Field observations of soft clay consolidation in the Fraser Lowland

1987 ◽  
Vol 24 (2) ◽  
pp. 308-317
Author(s):  
C. B. Crawford ◽  
L. J. DeBoer
Keyword(s):  
Key Words ◽  
Pore Water ◽  
Soft Clay ◽  
Field Tests ◽  
Maximum Load ◽  
Field Observations ◽  
Pore Pressures ◽  
Pore Water Pressures ◽  
Earth Embankment

This paper presents a 15-year record of consolidation settlements under an earth embankment where maximum settlements have exceeded 3 m since 1971. The rate of settlement was greatly accelerated by the use of sand drains under areas of maximum load. During construction, pore pressures in the subsoil were monitored and used to control the rate of loading, which had to be decreased to avoid failure. Settlements were underestimated and stability was overestimated on the basis of laboratory and field tests. Consolidation characteristics measured in the laboratory are compared with those calculated from field observations. Key words: settlements, consolidation, embankment, pore-water pressures, monitoring, in situ.

Experiences with prefabricated vertical (wick) drains at Vernon, B.C.

1992 ◽  
Vol 29 (1) ◽  
pp. 67-79 ◽  
Author(s):  
C.B. Crawford ◽  
R. J. Fannin ◽  
L. J. Deboer ◽  
C. B. Kern
Keyword(s):  
Key Words ◽  
Pore Water ◽  
Field Observations ◽  
Case Record ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
Pore Water Pressures ◽  
Input Parameters ◽  
Theoretical Predictions ◽  
Wick Drains

This case record describes the performance of two test embankments constructed over a soft compressible clay, one with prefabricated vertical drains and one without. The measured settlements were significantly different from the predicted settlements, and the pore-water pressures were inconsistent with the observed consolidation. The observed performance of the vertical drains is compared with theoretical predictions to assess the sensitivity of the predicted rate of consolidation to input parameters. Key words : case record, consolidation, field observations, prefabricated vertical drains, wick drains, preloading, settlements, test embankments.

Modelling unanticipated pore-water pressures in soft clays

1994 ◽  
Vol 31 (5) ◽  
pp. 773-778 ◽  
Author(s):  
Jianhua Yin ◽  
James Graham ◽  
Jack I. Clark ◽  
Longjun Gao
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Creep Behaviour ◽  
Soft Clay ◽  
Field Observations ◽  
Soft Clays ◽  
Secondary Compression ◽  
Pore Water Pressures ◽  
Clay Layers

Field observations in thin soft clay layers may show pore-water pressures that increase for some time after the loading is applied. Reasons for these observations are not well understood. The paper shows how an elastic viscoplastic constitutive model incorporated into the consolidation equation can predict these pore-water pressure increases in soils that exhibit significant creep behaviour (or secondary compression). The phenomenon has been related to relaxation in regions of the profile from which drainage has not yet begun. Key words : clay, consolidation, creep, secondary compression, viscous, relaxation, pore-water pressure, elastic–plastic.

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]

Effects of freeze–thaw and softening on a natural clay at low stresses

1985 ◽  
Vol 22 (1) ◽  
pp. 69-78 ◽  
Author(s):  
J. Graham ◽  
V. C. S. Au
Keyword(s):  
Pore Water ◽  
Compacted Clay ◽  
Lake Agassiz ◽  
Overburden Pressure ◽  
Freeze Thaw ◽  
Weathering Processes ◽  
Preconsolidation Pressure ◽  
Pore Water Pressures ◽  
Access To Water

Weathering processes such as softening and freeze–thaw cycling affect the properties of clays. Care must therefore be taken when selecting strength and compressibility parameters for analysis of natural slopes, compacted clay embankments, and trench excavations in which significant proportions of the cross section can be affected by climatic weathering.Samples of plastic Lake Agassiz clay from Winnipeg were consolidated anisotropically in the laboratory to axial stresses less than or equal to the in situ effective overburden pressure. They were therefore all overconsolidated with respect to the field preconsolidation pressure. The samples were then loaded under drained or undrained conditions along steeply rising stress paths in p′, q stress space. One group of samples was tested immediately to identify the "undisturbed" behavior, a second group was subjected to freeze–thaw cycles, and a third group allowed to swell freely before testing.The freeze–thaw cycling produced increased compressibility and pore-water pressures, and reduced strengths at low stresses compared with the behavior of undisturbed clay. Freezing also caused the development of a clearly defined fissure structure. Softening at low stresses with access to water produced less marked effects. Key words: clay, undisturbed, freeze–thaw, softening, strength, yielding, pore-water pressures.

scholarly journals Hydraulic Conductivity and Pore Water Pressures in a Clayey Landslide: Experimental Data

Geosciences ◽  
2020 ◽  
Vol 10 (3) ◽  
pp. 102 ◽  
Author(s):  
Caterina Di Maio ◽  
Jacopo De Rosa ◽  
Roberto Vassallo ◽  
Roberto Coviello ◽  
Giuseppe Macchia
Keyword(s):  
Experimental Data ◽  
Hydraulic Conductivity ◽  
Pore Water ◽  
Slip Surface ◽  
Field Tests ◽  
Hydrological Conditions ◽  
Pore Water Pressures ◽  
Landslide Body ◽  
Clay Formation ◽  
Stable Formation

To analyze the response to hydrological conditions of an instable slope in a structurally complex clay formation, the hydraulic conductivity of the subsoil was estimated and pore water pressures were monitored. Two types of field tests were carried out: falling head tests in the Casagrande piezometers and localized seepage measurements in test boreholes. The experimental data show that in a narrow band around the slip surface, the hydraulic conductivity is higher—more than two orders of magnitude—than that of the landslide body and of the stable formation. Furthermore, the data of a long-term monitoring by Casagrande piezometers and vibrating wire cells show that the response of pore water pressures to the site hydrological conditions along the shear band is far faster than in the landslide body and in the stable formation. The slip band seems largely connected to the atmosphere, and the water pressures in the band are correlated with the deep displacement rates of all the inclinometers crossing the active slip surface.

scholarly journals In-Situ Pore Water Pressures and Ground Motions During the 1987 Chiba-Toho-Oki Earthquake

1989 ◽  
Vol 29 (4) ◽  
pp. 75-90 ◽  
Author(s):  
Kenji Ishihara ◽  
Takahito Muroi ◽  
Ikuo Towhata
Keyword(s):  
Pore Water ◽  
Ground Motions ◽  
Pore Water Pressures

Field Tests on Suction Pile Installation in Sand

2002 ◽  
Author(s):  
Y. Cho ◽  
T. H. Lee ◽  
J. B. Park ◽  
D. J. Kwag ◽  
E. S. Chung ◽  
...  
Keyword(s):  
Pore Water ◽  
Applied Pressure ◽  
Field Tests ◽  
Soil Condition ◽  
Silty Sand ◽  
Detailed Measurement ◽  
Pile Installation ◽  
Pile Penetration ◽  
Pore Water Pressures

A series of field suction pile installation tests have been conducted inside the Onsan harbor located in southeastern Korea during the summer of 2001. The suction piles were made of steel, having inside diameters ranging from 0.5 meters to 2.5 meters and the length of five meters. The seafloor soil condition at the site is predominantly silty sand. Instrumentation includes the detailed measurement of the applied pressure vs. pile penetration and retrieval length relationships; the pile alignment during installation through a tiltmeter; and the pore water pressures both inside and outside the pile.

Comparison Analysis of Buildings Settlement, Calculated in Accordance with Rheological Properties of Soils (Based on the Geotechnical Conditions of St. Petersburg)

2014 ◽  
Vol 580-583 ◽  
pp. 320-323
Author(s):  
Ekaterina Astafyeva
Keyword(s):  
Development Process ◽  
Soil Mechanics ◽  
Field Tests ◽  
Field Observations ◽  
Comparison Analysis ◽  
Soft Soils ◽  
Calculation Results ◽  
Long Time ◽  
Calculation Models

Soft soils are well represented as the foundation of buildings all over the world. Settlements of buildings that are built on soft soils are developing over decades and often uneven. This can cause structural damages to constructions and as consequence unplanned repairs or even collapses of buildings in general. To justify the use of different models of soil mechanics it is necessary to carry out their verification. Verification of the model consists of compliance to the simple laboratory experiments and of the adequacy of the field tests description. And the most important thing is that the results of calculations should be based on comparison between series of field observations. The principal difficulty of comparing calculation results with field observations is that the actual soil deformation is developing over a long time, and most of the calculation methods are aimed to obtain finite values of deformations. Comparison between data of finite deformations and data of field observations is not quite correct, because, as a rule, in-situ (field) observations recorded incomplete development process of deformations but not only the final result of settlement. Therefore, to compare these calculations and observations we should select calculation models that can examine the development of deformations in time. Based on the above, it is interesting to analyze the applicability of the most common engineering methods and calculation models of the soils that underlie different calculation programs used in practice.

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