scholarly journals Effect of Suction on the Drained Seismic Compression of Unsaturated Sand

2019 ◽  
Vol 92 ◽  
pp. 08004 ◽  
Author(s):  
Wenyong Rong ◽  
John S. McCartney
Keyword(s):  
Shear Strain ◽  
Simple Shear ◽  
Bridge Decks ◽  
Matric Suction ◽  
Degree Of Saturation ◽  
Shear Tests ◽  
Unsaturated Sand ◽  
Seismic Compression ◽  
Unsaturated Sands ◽  
Constant Suction

Backfill soils in many geotechnical applications are compacted and are likely to be in an unsaturated state during operation. In earthquake-prone areas, seismic compression of unsaturated backfill soils should be understood as small settlements may have significant impacts on the performance of overlying infrastructure like bridge decks, roadways, or railways. Accordingly, the goal of this paper is to describe the results from a series of constant suction, drained, cyclic simple shear tests on unsaturated sands subjected to a range of shear strain amplitudes. A new cyclic simple shear apparatus was developed that involves control of the matric suction and monitoring of changes in degree of saturation using the hanging column approach along with monitoring of the matric suction using an embedded tensiometer.

Failure state of a sand in simple shear

1988 ◽  
Vol 25 (2) ◽  
pp. 395-400 ◽  
Author(s):  
Muniram Budhu
Keyword(s):  
Stress State ◽  
Shear Strain ◽  
Simple Shear ◽  
Shear Stresses ◽  
Stress Concentrations ◽  
Shear Tests ◽  
Failure State ◽  
Failure Loads ◽  
Test Soil ◽  
Geotechnical Problems

The stress state in many practical geotechnical problems is analogous to simple shear strain. However, the devices available to test soil samples in simple shear strain impose nonuniform stress and strain fields. Consequently, the interpretation of results from simple shear tests is often questioned. In this article, results of tests on loose and dense Leighton Buzzard sand from two specially instrumented simple shear devices–Cambridge University's device and a Norwegian Geotechnical Institute type–are used to interpret the failure mode and the failure stress state. The data were obtained from the centre of the samples, a region removed from stress concentrations. Failure was observed to be initiated on vertical planes and occurred very soon after shear displacement was applied. However, neither these vertical planes nor the horizontal planes were the planes of maximum stress obliquity mobilized during the tests. Key words: deformation, failure, loads, sand, shear tests, simple shear, stresses.

Strain Accumulation Procedure During Staged Cyclic Loading of Carbonate Sediments

2014 ◽  
Author(s):  
Nathalie Boukpeti ◽  
Barry Lehane ◽  
J. Antonio H. Carraro
Keyword(s):  
Shear Stress ◽  
Cyclic Loading ◽  
Shear Strain ◽  
Simple Shear ◽  
Soil Strength ◽  
Carbonate Sediments ◽  
Strain Accumulation ◽  
Shear Tests ◽  
Cyclic Shear ◽  
North West

Design of offshore foundation systems requires assessment of the effects of cyclic loading on the soil strength. This paper investigates the applicability of the strain accumulation procedure, which is used to assess the effects of wave loading on the soil strength. Staged undrained cyclic simple shear tests were conducted on a carbonate sediment from the North West shelf of Australia, with varying shear stress amplitude in each stage. The shear strain mobilised at the end of the staged tests is compared with the value predicted by the strain accumulation procedure, using shear strain contours constructed from the results of single amplitude undrained cyclic simple shear tests. It was found that the strain accumulation procedure gives adequate prediction for normalised cyclic shear stress less or equal to 0.3, but largely underestimates the cyclic shear strain for normalised cyclic shear stress greater than 0.3 (the cyclic shear stress being normalised by the effective vertical stress at the end of consolidation).

scholarly journals A Comparison between Simple Shear and Triaxial Tests for Evaluating the Variations of G and D with Matric Suction

2019 ◽  
Vol 92 ◽  
pp. 07010
Author(s):  
Kazem Fakharian ◽  
Danial Shirkavand ◽  
Manouchehr Hejazi
Keyword(s):  
Shear Strain ◽  
Simple Shear ◽  
Damping Ratio ◽  
Silica Sand ◽  
Triaxial Tests ◽  
Residual Water ◽  
Shear Tests ◽  
Confining Stress ◽  
Limit Value ◽  
Soil Dynamic

Shear modulus (G) and damping ratio (D) are both well known as principal soil dynamic parameters. In the present study, cyclic triaxial and simple shear tests are performed on Firuzkuh silica sand at various shear strain amplitudes using the developed testing devices and peripherals. It is well-understood that degrading curvature of G with shear strain appears in both triaxial and simple shear results. Nevertheless, mean confining stress has dissimilar effects in each of the two tests that does not provide comparable empirical correlations. It is noticed that the variations of G and D with suction stress in triaxial differs from those in simple shear. On the basis of cyclic simple shear results, the increase in suction pressure from zero to the end of transition zone in SWCC leads to increase in G values. In triaxial method, on the other hand, similar increase occurs only up to the inflection point in SWCC, starts reducing afterwards down to a limit value at residual water content. The damping ratio variations with shear strain are generally ascending despite local drops at the strain order of 0.1%, which has appeared in both triaxial and simple shear results.

scholarly journals Influence of Overburden on Seismic Compression

2019 ◽  
Vol 92 ◽  
pp. 08006
Author(s):  
Yee Eric
Keyword(s):  
Shear Strain ◽  
Simple Shear ◽  
Testing Machine ◽  
Volumetric Strain ◽  
Material Model ◽  
Vertical Stress ◽  
Seismic Compression ◽  
Power Rule ◽  
Density State ◽  
Simplified Procedure

The state of practice for estimating ground settlements from seismic compression is the simplified procedure. This method was developed in the 1980's and gets its name from the relatively easy method of estimating shear strain demands from potential earthquakes at a site. This procedure is generally split into two parts; a procedure that estimates shear strain demands and a volumetric strain material model. The volumetric strain material model essentially correlates shear strain to resultant volumetric strain. The volumetric strain material model used in the simplified procedure is based on a study from the 1970's, where it was observed that cyclic volumetric strain is independent of vertical stress. Laboratory testing was conducted on a variety of soil materials that are able to experience seismic compression. Reconstituted samples were subjected to cyclic loading in an advanced simple shear testing machine known as the Digitally Controlled Simple Shear device. Factors such as density state and fines content were kept constant across soil categories. Test results show volumetric strain behaviour is dependent on vertical stress and the relationship appears to be power rule based.

scholarly journals Modelling of simple shear tests on volcanic unsaturated sands

2020 ◽  
Vol 195 ◽  
pp. 02021
Author(s):  
Mariagiovanna Moscariello ◽  
Yanni Chen ◽  
Sabatino Cuomo ◽  
Giuseppe Buscarnera
Keyword(s):  
Simple Shear ◽  
Unsaturated Soils ◽  
Model Performance ◽  
Frictional Resistance ◽  
Flow Rule ◽  
Model Parameters ◽  
Shear Tests ◽  
Soil Response ◽  
Proposed Model ◽  
Unsaturated Sands

In landslide susceptibility analysis, a relevant issue is the proper modelling of the complex mechanisms that regulate the failure and post-failure stages. In this paper, simple shear experiments replicating the kinematics of failure in landslide-prone areas are interpreted through an elastoplastic strain-hardening constitutive model for both saturated and unsaturated soils. The material tested is an air-fall volcanic (pyroclastic) soil from Southern Italy which originated from the explosive activity of the Somma-Vesuvius volcanic apparatus. Data from triaxial and shear tests performed on remoulded specimens characterized by saturated and unsaturated conditions are used to calibrate the model parameters. The evolution of shear stress, volumetric and shear strain measured during the experiments are reproduced by means of a model formulation specific for simple shear conditions. To capture the strength emerging under different states of saturation, non-associated flow rule, and a suction-dependent yield surface are used. Examination of the experimental data available for various testing conditions enabled the quantification of the variability of fundamental model constants, such as those controlling frictional resistance and water retention behaviour. To account for such scatter in the physical properties, the constitutive analyses are performed by employing varying model constants within a band of admissible values. The resulting model performance is validated by comparing the simulations with the experimental results at different saturation conditions. The results show that the combination of the proposed model with a data-driven determination of the range of variation of hydro-mechanical properties is crucial to satisfactorily simulate the essential features of the soil response under a variety of simple shear testing regimes.

scholarly journals Dynamic Properties of Granulated Rubber Using Different Laboratory Tests

Buildings ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 186
Author(s):  
Ahmed Moussa ◽  
Hany El Naggar ◽  
Abouzar Sadrekarimi
Keyword(s):  
Shear Strain ◽  
Strain Amplitude ◽  
Simple Shear ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Shear Tests ◽  
Cyclic Triaxial ◽  
Scrap Tires ◽  
Direct Simple Shear ◽  
Shear Strain Amplitude

Due to the socio-environmental hazards arising from the stockpiling of disposed scrap tires, the necessity to utilize such material in civil construction and other applications is deemed mandatory. The lightweight of rubber and its high damping capacity are excellent properties of a geomaterial that could be used successfully in seismic isolation and vibration damping applications in civil construction. Scrap tires could be shredded into specific sizes, and their category and application depend on their particle size range. Thus, understanding the dynamic properties and behavior of shredded scrap tires under cyclic loading is of paramount importance. In this study, the dynamic characteristics of granulated rubbers (<12 mm) are investigated using cyclic triaxial and cyclic direct simple shear tests. The effect of using different testing techniques, i.e., cyclic triaxial test (CTT) and cyclic simple shear test (CSST), on the dynamic properties of granulated rubber material is further addressed. Undrained cyclic triaxial and constant-volume direct simple shear tests are conducted on granulated rubber samples under vertical consolidation stresses of 25, 50, 100 and 200 kPa at a frequency of 0.5 Hz. The shear strain amplitude is varied from 0.01% to 10%. Furthermore, the variations of shear modulus and damping ratio with shear strain amplitude are presented. In addition, the obtained dynamic properties from this study are compared with existing experimental data from the literature. It was found that the ranges of shear moduli of granulated rubber from the CTT and CSST are 278 to 2647 kPa and 85 to 2270 kPa, respectively. Moreover, the damping ratios obtained from CTT were higher than those from CSST at shear strains of less than 1%. The damping ratio of granulated rubber was also found to be independent of the vertical consolidation stress.

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