bluuebunny/crossref_metadata_2025 huggingface dataset:
Improved Thermal Conductivity Function for Unsaturated Soil with Physics-based Parameters
Authors: Musa Mohamed S. , Lu Yu , McCartney John S.
Published: April 2023

This paper proposes a new relationship between thermal conductivity and degree of saturation of unsaturated soils, referred to as the thermal conductivity function (TCF). The new sigmoidal relationship between thermal conductivity and degree of saturation was developed so that all parameters have a physical meaning. After calibration of the model using data from the literature and comparison with other available TCFs, the parameters of the new TCF were related to those of the soil-water retention curves for the soils investigated in the calibration process. The linkage between the parameters of the TCF and SWRC indicates that the parameters reflect the point of air entry and pore size distribution of the soil, as well as the maximum and minimum thermal conductivity values encountered at saturated and dry conditions, respectively.
The importance of permeability in modelling soil-atmosphere interaction
Authors: Tsiampousi Aikaterini
Published: April 2023

Soil-atmosphere interaction has been attracting increasing interest as the seasonal variation of pore water pressures (pwp) has been linked to a variety of geotechnical problems (e.g. slope stability and serviceability, foundation subsidence or swelling, desiccation cracking etc.) or has been identified as part of the solution of geotechnical problems (e.g. in sustainable urban drainage systems). Prediction of how the pwp will change within soils of low permeability under the combined effect of evapotranspiration and precipitation requires adequate knowledge of the soil permeability and how it varies spatially (e.g with depth) and temporally (e.g. with suction or degree of saturation, void ratio or due to the opening and closing of desiccation cracks). Nonetheless, in-situ measurements of permeability that satisfy both the spatial and temporal variation are difficult. In order to clarify the importance of variable permeability in predicting pwp variations under atmospheric loads, a series of one- and two-dimensional finite element analyses was performed, where the permeability model and the variation of permeability were parametrically studied. The results demonstrated that the variation of permeability, as well as the model employed in the analysis, e.g. allowing or not for desiccation cracking, influenced the values of suction calculated as well as the pwp profile with depth, highlighting the importance of estimating the spatial and temporal variation of permeability with some level of confidence.
Drying and wetting soil-water retention behaviour of a highly expansive clay under varying initial density
Authors: Murison Ruan A. , Jacobsz S.W. , Gaspar Tiago A.V. , da Silva Burke Talia S. , Osman Ashraf S.
Published: April 2023

Expansive (or swelling) clays are the most prolific problem soil across Southern Africa and many parts of the world. Large volume changes due to seasonal wetting and drying cause millions of dollars’ worth of damage to engineering infrastructure yearly. Soil-water retention behaviour is dependent ondensity, and determining the correct retention curve may be key for reliable design of infrastructure. Soilwater retention curves and shrinkage curves were measured for recompacted samples of a highly expansive bentonite clay from South Africa. Four samples were prepared at varying initial dry densities between approximately 1200 and 1500 kg/m3 and subjected to total suction testing in a dewpoint hygrometer. The water content of each sample was varied through wetting and drying. The sample volume was measured after each suction reading, allowing relationships between suction and void ratio, degree of saturation and water content to be determined. The relationship between gravimetric water content and suction was not significantly influenced by initial density. Degree of saturation at a given suction varied significantly according to initial density. Volume reductions of 25% to 36% from saturated to residual conditions were recorded, and samples tended to a residual void ratio of 0.35 to 0.4. The swelling clay showed propensity for maintaining high suctions (over 300 MPa at residual conditions) and hysteretic response between primary drying and wetting.
Water retention curve of clayey sands determined from pore structure by using various methods
Authors: Vu Quoc-Hung , Pereira Jean-Michel , Tang Anh Minh
Published: April 2023

Besides standard approaches, the soil water retention curve (SWRC) can be estimated either from pore size distribution obtained by mercury intrusion porosimetry or from the soil freezing characteristic curve. These methods are based on simplified laws such as Young-Laplace for capillary suction or ClausiusClapeyron for cryo-suction. These laws might not be valid for clayey sands where the presence of clay particles would induce other water retention mechanisms. This study aims to assess the clay content's effect on the validity of these two methods in determining the SWRC of clayey sands. Clay sands were prepared at different clay contents by mixing pure sand with kaolin clay prior to compaction at the Proctor maximum dry density. Five clay contents (dry mass of clay divided by dry mass of soil) were considered (0, 5, 10, 15, and 20%). The reference SWRC was obtained by standard suction measurements. The results show that SWRCs estimated from mercury intrusion porosimetry and soil freezing characteristic curve are generally in agreement with the reference SWRC. However, the results obtained by the soil freezing characteristic curve are limited in terms of suction range (500 to 5 MPa) which is not appropriate for clayey sands, while those from mercury intrusion porosimetry show significant discrepancy because of the structure heterogeneity obtained by Proctor compaction.
Nanoscale soil-water retention curve of unsaturated clay via molecular dynamics
Authors: Zhang Zhe , Song Xiaoyu
Published: April 2023

This paper characterizes nanoscale soil-water retention mechanism of unsaturated clay through molecular dynamics simulation. Series of molecular dynamics simulations of clay at low degrees of saturation were conducted. Soil water was represented by a point cloud through the centre-of-massmethod. Water-air interface area was measured numerically by the alpha shape method. Spatial variation of water number density is characterized and used to determine the adsorbed water layer. The soil-water retention mechanism at the nanoscale was analysed by distinguishing adsorptive pressure and capillary pressure at different mass water contents and considering apparent interface area (water-air interface area per unit water volume).
Impact of salinity and alkalinity on the microstructure of partially saturated Opalinus Clay from the lower sandy facies (LSF) of Mont Terri site
Authors: Barakat Yara , Mokni Nadia , Cui Yu-Jun , Delage Pierre , Bernier Frédéric
Published: April 2023

In the context of deep waste disposals, the geological barrier (i.e., the host rock) will be exposed to saline plumes from bituminous waste and alkaline plumes from concrete degradation. These chemical disturbances will affect the hydraulic and mechanical properties of the clay rock by modifying its microstructure. As a result, the self-sealing of the fractures created during excavation could be affected,further affecting the long-term safety of the repositories. To this end, the effect of salinity and alkalinity on the microstructure of a partially saturated Opalinus Clay from the lower sandy facies of Mont Terri was investigated. It was found that at 𝑤 = 4.1%, salinity decreases the density and the peak of the mesopores compared to the synthetic water. This is due to the water transfer from the meso to the macro pores and to the decrease of the thickness of the diffuse double layer. For the same water content, alkalinity generates meso and macro pores. The dissolutions of clay and non-clay minerals are the main mechanisms involved.
Microstructure of compacted low-plasticity soils: the initial fabric and its evolution on stress and suction paths
Authors: Gonzalez-Blanco Laura , Romero Enrique , Pinyol Núria M. , Alonso Eduardo E.
Published: April 2023

Soils used in earthworks undergo different hydro-mechanical paths due to the compaction and construction process, the change in climatic conditions or the groundwater level oscillations. Their hydromechanical behaviour is greatly affected by their initial microstructure set on compaction that evolves differently in compliance with the stress paths. The current study investigates the differences in the initial microstructure in a low-plasticity clayey silt compacted at the dry and wet of the optimum. Themicrostructure was characterized by mercury intrusion porosimetry. The definition of a microstructural void ratio (em) inside the soil aggregates and its ratio to the total void ratio (em /e) allowed plotting contours of equal em and em /e in the Proctor compaction plane for the as-compacted states. Additionally, the evolution of the initial microstructure along different stress and suction paths was evaluated. The microstructural voidratio reached after the hydro-mechanical paths did not reproduce the contours of the as-compacted states in the compaction plane. In fact, the microstructural void ratio inside saturated soil aggregates follows Terzaghi’s effective stress through a microstructural compressibility parameter, which provides a straightforward approach for predicting the evolution of the microstructure of compacted low-plasticity soils subjected to different stress-suction paths.
3D effects of soil-atmosphere interaction on infrastructure slope stability
Authors: Tsiampousi Aikaterini
Published: April 2023

It has long been established that pore water pressure (pwp) variations affect the stability and serviceability of slopes. Pwp variations may be due to consolidation/swelling processes within soils of low permeability or may be due to seasonal evapotranspiration and precipitation processes. The simultaneous study of such phenomena and of hydro-mechanical coupling in sloping ground requires use of advancednumerical methods. Often, infrastructure slopes are considered in plane strain (two-dimensional) conditions for simplicity and to date this is the case for most numerical analyses considering soil-atmosphere interaction. However, this approach makes it impossible to study the longitudinal extent of a possible slip surface forming following vegetation removal. Three-dimensional, fully-coupled numerical analyses of acut slope were performed herein to study the effect of vegetation clearance on stability and explore numerically ways of implementing effective vegetation management.
SimuIating landsIides using two-phase two-point material point method
Authors: Zhan Zhiqi , Zhou Chao
Published: April 2023

Material point method (MPM) is an effective numerical method for large-deformation analysis under unsaturated conditions. In the previous studies, water retention ability and permeability function were assumed to be Independent of soil deformation. Besides, most studies used a single set of material points, so some processes (e.g., the infiltration of free water into unsaturated soil) cannot be modelled. Thereby, a two-point MPM approach has been extended from saturated to unsaturated soils. The required information of soild and liquid phases is carried by two individual sets of material points, with the assumption of zero pore air pressure. GIMP is applied for space discretisation. In the modelling of hydraulic behaviour, the porosity-dependent water retention curve and permeability function are incorporated. A centrifuge test about rainfall-induced unsaturated soil slope failure is simulated to investigate the influence of the porosity-dependent water retention curve and permeability function. Parametric studies demonstrate soil parameters for water retention behaviour and shear strength play significant roles in the slope failure mechanisms.
Numerical modelling of unsaturated MX-80 bentonite subjected to two different hydration paths and subsequent loading to high-pressures
Authors: Pedone Giuseppe , Zdravkovi Lidija , Potts David , Tsiampousi Aikaterini
Published: April 2023

MX-80 bentonite has been considered as a suitable material for the construction of engineered barriers employed in deep geological radioactive waste repositories. These barriers are generally formed of compacted unsaturated bentonite, the latter experiencing a slow saturation due to its low permeability whileinteracting with the surrounding groundwater. In order to verify the long-term safety requirements of engineered barriers, their response to hydration has to be carefully assessed. As part of the recent European project BEACON (Bentonite Mechanical Evolution), the behaviour of MX-80 bentonite subjected to different hydration paths was investigated in a number of laboratory and field experiments and numerical studies. This paper is concerned with numerical simulations of two laboratory experiments performed during the project, with the objective of examining the predictive capabilities of the proposed numerical modelling approach. The experiments were selected due to the granular state of bentonite at its placement in the testingapparatus, which differed from the large number of previous experiments conducted on specimens of compacted bentonite blocks. The paper provides a brief introduction to the adopted modelling framework, a summary of calibrated parameters for the hydro-mechanical constitutive modelling and the results of numerical simulations, concluding that a satisfactory numerical simulation of the experiments was achieved.
Pore pressure response during tube sampling in gold tailings
Authors: Donald Gregory Darren Mc , de Lange Wallace , Jacobsz Schalk Willem
Published: April 2023

Capturing the in-situ state of mine tailings is important in determining its behaviour under loading for evaluating the risk of failure of tailings dams. Obtaining a high-quality undisturbed sample through tube sampling is thus of great value to the responsible engineer. However, the sampling process itself disturbs the soil and changes its state. Since soil behaviour is driven by effective stress, one method to evaluate the disturbance induced during tube sampling is to monitor the soil’s positive and negative pore water pressure response during the process. A laboratory study was conducted where tailings samples were prepared at a controlled void ratio and subsequently saturated with water. Tube samplers of different diameters were driven into the material and extracted by means of an electric actuator during which internal sample pore pressures were monitored using tensiometers. The material experienced significant instantaneous contractive and dilative tendencies during insertion. Instantaneous negative responses during extraction of the tube samplers were also measured. It was found that the largest tube sampler (100mm diameter) performed best in the study.
Evaluating the performance of three sensor types for long-term measurement of suctions in gold tailings
Authors: Narainsamy Yashay , Jacobsz Schalk Willem
Published: April 2023

A key aspect of the stability of a tailings dam is the pore pressure regime within the dam. Although gold tailings can exist in an unsaturated state in the field, the measurement of negative pore pressures (matric suctions) in active gold tailings dams is not common. One of the reasons for this may be the uncertainty regarding the ideal sensor type that should be used due to the shortcomings of various types of sensors. To investigate this, a long-term Drying Box experiment was conducted in the geotechnical laboratory at the University of Pretoria. Three sensor types were assessed: a commercially available water potential sensor and two versions of the TUKS tensiometer – a high capacity tensiometer designed and constructed at the University of Pretoria. Gold tailings was deposited in a slurry form and allowed to desiccate. The response from the three sensor types as a result of the change in suctions due to drying and subsequent re-wetting were observed. It was found that the TUKS tensiometer with the steel casing provided rapid, reliable, long-term suction readings. This sensor type is therefore recommended for long-term measurement of suction in gold tailings.
The influences of partial saturation on cone penetration tests in silty gold tailings
Authors: Russell Adrian , Vo Thanh , Ayala Juan , Wang Yanzhi , Reid David , Fourie Andy
Published: April 2023

Laboratory-controlled cone penetration test results of a silty gold tailings in a variety of saturated and unsaturated states, obtained using two calibration chambers, are presented then interpreted using a state parameter-based approach. The research was conducted as part of the TAILLIQ project (tailliq.com), funded by the Australian Research Council and six mining companies, and involving four Australian universities.Cone penetration resistances, which increase due to the presence of suction when the tailings are unsaturated, can be normalised using the initial mean effective stress to establish a relationship with the initial state parameter. The relationship is applicable to saturated and unsaturated conditions, as long as the presence of suction hardening as well as the influence of suction on the mean effective stress are accounted for, and as long as the cone penetrations occur under pseudo drained conditions. The relationships enable state parameters and void ratios to be back-calculated from normalised cone penetration resistances.
Numerical Investigation of Saturated-Unsaturated Flow and Stability Analysis of Tailings Dams Considering the Influence of Saline Solutions
Authors: Anbarestani Mona , Sadeghi Hamed , Darzi Ali Golaghaei
Published: April 2023

A tailings dam is normally constructed through self-consolidation with minimum compaction effort. Accordingly, special attention to the ultimate limit design in assessing the tailings dam instability condition is of primary importance. Furthermore, the existence of pore fluid chemical contaminants with high concentrations makes soil hydraulic and shear resistance properties subject to considerable changes.Therefore, this study aims to investigate the stability of a tailing dam using saturated-unsaturated flow analysis under 0.2 and 0.6 M sodium chloride solutions and pure water as a benchmark. To make the analyses as realistic as possible, recently developed solute-dependent hydraulic conductivity and water retention models are embedded into the numerical software. The results show that the saline-based model has higher pore water pressure than the pure water model due to more rainfall penetration by increasing the pore fluid salt concentration. Furthermore, increasing salt solution concentration enhances the tailing dam's drainagecondition, which leads to an increase in the dam's shear strength and, consequently, the factor of safety. Therefore, the stability of the tailings dam is improved by the combined impact of salt on both the flow and strength.
Strain Softening response of loose unsaturated tailings samples in undrained triaxial tests
Authors: Urbina Felipe , Reid David , Fourie Andy
Published: April 2023

For a soil that is contractive and strain softening at fully saturated conditions the question remains on which degree of saturation can trigger a strain softening response. A common engineering practice is to adopt a saturation threshold (e.g., 85%) and then assume a fully saturated response when saturation is above that value. This study aims to understand how the strain softening response change when tailings are not fully saturated and to propose a systematic method for determining the saturation threshold. A restraint when preparing unsaturated loose samples is that it is likely to have collapse during flashing, thus changing void ratio and making comparisons between different degrees of saturation problematic. A simple procedure to obtain loose samples at different degrees of saturation but at similar post-flushing void ratios is explained and preliminary results of undrained shear strength obtained for gold tailings in triaxial device are presented and discussed.
Investigation of the properties and behaviour of ancient and newly constructed mudbricks from the ancient walls of Eleusis
Authors: Bardanis Michail , Marinis Theodoros , Toumbakari Eleni-Eva , Dounias Georgios
Published: April 2023

The paper presents the test results from the investigation of the nature and mechanical behaviour of mudbricks from the ancient mudbrick wall of Eleusis in Attica, Greece. The mudbrick wall remains preserved to date in the site of Eleusis are some of the largest preserved in Greece. Small fragments of mudbricks were taken to the laboratory for experimental investigation. Testing included index tests toclassify the soil material the mudbricks were made of, mineralogical analyses of their fines’ content, mechanical testing suitable for the nature of the materials and the ability to trim the samples without causing damage and measurements of suction on samples as they were obtained, further dried, or rewetted. The soil material used for ancient mudbrick construction was a silty sand to sandy silt with a small fraction clay content, with marginally plastic to non-plastic fines. Dry unit weight was found to be close to the dry unit weight of fresh mudbrick material after being compacted with a minimum compaction energy of only 45 kNm/m3 and left to dry to residual water content conditions. Similarly, field water content was found close to the residual water content of these recompacted soil samples. Consequently, unconfined compression strength was found very high corresponding to the residual water content condition, with similarly high cohesion obtained from direct shear tests and a very high yield stress under one-dimensional conditions of loading.
The Amazing Mechanism of the Standing for 700years of the Tall Masonry Stone Tower of 32m in height on Manmade Sandy High Mound by Shallow Direct Foundation, Bayon Temple, Angkor, Cambodia
Authors: Iwasaki Yoshinori , Fukuda Mitsuharu , Ishizuka Mitsumasa , McCarthy Robert , Ly Vanna , Nakagawa Takeshi
Published: April 2023

Soils and foundation of Bayon temple of Angkor Thom has been studied since 1994 by Japanese Government Team for Safeguarding Angkor (JSA). The main tower of Bayon of 32m in height from the base foundation mound consists of manmade fill of 14 m in thickness. The foundation was studied and found as a simple shallow direct foundation. This is just like a 10 story RC building standing upon thick manmade sand fill without such a deep foundation as piling. At present, such a structure based upon thick sandy fill shall lose the foundation stability in the dry season under the monsoon climate of South-eastern Asia. The amazing mechanism, standing for 700 years, has been identified as the unsaturated characteristics of well compacted silty sand.
Thermal conductivity of compacted Opalinus Clay at different degrees of saturation
Authors: Sau Nuria , Christ Florian , Romero Enrique , Lavasan Arash Alimardani
Published: April 2023

Tunnelling in bedded shale rocks induces damage around the excavation. Consequently, the rock mass in the excavation damaged zone (EDZ) shows different thermo-hydro-mechanical (THM) properties from the intact rock. In turn, the damaged material close to the tunnel wall is affected by seasonal fluctuations in temperature and relative humidity (RH) variations associated with tunnel ventilation, impacting the total suction and the saturation state of the EDZ. The monitoring data at the new Swiss BelchenA2 highway tunnel excavated in Opalinus Clay (OPA) captured these seasonal variations in the total stressacting on the lining associated with this temperature and RH fluctuation. Within this context, assessing the temperature field in the EDZ requires determining the thermal conductivity of the damaged rock at different degrees of saturation. However, obtaining good-quality cores of OPA from the EDZ is not straightforward, and partially desaturating them using controlled RH techniques is time-consuming. Consequently, instead of testing damaged OPA, statically compacted samples of OPA powder at different degrees of saturation have been considered to study the thermal conductivity. In addition, two natural OPA samples (with different bedding orientations) retrieved from the Belchen tunnel have been tested to cross-check the experimental procedure and results, which indicated a consistent increase in thermal conductivity with the degree of saturation.
Evolution of Water Retention Characteristics in Bio-Geochemically Altered Unsaturated Soils: A Pore-Scale Study
Authors: Nassiri Sina , Zapata Claudia , Mahabadi Nariman
Published: April 2023

Biogeochemical processes in subsurface can dramatically alter the behavior of multiphase fluid flow and the hydrodynamics of porous media by bio-clogging. There exist analytical solutions such as soilsuction – saturation equations which can be used to predict the water retention curve relations in unsaturated soils. However, due to the complexity of various biogeochemical products, their pore-scale behavior and their interplay with pore structure, such analytical solutions would not provide accurate predictions. In this study, a large database of pore-networks were generated by adjusting the statistical and spatial pore and tube size distribution of the networks resembling various levels of bio-clogging. Numerical simulations including the evolution of pore structure, water retention relationship, and air invasion dynamics during desaturationwere explored. The numerical simulations verified that local pore-clogging leads to the development of isolated pore clusters and impermeable zones. The evolution of impermeable zones results in the formation of preferential flow paths towards the mobile zones for the multiphase flow problems. Using parallel computation, the critical predictors of water retention curves in bio-clogged porous media are found.
Investigation of water-retention and uniaxial compression behaviour of MX80 bentonite pellet at various suctions
Authors: Yang Jin-Wen , Cui Yu-Jun , Mokni Nadia
Published: April 2023

MX80 bentonite pellet/powder mixture has been regarded as a candidate sealing material in deep geological high-level radioactive waste disposal. As single pellet plays an important role in the global hydromechanical behaviour of the mixture, a series of single pellet compression tests were conducted on cylindershape MX80 bentonite 32-mm pellet after reaching suction equilibrium. The changes in volume and water content during the suction equilibration with the vapour equilibrium technique allowed the water-retention properties to be investigated. X-ray μCT observations were also made on pellets after reaching the target suctions. Results showed that upon drying the water content, void ratio and volumetric strain decreased slightly, but increased significantly upon wetting. Moreover, upon drying the network of cracks presented insignificant change and the cracks were mainly located in the marginal areas of pellet, while on wetting, cracks substantially propagated from the marginal areas to the core of pellet. The uniaxial compression tests on single pellets showed that the axial strain εaxial contributed to the contractancy, while the lateral strain εlateral to the dilatancy. The uniaxial shear strength σa, max, the crack closure (CC) stress σcc, the crack initiation (CI) stress σci, the crack damage (CD) stress σcd and the Young’s modulus E were found to decrease with suction decreasing, evidencing the suction effect through softening and cracking. Because of the combined effect of suction and wetting-induced cracks, the Poisson’s ratios v increased until the suction decreased to 38-25 MPa, and then decreased with further suction decrease. Uniaxial loading closed the horizontal wetting-induced cracks at suctions ≤ 9 MPa, leading to a drop of εlateral before CC.
An experimental setup to investigate the effect of mycorrhizal fungi inoculation on plant water uptake in unsaturated soils
Authors: Roberts-Self Eve , Tarantino Alessandro
Published: April 2023

The use of vegetation as a Nature Based Solution, NBS, is increasingly being used for climate adaptation and resilience for engineered and natural slopes. As such it is important to understand the biological processes associated with vegetation and how they could be beneficially implemented. Due to the large repetition required when experimenting with biological components it is impossible to carry out experiments that are highly instrumented. This paper looks at mycorrhizal fungi as a method to improve plant water uptake and presents an experimental setup to allow for a low level of instrumentation in triplicate, with a few being well instrumented. Through benchmarking against TDR-probes, it was found that the method of monitoring soil water content changes in a mini-lysimeter with a loadcell provides a reliable and convenient approach to carry out experiments in three replicates at least.
Drying Front and Vaporization Plane Dynamics during Evaporation from Homogeneous Soil Profiles
Authors: Hussary Jumana , Alowaisy Adel , Yasufuku Noriyuki , Ishikura Ryohei , Abdelhadi Monther
Published: April 2023

Global warming has caused many lands to degrade, making them vulnerable to desertification. Therefore, finding innovative solutions is essential to prevent such phenomena from exacerbating. However, this requires a comprehensive understanding of the unsaturated layer formed due to the high-water loss from soil profiles by evaporation. In the present study, a new technique to trace the unsaturated layer from drying soil profiles was developed, and its accuracy and reliability were confirmed. Consequently, the spatial and temporal development of the drying front, vaporization plane, and film region were investigated for two soil profiles of different pore structures. It was found that soil profiles with broader pore distribution lose water from deeper drying fronts during Stage 1, while diffusion during Stage 2 occurs from shallower depths. Moreover, the film region’s thickness increased at early drying stages, followed by a slight drop associated with the onset of Stage 2. During Stage 2, the thickness slightly fluctuated until reaching the same thickness at the end of Stage 1, where a second significant drop in the thickness was observed.
Coupled hydro-mechanical behaviour of a Kaolin Clay in the context of the geothermal use of geotechnical structures
Authors: Kayser Timon , Baille Wiebke , Tafili Merita , Wichtmann Torsten
Published: April 2023

An experimental study regarding the hydro-mechanical behaviour of a Malaysian Kaolin is presented. Strain rate-controlled oedometer tests have been conducted on compacted samples. The influence of initial water content on the pore-size distribution (PSD) of compacted samples was investigated by Mercury Intrusion Porosimetry (MIP) tests. The drying path of the soil-water characteristic curve was experimentally determined for initially compacted samples and slurry samples. The preconsolidation stress was found to increase with increase in initial dry density and with decrease in initial water content. The compression curves merge into a single line, as soon as they have reached full saturation during loading. Samples at the dry side of Proctor water content showed a bi-modal PSD, whereas a mono-modal PSD was found for Proctor water content and at the wet side. The different initial compaction states of the samples were getting reflected in the drying SWCC until a suction of about 2 MPa, beyond which the drying paths were found to be identical.
Hygrothermal characterization of rammed earth according to humidity variations
Authors: Losini Alessia Emauela , Chitimbo Taini , Létévé Laura , Woloszyn Monika , Grillet Anne-Cecile , Prime Noemie
Published: April 2023

Rammed earth construction is built by compacting humid soil into formworks layer by layer, using clay fraction as only binder between the grains, without firing procedure. At this stage, the material is unsaturated, and capillary forces thus act to add cohesion between particles. Indeed, a peculiarity of this material is its high hygroscopic capacity, which allows water vapor to be absorbed and desorbed into the clay matrix. The variation of hydric state in the material leads to a variety of mechanical and thermal properties. Consequently, the complexity in studying this material is due to the strong dependence of many parameters on the moisture content and still few data are available in the literature on this subject for rammed earth materials. A soil used for an existing rammed earth building in Lyon is here characterized in order to determine its hygrothermal properties. Earth conductivity was firstly characterized in a reference dry state, then the influence of humidity variations was investigated. Sorption and desorption isotherms were determined to investigate the ability of the material to store and release humidity. Thermal conductivities were measured at different relative humidity, to put into evidence the influence of environmental conditions.
Capillary absorption into CEBs and 2-layer composite building materials comprising of natural stone and CEBs
Authors: Panagiotou Rafail , Ioannou Ioannis
Published: April 2023

Earth-based building materials have been used since antiquity for the construction of various structures. The main drawback of these materials is their vulnerability to direct contact with liquid water, such as rising damp. To protect earthen structures from rising damp, a stone foundation was used, resulting in composite masonry. In the current study, an experimental investigation of the capillary absorption of non-stabilized CEBs produced with soils sourced from different areas of Cyprus, as well as of 2-layer composite building materials comprising of natural stone and CEBs was carried out. The tests on CEBs indicated that the use of water as the wetting liquid led to the disintegration of the specimens and consequently to non-linear response. Thus, a non-reactive liquid was used instead to measure the capillary absorption coefficient of the materials. The test results showed that the capillary absorption coefficient of CEBs varied between 140-260 gr/m2sec1/2. In the case of the composites, capillary absorption with water as the wetting liquid showed perfectly linear response, following the t1/2 law, with no disintegration of the specimens. The results showed that there are two distinct capillary absorption branches with different gradients, in line with the theory of capillary absorption into 2-layer composite materials.
Some examples and lessons from long-term field measurements of suction in Greece
Authors: Bardanis Michael , Kokoviadis Dimitrios
Published: April 2023

The occurrence of unsaturated soils in the field has been well documented worldwide by measurements of the degree of saturation on samples taken during geotechnical investigations. On the other hand, the suction of unsaturated soils in the field, especially as part of long-term measurements, is documented very rarely and references on the subject are very few and for very few places around the world. The scarceness of this kind of measurements denies researchers perception of the anticipated suction and its possible loss, or retention, as a result of climatic conditions, especially in countries with warm temperate climate. Suction measurements from temporary and permanent stations in Greece and Cyprus have been presented in the past showing that considerably high values of suction can develop and be maintained even during wet periods. This paper focuses on examples and lesson learned from stations in Greece, especially magnitude and change of suction with time, as well as longevity of stations and associated problems.
Numerical Evaluation of Slope Stability based on Temporal Variation of Hydraulic Conductivity
Authors: Gupta Alinda , Islam Md Azijul , Alam Md Jobair Bin
Published: April 2023

Slope failure is a common phenomenon all over the world on both man-made and natural slopes. Prolonged rainfall is one of the climatic factors which is largely responsible for slope failure. During heavy and prolonged rainfall, a part of the rainwater infiltrates through the soil and seeps into the slope. The infiltrated water lowers the matric suction and increases the porewater pressure. Eventually, the generated porewater pressure decreases the strength of the soil which results in slope failures. To evaluate the effect of rainwater seepage on slope stability, it is necessary to investigate the hydraulic conductivity of the slope soil. The objective of this study is to evaluate the effect of hydraulic conductivity on slope failure mechanisms. A finite element analysis of slope stability was conducted using Geo-Studio software. A numerical model was developed and calibrated with field monitoring data. The field monitoring data included the observation of hydraulic conductivity using a Guelph Permeameter. Afterward, the temporal variation of rainfall and hydraulic conductivity was incorporated into the SEEP/W program and the consequent changes in slope stability were evaluated in SLOPE/W. From the numerical analysis, with the identical strength parameters of the soil, different factors of safety were observed when the slope sections retain different hydraulic properties. Based on the numerical analysis, it was observed that hydraulic conductivity greater than 4×10-6 cm/s leads to slope failure. Periodic monitoring of hydraulic conductivity in the field may provide deep insight into rainfall-induced slope failures.
Numerical Investigation into the effects of rainfall and long stem plants spacing on Root Water Uptake (RWU)
Authors: Bertolini Ilaria , Vidler Andrew , Gottardi Guido , Buzzi Olivier
Published: April 2023

Woody plants on earthen slopes are a bioengineering solution for the prevention of shallow landslides that occur mostly during a wet season. From a soil-hydrological point of view, slope stability is influenced by plant roots reducing soil water content through transpiration. Despite this, conventional engineering practice tends to ignore the effects of Root Water Uptake (RWU), in part due to the complexity of soil-vegetation-atmosphere interactions. This paper investigates the hydrological effects of plants, which involved seepage simulations performed on two different soil types. Each soil was exposed to different rainfall intensities, and the influence of plants over time was seen from the RWU over time for different configurations of plant spacing and canopy densities. This information with in-situ rainfall data, is useful to assess the effectiveness of plants for slope stability. Further, the relative importance of different mechanisms acting in soil-plant-atmosphere interactions was seen in the RWU data. Although the conducted simulations refer to a horizontal soil profile, the results are useful in more complex geometries such as earthen slopes and may help the design of bioengineering solutions (woody plants) and slope stability assessment. Future research is aimed to investigate additional soil-vegetation-atmosphere mechanisms and additional model geometries and plant species.
Reliability of HCT-based Soil Water Retention Curves
Authors: Bagheri Meghdad , Matziaris Vasileios , Akinniyi Damilola
Published: April 2023

The measurement of SWRCs using HCTs has been the subject of several recent studies. Consequently, there have been several design and experimental procedures developed. However, despite these developments, the accuracy, range and duration of HCT-based measurement is still largely characterized by uncertainties and inconsistencies, thereby, reducing the reliability of the obtained SWRCs. In this work, an experimental program is designed to address these uncertainties. SWRCs of reconstituted London clay were measured using the continuous drying method with evaporation rate control. The obtained SWRCs were analysed based on the maximum suction value recorded by HCTs (smax), the obtained air-entry value (saev), the suction at inflection point (si), the water content at inflection point (wi), and the slope of tangent to inflection point (mi). A percentage uncertainty of ±4% was obtained for the saev and si values. Similarly, percentage uncertainties of ±6% and ±0.5% were obtained respectively for the mi and wi values. These results were further compared with parametric analysis of the reported SWRCs of the same soil in the literature. Given the observed tolerance ranges, cautions must be taken in selecting values for these parameters e.g. as input values in mathematical curve fitting equations for prediction of the entire SWRC, or in unsaturated constitutive modelling, to enhance reliability of the outputs.
Investigation into the compression behaviour of unsaturated damaged Callovo-Oxfordian claystone
Authors: Wang Hao , Cui Yu-Jun , Vu Minh-Ngoc , Talandier Jean
Published: April 2023

In this study, the compression behaviour of unsaturated damaged COx claystone is investigated by performing high pressure oedometer tests with controlled suction. The damaged oedometer samples were prepared by shearing the claystone in triaxial conditions. Four high pressure oedometer tests were conducted using different controlled suctions. The effects of suction and damage on the swelling and compression were investigated in oedometer. Results show that the intact claystone exhibits a larger swelling strain than that of the damaged one at the same imposed suction. The damaged claystone at a lower suction displays a smaller yield stress and higher compressibility, and exhibits a larger compression index Cc than the intact one, evidencing the effect of damage. In addition, the step compression index Cc* increases with the increase of vertical stress, while deceases with the decrease of suction. This indicates the dependencies of compression behaviour on vertical stress and suction.
Rolling stock vibrodynamic impact model on railway pipelines
Authors: Postnova E.V. , Runev E.V.
Published: April 2023

The present paper presents the rolling stock vibrodynamic impact model on railway pipelines, obtained on the basis of experimental studies conducted under field conditions at a railway station. The experimental research program provided for the determination of the effect of vibration-dynamic effects of rolling stock on the working condition of pipes and butt joints by conducting vibration-measuring work on the investigated section of the railway pipeline during the passage of various series of locomotives. The proposed modeling method makes it possible to obtain a correlation function of the oscillatory process of a railway pipeline, on the basis of which a spectral density is constructed to identify the amplitude-frequency range at which a stable resonance region occurs, leading to the destruction of the pipeline.
“Smart station”-a complex of automated control system
Authors: Shmanev T.M. , Ulyanitskaya V.I. , Fedorova N.B. , Sitnikov A.YU.
Published: April 2023

The present research paper considers the way of automation of control systems of life support processes and service delivery processes at the infrastructure facilities of the passenger complex, in a single information space, through digital platforms. This issue is relevant, as progress is at the stage of formation of the industrial revolution and the constant technological overturn. Digitization of boundaries, technologies, technical, technological, and organizational processes involved in providing services for passengers, in the work of station complexes, will allow effective management of engineering networks, minimizing gaps in the infrastructure and processes of transport systems. The work considers the transition from manual (personalized) labor at station complexes to an automated system as a whole, in the new construction or reconstruction, or commissioning of local digital facilities related to passenger services.
Assessment of compliance of foreign geotechnical complexes for calculations of freezing-thawing of soils with Russian legal normatives
Authors: Paramonov V. , Slivets K.
Published: April 2023

The design of construction objects in the conditions of the far north relates to changes in the temperature regime of the soil mass. In this regard, to choose the right design, it is necessary to be able to predict the change in the temperature field over time. Taking into account that heat release or absorption occurs when passing through the freezing onset temperature, the thermal conductivity equation, even for the onedimensional case, becomes non-linear. Several software packages have been developed to solve heat conduction problems. Meanwhile, theoretical assumptions concerning the assignment of heat capacity and heat conductivity coefficients may differ. It is of interest to assess the compliance of the results of calculations of freezing and thawing issues with Russian norms.
Digital platform solutions of Russian Railways as a tool for the development of the concept of MaaS (Mobility as a Service)
Authors: Gulyi Ilia , Shavurskaya Viktoriya
Published: April 2023

The purpose of the study: to substantiate the advantages of the Maas (Mobility as a Service) concept as a universal digital Smart aggregator, a platform integrating all participants in passenger transportation. Methods: content analysis, analysis of digital platform technologies, monitoring of digital processes and solutions at the level of a separate transport company. Results: the main advantages of digital transport multimodality as a concept of integrated digital platforms of the future transport are substantiated. The hypothesis is put forward that electronic digitalized communication technologies of market participants will become the main factor of economic growth. And the ideal MaaS-economic model will be a comprehensive integration of all existing digital platforms in the world and on national markets. The functionality and advantages for users of the development of MaaS solutions of the Russian railway carrier - the Russian Railways company — the Travel.RZD application and a pilot project within the framework of Innovative mobility implemented in the Samara region are presented.
Solving a multi-criteria problem in the logistics of special rail transport
Authors: Kruchek Victor , Shumov Sergey , Kobzar Andrey
Published: April 2023

Under the present conditions, there is a need to assess the effectiveness of the functioning of the technical base of railway transport involved in the performance of special (military) transportation, taking into account the current operational and transport situation. To make a management decision on the choice of the option for further following of a special cargo (reloading, following its course, a combined method, as well as following a detour route [4]), when an obstacle occurs along the route, it is necessary to find an option that best meets the requirements of the planned deadlines. This is possible with a systematic approach to finding an alternative way of transportation. For a reasonable choice of the method when making a decision, it is proposed to use the method of hierarchy analysis [5], which allows a comprehensive assessment of all transportation options, taking into account factors affecting the priorities of possible solutions when assessing the effectiveness of the functioning of the railway network when transporting special (military) cargo. The purpose of making a decision is to choose the option of deciding on the method of transportation of special (military) cargo during a break in the movement of trains with available alternatives (B) (4 methods of transportation) the main indicators (K) are the time of arrival of cargo to the designated area, the consumption of material resources (hereinafter- MS) when following their course or using other modes of transport (in particular - fuel), operational losses of automotive equipment (hereinafter - AT) during forced unloading, as well as the consumption of motor resources Kc = f (T, S, N, M)→min (see figure).