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]

scholarly journals Downdrag Measurements on a 160-Ft Floating Pipe Test Pile in Marine Clay

1972 ◽  
Vol 9 (2) ◽  
pp. 127-136 ◽  
Author(s):  
M. Bozozuk
Keyword(s):  
Skin Friction ◽  
Compressive Load ◽  
Marine Clay ◽  
Positive Skin ◽  
Negative Skin Friction ◽  
Pore Pressures ◽  
Excess Pore Pressures ◽  
Test Pile ◽  
Excess Pore

Large negative skin friction loads were observed on a 160 ft (49 m) steel pipe test pile floating in marine clay. The test pile was driven, open-ended, on the centerline of a 30 ft (9 m) high granular approach fill on the Quebec Autoroute near Berthierville. Since the installation was made in 1966 the fill has settled 21 in. (53 cm), dragging the pile down with it. Negative skin friction acting along the upper surface of the pile was resisted by positive skin friction acting along the lower end as it penetrated the underlying clay. Under these conditions the pile compressed about [Formula: see text] (2 cm). Analysis of the axial strains indicated that a peak compressive load of 140 t developed at the inflection point between negative and positive skin friction 73 ft (22 m) below the top of the pile. Negative and positive skin friction acting on the upper surface of the pile exceeded the in situ shear strength and approached the drained strength of the soil where excess pore water pressures had dissipated. At the lower end where the positive excess pore pressures were high and relative movement between the pile and the soil was large, the positive skin friction approached the remoulded strength as measured with the field vane. Skin friction was increasing, however, as positive escess pore pressures dissipated.This paper shows that skin friction loads are related to the combination of (a) in situ horizontal effective stresses, (b) horizontal stresses due to embankment loads, and (c) horizontal stresses due to differential settlement of the fill.

scholarly journals Dynamic, In-situ, Nonlinear-Inelastic Response and Post-Cyclic Strength of a Plastic Silt Deposit

2021 ◽  
Author(s):  
Amalesh Jana ◽  
Armin W. Stuedlein
Keyword(s):  
Shear Strain ◽  
Low Frequency ◽  
Seismic Energy ◽  
Cyclic Strength ◽  
Excess Pore Pressure ◽  
Inelastic Response ◽  
Pore Pressures ◽  
Excess Pore Pressures ◽  
Excess Pore

This study presents the use of controlled blasting as a source of seismic energy to obtain the coupled, dynamic, linear-elastic to nonlinear-inelastic response of a plastic silt deposit. Characterization of blast-induced ground motions indicate that the shear strain and corresponding residual excess pore pressures (EPPs) are associated with low frequency near- and far-field shear waves that are within the range of earthquake frequencies, whereas the effect of high frequency P-waves are negligible. Three blasting programs were used to develop the initial and pre-strained relationships between shear strain, EPP, and nonlinear shear modulus degradation. The initial threshold shear strain to initiate soil nonlinearity and to trigger generation of residual EPP ranging from 0.002 to 0.003% and 0.008 to 0.012%, respectively, where the latter corresponded to ~30% of Gmax. Following pre-straining and dissipation of EPPs within the silt deposit, the shear strain necessary to trigger residual excess pore pressure increased two-fold. Greater excess pore pressures were observed in-situ compared to that of intact direct simple shear (DSS) test specimens at a given shear strain amplitude. The reduction of in-situ undrained shear strength within the blast-induced EPP field measured using vane shear tests compared favorably with that of DSS test specimens.

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.

Numerical analysis of strengthening by rockfill embankments on an upstream tailings dam

2013 ◽  
Vol 50 (4) ◽  
pp. 391-399 ◽  
Author(s):  
Linda Ormann ◽  
Muhammad Auchar Zardari ◽  
Hans Mattsson ◽  
Annika Bjelkevik ◽  
Sven Knutsson
Keyword(s):  
Finite Element ◽  
Minimum Cost ◽  
Tailings Dam ◽  
Consolidation Process ◽  
Downstream Side ◽  
Pore Pressures ◽  
Staged Construction ◽  
The Stability ◽  
Excess Pore Pressures ◽  
Excess Pore

The consolidation process could be slow in an upstream tailings dam; therefore, the stability can reduce due to an increase in excess pore pressures when the dam is raised. The safety of the dam can be enhanced by constructing rockfill berms on the downstream side. This paper presents a case study on the strengthening of an upstream tailings dam with rockfill berms. The finite element analyses were performed for modelling the staged construction of the dam and for optimizing the volume of the rockfill berms. The dam was raised in 11 stages; each stage consisting of a raising phase and a consolidation phase. The study shows that the slope stability of the dam reduced due to an increase of excess pore pressures during the raising phase. The stability of the dam was successfully improved by utilizing rockfill berms as supports on the downstream side. A technique has been presented to minimize the volume of the rockfill berms so that the required stability can be achieved at minimum cost. This paper shows that the finite element method can be a useful tool for modelling the consolidation behaviour of an upstream tailings dam and minimizing the volume of the rockfill berms that may be needed to maintain the stability of the dam during staged construction.

scholarly journals Performance of vertical drains in liquefaction mitigation under structures

2019 ◽  
Vol 17 (11) ◽  
pp. 5849-5866 ◽  
Author(s):  
Samy García-Torres ◽  
Gopal Santana Phani Madabhushi
Keyword(s):  
Point Of View ◽  
Shallow Foundations ◽  
Centrifuge Test ◽  
Vertical Drains ◽  
Liquefaction Mitigation ◽  
Pore Pressures ◽  
Dynamic Centrifuge Test ◽  
Excess Pore Pressures ◽  
Positive Results ◽  
Excess Pore

Abstract Several techniques have been developed in order to mitigate damage to buildings during and after liquefaction events. Benefits of using vertical drains have been verified by analysing their performance in the soil and evaluating their effectiveness in dissipation of excess pore pressures generated by the earthquake. However, the effect of drains in the soil below structures requires further investigation. In this paper, a dynamic centrifuge test series was carried out to evaluate the performance of a vertical drains arrangement below shallow foundations. High permeable rubble brick was used as coarse material inside the drains to provide positive results not only from a geotechnical point of view but also from an environmental and sustainable perspective. The behaviour of drains was analysed when they are located under shallow foundations of a building, in terms of the excess pore pressures generated during the earthquake and subsequent post-seismic dissipation, the foundation settlement and its dynamic response.

The transition from weakening to strengthening in dehydrating gypsum: Evolution of excess pore pressures

1995 ◽  
Vol 22 (9) ◽  
pp. 1009-1012 ◽  
Author(s):  
Suz-chung Ko ◽  
David L. Olgaard ◽  
Ueli Briegel
Keyword(s):  
Pore Pressures ◽  
Excess Pore Pressures ◽  
Excess Pore
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