Engineering geology characterization of lacustrine overconsolidated clays in an alpine area of Italy

2000 ◽  
Vol 37 (6) ◽  
pp. 1241-1251
Author(s):  
R Meriggi ◽  
P Paronuzzi ◽  
L Simeoni
Keyword(s):  
Triaxial Compression ◽  
Mechanical Resistance ◽  
Compression Tests ◽  
Stress History ◽  
Depositional Processes ◽  
Geotechnical Characteristics ◽  
Lithostratigraphic Units ◽  
Overconsolidated Clays ◽  
History Of

This study reports the main geotechnical characteristics of the Steggio Clay unit, a lacustrine sequence located in a valley of the Veneto Piedmont area (northern Italy). Analyzing the variations of overconsolidation pressure with depth, and the compressibility characteristics of natural, swelled, and reconstituted samples, one can hypothesize about the existence and influence of swelling processes on the stress history of the deposit. The yield pressures, determined by oedometric tests for the various lithostratigraphic units, are compared with the preconsolidation pressures deduced from the geological analysis, and a reduction in apparent preconsolidation pressures is evident in the upper layers. Comparing the natural water content of each stratigraphic unit with that of the overconsolidated and normally consolidated states, it can be seen that the same layers are softened. These phenomena could have been caused by swelling induced by erosion of the overlying deposits, sliding of glacial masses, and unloading due to deglaciation. The results of undrained consolidated triaxial compression tests indicate that the variations between the parameters of mechanical resistance of some lithological units can be attributed to the different values of the void index, Ivo, corresponding to the lithostatic in situ stress.Key words: overconsolidated clays, stress history, swelling, intrinsic characteristics, post-depositional processes, glaciation.

scholarly journals Semi-empirical elastic–thermoviscoplastic model for clay

2016 ◽  
Vol 53 (10) ◽  
pp. 1583-1599 ◽  
Author(s):  
David Kurz ◽  
Jitendra Sharma ◽  
Marolo Alfaro ◽  
Jim Graham
Keyword(s):  
Stress Level ◽  
Axial Strain ◽  
Triaxial Compression ◽  
Compression Tests ◽  
One Dimensional ◽  
Load Duration ◽  
Compression Creep ◽  
Overconsolidated Clays ◽  
Semi Empirical ◽  
Triaxial Compression Tests

Clays exhibit creep in compression and shear. In one-dimensional compression, creep is commonly known as “secondary compression” even though it is also a significant component of deformations resulting from shear straining. It reflects viscous behaviour in clays and therefore depends on load duration, stress level, the ratio of shear stress to compression stress, strain rate, and temperature. Research described in the paper partitions strains into elastic (recoverable) and plastic (nonrecoverable) components. The plastic component includes viscous strains defined by a creep rate coefficient ψ that varies with plasticity index and temperature (T), but not with stress level or overconsolidation ratio (OCR). Earlier elastic–viscoplastic (EVP) models have been modified so that ψ = ψ(T) in a new elastic–thermoviscoplastic (ETVP) model. The paper provides a sensitivity analysis of simulated results from undrained (CIŪ) triaxial compression tests for normally consolidated and lightly overconsolidated clays. Axial strain rates range from 0.15%/day to 15%/day, and temperatures from 28 to 100 °C.

scholarly journals Appraisal of Geotechnical Characteristics of Ormara Soil, Baluchistan, Pakistan

2019 ◽  
Vol 10 (3) ◽  
pp. 22-26
Author(s):  
Abdul Jabbar Khan ◽  
Naveed Ahsan ◽  
Muhammad Sanaullah ◽  
Gulraiz Akhter
Keyword(s):  
Triaxial Compression ◽  
Liquid Limit ◽  
Soil Samples ◽  
Engineering Properties ◽  
Clay Layer ◽  
Compression Tests ◽  
Geotechnical Characteristics ◽  
Density Values ◽  
Construction Plans ◽  
Triaxial Compression Tests

Ormara is located 240 km west of Karachi which is a coastal and port city (25° 16' 29N, 64° 35' 10E) ofPakistan. Present study evaluates engineering properties of soils of Ormara for future construction plans and possibleexpansions in the area. Fifty bore holes were done in study area at depths of 20m, 40m and some (10 bore holes) were60m deep. The study area was divided into three major zones i.e. Foot hills, on-shore and off-shore. Groundwater wasencountered at depths of 2.75m on onshore and offshore zones and at 3.65m depth in foothill zone. Laboratory testingi.e. moisture content (12 to 38 %), liquid limit (from 26 to 34), plasticity index (10 to 18) of soil samples indicate thatsoils are low plastic to moderate plastic in nature. Soil samples of granular soils indicate angles of internal friction (ø)varying from 260- 36ºin upper sand layers while 260 to 30º in lower silt layers (encountered after the clay layer) andCohesion ranges 0 to 0.04kg/cm2 in all three zones. Further, unconsolidated undrained triaxial compression tests on aclayey soil sample indicated an undrained cohesion value of 28 kPa. Density values ranges from 1.6 to 2.05gm/cm3.Consolidation (Cv = 0.20 to 0.40 cm2/minute, Cc = 0.149 to 0.17) has been calculated for clay layer. Chemical testscarried out on soil samples indicated that soil and water both are reactive aggressively and may cause corrosion to steeland concrete disintegration.

Investigations geomecaniques des emplacements de tunnels en rocher sur l'ile de Montreal

1976 ◽  
Vol 13 (4) ◽  
pp. 481-497
Author(s):  
D. E. Gill ◽  
G. Ballivy
Keyword(s):  
Triaxial Compression ◽  
Site Investigation ◽  
Compression Tests ◽  
Testing Program ◽  
Boring Machines ◽  
Permeameter Tests ◽  
Usual Site ◽  
Full Face ◽  
École Polytechnique

Due to the extent of projects of the Montreal Urban Community involving rock tunnelling, the possibility of using full face boring machine had to be considered. The usual site investigation techniques had to be revised. The main purpose of this paper is to describe, discuss and illustrate the new investigation techniques.Problems related to geology that might be encountered with full face boring machines are reviewed and the various investigations which lead to a better geomechanical knowledge of tunnel sites are presented. The diamond drilling program and the aspects which need to be stressed in the reports are discussed.The laboratory testing program includes splitting tests, uniaxial and triaxial compression tests, and modified Handewith punching tests. In situ testing program comprises Ménard pressio-permeameter tests, Goodman jack tests, and borehole punching tests performed with an apparatus developed at Ecole Polytechnique de Montréal.

scholarly journals The mechanics of subglacial sediment: an example of new “transitional” behaviour

2010 ◽  
Vol 47 (7) ◽  
pp. 775-790 ◽  
Author(s):  
Fatin Altuhafi ◽  
Béatrice A. Baudet ◽  
Peter Sammonds
Keyword(s):  
Critical State ◽  
Triaxial Compression ◽  
Interesting Case ◽  
Strain History ◽  
Compression Tests ◽  
Specimen Density ◽  
The Difference ◽  
Triaxial Compression Tests ◽  
Normal Compression

A series of isotropic compression tests and drained and undrained triaxial compression tests have been performed on glacial sediment from Iceland. Langjökull sediment, which is well graded, is thought to have reached a critical grading during deposition and transportation. Multiple parallel normal compression lines (NCLs) were found, but a unique critical state line (CSL) could be identified. This is unlike other so-called “transitional” soils, whose grading varies between reasonably well graded to gap graded, which tend to have distinct NCLs and critical state lines depending on the specimen density. It is thought that in the case of the Langjökull sediment studied, its particular strain history that involved incessant shearing during deposition accounts for the difference in behaviour. This provides the interesting case of a soil that has been crushed to a critical grading in situ, which depends on the mineralogy of the grains, which was then sampled and tested. Despite the unique grading, samples with a range of different void ratios can be prepared and the combination of grading and density seems to set a fabric that cannot be changed by compression, resulting in multiple parallel NCLs. At the critical state, however, the fabric has been destroyed and the CSL is unique.

True Shear Parameters of Saturated Clays

1973 ◽  
Vol 10 (4) ◽  
pp. 652-663
Author(s):  
A. Sridharan ◽  
S. Narasimha Rao
Keyword(s):  
Stress Level ◽  
Pore Water Pressure ◽  
Initial Conditions ◽  
Water Pressure ◽  
Triaxial Compression ◽  
Compression Tests ◽  
Strength Parameters ◽  
Test Procedures ◽  
Stress History ◽  
Triaxial Compression Tests

Ever since Hvorslev proposed a failure criterion incorporating intrinsic parameters, several test procedures have come into practice to determine these ‘true’ strength parameters. Several consolidated undrained triaxial compression tests with pore water pressure measurement were conducted on both montmorillonite and kaolinite clays and the results were analyzed using different existing methods. All the methods through which the data were analyzed fail to assign any unique true strength parameters. Even a particular method yields different values depending upon the initial conditions (stress history, water content) of the sample and stress level during testing. It has been reasoned that these variations are due to the probable differences in fabric between the samples which are involved in various methods. There seems to be a unique linear relationship between tan [Formula: see text] and Cc/pe irrespective of the sample state, stress level, and stress history in both undisturbed and remolded conditions for all the procedures adopted.

The effect of tamping conditions and sample preparation on undrained shear strengths of a non-plastic sandy silt tailings

2021 ◽  
Author(s):  
David Reid ◽  
Riccardo Fanni ◽  
Peter DiDonna
Keyword(s):  
Critical State ◽  
Triaxial Compression ◽  
Engineering Practice ◽  
Compression Tests ◽  
In Situ Testing ◽  
Sandy Silt ◽  
Direct Simple Shear ◽  
Lead Zinc ◽  
Increased Strength

A series of direct simple shear (DSS) tests were carried out on a non-plastic sandy silt lead-zinc-silver tailings to develop a relationship between undrained shearing behaviour and density, where in situ testing had identified contractive behaviour. The critical state line was also obtained through triaxial compression tests to enable the DSS tests to be viewed in a critical state framework and allow comparison with in situ testing. It was found that the gravimetric water content (GWC) used to tamp the specimens had a significant effect on the resulting undrained strengths when attempting to achieve dense states - with higher GWC giving lower strength at a given density than a lower GWC. Intact and slurry deposited (SD) samples were also tested to access denser states without inducing tamping-related stresses. These showed a more consistent trend with the loose-tamped specimens, and with other data from the literature. Plausible explanations as to the causes of the increased strength of dense-tamped samples were obtained through estimating potential preconsolidation stresses and “locked in” horizontal stresses that may occur from dense tamping. The importance of these observations on the development of density - strength profiles in engineering practice was outlined.

scholarly journals Appraisal of Geotechnical Characteristics of Ormara Soil, Baluchistan, Pakistan

2019 ◽  
Vol 10 (3) ◽  
pp. 22-26
Author(s):  
Abdul Jabbar Khan ◽  
Naveed Ahsan ◽  
Muhammad Sanaullah ◽  
Gulraiz Akhter
Keyword(s):  
Triaxial Compression ◽  
Liquid Limit ◽  
Soil Samples ◽  
Engineering Properties ◽  
Clay Layer ◽  
Compression Tests ◽  
Geotechnical Characteristics ◽  
Density Values ◽  
Construction Plans ◽  
Triaxial Compression Tests

Ormara is located 240 km west of Karachi which is a coastal and port city (25° 16' 29N, 64° 35' 10E) ofPakistan. Present study evaluates engineering properties of soils of Ormara for future construction plans and possibleexpansions in the area. Fifty bore holes were done in study area at depths of 20m, 40m and some (10 bore holes) were60m deep. The study area was divided into three major zones i.e. Foot hills, on-shore and off-shore. Groundwater wasencountered at depths of 2.75m on onshore and offshore zones and at 3.65m depth in foothill zone. Laboratory testingi.e. moisture content (12 to 38 %), liquid limit (from 26 to 34), plasticity index (10 to 18) of soil samples indicate thatsoils are low plastic to moderate plastic in nature. Soil samples of granular soils indicate angles of internal friction (ø)varying from 260- 36ºin upper sand layers while 260 to 30º in lower silt layers (encountered after the clay layer) andCohesion ranges 0 to 0.04kg/cm2 in all three zones. Further, unconsolidated undrained triaxial compression tests on aclayey soil sample indicated an undrained cohesion value of 28 kPa. Density values ranges from 1.6 to 2.05gm/cm3.Consolidation (Cv = 0.20 to 0.40 cm2/minute, Cc = 0.149 to 0.17) has been calculated for clay layer. Chemical testscarried out on soil samples indicated that soil and water both are reactive aggressively and may cause corrosion to steeland concrete disintegration.

scholarly journals Effect of Clay Content on the Mechanical Properties of Hydrate-Bearing Sediments during Hydrate Production via Depressurization

Energies ◽  
2019 ◽  
Vol 12 (14) ◽  
pp. 2684
Author(s):  
Dongliang Li ◽  
Zhe Wang ◽  
Deqing Liang ◽  
Xiaoping Wu
Keyword(s):  
Mechanical Properties ◽  
Triaxial Compression ◽  
Clay Content ◽  
Compression Tests ◽  
Triaxial Apparatus ◽  
Multi Stage ◽  
Strain Relationship ◽  
Hydrate Bearing Sediments ◽  
Relationship Of

The effects of sediments with different clay contents on the mechanical properties of hydrate deposits were studied using a high-pressure, low-temperature triaxial apparatus with in-situ synthesis, as well as the mechanical properties of self-developed hydrate sediments. Through multi-stage loading, triaxial compression tests were conducted by adding quartz sand with different clay contents as the sediment skeleton, and the stress–strain relationship of the shearing process and the strength of sediments with different clay contents were determined. Volumetric changes were also observed during shearing. The results show that the strength of hydrate sediments decreases with the increasing clay content of sediments; in the processes of depressurization and shearing, the hydrate samples exhibited obvious shear shrinkage, regardless of the sediment particle size.

scholarly journals New data on settlement and environment at the Pleistocene/Holocene boundary in Sudano-Sahelian West Africa: Interdisciplinary investigation at Fatandi V, Eastern Senegal

PLoS ONE ◽  
2020 ◽  
Vol 15 (12) ◽  
pp. e0243129
Author(s):  
Benoît Chevrier ◽  
Laurent Lespez ◽  
Brice Lebrun ◽  
Aline Garnier ◽  
Chantal Tribolo ◽  
...  
Keyword(s):  
Initial Phase ◽  
Raw Materials ◽  
Stone Age ◽  
Cultural Group ◽  
Western Africa ◽  
Late Stone Age ◽  
Depositional Processes ◽  
Cultural Pattern ◽  
History Of

The end of the Palaeolithic represents one of the least-known periods in the history of western Africa, both in terms of its chronology and the identification of cultural assemblages entities based on the typo-technical analyses of its industries. In this context, the site of Fatandi V offers new data to discuss the cultural pattern during the Late Stone Age in western Africa. Stratigraphic, taphonomical and sedimentological analyses show the succession of three sedimentary units. Several concentrations with rich lithic material were recognized. An in situ occupation, composed of bladelets, segments, and bladelet and flake cores, is confirmed while others concentrations of lithic materials have been more or less disturbed by erosion and pedogenic post-depositional processes. The sequence is well-dated from 12 convergent OSL dates. Thanks to the dating of the stratigraphic units and an OSL date from the layer (11,300–9,200 BCE [13.3–11.2 ka at 68%, 14.3–10.3 ka at 95%]), the artefacts are dated to the end of Pleistocene or Early Holocene. Palaeoenvironmental data suggest that the settlement took place within a mosaic environment and more precisely at the transition between the open landscape of savanna on the glacis and the plateau, and the increasingly densely-wooded alluvial corridor. These humid areas must have been particularly attractive during the dry season by virtue of their rich resources (raw materials, water, trees, and bushes). The Fatandi V site constitutes the first stratified site of the Pleistocene/Holocene boundary in Senegal with both precise geochronological and palaeoenvironmental data. It complements perfectly the data already obtained in Mali and in the rest of western Africa, and thus constitutes a reference point for this period. In any case, the assemblage of Fatandi V, with its bladelets and segments and in the absence of ceramics and grinding material, fits with a cultural group using exclusively geometric armatures which strongly differs from another group characterized by the production of bifacial armatures, accompanied in its initial phase by ceramics (or stoneware) and grinding material.

A Comparative Study of Hydromechanical Properties in Saturated and Partially Saturated Conditions of Two Soils from the Runway of Oran Airport

2017 ◽  
Vol 21 ◽  
pp. 319-326
Author(s):  
Mohamed Chikhaoui ◽  
Dashnor Hoxha ◽  
Naima Belayachi ◽  
Ammar Nechnech
Keyword(s):  
Triaxial Compression ◽  
Confining Pressure ◽  
Natural Soil ◽  
Compression Tests ◽  
Partially Saturated ◽  
Laboratory Results ◽  
Pressure Meter ◽  
Statistical Representativeness ◽  
Triaxial Compression Tests

This study concerns the ground soils of the second runway of the Es-Sénia airport in Oran (Algeria). This airport was built on a very complex hydro geotechnical site when underground cavities, following the dissolution of gypsum soil, were found during the before-construction geologic studies. Several, techniques are used in laboratory (Permeability, triaxial compression tests at various confining pressure, and hydric tests in saturated and unsaturated conditions) and for in situ it’s used the results of SPT and pressure-meter tests. A comparison of parameters of two soils identified in saturated and partially saturated conditions by in situ and laboratory tests was performed in order to respond to questions of the similarity of hydro mechanical properties of two soils as well as their statistical representativeness of the in-situ reality. It is found that, in respect to the studied parameters, laboratory results are statistically significant and reconstituted soils is statistically representative of natural soil reconstitution.

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