Quantification of the effects of structure on the compression of a stiff clay

2008 ◽  
Vol 45 (9) ◽  
pp. 1324-1334 ◽  
Author(s):  
A. Gasparre ◽  
M. R. Coop
Keyword(s):  
Natural Soil ◽  
Compression Behaviour ◽  
Sample Depth ◽  
Stiff Clay ◽  
Loading And Unloading ◽  
London Clay ◽  
Intact Soil ◽  
Very High ◽  
Oedometer Tests ◽  
Compression Line

A detailed analysis was made of the compression behaviour of London Clay from oedometer tests, investigating the effects of the clay structure through comparisons between the behaviour of the intact soil and that of the same soil in a reconstituted state. The normalizing parameters commonly used in the literature to analyze the effects of structure on the compression behaviour of clays were found not to represent accurately the real behaviour of those clays that have a gradual yield in compression and require very high stresses to reach and cross the intrinsic compression line. For these soils, it is often difficult to identify a clear yield stress and the effects arising from the structure of the intact material may be concealed by the effects arising from the sample depth and the curvature of the intrinsic compression line at high stresses. A new normalizing parameter is introduced that refers the compression of the natural soil to the intrinsic swelling behaviour and the intrinsic compression line of the material. This was found to better represent the enhanced resistance of the intact material in compression while not requiring numerous loading and unloading stages in the oedometer tests as required by other methods.

scholarly journals Influence of structure on the behavior of a saturated clayey loess

2016 ◽  
Vol 53 (6) ◽  
pp. 1026-1037 ◽  
Author(s):  
L. Xu ◽  
M.R. Coop
Keyword(s):  
Chinese Loess Plateau ◽  
Triaxial Tests ◽  
Scanning Electron Micrographs ◽  
Soil Behavior ◽  
Chinese Loess ◽  
Southern Chinese ◽  
Reconstituted Soil ◽  
Very High ◽  
Oedometer Tests ◽  
Compression Line

An intensive experimental investigation by means of triaxial and oedometer tests was performed on a clayey loess that was retrieved from two depths at a location on the southern Chinese Loess Plateau. Intact and reconstituted samples were used to identify the effects of the natural structure on soil behavior in saturated conditions. The behavior in compression was clearly affected by structure with the intact samples reaching well-defined gross yield points outside the intrinsic compression line of the reconstituted soil, after which the compression paths converged towards the intrinsic compression lines, behavior which is consistent with destructuration. However, very high stresses were required to give complete convergence. Similarly the triaxial tests that were carried out at lower stress levels also did not give convergence of the critical states so that different critical state lines could be defined for the intact and reconstituted soils. This was consistent with qualitative observations from scanning electron micrographs that natural elements of fabric and possibly bonding persisted even after triaxial shearing. The effects of structure at the two depths on the compression and shearing behavior were slightly larger for the shallower samples. Despite the very different genesis of the soils, it was found that similar frameworks could be applied to those used for sedimentary clays and that the degree of structure was equivalent to a clay of medium sensitivity.

scholarly journals Creep and consolidation of a stiff clay under saturated and unsaturated conditions

2020 ◽  
Vol 57 (5) ◽  
pp. 728-741 ◽  
Author(s):  
Mohammad Rezania ◽  
Meghdad Bagheri ◽  
Mohaddeseh Mousavi Nezhad
Keyword(s):  
High Capacity ◽  
Creep Tests ◽  
Stiff Clay ◽  
Time Dependent Behaviour ◽  
London Clay ◽  
The One ◽  
Dependent Behaviour ◽  
Oedometer Tests ◽  
Stress Dependency

In this paper, the one-dimensional (1D) time-dependent behaviour of natural and reconstituted London Clay samples under saturated and unsaturated conditions is studied. For this purpose, a set of 1D consolidation tests including multi-staged loading (MSL) oedometer tests and single-staged loading (SSL) long-term oedometer creep tests were carried out on saturated and unsaturated specimens. Conventional oedometer cells were used for tests on saturated specimens, whereas a newly designed unsaturated oedometer cell, equipped with two high-capacity tensiometers (HCTs) for suction measurements, was used for unsaturated tests. The tests results revealed stress dependency and suction dependency of primary and secondary consolidation responses of the soil samples. Furthermore, counter to formerly acknowledged suggestions of independency of the slope of normal consolidation line to suction changes, it was observed that an increase in suction results in a decrease of the slope of compression curve (Cc) and the creep index (Cαe) values and an increase in yield vertical net stress (σp). Moreover, the Cαe/Cc ratio for London Clay was found to be stress- and suction-dependent, unlike the previously suggested hypotheses.

Volume change indices during loading and unloading of an unsaturated soil

1992 ◽  
Vol 29 (2) ◽  
pp. 195-207 ◽  
Author(s):  
D. Y. F. Ho ◽  
D. G. Fredlund ◽  
H. Rahardjo
Keyword(s):  
Soil Properties ◽  
Key Words ◽  
Volume Change ◽  
Unsaturated Soil ◽  
Constitutive Relations ◽  
Change Theory ◽  
Glacial Till ◽  
Testing Procedures ◽  
Loading And Unloading ◽  
Oedometer Tests

The paper presents the volume change theory and the designation of associated soil properties that must be measured for an unsaturated soil. The equipment required for the measurement of each of the relevant volume relationships is described. Several testing procedures for obtaining the volume change indices during loading and unloading of an unsaturated soil are presented. Typical results from loading and unloading tests on compacted silt and compacted glacial till specimens are presented and analyzed. The analysis is given in order to illustrate the application of the volume change theory to practical problems. Key words : unsaturated soil, volume change indices, constitutive relations, coefficients of volume change, oedometer tests.

scholarly journals Observations on the Bone Bed at Clacton

1912 ◽  
Vol 1 (2) ◽  
pp. 158-159 ◽  
Author(s):  
Harold Picton
Keyword(s):  
Thin Layer ◽  
Lower Limit ◽  
Full Thickness ◽  
Total Thickness ◽  
Dark Layer ◽  
Stiff Clay ◽  
Characteristic Features ◽  
London Clay ◽  
Sea Wall ◽  
Horn Core

The estuarine peaty shale still to be seen in the cliff section below the Martello tower at Clacton has a thickness of 10 or 12 feet, and seems to pass gradually into a dark clay which we find as the top layer of the shore deposit. On the shore below the Martello, and east of the stone groyne, the following layers were observed:—1. Dark, stiff clay, without shells. To be seen only on the upper part of the shore, near the sea-wall. Further down, it. has been denuded. Thickness, c. 9 in. from shore sand.2. A shelly layer, containing much Unıo littoralis: more sandy than the last. c. 3 in.3. A dark layer with occasional shells. Lower limit variable. c. 4 in.4. Blue loam: one of the most characteristic features of the deposit. Shells of Unio occur. Helix was also found. There is also in some parts much wood. Partly embedded in this layer most of the bones are found on the shore surface. Eastwards the layer grows less homogeneous and comes to rest directly on the London Clay. I am not sure what is the full thickness of this layer, but, where it is covered by others, I have dug 18 in. into it without reaching anything else. Accumulation of water and return of the tide prevented deeper trenching, but I think if we gave 2 feet as the total thickness we should not be far wrong.5. A very thin layer, made up almost wholly of fragments of Unio.6. Sand, shells, and broken flints. Thickness varies; 3 in. and 5 in. were measured in two trenches.7. Stony layer. Flint pebbles, broken flints, some sand, some shells. Astragalus of deer, horn core (probably of deer), tibia of deer were found in trenching this layer.

scholarly journals Initial investigation of the intrinsic geomechanical properties of soils in area of landslide Černá Pole

2019 ◽  
Author(s):  
Karolína Faktorová ◽  
Juraj Chalmovský ◽  
Pavel Koudela ◽  
Lumír Míča
Keyword(s):  
Mechanical Properties ◽  
Shear Strength ◽  
Laboratory Tests ◽  
Triaxial Tests ◽  
Geomechanical Properties ◽  
Important Type ◽  
Initial Investigation ◽  
Loading And Unloading ◽  
Oedometer Tests

One of the most important type of Brno’s subsoil is Miocene’s clay. Mechanical properties of these clays were already studied by various methods, authors, in several locations. These parameters, however, varies across the locations and therefore new data are needed to further refineme them. The objective of the laboratory tests presented in this paper was to determine shear strength and compressibility parameters on reconstituted samples, locality Černá Pole. Stiffness parameters for primary loading and unloading – reloading were obtained from series of oedometer tests. Consolidated undrained triaxial tests were performed for evaluation of soil critical shear strength. Obtained results were compared with another available data.

The Manta and the Kanuk: Novel 4-DOF Parallel Mechanisms for Industrial Handling

1999 ◽  
Author(s):  
Luc H. Rolland
Keyword(s):  
Parallel Mechanism ◽  
Kinematic Chain ◽  
Parallel Robot ◽  
Chain Structure ◽  
Parallel Robots ◽  
Parallel Mechanisms ◽  
End Effector ◽  
Low Mass ◽  
Loading And Unloading ◽  
Very High

Abstract Two novel 4-DOF very fast parallel robots were designed. This paper introduces the new parallel mechanism designs which are named the Manta and the Kanuk. In order to reduce manipulator overall costs, the actuator and encoder numbers are minimized to the exact effective degrees-of-freedoms (DOF) which is usually not the case in most parallel robot designs. The robots allow end-effector displacements along the three Cartesian translations and one platform transversal rotation. The two remaining rotations are blocked by the intrinsic mechanical structure including the rotation along the platform normal which is always limited in range. The main advantages are high stiffness through the multiple kinematic chain structure which allow for low mass designs. Moreover, they feature simple mechanical construction. Thus, it shall be possible to achieve very high throughput since high accelerations are feasible. To circumvent the known workspace limitations, the actuators were selected to be prismatic along linear axes. The applications are automated warehouse manipulation, mediatheque manipulation, machine tool tool changers, loading and unloading.

Some aspects of the compressibility behaviour of a clayey sand

2001 ◽  
Vol 38 (6) ◽  
pp. 1177-1186 ◽  
Author(s):  
Flavia Burmeister Martins ◽  
Luiz Antônio Bressani ◽  
Matthew Richard Coop ◽  
Adriano Virgilio Damiani Bica
Keyword(s):  
Published Data ◽  
Clayey Sand ◽  
One Dimensional ◽  
Sand Mixture ◽  
Oedometer Tests ◽  
Compression Line ◽  
Normal Compression

The intrinsic behaviour of a residual clayey sand derived from sandstone was investigated in one-dimensional compression. The data show some interesting differences when compared with other published data, in that no unique normal compression line can be identified. Although the compressibility on first loading is similar to that for many sandy materials at states on their normal compression lines, the locations of the compression curves were found to be a function of the initial voids ratio, and there was no convergence at higher stresses. Tests on a model clay-sand mixture indicated that this behaviour is common to gap-graded clayey sands.Key words: sands, compressibility, oedometer tests.

scholarly journals Numerical investigation of the performance of engineered barriers in reducing flood risk

2021 ◽  
Vol 337 ◽  
pp. 04003
Author(s):  
Alexandros L. Petalas ◽  
Aikaterini Tsiampousi ◽  
Lidija Zdravkovic ◽  
David M. Potts
Keyword(s):  
Flood Risk ◽  
Soil Layer ◽  
Urban Environments ◽  
Water Infiltration ◽  
Natural Soil ◽  
Water Storage Capacity ◽  
Run Off ◽  
London Clay ◽  
Parametric Analyses ◽  
Precipitation Events

In this paper, 2-dimensional, hydro-mechanically coupled finite element analyses are performed to assess the performance of an engineered barrier aimed at reducing flood risk in urban environments. The barrier consists of an unsaturated compacted soil layer and a drainage layer of a coarse granular material, constructed on top of the natural soil, in this case London clay. The barrier is vegetated so that its water storage capacity is renewed after each rainfall event. Sophisticated boundary conditions are used to simulate the effect of precipitation and evapotranspiration. The rainfall water infiltration and the initiation of water run-off during intense precipitation events are simulated. The effect of the hydraulic properties of the unsaturated soil layer on the performance of the system is investigated by means of parametric analyses. The effect of precipitation rate and geometry of the barrier is also discussed. Design recommendations for the properties of the compacted layer and the dimensions of the system are given at the end of the paper.

Temporary and Permanent Earth Anchors: Three Monitored Installations

1974 ◽  
Vol 11 (2) ◽  
pp. 257-268 ◽  
Author(s):  
William A. Trow
Keyword(s):  
Load Transfer ◽  
Fine Sand ◽  
Deep Excavation ◽  
The Third ◽  
First Case ◽  
Stiff Clay ◽  
Design Value ◽  
Uplift Resistance ◽  
Measured Load ◽  
Very High

This paper presents the results of measurements of earth anchor performance for three separate installations in Metropolitan Toronto. The first case records the results of instrumentation on the high grout pressure Bauer anchor used to support an approximately 30 ft (9.1 m) deep excavation in dense fine sand. The second presents the load measurements made on low grout pressure earth anchors installed in very stiff clay of a 29 ft (8.8 m) excavation. The third installation involved measurements on permanent vertical anchors set in extremely dense silt till.In the first instance the average measured load was somewhat lower than the installed load and the design assumption. In the second case, in the stiff clay, the load was somewhat higher than the design value but this was attributed to the probability of load transfer because of inadequate support at lower levels. In this case, considerable variation and possible overstressing of anchor wires was noted.A very high uplift resistance was recorded for the permanent anchors in dense till. Control of groundwater during installation of these anchors was the principal lesson learned from this work.

Experimental study on volumetric behaviour of Maryland clay and the role of degree of saturation

2014 ◽  
Vol 51 (12) ◽  
pp. 1449-1455 ◽  
Author(s):  
Glen J. Burton ◽  
Daichao Sheng ◽  
David Airey
Keyword(s):  
Water Content ◽  
State Parameter ◽  
Degree Of Saturation ◽  
State Variable ◽  
Optimum Water Content ◽  
Constant Suction ◽  
Compaction Energy ◽  
Oedometer Tests ◽  
Compression Line

In this paper, the volume change behaviour of Maryland clay compacted on the wet side of standard Proctor optimum water content (with lower compaction energy) is studied in reference to the saturated reconstituted state. Oedometer tests over a range of suctions and vertical stresses have been carried out, and the results have shown that the compression index reaches a peak (approximately twice that of the reconstituted material) and then gradually reduces to the reconstituted value as the stress level is increased. The results are analyzed in a framework where the degree of saturation is treated as a state parameter and controls the slope of the unsaturated normal compression line. Tests conducted under constant suction and constant water content have been used to demonstrate the effectiveness of using the degree of saturation as a state variable.

Sign in / Sign up

Export Citation Format

Share Document