Isotropic yielding of unsaturated cemented silty sand

2013 ◽  
Vol 50 (8) ◽  
pp. 807-819 ◽  
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.

scholarly journals Definition and experimental determination of a soil-water retention surface

2010 ◽  
Vol 47 (6) ◽  
pp. 609-622 ◽  
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.

scholarly journals Investigation into water retention behaviour of deformable soils

2013 ◽  
Vol 50 (2) ◽  
pp. 200-208 ◽  
Author(s):  
Simon Salager ◽  
Mathieu Nuth ◽  
Alessio Ferrari ◽  
Lyesse Laloui
Keyword(s):  
Water Content ◽  
Soil Water ◽  
Water Retention ◽  
Void Ratio ◽  
Degree Of Saturation ◽  
Retention Data ◽  
Soil Water Retention ◽  
Retention Behaviour ◽  
Wide Range ◽  
Water Retention Behaviour

The paper presents an experimental and modelling approach for the soil-water retention behaviour of two deformable soils. The objective is to investigate the physical mechanisms that govern the soil-water retention properties and to propose a constitutive framework for the soil-water retention curve accounting for the initial state of compaction and deformability of soils. A granular soil and a clayey soil were subjected to drying over a wide range of suctions so that the residual state of saturation could be attained. Different initial densities were tested for each material. The soil-water retention curves (SWRCs) obtained are synthesized and compared in terms of water content, void ratio, and degree of saturation, and are expressed as a function of the total suction. The studies enable assessment of the effect of the past and present soil deformation on the shape of the curves. The void ratio exerts a clear influence on the air-entry value, revealing that the breakthrough of air into the pores of the soil is more arduous in denser states. In the plane of water content versus suction, the experimental results highlight the fact that from a certain value of suction, the retention curves corresponding to different densities of the same soil are convergent. The observed features of behaviour are conceptualized into a modelling framework expressing the evolution of the degree of saturation as a function of suction. The proposed retention model makes use of the theory of elastoplasticity and can thus be generalized into a hysteretic model applicable to drying–wetting cycles. The calibration of the model requires the experimental retention data for two initial void ratios. The prediction of tests for further ranges of void ratios proves to be accurate, which supports the adequacy of formulated concepts.

scholarly journals Analysis of the suction evolution during direct shear test in a silty sand soil

2020 ◽  
Vol 195 ◽  
pp. 03031
Author(s):  
Omar AL-Emami ◽  
Gabriela M Medero ◽  
Fernando A M Marinho ◽  
Melis Sutman
Keyword(s):  
Shear Strength ◽  
Water Content ◽  
Large Scale ◽  
Matric Suction ◽  
Vertical Stress ◽  
Silty Sand ◽  
Experimental Program ◽  
Direct Shear ◽  
Initial Void Ratio ◽  
Study Results

Shear strength of soils is one of the essential parameters for analysing and solving divers geotechnical problems (e.g. the bearing capacity of shallow footings pile foundations, slope stability and earth embankments). In this study, a series of conventional large-scale (300 X 300 mm) direct shear tests were carried out on saturated and constant water content silty sand specimens at ei = 0.6 and 1.0 tested under applied vertical stresses of 100, 200, or 400 kPa to investigate the influence of matric suction on the shear strength characteristics of the tested material. A loading steel cap was modified to allow the direct measurements of the matric suction using two commercial available Equitensiometer suction probes (EQ3). The experimental program indicated that, for both studied void ratios, the obtained shear strength of specimens under constant water content is found to be distinctly greater than those obtained from saturated samples. The results showed that the samples compacted at ei = 1.0 exhibited collapse behaviour during saturation stage, whereas same samples did not show any volume change during stabilisation stage when tested under constant water content condition. The study results also showed that the matric suction reduction during consolidation stage depends on initial void ratio of the tested samples as well as the level of applied vertical stress. Moreover, the matric suction evolution during shearing process of both studied void ratios specimens decreased with increasing the level of applied vertical stress.

scholarly journals Deformation induced by wetting: a simple model

2012 ◽  
Vol 49 (8) ◽  
pp. 954-960 ◽  
Author(s):  
Francesca Casini
Keyword(s):  
Simple Model ◽  
Void Ratio ◽  
Simple Expression ◽  
Silty Sand ◽  
Water Retention Curve ◽  
Retention Curve ◽  
Initial Void Ratio ◽  
Homogeneous Soil ◽  
Gravimetric Water Content ◽  
Compression Line

This paper presents a simple model for predicting the deformation induced by wetting. The objective is to quantify the deformation induced by saturation of an unsaturated layer of homogeneous soil, causing variation of the initial void ratio and gravimetric water content. The soil is a low-plasticity silty sand. A simple expression for the normal compression line (NCL), which depends on the parameter χ and one more parameter, will be proposed. The model may capture the progressive degradation induced by loading and wetting by linking the dependency of NCL by the parameter χ and water retention curve by porosity.

scholarly journals Water retention and characteristic curves representing tropical clay soils from Africa

2020 ◽  
Vol 195 ◽  
pp. 01019
Author(s):  
K.M.A. Alhaj ◽  
G. Biscontin ◽  
M.Z.E.B Elshafie ◽  
A.S. Osman
Keyword(s):  
Unsaturated Soils ◽  
Water Retention ◽  
Void Ratio ◽  
Energy Levels ◽  
Dew Point ◽  
Degree Of Saturation ◽  
Measuring Instruments ◽  
High Plasticity ◽  
Soil Water Retention ◽  
Initial Void Ratio

Soil water retention curves (SWRCs) form an essential component of frameworks coupling the hydromechanical behaviour of unsaturated soils. The curves describe how suction changes with variables such as degree of saturation, void ratio and volumetric/gravimetric water content. SWRCs can be determined from incrementally drying initially saturated reconstituted samples to a final residual state, thus developing the primary drying curve (PDC). The primary wetting curve (PWC) is established from subsequent incremental wetting from residual state and is hysteretic compared with the PDC. SWRCs for reconstituted, high-plasticity, tropical clays from Africa (Sudan, Tanzania and South Africa) will be produced using suction measuring instruments, a tensiometer, filter paper and a dew point potentiometer. The development of SWRCs under various subsequent cycles of drying will be presented and discussed along with details concerning volumetric changes and cracking during drying. In order to investigate the uniqueness of the PDC and PWC and the effect of initial void ratio, SWRCs will be determined for samples formed by reconstituted from slurry under different applied energy levels.

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

2019 ◽  
Vol 56 (7) ◽  
pp. 1049-1055 ◽  
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.

scholarly journals Water retention curve and hydraulic conductivity function of highly compressible materials

2007 ◽  
Vol 44 (10) ◽  
pp. 1200-1214 ◽  
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.

Strength of field compacted clays

1983 ◽  
Vol 20 (1) ◽  
pp. 36-46 ◽  
Author(s):  
Y. Liang ◽  
C. W. Lovell
Keyword(s):  
Water Content ◽  
Effective Stress ◽  
Void Ratio ◽  
Volumetric Strain ◽  
Test Series ◽  
Dry Density ◽  
Regression Equations ◽  
Strength Parameters ◽  
Long Term Conditions ◽  
Initial Void Ratio

The reported research established the relationships among the compaction variables (dry density, water content, roller type, and number of passes) and the shearing behavior of a residual clay (St. Croix) from sandstone and shale. Compacted material was tube sampled from test pads, and subjected to two test series: unconsolidated-undrained (UU), and saturated consolidated-undrained [Formula: see text] triaxials. Both test series were run at various confining pressures to approximate the end of construction and long-term conditions for several embankment depths.The UU tests showed an increase in strength with an increase in density or a decrease in water content. For the as-compacted samples, significant volume changes occurred during shear. The volumetric strain at failure decreased with increasing prestress effected by the roller.In the [Formula: see text]testing program, sample behavior after saturation under confinement was interpreted in terms of initial compacted conditions (and confinement). The effective stress strength parameters were functions of the compacted water content and void ratio. For a given initial void ratio, as the compaction water content increased, c′ increased and [Formula: see text] decreased. The volumetric strain upon saturation varied with the compacted water content, dry density, compactive energy, and the level of confinement. Skempton's A factor at undrained shear failure was dependent upon the initial void ratio and the degree to which the sample had been prestressed by the roller.Statistically valid regression equations for these dependent variables, viz., as-compacted strength, percent volume change due to saturation and consolidation, Skempton's A parameter at failure, and the effective stress strength parameters, were developed for field compacted St. Croix clay. Uses for such equations are given.

Mechanical improvement and vertical yield stress prediction of clayey soils from eastern Canada treated with lime or cement

2001 ◽  
Vol 38 (3) ◽  
pp. 567-579 ◽  
Author(s):  
Hélène Tremblay ◽  
Serge Leroueil ◽  
Jacques Locat
Keyword(s):  
Water Content ◽  
Yield Stress ◽  
Void Ratio ◽  
Soil Stabilization ◽  
High Water ◽  
High Water Content ◽  
Clayey Soils ◽  
Eastern Canada ◽  
Simple Method ◽  
Initial Void Ratio

The method of soil stabilization is well known and has been used throughout the world for many decades to improve some soil properties. Although many researchers have studied the effect of adding a cementing agent to a soil, not many of these researchers have explored the effect of treatment on the resulting properties of high water content soils like dredged material. Also, there has been little work concerning the prediction of the mechanical changes to the soil. Therefore, this paper summarizes the results of a research project conducted to define the general mechanical behavior of high water content clayey soils from eastern Canada treated with lime or cement, in terms of compressibility. In the light of this research, the general compressibility behavior has been obtained, defined by relationships between initial void ratio, additive content, and vertical yield stress for a given inorganic or organic soil. These relationships have been normalized on the basis of the one-dimensional compression curve of the remolded and reconstituted untreated soil to give a simple method for predicting the vertical yield stress of a treated soil for any initial void ratio and its resistance to compression.Key words: stabilization, compressibility, yield stress, clayey soils, lime, cement.

Yield strength ratios, critical strength ratios, and brittleness of sandy soils from laboratory tests

2011 ◽  
Vol 48 (3) ◽  
pp. 493-510 ◽  
Author(s):  
Abouzar Sadrekarimi ◽  
Scott M. Olson
Keyword(s):  
Yield Strength ◽  
Critical State ◽  
Void Ratio ◽  
Triaxial Compression ◽  
Silty Sand ◽  
Strength Ratio ◽  
Critical Strength ◽  
Initial Void Ratio ◽  
Ring Shear ◽  
Particle Damage

In this study, we performed 26 undrained triaxial compression and 32 constant-volume ring shear tests on two clean sands and one silty sand. We then used these results to evaluate the critical states, and shear strength ratios mobilized at yield and at critical state. We obtained yield strength ratios that ranged from 0.16 to 0.32 and from 0.20 to 0.35 in triaxial compression and ring shear, respectively. Critical strength ratios mobilized prior to particle damage ranged from 0.01 to 0.26 in triaxial compression and from 0.04 to 0.22 in ring shear. Particle damage and shear displacement increased the slopes of the critical-state lines during ring shear testing, and consequently the critical strength ratios incorporating particle damage decreased from 0.02 to 0.12. In addition, specimen brittleness (before particle damage) increases with initial void ratio and state parameter and is affected by initial fabric and particle shape. However, particle damage and crushing considerably increases sand brittleness, making it essentially independent of initial void ratio. A unique relation is found between sand brittleness and critical strength ratio independent of sand type, mode of shear, fabric, and particle damage, which indicates an upper bound critical strength ratio of about 0.3 for mildly contractive sands.

Sign in / Sign up

Export Citation Format

Share Document