Effect of biochar type on infiltration, water retention and desiccation crack potential of a silty sand

AbstractReliable measurements of the Soil Water Retention Curve, SWRC, are necessary for solving unsaturated flow problems. In this sense, a method to obtain the SWRC of a silty sand using a flow pump, as well as details about procedures and some results, are herein presented. The overall conclusion is that the new method is very convenient, fully automated, and produces reliable results in a fast and easy way, making the technique very promising.

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Isotropic yielding of unsaturated cemented silty sand

Canadian Geotechnical Journal ◽

10.1139/cgj-2012-0216 ◽

2013 ◽

Vol 50 (8) ◽

pp. 807-819 ◽

Cited By ~ 8

Author(s):

M. Arroyo ◽

M.F. Amaral ◽

E. Romero ◽

A. Viana da Fonseca

Keyword(s):

Water Content ◽

Water Retention ◽

Void Ratio ◽

Dry Weight ◽

Silty Sand ◽

Initial Void Ratio ◽

Naturally Occurring ◽

Experimental Campaign ◽

Hardening Mechanisms ◽

Designed Materials

Unsaturated cemented soils are frequent both as designed materials and as naturally occurring layers. Both desiccation and cementation act separately as hardening mechanisms, but it is not clear how exactly their effects combine. Do they enhance one another? Are they mutually reinforcing? This study presents results from an experimental campaign aimed at answering these questions. Five different mixtures of soil (a granite saprolite) and cement (with cement contents in the range 0% to 7% on a dry weight basis) are tested in isotropic compression at four different water content levels. Initial void ratio is also controlled, using two initial compaction densities. Loading is performed at constant water content and suction is inferred from a set of water retention curves obtained from parallel psychrometric and pore-size distribution measurements. The range of yield stresses explored in this study covers almost two orders of magnitude and extends up to 7 MPa at suction values of up to 14 MPa. Both desiccation and cementation increase yield stress, but their effects are less marked when both act together, and therefore they are not mutually reinforcing.

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A relook into plant wilting: observational evidence based on unsaturated soil–plant-photosynthesis interaction

Scientific Reports ◽

10.1038/s41598-020-78893-z ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Ankit Garg ◽

Sanandam Bordoloi ◽

Suriya Prakash Ganesan ◽

Sreedeep Sekharan ◽

Lingaraj Sahoo

Keyword(s):

Stomatal Conductance ◽

Soil Water ◽

Water Uptake ◽

Water Retention ◽

Root Zone ◽

Clayey Loam ◽

Silty Sand ◽

Water Retention Curve ◽

Soil Matrix ◽

Photosynthetic Status

AbstractPermanent wilting point (PWP) is generally used to ascertain plant resistance against abiotic drought stress and designated as the soil water content (θ) corresponding to soil suction (ψ) at 1500 kPa obtained from the soil water retention curve. Determination of PWP based on only pre-assumed ψ may not represent true wilting condition for soils with contrasting water retention abilities. In addition to ψ, there is a need to explore significance of additional plant parameters (i.e., stomatal conductance and photosynthetic status) in determining PWP. This study introduces a new framework for determining PWP by integrating plant leaf response and ψ during drought. Axonopus compressus were grown in two distinct textured soils (clayey loam and silty sand), after which drought was initiated till wilting. Thereafter, ψ and θ within the root zone were measured along with corresponding leaf stomatal conductance and photosynthetic status. It was found that coarse textured silty sand causes wilting at much lower ψ (≈ 300 kPa) than clayey loam (≈ 1600 kPa). Plant response to drought was dependent on the relative porosity and mineralogy of the soil, which governs the ease at which roots can grow, assimilate soil O2, and uptake water. For clay loam, the held water within the soil matrix does not facilitate easy root water uptake by relatively coarse root morphology. Contrastingly, fine root hair formation in silty sand facilitated higher plant water uptake and doubled the plant survival time.

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Hydromechanical behaviour of a silty sand from a steep slope triggered by artificial rainfall: from unsaturated to saturated conditions

Canadian Geotechnical Journal ◽

10.1139/cgj-2012-0095 ◽

2013 ◽

Vol 50 (1) ◽

pp. 28-40 ◽

Cited By ~ 23

Author(s):

Francesca Casini ◽

Victor Serri ◽

Sarah M. Springman

Keyword(s):

Mechanical Behaviour ◽

Water Retention ◽

Stress Path ◽

Steep Slope ◽

Silty Sand ◽

Water Retention Curve ◽

Retention Curve ◽

Hydromechanical Behaviour ◽

Water Contents

This paper presents an experimental investigation aimed at studying the hydromechanical behaviour of a silty sand from a steep slope in Ruedlingen in the northeast of Switzerland, where a landslide-triggering experiment was carried out. The hydromechanical behaviour of the statically compacted Ruedlingen silty sand has been studied under saturated and unsaturated conditions, beginning with different initial void ratios and water contents. The specimens were prepared in the laboratory using static compaction, to reproduce the mean dry density and mean water content expected in natural unsaturated in situ conditions, thus promoting specimen homogeneity and test repeatability. The choice of compaction parameters was supported by a detailed physical and microstructural investigation to produce laboratory specimens with a similar microstructure to that of the natural soil. The aim of the work was to characterize the mechanical behaviour of the soil at different gravimetric water contents in a triaxial stress path apparatus and to link the mechanical behaviour with the soil-water retention curve obtained under suction-controlled conditions with different void ratios. Soil specimens with three different gravimetric water contents were exposed to conventional isotropically consolidated drained and undrained stress paths for the water phase and to stress paths simulating in situ anisotropic compression followed by a decrease of mean effective stress at constant axial load. The radial deformation of the unsaturated specimens was measured with a laser device installed in a triaxial stress path cell. Results have been interpreted using a Bishop stress approach, evaluating the suction through the water retention curve. A simple equation has been proposed to model the compressibility behaviour of the soil tested, which depends on the parameter χ and the stress ratio η. Possible unstable response along the stress path analysed has been investigated by means of second-order work and the validity of a unified framework has also been verified under unsaturated conditions.

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Definition and experimental determination of a soil-water retention surface

Canadian Geotechnical Journal ◽

10.1139/t09-123 ◽

2010 ◽

Vol 47 (6) ◽

pp. 609-622 ◽

Cited By ~ 61

Author(s):

S. Salager ◽

M. S. El Youssoufi ◽

C. Saix

Keyword(s):

Water Content ◽

Soil Water ◽

Water Retention ◽

Void Ratio ◽

Silty Sand ◽

Soil Water Retention ◽

Initial Void Ratio ◽

Hydromechanical Behaviour ◽

Determination Methods

This paper deals with the definition and determination methods of the soil-water retention surface (SWRS), which is the tool used to present the hydromechanical behaviour of soils to highlight both the effect of suction on the change in water and total volumes and the effect of deformation with respect to the water retention capability. An experimental method is introduced to determine the SWRS and applied to a clayey silty sand. The determination of this surface is based on the measurement of void ratio, suction, and water content along the main drying paths. These paths are established for five different initial states. The experimental results allow us to define the parametric equations of the main drying paths, expressing both water content and void ratio as functions of suction and initial void ratio. A model of the SWRS for clayey silty sand is established in the space (void ratio – suction – water content). This surface covers all possible states of the soil inside the investigated range for the three variables. Finally, the SWRS is used to study the relations between water content and suction at a constant void ratio and between void ratio and suction at a constant water content.

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Modelling effects of root growth and decay on soil water retention and permeability

Canadian Geotechnical Journal ◽

10.1139/cgj-2018-0402 ◽

2019 ◽

Vol 56 (7) ◽

pp. 1049-1055 ◽

Cited By ~ 9

Author(s):

J.J. Ni ◽

A.K. Leung ◽

C.W.W. Ng

Keyword(s):

Root Growth ◽

Soil Water ◽

Water Retention ◽

Void Ratio ◽

Silty Sand ◽

Coarse Grained ◽

Water Retention Curve ◽

Soil Water Retention Curve ◽

Soil Water Retention ◽

Root Decay

Plant roots can change the soil water retention curve (SWRC) and saturated permeability (ksat) of vegetated soils. However, there is no model that could capture both the effects of root growth and root decay on these soil hydraulic properties simultaneously. This note proposes a new void ratio function that can model the decrease and increase in soil void ratio due to root occupancy (upon growth) and root shrinkage (upon decay), respectively, in an unsaturated vegetated coarse-grained soil. The function requires two root parameters; namely, root volume ratio and root decay ratio, both of which can be readily measured through root excavation and image-based analysis. The new function is incorporated into a void ratio–dependent SWRC model for predicting the SWRC of vegetated soils. Similarly, the same function can be combined with the Kozeny–Carman equation for predicting ksat. The model prediction is then compared with a set of new field test data and an existing laboratory dataset for a silty sand vegetated with plant species under the family Schefflera. Good agreements are obtained between the measurements and predictions.

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Water retention curve and hydraulic conductivity function of highly compressible materials

Canadian Geotechnical Journal ◽

10.1139/t07-091 ◽

2007 ◽

Vol 44 (10) ◽

pp. 1200-1214 ◽

Cited By ~ 14

Author(s):

Serge-Étienne Parent ◽

Alexandre Cabral ◽

Jorge G. Zornberg

Keyword(s):

Hydraulic Conductivity ◽

Water Retention ◽

Void Ratio ◽

Silty Sand ◽

Water Retention Curve ◽

Volume Changes ◽

Retention Curve ◽

Conductivity Function ◽

K Function ◽

Compressible Materials

A model capable of describing the suction-induced consolidation curve (void ratio function) and water retention curve (WRC) of highly compressible materials (HCM) is developed, validated, and finally applied to describe the WRC of deinking by-products (DBP). DBP are a highly compressible by-product of paper recycling used in geoenvironmental applications. Validation is conducted by modelling the WRC and the void ratio function for a well documented silty sand from Saskatchewan, Canada. The WRC and void ratio function were used to predict its hydraulic conductivity function (k-function). The water content, suction, and volumetric deformation data of DBP are obtained using an experimental technique that allows determination of the WRCs of HCMs that is suitable for prediction of the DBP k-function. The results show that volumetric water contents are underestimated if volume changes are not accounted for, leading to inaccuracies in the WRCs, thus inaccurately predicted k-functions. It is shown that the newly developed model is better suited for HCMs than currently available models, in particular for HCMs that continue to undergo significant volume changes when the applied suction exceeds the air-entry value.

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