In situ estimation of the coefficient of consolidation in clays

1990 ◽  
Vol 27 (1) ◽  
pp. 58-67 ◽  
Author(s):  
Mohammed G. Kabir ◽  
Alan J. Lutenegger
Keyword(s):  
Key Words ◽  
Pore Pressure ◽  
Reference Values ◽  
Time Factors ◽  
In Situ Tests ◽  
Coefficient Of Consolidation ◽  
Oedometer Test ◽  
Undisturbed Samples ◽  
Oedometer Tests

An investigation was conducted to demonstrate the applicability of cylindrical piezocone and flat piezoblade tests for providing reliable estimates of the coefficient of consolidation in clays. Coefficients of consolidation were calculated from piezocone dissipation tests for different degrees of consolidation using theoretical time factors to provide a comparison with laboratory oedometer tests. Three techniques were developed to calculate the coefficient of consolidation from piezoblade dissipation tests. Results from in situ pore pressure dissipation tests were compared with laboratory oedometer tests performed on undisturbed samples oriented in both the vertical and horizontal directions, to provide reference values of cv and ch. The results of investigations conducted at several clay sites are presented. Key words: in situ tests, piezocone, piezoblade, coefficient of consolidation, oedometer test, clays.

A geotechnical investigation of marine deposits in a nearshore seabed for land reclamation

1999 ◽  
Vol 36 (6) ◽  
pp. 981-1000 ◽  
Author(s):  
Kin-Man Lee ◽  
Patrick CC Ng
Keyword(s):  
Land Reclamation ◽  
Large Diameter ◽  
Field Tests ◽  
In Situ Tests ◽  
Coefficient Of Consolidation ◽  
Marine Deposits ◽  
Undisturbed Samples ◽  
Horizontal Drainage ◽  
Rowe Cell

The properties of marine deposits in a nearshore seabed at a land reclamation site in Hong Kong were investigated. A variety of laboratory and in situ tests were conducted to define the geotechnical and consolidation characteristics of the marine deposits. The reliability and applicability of various laboratory and in situ testing techniques in evaluating the coefficient of consolidation were examined. Coefficients of consolidation were calculated from conventional oedometer tests, large-diameter (250 mm) Rowe cell tests, field permeability tests, and piezocone dissipation tests. Three techniques were adopted to evaluate the horizontal coefficient of consolidation ch from the results of in situ piezocone dissipation tests. Results from in situ pore pressure dissipation tests are compared with those from large-diameter Rowe cell tests performed on undisturbed samples under both vertical and horizontal drainage conditions and in situ permeability tests to provide reference values of the vertical coefficient of consolidation cv and ch. The engineering implications, particularly those related to land reclamation work in the nearshore environment, of various laboratory and field tests are discussed.

Weighted residual approach to constant strain rate test

2011 ◽  
Vol 48 (4) ◽  
pp. 671-675 ◽  
Author(s):  
Dieter Stolle ◽  
Jonathan Stolle
Keyword(s):  
Strain Rate ◽  
Pore Pressure ◽  
Constant Strain Rate ◽  
Time Factors ◽  
Transient Effects ◽  
Coefficient Of Consolidation ◽  
Virtual Displacement ◽  
Constant Rate ◽  
Rate Test ◽  
Displacement Approach

This note presents a virtual displacement approach to analyze the constant rate of strain consolidation test. It yields simplified “exact” equations within the weighted residual context for interpreting test data. Equations corresponding to larger time factors are similar to those presented in the literature, although the transient effects are clearer than in previous formulations. An advantage of the framework is that assumptions concerning the uniformity of properties through a sample can be relaxed. The derivation shows that E must be constant for the coefficient of consolidation to be independent of position. Depending on the sequencing of sublayers, it is shown that basal pore pressure can be higher or lower for layered media compared with uniform material when allowing E to vary, even though cv is kept constant.

Back-calculation of consolidation parameters from field measurements at a reclamation site

2001 ◽  
Vol 38 (4) ◽  
pp. 755-769 ◽  
Author(s):  
Lai Fa Cao ◽  
Ming-Fang Chang ◽  
Cee Ing Teh ◽  
Yung Mook Na
Keyword(s):  
Pore Pressure ◽  
Land Reclamation ◽  
Ground Improvement ◽  
Field Measurements ◽  
Coefficient Of Consolidation ◽  
Vertical Drains ◽  
Undisturbed Samples ◽  
Back Calculation ◽  
Reclamation Project ◽  
Consolidation Parameters

A pilot test was carried out at a land reclamation project site to study the effect of vertical drains on the rate of consolidation of a marine clay deposit in Singapore. Theoretical and numerical analyses were conducted to interpret the field measurements of pore pressure and settlement, and consolidation parameters were back-calculated. The back-calculated preconsolidation pressure is similar to that obtained from the laboratory consolidation test on undisturbed samples, but the field-deduced compression index is generally larger than that measured in the laboratory. The coefficient of consolidation back-calculated from the settlement measurement is larger than that from the pore-pressure measurement. The coefficient of consolidation for horizontal flow obtained from the Rowe cell test, which is comparable to that back-calculated from the field settlement measurement, is recommended for the preliminary design of vertical drains without the need of considering the smear effect.Key words: clays, consolidation, ground improvement, numerical modelling and analysis, permeability, vertical drains.

scholarly journals Observations and modelling of soil slip-debris flow initiation processes in pyroclastic deposits: the Sarno 1998 event

2003 ◽  
Vol 3 (1/2) ◽  
pp. 53-69 ◽  
Author(s):  
G. B. Crosta ◽  
P. Dal Negro
Keyword(s):  
Numerical Modelling ◽  
Pore Pressure ◽  
Extreme Rainfall ◽  
Critical Conditions ◽  
Alluvial Fans ◽  
In Situ Tests ◽  
Pyroclastic Deposits ◽  
Stability Analyses ◽  
Soil Slip

Abstract. Pyroclastic soils mantling a wide area of the Campanian Apennines are subjected to recurrent instability phenomena. This study analyses the 5 and 6 May 1998 event which affected the Pizzo d’Alvano (Campania, southern Italy). More than 400 slides affecting shallow pyroclastic deposits were triggered by intense and prolonged but not extreme rainfall. Landslides affected the pyroclastic deposits that cover the steep calcareous ridges and are soil slip-debris flows and rapid mudflows. About 30 main channels were deeply scoured by flows which reached the alluvial fans depositing up to 400 000 m3 of material in the piedmont areas. About 75% of the landslides are associated with morphological discontinuities such as limestone cliffs and roads. The sliding surface is located within the pyroclastic cover, generally at the base of a pumice layer. Geotechnical characterisation of pyroclastic deposits has been accomplished by laboratory and in situ tests. Numerical modelling of seepage processes and stability analyses have been run on four simplified models representing different settings observed at the source areas. Seepage modelling showed the formation of pore pressure pulses in pumice layers and the localised increase of pore pressure in correspondence of stratigraphic discontinuities as response to the rainfall event registered between 28 April and 5 May. Numerical modelling provided pore pressure values for stability analyses and pointed out critical conditions where stratigraphic or morphological discontinuities occur. This study excludes the need of a groundwater flow from the underlying bedrock toward the pyroclastic cover for instabilities to occur.

Preconsolidation pressure of Champlain clays. Part I. In-situ determination

1983 ◽  
Vol 20 (4) ◽  
pp. 782-802 ◽  
Author(s):  
P. Morin ◽  
S. Leroueil ◽  
L. Samson
Keyword(s):  
Laboratory Tests ◽  
Research Study ◽  
Simple Correlation ◽  
Eastern Canada ◽  
Existing Structures ◽  
Undisturbed Samples ◽  
Preconsolidation Pressure ◽  
Oedometer Tests

The preconsolidation pressure of sensitive clays is an important parameter for the design of foundations on these soils, which are widespread in Eastern Canada and above all in the St. Lawrence and Ottawa Valleys where Champlain clays are found. A research study was initiated in 1979 to assess whether the preconsolidation pressure values derived from laboratory tests are representative of the preconsolidation pressure effectively mobilized in situ.Several existing structures were investigated and five of them are presented with performance records taken during and after construction together with data obtained from recent soil investigations. For each case study, the in-situ preconsolidation pressure is determined from the analysis of settlement and/or pore pressure records.The preconsolidation pressure values derived from conventional oedometer tests on good quality undisturbed samples are compared with the in-situ values and a simple correlation taking into account the overconsolidation ratio of the clay is proposed. Keywords: preconsolidation pressure, in-situ, laboratory, Champlain sea clays.

Determination of horizontal geostatic stress in clay with self-bored pressuremeter

1988 ◽  
Vol 25 (3) ◽  
pp. 559-573 ◽  
Author(s):  
M. G. Jefferies
Keyword(s):  
Key Words ◽  
Image Matching ◽  
The Self ◽  
In Situ Tests ◽  
Extended Theory ◽  
Computer Aided ◽  
Modelling Procedure

The Gibson–Anderson theory for interpretation of pressuremeter data in clay is extended to include the unloading part of the test for the particular circumstances that prevail with a self-bored pressuremeter (SBP). Incorporation of the extended theory in a computer-aided modelling procedure allows horizontal geostatic stress to be unambiguously determined from SBP data by image matching irrespective of imperfections in the self-boring process. The procedure is illustrated by example on a previously reported test carried out in Beaufort Shelf clay. Key words: clay, in situ tests, self-bored pressuremeter, K0.

Effect of sample size on consolidation of a fissured clay

1988 ◽  
Vol 25 (1) ◽  
pp. 76-84 ◽  
Author(s):  
Vinod K. Garga
Keyword(s):  
Experimental Investigation ◽  
Size Effect ◽  
Sample Size ◽  
Coefficient Of Consolidation ◽  
Different Depths ◽  
In Situ Permeability ◽  
London Clay ◽  
Constant Head ◽  
Oedometer Tests

This paper describes an experimental investigation on the effect of sample size on consolidation characteristics of fissured London Clay. Pore pressure dissipation tests on 38, 100, and 300 mm diameter samples were undertaken in the laboratory. Constant-head in situ permeability tests were conducted in four boreholes at different depths in the clay. Conventional oedometer tests on 76 mm diameter samples recovered from the same depths at which in situ permeability tests were carried out were also undertaken. The results show that both the coefficient of compressibility mv and the coefficient of consolidation determined in the laboratory are not significantly affected by sample size. It is concluded that estimate of in situ coefficient of consolidation can best be made from mv determined in the laboratory, and from in situ permeability measurements. Key words: consolidation, compressibility, fissured clay, permeability, size effect, testing.

Interpretation of field measurements for ice engineering applications

1996 ◽  
Vol 23 (1) ◽  
pp. 180-185
Author(s):  
Lorne W. Gold
Keyword(s):  
Mechanical Properties ◽  
Key Words ◽  
Mechanical Behaviour ◽  
Deformation Behaviour ◽  
Field Measurements ◽  
In Situ Testing ◽  
In Situ Tests ◽  
Engineering Applications ◽  
Inhomogeneous Bodies

A description is given of the nature of problems caused by ice for the engineer. Factors controlling the deformation behaviour and strength of ice are discussed briefly. A distinction is made between the behaviour of the relatively small volumes of competent ice that are normally used for tests and the large, inhomogeneous bodies that must be considered by the engineer. Consideration is given to the implications of this for the conduct of in situ tests and the interpretation of their results. Key words: ice, mechanical properties, mechanical behaviour, in situ testing, pressuremeter.

Deep-seated consolidation settlements in the Fraser River delta

1991 ◽  
Vol 28 (2) ◽  
pp. 298-303 ◽  
Author(s):  
C. B. Crawford ◽  
N. R. McCammon ◽  
R. C. Butler
Keyword(s):  
River Delta ◽  
Fraser River ◽  
In Situ Tests ◽  
Case Record ◽  
The Past ◽  
Undisturbed Samples ◽  
Consolidation Settlement ◽  
Fraser River Delta ◽  
Heavy Loads

This paper describes the settlements of three heavy silo structures at two cement plants located along the south arm of the Fraser River delta. In this area, it has not been possible to obtain sufficiently undisturbed samples for reliable consolidation tests, and it has been necessary therefore to employ in situ tests and site improvement techniques such as preloading and vibrocompaction for the design of foundations. In some cases, piles were used to redistribute heavy loads. Observations during the past 35 years have shown that most of the consolidation settlement has occurred in a deep layer of marine sediments and that it is largely completed within 10 years of the loading. Key words: case record, consolidation, foundation performance, in situ tests, preloading, settlements, site improvement.

scholarly journals Evaluation of the Organic Soil Compressibility from In-Situ and Laboratory Tests for Road Application

2021 ◽  
Vol 16 (2) ◽  
pp. 110-126
Author(s):  
Iwona Chmielewska
Keyword(s):  
Organic Soil ◽  
Soil Improvement ◽  
Optimal Range ◽  
In Situ Tests ◽  
Constrained Modulus ◽  
North Eastern ◽  
Different Depths ◽  
Soil Compressibility ◽  
Oedometer Tests

Organic soil is characterised by high compressibility and should be improved so that it can be used for construction. The use of every method of soil improvement requires knowledge of the compressibility parameters. One of these parameters is the constrained modulus. The constrained modulus can be determined using laboratory or in-situ tests. In this study, the constrained modulus of organic soil was determined using oedometer and piezocone tests (CPTU). The author analysed subsoil under an approximately 250 m section of a designed road in north-eastern Poland. The constrained modulus of organic soil sampled from four different depths was determined in oedometer tests. Piezocone tests were conducted at 18 points located every 15 m along the length of the section concerned. To determine the constrained modulus based on the cone resistance from CPTU tests, the knowledge of the α and αM coefficients is needed. For the tested soil, the optimal range of the α coefficient from 0.4 to 0.7 was determined. The αM coefficient ranged from 0.4 to 0.8. The value of the constrained modulus of organic soil obtained from the oedometer tests, depending on the effective stress, ranged from approximately 100 kPa to 400 kPa. The constrained modulus of the tested soil decreased with depth, which both research methods proved.

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