Small-strain stiffness of Zenoz kaolin in unsaturated conditions

2012 ◽  
Vol 49 (3) ◽  
pp. 311-322 ◽  
Author(s):  
Mahnoosh Biglari ◽  
Anna d’Onofrio ◽  
Claudio Mancuso ◽  
Mohammad Kazem Jafari ◽  
Ali Shafiee ◽  
...  
Keyword(s):  
Shear Stiffness ◽  
Stress Path ◽  
Small Strain ◽  
Complex Stress ◽  
Resonant Column ◽  
Wetting And Drying ◽  
Isotropic Compression ◽  
Remarkable Effect ◽  
Constant Suction

An experimental study has been carried out to investigate the effects of isotropic compression, wetting, and drying on the initial shear stiffness of Zenoz kaolin, an unsaturated lean clay, both in normally consolidated and overconsolidated conditions. The proposed study was conducted using fixed–free resonant column – torsional shear (RCTS). Specimens were compacted using the undercompaction technique. Initial shear stiffness was measured almost continuously along complex stress paths including (i) an initial equalization stage to a suction value of 0, 50, 150, and 300 kPa; (ii) an isotropic compression stage at constant suction, up to a net stress high enough to move the loading collapse line; (iii) an isotropic unloading stage at constant suction; (iv) a wetting and (or) drying path. The mentioned stress path allowed elimination or determination of the overconsolidation effect on the initial shear stiffness measured. The behavior observed is qualitatively similar to that of saturated soil, while wetting data clearly indicate that G0 depends significantly on volumetric behavior. In normally consolidated samples where wetting is accompanied by collapse, reduction in suction has no remarkable effect on G0. Conversely, in overconsolidated samples G0 reduces significantly as suction decreases.

Small strain behavior of a silty sand in controlled-suction resonant column – torsional shear tests

2002 ◽  
Vol 39 (1) ◽  
pp. 22-31 ◽  
Author(s):  
Claudio Mancuso ◽  
Roberto Vassallo ◽  
Anna d'Onofrio
Keyword(s):  
Shear Stiffness ◽  
Small Strain ◽  
Bulk Water ◽  
Silty Sand ◽  
Resonant Column ◽  
Soil Behavior ◽  
Soil Response ◽  
Strain Behavior ◽  
Torsional Shear ◽  
Constant Suction

An experimental study has been carried out using a new resonant column – torsional shear cell to investigate the small strain behavior of an unsaturated compacted silty sand. The device, recently developed at the Dipartimento di Ingegneria Geotecnica di Napoli (Italy), is fitted for controlled-suction testing using the axis-translation technique. Both optimum and wet of optimum compacted specimens have been tested to analyze the effects of suction and fabric on soil behavior. Shear stiffness measurements have been taken during constant-suction tests. Collected data indicate an S-shaped initial shear stiffness versus suction variation, which can be explained considering the progressive change from a bulk-water regulated soil response to a menisci-water regulated soil response. A model is proposed to account for the observed trend. Results highlight significant effects of suction and fabric on soil behavior.Key words: compacted soil, small strain behavior, shear stiffness, suction, soil fabric.

Effects of stress paths on the small-strain stiffness of completely decomposed granite

2005 ◽  
Vol 42 (4) ◽  
pp. 1200-1211 ◽  
Author(s):  
Y. Wang ◽  
C WW Ng
Keyword(s):  
Shear Strain ◽  
Shear Stiffness ◽  
Stress Path ◽  
Small Strain ◽  
Bender Elements ◽  
Small Strain Stiffness ◽  
Small Strains ◽  
Average Shear ◽  
Decomposed Granite ◽  
Completely Decomposed Granite

Research on the small-strain (0.001%–1%) characteristics of sedimentary soils and sands has advanced to the stage where it has been utilized in engineering analysis and design for some time. Despite the progress, the stiffness characteristics of weathered materials such as completely decomposed granite (CDG) at small strains have still attracted relatively little research attention. This paper describes a systematic laboratory investigation of the small-strain characteristics of intact CDG subjected to various triaxial stress paths, including drained compression and extension tests. The small-strain stiffness was measured using bender elements and internal local transducers. Measurements from bender elements illustrate that the elastic shear modulus of CDG increases as the mean effective stress increases and the void ratio decreases. Significant nonlinear shear stiffness – shear strain and bulk modulus – volumetric strain relationships were observed. At 0.01% shear strain, the measured average shear stiffness obtained from the extension tests was about 60% higher than that from the compression tests. The average shear stiffness for the tests with a 90° rotation of the stress path was about 50%–70% higher than that of tests without a change in the direction of the stress path after saturation.Key words: completely decomposed granite, nonlinearity, small strains, extension, compression, recent stress history.

Modelling the influence of stress–strain history on the initial shear stiffness of an unsaturated compacted silt

2007 ◽  
Vol 44 (4) ◽  
pp. 463-472 ◽  
Author(s):  
Roberto Vassallo ◽  
Claudio Mancuso ◽  
Filippo Vinale
Keyword(s):  
Unsaturated Soil ◽  
Shear Stiffness ◽  
Small Strain ◽  
Complex Stress ◽  
Strain History ◽  
Strain Behaviour ◽  
Observed Behaviour ◽  
Suction History ◽  
Simple Stress

This is the follow-up paper to Vassallo et al. (2007), which discussed the experimentally observed small-strain behaviour of an unsaturated compacted silt. The influence that suction and, more in general, mean net stress – suction history has on the initial shear stiffness was analysed and ascribed to the accumulation of irreversible volumetric strains. In this study, a model able to predict the observed behaviour is proposed, based on classical unsaturated soil volumetric hardening elastoplastic formulations. Starting from the interpretation of the results relative to simple stress paths, such as preliminary equalization and loading–unloading compression, the results of "complex" stress paths, such as those including drying–wetting cycles, have subsequently been modelled by introducing some additional parameters.Key words: unsaturated, compacted, small strain, stiffness, volumetric behaviour, stress history.

scholarly journals Evaluation of the coefficient of earth pressure at rest (K0) of a saturated-unsaturated colluvium soil

2019 ◽  
Vol 92 ◽  
pp. 07006 ◽  
Author(s):  
Lorena Gomes Abrantes ◽  
Tácio Mauro Pereira de Campos
Keyword(s):  
Earth Pressure ◽  
Stress Path ◽  
Tropical Regions ◽  
Suction Control ◽  
Catholic University ◽  
Strain Behaviour ◽  
Constant Suction ◽  
Flexible Wall ◽  
Loading And Unloading

To predict the stress-strain behaviour of soils under loading it is relevant the knowledge of its natural stress state, expressed by the coefficient of earth pressure at rest (K0). There are correlations in theliterature for K0 determination that comes from researches developed considering sedimentary soils,typically from temperate or cold regions. In dealing with residual and colluvium soils, typical of tropical regions, it is not appropriate to use these correlations, since K0 is affected by factors such as degree of weathering, laterization processes and suction, among others that also affect saturated sedimentary soils. This work analysed samples of a colluvium soil from a natural slope at the Pontifical Catholic University of Rio de Janeiro. For the determination of the coefficient of earth pressure at rest of the unsaturated colluvium soil, a flexible wall equipment, with a system of suction control was used. The influence of the net stress level on the value of the coefficient of earth pressure at rest was investigated under a constant suction of 10 kPa, following a loading and unloading cycle of applied vertical stress. The coefficient of earth pressure at rest of the saturated colluvium (null suction) was also determined using a stress-path, Bishop and Wesley type, servo-controlled triaxial equipment. The obtained results are presented and discussed.

Effects of net stress and suction history on the small strain stiffness of a compacted clayey silt

2007 ◽  
Vol 44 (4) ◽  
pp. 447-462 ◽  
Author(s):  
Roberto Vassallo ◽  
Claudio Mancuso ◽  
Filippo Vinale
Keyword(s):  
Shear Stiffness ◽  
Small Strain ◽  
Resonant Column ◽  
Stress History ◽  
Small Strain Stiffness ◽  
Maximum Value ◽  
Clayey Silt ◽  
Triaxial Cell ◽  
The Mean ◽  
Suction History

An experimental study was carried out to investigate the effects of the mean net stress and suction history on the initial shear stiffness, G0, of a compacted clayey silt. Isotropic tests were performed using two suction-controlled devices, a triaxial cell and a resonant column torsional shear (RCTS) cell, so as to investigate the volumetric behaviour of this material. As for saturated soils, one can expect to find a strong correlation among stress history, volumetric state, and G0. Initial shear stiffness was measured almost continuously along various isotropic stress paths, including compressions and drying–wetting single stages or cycles, by using the RCTS cell. The collected data demonstrate a strong dependency of G0 on mean net stress (p – ua) and suction (ua – uw). Cycles of suction, in particular increasing suction beyond the past maximum value, induce significant accumulation of irreversible strains and increase of stiffness, confirming that G0 is not univocally related to the stress state (p – ua, ua – uw).Key words: unsaturated, compacted, small strain, stiffness, volumetric behaviour, stress history.

scholarly journals Determination of Transverse Shear Stiffness of Sandwich Panels with a Corrugated Core by Numerical Homogenization

Materials ◽  
2021 ◽  
Vol 14 (8) ◽  
pp. 1976
Author(s):  
Tomasz Garbowski ◽  
Tomasz Gajewski
Keyword(s):  
Transverse Shear ◽  
Shear Stiffness ◽  
The Finite Element Method ◽  
Homogenization Procedure ◽  
Plate Structures ◽  
Corrugated Board ◽  
Energy Equivalence ◽  
The Stability ◽  
Global Stiffness Matrix

Knowing the material properties of individual layers of the corrugated plate structures and the geometry of its cross-section, the effective material parameters of the equivalent plate can be calculated. This can be problematic, especially if the transverse shear stiffness is also necessary for the correct description of the equivalent plate performance. In this work, the method proposed by Biancolini is extended to include the possibility of determining, apart from the tensile and flexural stiffnesses, also the transverse shear stiffness of the homogenized corrugated board. The method is based on the strain energy equivalence between the full numerical 3D model of the corrugated board and its Reissner-Mindlin flat plate representation. Shell finite elements were used in this study to accurately reflect the geometry of the corrugated board. In the method presented here, the finite element method is only used to compose the initial global stiffness matrix, which is then condensed and directly used in the homogenization procedure. The stability of the proposed method was tested for different variants of the selected representative volume elements. The obtained results are consistent with other technique already presented in the literature.

Small strain stiffness for granite residual soil: effect of stress ratio

2021 ◽  
Author(s):  
Xianwei Zhang ◽  
Xinyu Liu ◽  
Lingwei Kong ◽  
Gang Wang ◽  
Cheng Chen
Keyword(s):  
Stress Ratio ◽  
Small Strain ◽  
Residual Soil ◽  
Resonant Column ◽  
Residual Soils ◽  
Column Tests ◽  
Small Strain Stiffness ◽  
Deviator Stress ◽  
Granite Residual Soil ◽  
Stress Ratios

Most previous studies have focused on the small strain stiffness of sedimentary soil while little attention has been given to residual soils with different properties. Most studies also neglected the effects of the deviator stress, which is extensively involved in civil engineering. This note considers the effects of the deviator stress on the small-strain stiffness of natural granite residual soil (GRS) as established from resonant column tests performed under various stress ratios. Although increasing the stress ratio results in a greater maximum shear modulus for both natural and remolded residual soils, remolded soil is more sensitive to changes in the stress ratio, which highlights the effects of soil cementation. The data herein offers new insights to understand the stiffness of residual soil and other weathered geomaterials.

scholarly journals Effect of Fertilizer Management on NPKS Leaching Loss from Sandy Loam Soil under Alternate Wetting and Drying Condition

2016 ◽  
Vol 20 (1) ◽  
pp. 59-64
Author(s):  
MN Islam ◽  
MM Rahman ◽  
MJA Mian ◽  
MH Ali
Keyword(s):  
Sandy Loam ◽  
Foliar Spray ◽  
Sandy Loam Soil ◽  
Fertilizer Management ◽  
Wetting And Drying ◽  
Leaching Loss ◽  
Randomized Design ◽  
Loam Soil ◽  
Dry Soil

Leaching loss of nutrients hampers plant growth and contributes to environmental pollution. An experiment was conducted at the net house of Soil Science Department, Bangladesh Agricultural University, Mymensingh during January to May 2009 to find out the leaching loss of N, P, K and S from sandy loam soil. Each pot received 6.67 kg dry soil with an opening at the bottom for collecting leachates. Six treatments were used: T0 = control, T1 = NPKS (120, 25, 60 and 20 kg ha-1), T2 = NPKS (180, 37, 90 and 30 kg ha-1), T3 = NPKS (90, 5, 28 and 17 kg ha-1) + cowdung (2.5 t ha-1), T4 = NPKS (109, 25, 60 and 20 kg ha-1, N as USG) and T5 = as T1 but N applied as foliar spray. Treatments were arranged in a completely randomized design with three replications. Leachates were collected at 15 days interval for determination of NPKS. The total leaching loss of N, P, K and S due to different treatments ranged from 16.00 to 90.21, 0.07 to 0.29, 9.60 to 11.20 and 3.75 to 17.81 kg ha-1, respectively. Application of chemical fertilizer at higher rates resulted in greater loss of nutrients. Integrated fertilizer management with cowdung (T3) minimized such losses. Use of USG also reduced leaching loss of N, P, K and S. The application of cowdung and USG with recommended balanced fertilizer might be useful for minimizing N, P, K and S loss from wetland rice field.Bangladesh Rice j. 2016, 20(1): 59-64

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