressures and continental slope stability in response to ice-sheet dynamics

2019 ◽  
Vol 500 (1) ◽  
pp. 255-266 ◽  
Author(s):  
Morelia Urlaub ◽  
Isabel Kratzke ◽  
Berit Oline Hjelstuen
Keyword(s):  
Pore Pressure ◽  
Continental Slope ◽  
Large Scale ◽  
Ice Sheets ◽  
Ice Sheet ◽  
Excess Pore Pressure ◽  
Submarine Landslides ◽  
Pore Pressures ◽  
Ice Sheet Dynamics ◽  
Excess Pore

AbstractSubmarine landslides are common at glaciated continental margins. The onset of large-scale landslides coincides with the initiation of Northern Hemisphere glaciations in the Quaternary. This implies that processes related to glacial cycling provide favourable conditions for submarine landslides at high-latitude margins. Potential processes include glacial deposition patterns and enhanced seismicity. It is also possible that advances and retreats of ice sheets, a highly dynamic process in geological terms, makes slopes discernible to failure by modifying the stress regime. Here, we quantify this effect using 2D finite element modelling of a glaciated continental margin. Different model runs investigate the pore-pressure development in homogeneous, as well as layered, slopes during glaciation when loaded by an ice stream with one or more ice advances. Ice streams cause significant variations in excess pore pressure in the very shallow sediment sequences at the continental shelf. However, lateral fluid flow is not efficient enough to increase pore pressures significantly at the slope, where large-scale submarine slides are observed. Hence, while ice-sheet dynamics appear to favour the occurrence of shallow slides close to the shelf edge, ice sheets seem to be irrelevant for the generation of large-scale submarine landslides at the continental slope.

Excess Pore Pressures During Undrained Clay Creep

1973 ◽  
Vol 10 (1) ◽  
pp. 12-24 ◽  
Author(s):  
Thomas L. Holzer ◽  
Kaare Höeg ◽  
Kandiah Arulanandan
Keyword(s):  
Pore Pressure ◽  
San Francisco ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Excess Pore Pressure ◽  
Time Behavior ◽  
Pore Pressures ◽  
Undrained Creep ◽  
Excess Pore

The objective of this presentation is to examine experimentally how the excess pore-water pressure is related to the mechanism for undrained creep of San Francisco Bay mud. The results are discussed in the context of creep mechanisms previously suggested in the literature and based on laboratory testing.It is found that shear strains occurring during undrained creep are directly related to a gradual but significant increase in excess pore pressure and, hence, reduction in effective stresses. The increase in magnitude of the pore pressure is, except immediately after the creep shear stress is applied, solely a function of the initial consolidation stress and consolidation period. The magnitude of the long-term build-up may be related to the amount of secondary compression which would occur during drained conditions. It increases with the organic content of the soil and decreases with the degree of remolding. The mechanism for the increase in pore-water pressure may be explained by drainage of water from micropores in the microstructure into the macrostructure.Unless one accounts for the increase in pore pressures during undrained creep, it is unlikely that one will be successful in formulating a generally valid mathematical model for stress–strain–strength–time behavior based on laboratory testing.

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.

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