Coupling cyclic and water retention response of a clayey sand subjected to traffic and environmental cycles

Géotechnique ◽  
2021 ◽  
pp. 1-45
Author(s):  
Arash Azizi ◽  
Ashutosh Kumar ◽  
David G. Toll
Keyword(s):  
Unsaturated Soils ◽  
Water Retention ◽  
Resilient Modulus ◽  
Degree Of Saturation ◽  
Triaxial Tests ◽  
Soil Water Retention ◽  
Clayey Sand ◽  
Retention Model ◽  
Cyclic Response ◽  
The Impact

Compacted soils used as formation layers of railways and roads continuously undergo water content and suction changes due to seasonal variations. Such variations together with the impact of cyclic traffic-induced loads can alter the hydro-mechanical behaviour of the soil, which in turn affects the performance of the superstructure. This study investigates the impact of hydraulic cycles on the coupled water retention and cyclic response of a compacted soil. Suction-monitored cyclic triaxial tests were performed on a compacted clayey sand. The cyclic response of the soil obtained after applying drying and wetting paths was different to that obtained immediately after compaction. The results showed that both suction and degree of saturation are required to interpret the cyclic behaviour. A new approach was developed using (i) a hysteretic water retention model to predict suction variations during cyclic loading and (ii) Bishop's stress together with a bonding parameter to predict accumulated permanent strain and resilient modulus. The proposed formulations were able to predict the water retention behaviour, accumulated permanent strains and resilient modulus well, indicating the potential capability of using the fundamentals of unsaturated soils for predicting the effects of drying and wetting cycles on the coupled soil water retention and cyclic response.

Evaluation of capillary water retention effects on the development of the suction stress characteristic curve

2020 ◽  
Vol 57 (10) ◽  
pp. 1439-1452 ◽  
Author(s):  
Emad Maleksaeedi ◽  
Mathieu Nuth
Keyword(s):  
Shear Strength ◽  
Soil Water ◽  
Unsaturated Soils ◽  
Water Retention ◽  
Characteristic Curve ◽  
Degree Of Saturation ◽  
Soil Water Retention ◽  
Retention Model ◽  
Suction Stress ◽  
Effective Degree

The suction stress characteristic framework is a practical approach for relating the suction and the water-filled pore volume to the stress state of unsaturated soils. It predicts the effective stress by developing the suction stress characteristic curve from the soil-water retention curve. In this framework, the effective degree of saturation is usually calculated by the empirical water retention model of van Genuchten (published in 1980). In this paper, the use of a generalized soil-water retention model proposed by Lu in 2016, which differentiates the role of capillary and adsorption mechanisms, in the suction stress characteristic framework is studied. A redefinition of the effective degree of saturation is suggested, by choosing the retention state where capillarity approaches zero instead of the residual retention state. The validity of this assumption is examined using experimental data obtained by unsaturated shear strength and retention tests and datasets collected from the literature. The proposed definition is applicable for a variety of soils where capillarity is the dominant mechanism in producing suction stress within the range of suction 0–1500 kPa. In addition, it is observed that the generalized soil-water retention model presents a more realistic prediction of unsaturated shear strength compared with empirical water retention models.

scholarly journals Implementation of biocementation for a partially saturated problematic soil of the UK railway network

2020 ◽  
Vol 195 ◽  
pp. 05006
Author(s):  
Muhammad Umair Safdar ◽  
Maria Mavroulidou ◽  
Michael J. Gunn ◽  
Christopher Gray ◽  
Diane Purchase ◽  
...  
Keyword(s):  
Unsaturated Soils ◽  
Water Retention ◽  
Degree Of Saturation ◽  
Water Retention Curve ◽  
Soil Water Retention Curve ◽  
Soil Water Retention ◽  
Railway Network ◽  
Foundation Soil ◽  
The Uk ◽  
Problematic Soil

This paper refers to biocementation of a problematic soil of the UK railway network as a potential stabilisation technique of this soil using indigenous ureolytic bacteria. The soil is peat, a soft foundation soil also subject to oxidation wastage. As the peat is under existing embankments, electrokinetics (EK) is proposed as a promising technique to implement treatments. In the context of unsaturated soils the paper thus focuses on two particular aspects relevant for the implementation of treatments and the stability of this soil, namely: a) the effect of degree of saturation of the peat on the bio-electrokinetic treatment ; b) the soil water retention curve of the soil affecting flow and transport; these are relevant as we focus on understanding and modelling the implementation of treatments through electrokinetics; moreover for the peat it is of importance to understand moisture exchange in the vadose zone and control groundwater table levels (e.g. during electrokinetics) in order to prevent further oxidation. After isolation and screening of indigenous microorgansisms Bacillus licheniformis was selected for further testing. The results in terms of unconfined compressive strength, CaCO3 content, swelling and compression behaviour and water retention proved the feasibility of biocementation using this indigenous microorganism. Ongoing work is assessing the required treated soil characteristics and related required biocementation degree to solve UK rail's peat foundation problems. Upscaling of the techniques towards in situ implementation is also planned in the next stage of the research.

scholarly journals Unification of plastic compression in a coupled mechanical and water retention model for unsaturated soils

2014 ◽  
Vol 51 (12) ◽  
pp. 1488-1493 ◽  
Author(s):  
Martí Lloret-Cabot ◽  
Simon J. Wheeler ◽  
Marcelo Sánchez
Keyword(s):  
Unsaturated Soils ◽  
Water Retention ◽  
Yield Curve ◽  
Stress Path ◽  
Degree Of Saturation ◽  
Retention Model ◽  
Plastic Compression ◽  
Single Process ◽  
Elastoplastic Constitutive Model ◽  
Water Retention Behaviour

In 2003, Wheeler, Sharma, and Buisson presented an elastoplastic constitutive model for unsaturated soils that represents both the mechanical behaviour and water retention behaviour, including the coupling between them. A crucial feature of the model is that the occurrence of plastic compression during all types of stress path is unified as a single process, with plastic compression during loading, plastic compression during wetting (collapse compression), and plastic compression during drying (irreversible shrinkage) all represented by yielding on a single loading–collapse yield curve. This paper explains how the model is able to predict the possible occurrence of plastic compression during each type of stress path and, in each case, links this to a physical explanation of the process involved. A simulation of an experimental test demonstrates the capability of the model to accurately predict the variation of both the void ratio and degree of saturation during successive stages of drying, loading, and wetting, where large magnitudes of compression occurred in all three test stages.

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.

scholarly journals An Insight into the Projection Characteristics of the Soil-Water Retention Surface

Water ◽  
2018 ◽  
Vol 10 (12) ◽  
pp. 1717 ◽  
Author(s):  
Yun-xue Ye ◽  
Wei-lie Zou ◽  
Zhong Han
Keyword(s):  
Soil Water ◽  
Unsaturated Soils ◽  
Water Retention ◽  
Degree Of Saturation ◽  
Soil Water Retention ◽  
Mechanical Coupling ◽  
Tangential Approximation ◽  
Coupling Behavior ◽  
Constant E ◽  
New Criterion

The soil-water retention surface (SWRS), which describes the variation of the degree of saturation (Sr) with suction (s) and void ratio (e), is of crucial importance for understanding and modeling the hydro-mechanical behavior of unsaturated soils. As a 3D surface in the Sr –e–s space, the SWRS can be projected onto the constant Sr, constant s, and constant e planes to form three different 2D projections, which is essential for establishing the SWRS and understanding its various characteristics. This paper presents a series of investigations on the various characteristics of the three SWRS projections. For the Sr –s and Sr –e relationships, (i) a tangential approximation approach is proposed to quantitatively capture their asymptotes, and (ii) a new criterion is presented to distinguish the low and high suction ranges within which these two relationships exhibit different features. On the other hand, a modified expression is introduced to better capture the characteristics of the s–e relationships. The various projection characteristics and the proposed approaches are validated using a wide set of experimental data from the literature. Studies presented in this paper are useful for the rational interpretation of the SWRS and the hydro-mechanical coupling behavior of unsaturated soils.

scholarly journals A general mathematical framework for modelling soil-water retention behaviour

2021 ◽  
Vol 337 ◽  
pp. 02006
Author(s):  
Carlos Pereira ◽  
João Ribas Maranha ◽  
Rafaela Cardoso
Keyword(s):  
Soil Water ◽  
Specific Volume ◽  
Unsaturated Soils ◽  
Water Retention ◽  
Degree Of Saturation ◽  
Mathematical Framework ◽  
Soil Water Retention ◽  
Retention Behaviour ◽  
Entrapped Air ◽  
Water Retention Behaviour

A new constitutive model for the soil-water retention behaviour of unsaturated soils is proposed, able to reproduce the main drying and wetting paths, the cyclic retention behaviour and its dependence on the specific volume. The most significant aspect is the inclusion of the evolution, with the specific volume, of the degree of saturation when suction tends to zero in wetting paths considering the presence of entrapped air bubbles. The model is used to reproduce with success the drying/wetting cycles of two Pearl clay samples.

scholarly journals The Mechanical Impact of Water Affected the Soil Physical Quality of a Loam Soil under Minimum Tillage and No-Tillage: An Assessment Using Beerkan Multi-Height Runs and BEST-Procedure

Land ◽  
2021 ◽  
Vol 10 (2) ◽  
pp. 195 ◽  
Author(s):  
Mirko Castellini ◽  
Anna Maria Stellacci ◽  
Danilo Sisto ◽  
Massimo Iovino
Keyword(s):  
Soil Water ◽  
Water Retention ◽  
Management Practices ◽  
Soil Management ◽  
Soil Water Retention ◽  
Physical Quality ◽  
Soil Physical Quality ◽  
Loam Soil ◽  
The Impact

The multi-height (low, L = 3 cm; intermediate, M = 100 cm; high, H = 200 cm) Beerkan run methodology was applied on both a minimum tilled (MT) (i.e., up to a depth of 30 cm) and a no-tilled (NT) bare loam soil, and the soil water retention curve was estimated by the BEST-steady algorithm. Three indicators of soil physical quality (SPQ), i.e., macroporosity (Pmac), air capacity (AC) and relative field capacity (RFC) were calculated to assess the impact of water pouring height under alternative soil management practices. Results showed that, compared to the reference low run, M and H runs affected both the estimated soil water retention curves and derived SPQ indicators. Generally, M–H runs significantly reduced the mean values of Pmac and AC and increased RFC for both MT and NT soil management practices. According to the guidelines for assessment of SPQ, the M and H runs: (i) worsened Pmac classification of both MT and NT soils; (ii) did not worsen AC classification, regardless of soil management parameters; (iii) worsened RFC classification of only NT soil, as a consequence of insufficient soil aeration. For both soil management techniques, a strong negative correlation was found between the Pmac and AC values and the gravitational potential energy, Ep, of the water used for the infiltration runs. A positive correlation was detected between RFC and Ep. The relationships were plausible from a soil physics point of view. NT soil has proven to be more resilient than MT. This study contributes toward testing simple and robust methods capable of quantifying soil degradation effects, due to intense rainfall events, under different soil management practices in the Mediterranean environment.

Capillary-based effective stress formulation for predicting shear strength of unsaturated soils

2015 ◽  
Vol 52 (12) ◽  
pp. 2067-2076 ◽  
Author(s):  
Jean-Marie Konrad ◽  
Marc Lebeau
Keyword(s):  
Shear Strength ◽  
Effective Stress ◽  
Unsaturated Soils ◽  
Water Retention ◽  
Adsorbed Water ◽  
Soil Strength ◽  
Liquid Films ◽  
Degree Of Saturation ◽  
Stress Parameter ◽  
Effective Stress Parameter

A number of investigations have shown that the shear strength of unsaturated soils can be defined in terms of effective stress. The difficulty in this approach lies in quantifying the effective stress parameter, or Bishop’s parameter. Although often set equal to the degree of saturation, it has recently been suggested that the effective stress parameter should be related to an effective degree of saturation, which defines the fraction of water that contributes to soil strength. A problematic element in this approach resides in differentiating the water that contributes to soil strength from that which does not contribute to soil strength. To address this difficulty, the paper uses theoretical considerations and experimental observations to partition the water retention function into capillary and adsorptive components. Given that the thin liquid films of adsorbed water should not contribute to effective stress, the effective stress parameter is solely related to the capillary component of water retention. In sample calculations, this alternative effective stress parameter provided very good agreement with experimental data of shear strength for a variety of soil types.

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