Use of Oedometer Equipped with High-Suction Tensiometer to Characterize Unsaturated Soils

2016 ◽  
Vol 2578 (1) ◽  
pp. 58-71
Author(s):  
Xiong Zhang ◽  
Haijun Lu ◽  
Lin Li
Keyword(s):  
Unsaturated Soils ◽  
High Suction

scholarly journals Suction effects on the tensile strength and unconfined compression of unsaturated soils

2021 ◽  
Vol 337 ◽  
pp. 01016
Author(s):  
Pedro Roque ◽  
Mariana Motta ◽  
Tácio de Campos
Keyword(s):  
Tensile Strength ◽  
Unsaturated Soils ◽  
Characteristic Curve ◽  
Great Influence ◽  
Dew Point ◽  
Unconfined Compression ◽  
Residual Soils ◽  
Colluvial Soil ◽  
First Moment ◽  
High Suction

The soil-water characteristic curve is an important relation of unsaturated soils, that expresses the variation of the amount of water retained in the soil as a function of its suction. In these soils, drying or wetting can have a great influence on their resistance parameters. This work presents and discusses the effects of increased suction on the tensile strength and unconfined compression of unsaturated soils. Suction was evaluated using the filter paper and the dew point technique, while the resistance parameters were obtained through the “Brazilian Test” and uniaxial compression. Three different soils from Rio de Janeiro were studied: two young residual soils, in which the influence of the soil structure was also verified through tests on undisturbed and reconstituted samples, and a colluvial soil. The results allowed to conclude that the increase of suction, in a first moment, generates an increase in the resistance parameters of these soils. With the continuation of the drying process, the mechanical behaviour of the soils varied, being able to maintain the resistance or showing a drop related to high suction values.

scholarly journals Modelling Unsaturated Soil Response Beyond Residual Suction State via Vapor-Pressure Controlled Triaxial Testing

2020 ◽  
Vol 195 ◽  
pp. 03029
Author(s):  
Mathilde Morvan ◽  
Ujwalkumar D. Patil ◽  
Laureano R. Hoyos ◽  
Surya S. C. Congress ◽  
Anand J. Puppala
Keyword(s):  
Unsaturated Soils ◽  
Silty Sand ◽  
Flow Rule ◽  
Model Parameters ◽  
Peak Strain ◽  
Reasonable Accuracy ◽  
Soil Response ◽  
Proposed Model ◽  
High Suction ◽  
Volumetric Response

Most of the previous research has been focused on developing and validating constitutive models to predict response of unsaturated soils in low-medium suction range. However, there is a scarcity of efforts in developing soil models to simulate its mechanical response in high suction range, particularly above the residual suction. This article presents a new constitutive model introducing net stress and suction as two independent variables. Furthermore, non-associative flow rule incorporating modified stress-dilatancy relationship to take unsaturated state into account is introduced to improve the model results in low-medium to high suction range. The essential soil model parameters are calibrated using suction-controlled triaxial test results for predictions of compacted silty sand response at high values of total suction above residual suction. Preliminary simulations show that proposed model can reasonably simulate the post-peak strain softening response obtained from suction-controlled CTC tests above residual suction value with reasonable accuracy. Although, the proposed model captures initial compression followed by dilation volumetric response with reasonable accuracy, it needs some improvements to be able to capture volumetric response accurately over entire suction range.

scholarly journals Behaviors of rainfall infiltration and drainage characteristics of unsaturated soils under relatively high suction state

2021 ◽  
Vol 16 (1) ◽  
pp. 35-47
Author(s):  
Takafumi KITAOKA ◽  
Hiroyasu OHTSU ◽  
Satoshi NONAMI ◽  
Thirapong PIPATPONGSA ◽  
Atsushi MATSUMOTO
Keyword(s):  
Unsaturated Soils ◽  
Rainfall Infiltration ◽  
High Suction

Crop infestation by aphids is related to flight activity detected with 75 metre high suction traps

2004 ◽  
Vol 57 ◽  
pp. 227-232 ◽  
Author(s):  
D.A.J. Teulon ◽  
M.A.W. Stufkens ◽  
J.D. Fletcher
Keyword(s):  
Positive Relationship ◽  
Rhopalosiphum Padi ◽  
Flight Activity ◽  
Aphid Infestation ◽  
Potato Aphid ◽  
Suction Traps ◽  
Suction Trap ◽  
Trap Catches ◽  
The Relationship ◽  
High Suction

The flight activity of aphid pests of wheat potato lettuce and squash is currently monitored in New Zealand using 75 m suction traps However there has been little research comparing aphid suction trap catches with crop infestation levels The relationship between the average number of aphids (Rhopalosiphum padi) sampled from wheat plants and the average number of aphids caught in weekly 75 m suction trap samples was examined A significant positive relationship indicated that numbers of aphids caught in suction traps reflected the numbers of aphids infesting wheat fields In another experiment potato aphid flights (mostly Myzus persicae) caught in a 75 m suction trap were compared with a nearby windvane trap Aphid numbers in both traps reflected similar trends However the suction trap caught approximately 10 times more aphids than the windvane trap Thus 75 m suction traps provide a useful tool for assessing aphid infestation levels in crops

Stability of Nitroguanidine in Moist, Unsaturated Soils

2005 ◽  
Author(s):  
Nathan D. Mulherin ◽  
Thomas F. Jenkins ◽  
Marianne E. Walsh
Keyword(s):  
Unsaturated Soils

Acoustic Tomography Applied to Water Flow in Unsaturated Soils

2004 ◽  
Vol 3 (1) ◽  
pp. 288
Author(s):  
Andreas Blum ◽  
Ivo Flammer ◽  
Thomas Friedli ◽  
Peter Germann
Keyword(s):  
Water Flow ◽  
Unsaturated Soils ◽  
Acoustic Tomography

Development of allowable bearing capacity for strip foundations in unsaturated soils

2019 ◽  
Vol 114 ◽  
pp. 103138 ◽  
Author(s):  
Changguang Zhang ◽  
Benxian Gao ◽  
Qing Yan ◽  
Junhai Zhao ◽  
Lizhou Wu
Keyword(s):  
Bearing Capacity ◽  
Unsaturated Soils ◽  
Allowable Bearing Capacity

Soil Strength Reduction Method Induced by Variation of Water Content

2012 ◽  
Vol 170-173 ◽  
pp. 847-852
Author(s):  
Peng Ming Jiang ◽  
Zhong Lei Yan ◽  
Peng Li
Keyword(s):  
Slope Stability ◽  
Unsaturated Soil ◽  
Unsaturated Soils ◽  
Characteristic Curve ◽  
Strength Reduction ◽  
Actual State ◽  
Soil Slope ◽  
Simple Method ◽  
The Common ◽  
The Stability

As the complexity of unsaturated soil theory, and it must have a long test period when we study the unsaturated soils, so the conventional design analysis software does not provide such analysis, so we can imagine that such a slope stability analysis does not accurately reflect the actual state of the slope. Based on the known soil moisture content，this paper use the soil water characteristic curve and strength theory of unsaturated soil to calculate the strength reduction parameters of soil which can calculate the stability of the soil slope when using the common calculation method. It is noticeable that this method can be extended and applied if we establish regional databases for this simple method, and these databases can improve the accuracy of the calculation of slope stability.

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