Volume Change Behavior Research Articles

Application of eco-friendly and smart materials in geotechnical engineering for subgrade stabilization: a review

The performance of road pavement mainly depends upon the properties of subgrade soil. The failures occur in case of road pavement is due to poor strength characteristics and high volume change behaviour of subgrade soil. Thus, considering the performance criteria, subgrade soil needs to be treated so as to make it suitable for the construction of road pavement. It was observed that, soil stabilization using various admixtures is more effective and commonly used practice for enhancing the properties of subgrade soil. The previous research shows that subgrade soil stabilization can be achieved with the application of various environmental friendly (Bio – Enzymes) and smart materials (Agricultural and Industrial waste) in required quantity to enhance the physical, strength and volume change characteristics of natural soil. It was also observed that, the combined use of such materials makes the subgrade soil more suitable for the construction of road pavement. From the experimental investigations of various available research works on subgrade stabilization, it was observed that strength and volume change properties such as California Bearing Ratio (CBR), Unconfined Compressive Strength (UCS) and Swell Pressure of subgrade soil can be effectively changed with the help of use of such materials. It was also observed that use of conventional methods has negative impact on environment. Thus, subgrade can be stabilized with eco – friendly and cost effective materials to achieve both economic and serviceability criteria.

Thermo-mechanical volume change behavior of municipal solid waste: experimental study and constitutive model

This paper investigates the thermo-mechanical volume change behavior of municipal solid waste (MSW) by conducting drained heating–cooling tests at constant stresses and isothermal consolidation tests using a temperature-controlled triaxial apparatus. The experimental results show that the compression and swelling indexes of MSW specimen were temperature independent, and the heating-induced volumetric contraction was partially reversible upon cooling. Different from conventional soils, the thermally induced reversible and irreversible volumetric strains of MSW were much larger and stress level dependent. Apart from the experimental study, an isotropic thermo-elastoplastic constitutive model was developed in the framework of existing modified Cam-clay model, which allows the prediction of thermally induced volume changes of MSW. An important feature in this model was the derivation of thermally induced plastic volumetric strain based on the concept of equivalent stress. The capability of the proposed model was validated against the experimental results and showed good predictions. This paper serves as the first attempt to study the thermo-mechanical volume change behavior of MSW, and has provided additional data for the serviceability evaluation of existing pipes as well as settlement and capacity estimation of MSW landfills at elevated temperatures.

Deformation of unsaturated collapsible soils under suction control

Abstract Collapsible soils present significant geotechnical and structural engineering challenges worldwide. They can be found in arid or semi-arid regions and are directly affected by the multi-step wetting procedure due to the reduction of soil suction. The main objectives of this paper are to investigate the volume change behaviour, collapse mechanism and deformation characteristics under the control of suction and net vertical stress. In this study, three types of collapsible soils were investigated such as natural soils of sandy gypseous, silty loess, and artificial soil of gypsum–sand mixture. A series of constant net stress-suction control (wetting and drying) tests using a combination of axis-translation and vapor equilibrium techniques were deployed to cover a wide range of applied suction. The test results show that large volume change and collapse deformation occur upon a stepwise suction decrease. On the other hand, shrinkage behaviour resulting from increases in imposed suction is observed during the drying path. The collapse deformation depends on the stress path and is a function of net normal stress, suction, dry density, and degree of saturation. The water content and the degree of saturation dramatically increase as the applied suction decreases from the initial high to zero values at the drying path.

A general plastic model for rockfill material developed by using Caputo fractional derivative

The gradient direction and fractional derivative direction of one function can be coaxial or non-coaxial, and this depends on the order value of fractional derivative. A fractional plasticity model was developed by using Caputo fractional derivative and a dilatancy equation pondering particle breakage for rockfill material in this study. In this fractional plasticity model, the gradient direction and fractional derivative direction of the plastic potential function derived from a dilatancy equation were deduced and further used as the plastic flow direction and loading direction respectively, and the order controls the non-associated feature between the plastic flow direction and loading direction. For validation, drained triaxial test results under different stress paths of five rockfill materials are simulated by the proposed fractional plasticity model. It can be found from comparisons between the drained triaxial compression test results of rockfill materials and corresponding model predictions that the proposed model can well capture the stress-strain characteristics of rockfill material, including strain hardening and volume change behaviors etc.

Investigation into the hydro-mechanical behaviour and microstructural evolution of MX80 bentonite pellet upon wetting/drying

Bentonite pellet/powder mixtures have been proposed as the candidate sealing plugs of boreholes or galleries in deep geological disposal of high-level radioactive waste. During the long-term operation of repository, the filled bentonite pellets will be subjected to a coupled wetting/drying process, and their hydro-mechanical behaviors are accordingly expected to undergo complex changes. To clarify this point, the water retention and volume change behaviors of bentonite pellets were investigated by conducting hydration/dehydration tests under free-swell condition. Afterwards, the microstructure of bentonite pellets was studied by mercury intrusion porosimetry (MIP) tests. Results revealed that the water retention curves of pellets exhibited an obvious hysteresis in the high-suction range. The volume change of pellet was attributed to the combined actions from the expansion of micro-pores and the propagation of cracks. Meanwhile, the swelling of bentonite pellets exhibited a significant anisotropy during hydration, with a greater swelling strain in the axial direction. But this phenomenon became insignificant during the subsequent drying/rewetting processes. After a wetting/drying cycle, the bentonite pellets yielded an obvious plastic deformation, which was primarily related to the irrecoverable wetting-induced cracks.

Volume Change Behavior of Graphite Electrode for Lithium-Ion Battery By in Situ Electrochemical Dilatometry

Graphite undergoes volume expansion and contraction upon lithium ion intercalation and deintercalation process, which affect the internal microstructure of graphite electrode during cycling. In this work, the expansion and contraction in graphite electrode was investigated using in situ electrochemical dilatometry to determine which factor affect the volume change behavior. It was found that the thickness change of the graphite electrode was highly correlated with the microstructure of graphite electrode, such as the preferential orientation of graphite particles, pore structure of graphite electrodes. It was also found that the differential expansion plots of graphite electrodes provides more detailed information on the expansion and contraction behavior of Li ions inserted into graphite. Detailed findings obtained from in situ dilatometry on the graphite electrode will be discussed in the presenation.

Mechanical Behavior of Piles in Typical Unsaturated Expansive and Collapsible Soils Upon Water Infiltration

Pile foundations are widely used in all types of soils including expansive and collapsible soils that are typically found in nature in a state of unsaturated condition. Opposite trends in volume change behavior are typically observed when water infiltrates into expansive and collapsible soils. The design of pile foundations in these soils is conventionally based on saturated soil mechanics assuming drained conditions ignoring the influence of unsaturated conditions. In this study, infiltration tests were performed on two model piles; one of these piles was tested in an expansive soil and the other in a collapsible soil. The focus of this study was to determine the pile mechanical behavior including the pile head load, displacement response, pile axial force, shaft friction, and pile base pressure taking account of suction changes associated with water infiltration. The pile mechanical behavior is significantly influenced due to changes in the pile shaft friction in both expansive and collapsible soils. The responses of the pile mechanical behavior variations were explained extending the concepts of unsaturated soil mechanics. The results of this study provide valuable information for the practicing engineers to gain a more comprehensive understanding of mechanical behaviors of pile foundations in expansive soils and collapsible soils upon water infiltration.

Volumetric behavior of an unsaturated clayey soil-rock mixture subjected to freeze-thaw cycles: A new insight

The volumetric behavior of clayey soil-rock mixtures under freeze-thaw action is very important for the design of anti-frost heave in cold-region engineering. However, existing studies mainly focus on the effect of freeze-thaw cycles on the global volume change of fine-grained soils, and few attempts have focused on mixed soils with coarse particles such as clayey soil-rock mixtures. In this study, a series of laboratory freezing-thawing tests were conducted to investigate the effects of the freeze-thaw cycles and rock content on the global volume change, diameter change, and height change behaviors of cylindrical soil-rock mixture samples. The results demonstrate that: 1) the volumetric behavior of the samples under freeze-thaw cycles is closely related to the rock content, which is mainly because different rock contents dominate the different skeleton structures. 2) For samples with 0%, 10%, and 30% rock content, the global volume of compacted samples shows shrinkage upon freezing and expansion after thawing. However, the global volume of the sample with 50% rock content began to shrink after three freeze-thaw cycles. 3) Compared with the samples not subjected to freeze-thaw weathering, the height of samples with 0%, 10%, and 30% rock content shows shrinkage upon freezing and expansion after thawing no matter what the number of freeze-thaw cycles is. However, the diameter and height of the sample are always shrinking, regardless of whether they are frozen or thawed. 4) Upon freezing, the shrinkage of the sample's global volume and diameter tends to decrease linearly with the increase of rock content, but the shrinkage of the sample's height is not sensitive to the change of rock content. Upon thawing, the global volume and height of the sample exhibit a trend from expansion to contraction with increasing rock content, but the shrinkage of the diameter of the sample is nearly the same no matter what the rock content is. Furthermore, a computed tomography (CT)-based mesoscopic structural characteristic and two idealized schematic diagrams well illustrated the evolution mechanism of the volumetric behavior of an unsaturated clayey soil-rock mixture subjected to freeze-thaw cycles.

Coupled hydromechanical model for evaluating the volume change and fluid permeation behavior of expansive clay smear in a fault upon interaction with CO2

The interaction between clay minerals and CO2 at in-situ conditions of geological carbon sequestration leads to adsorption-induced strain, which increases the mineral's interlayer space. The effect of change in interlayer spacing of minerals on the evolution of macro-permeability, gas storage capacity, gas pore pressure, and stress state of compacted clays is unknown. The present study described a coupled numerical model to investigate the effect of adsorption-induced swelling of smectite-based clay on its gas permeation and mechanical properties upon interaction with CO2. To simulate the interaction of the fill material present in caprock faults with the injected CO2, compacted clay under confined, free and uniaxial confinement conditions are analyzed. It is evident under confined conditions, permeability of the clay filled in fault reduced, and mean compressive stress increased due to gas adsorption-induced strain. On the contrary, the permeability of the clay increased for both free and uniaxial conditions. The magnitude of the swelling stress within the media under uniaxial conditions depends on the degree of expansion caused by the adsorption-induced effect and applied overburden pressure. Overall, the study contributes to a comprehensive approach to evaluate the efficacy of geological formations having faults for long-term storage of CO2 in them.

Effects of Freeze–Thaw Cycles on Volume Change Behavior and Mechanical Properties of Expansive Clay with Different Degrees of Compaction

Freeze–thaw (F-T) cycles are one of the main deterioration factors for the performance of expansive clay in seasonally frozen soil regions. This study designed a unidirectional environmental boundary loading device for F-T cycle tests. Laboratory tests were conducted to quantitatively evaluate the effects of the F-T cycle on volume change behavior and mechanical properties of expansive clay with different degrees of compaction below the canal in Xinjiang. The SEM image processing was performed with the Image-Pro Plus image processing software to get pore parameters. The results showed that during the F-T cycle, the volume change of the sample gradually changes from contraction to expansion as the degree of compaction increases. As the degree of compaction increases, the hardening characteristics of the expansive clay are weakened, and the F-T cycle promotes the softening of the stress–strain relationship. The first F-T cycle resulted in a significant decrease of failure strength, and the failure strength of different compaction degrees decreased by 56.07%–67.54% after seven cycles. The failure strain and resilient modulus of the samples are attenuated to varying degrees after F-T cycles. The correlation rate between the porosity and the attenuation rate of the failure strength is 0.719–0.882, the corresponding weight reaches 0.419–0.445, and there is an excellent linear relationship between them. The research offers some important insights into the construction and maintenance of expansive clay engineering such as the Xinjiang Canal.

A critical saturated state-based constitutive model for volumetric behavior of compacted bentonite

In recent years, more and more unique volumetric behaviors, including the nonlinear compression and unloading curves in the e-lnp plane, and different types of swelling and shrinkage curves obtained from suction-controlled swelling and shrinkage tests, etc., which are significantly different from those of nonexpansive clays, have been reported on compacted bentonite. More importantly, limitations were encountered when describing the unique behavior with existing constitutive models for unsaturated expansive soils. In this study, a new concept of critical saturation state (CSS) was proposed for compacted bentonite, in which, as the saturated state was reached, the matric suction still remained nonzero in the soil. Incorporated with this concept, a constitutive model was proposed. In this model, the CSS curve was defined in the suction-isotropic stress plane, delimiting the unsaturated zone. To validate the model, the volume change tests conducted on compacted GMZ bentonite under different stress paths were simulated. Good agreement confirmed that the proposed model could well describe the volume change behavior, including the swelling on hydration, shrinkage during drying, nonlinear compression, and unloading behavior.

The Influence of Mechanical Granulation Process and Granular Bentonite Plasticity on Self-Sealing and Volume Change Behavior

Geosynthetic clay liners (GCLs) are widely used as hydraulic barriers in landfills and mine tailings facilities due to their low hydraulic conductivity. The average grain size of the granular bentonites (GBs) used in GCLs varies depending on the manufacturer and also between batches from the same manufacturer. The influence of GB grain size and plasticity on the sealing ability and volume-change characteristics under extreme chemical loads is important for long-term stability. Furthermore, GCLs are subjected to mechanical loading from landfill waste. The influence of different grain-size distributions in GB samples was assessed in terms of their self-sealing ability, hydraulic infiltration, and volume-change behavior under extreme chemical loadings and a 50-kPa mechanical load. The performance of fine-grained GBs was found to be satisfactory, in terms of hydraulic infiltration and volume change, under the test conditions. The plasticity of the GB also influenced its sealing and swelling ability under chemomechanical loading. The mechanism underpinning the influence of plasticity and grain size on the self-sealing behavior and hydraulic conductivity equilibrium is explained. We recommend fine-grained GBs for use in GCLs for containment applications.

An Experimental Study on the Effect of Temperature on the Shear Strength Behavior of a Silty Clay Soil

In this paper, we report on the results of an experimental study of the yielding and shear strength behavior of a normally consolidated silty clay soil from eastern Germany. The shear strength tests were performed on remolded forms of the soil using a triaxial cell which can regulate the temperature of the specimen. The experimental program comprised a series of pressure stepping compression consolidated drained (CD) triaxial tests at temperatures of 20, 40 and 60 °C. Overall, although the volume change behavior of the soil was found to exhibit some variations with changes in temperature, possibly due to changes in the double layer thickness of the clay fraction of the soil upon heating, the shear strength behavior (in terms of effective angle of internal friction) of the silty clay soil was found to exhibit minor changes with variations in temperature and can be assumed to be independent of temperature for the range considered in this study.

Molecular Design of Isocyanurate Core-Based Acrylates Undergoing Volume Expansion on Radical Photo-Polymerization.

The synthesis of acrylates with an isocyanurate substituent that show significant volume expansion on radical photo-polymerization is reported. The acrylate consisting of benzyl bisurethane moieties exhibits the largest volume expansion among them and contributes to restrict volume change upon its radical photo-copolymerization with a diacrylate exhibiting volume shrinkage. Furthermore, a correlation is revealed between the volume change behavior and the polymer structure through the radical photo-polymerization of the isocyanurate core-based diacrylate with benzyl bisurethane moieties under various concentration conditions.

Swell–shrink behaviour of fly ash-stabilised expansive soils

Class C fly ash, a byproduct of thermal power plants, is often preferred for the stabilisation of expansive soils. However, improper optimisation of the stabiliser may lead to the premature failure of treated soils during wet–dry cycles. This study demonstrates the volume change behaviour of fly ash-stabilised expansive soils subjected to wet–dry cycles. Furthermore, the effect of class C fly ash and lime–class C fly ash on the physical and engineering properties is also studied. The experimental results showed that addition of 20% fly ash to the expansive soil reduced the swell potential to 0% from an untreated swell value of 10.5%. However, when it was subjected to five wet–dry cycles, the initial cementitious effect of the fly ash on controlling the swell was partially lost, and therefore the volumetric deformation of the stabilised expansive soil increased from 0 to 14.5%. Furthermore, among the different additive combinations used for the treatment of expansive soils, it was observed that the combination of 4% lime and 20% fly ash resulted in the volumetric deformation of only 2.05% even after the fifth wet–dry cycle. Besides, the percentage of desiccation cracks has also reduced significantly from 29 to 0.5%.

Volume change response and fabric evolution of granular MX80 bentonite along different hydro-mechanical stress paths

Despite the increasing understanding of bentonite behaviour, there is still missing evidence on how different hydro-mechanical loadings, including sequences of hydration and compression, affect the fabric and the volume change behaviour of the material. It is generally assumed that the interplay between the behaviour of clay assemblages and the overall fabric of the material is the reason of having final states that are dependent on the stress path followed. Here the results of an experimental campaign aiming to study these factors are reported and discussed. Free swelling and swelling pressure tests were performed, both followed by compression to a relatively high stress. The experimental program involved various samples that were dismantled at intermediate states in order to perform microstructural observations by means of mercury intrusion porosimetry and electronic scanning microscopy. It was observed that while the void ratio at a given stress level depends on the stress path, subsequent compression led to a unique virgin compression line. The data obtained at the microscale gave further insight for an interpretation of the volume change behaviour observed at the macroscale, showing that at high stress the material tends to recover the same fabric regardless of the path to saturation.

Experimental Elucidation of volume change and local behavior of deformation of Nylon 66 and PC Materials by DIC Method and Micro-Vickers Hardness Test

It is a well-known fact that there is significant difference in magnitude of flow stresses and work hardening rates of polymeric materials between in tension and compression. There is a possibility that hydrostatic pressure is involved in this asymmetry to the loading axis, in which case volume change occurs in plastic deformation. And also, the propagation of localized deformations is often observed as a deformation behavior of polymeric materials. In such cases, it has been confirmed that the propagating portion of the crack must be hardened, but the deformed portion is softened. The aim of this study is to measure the variation of plastic Poisson’s ratio by means of Digital Image Correlation method to clarify the existence of the plastic compressibility of Naylon66 and Polycarbonate. Another aim is to elucidate the mechanism of softening at the neck. The authors conducted tensile tests of thin strip specimens and measured the axial and lateral strains by DIC method, then, plastic Poisson's ratio was derived. The result showed that plastic Poisson’s ratio of Naylon66 and Polycarbonate was smaller than the value of 0.5, that result in the existence of plastic compressibility in these materials. The Micro-Vickers hardness measurement for a gauge length was also performed to clarify the strength distribution of a specimen, and the results showed that the necking part of the materials was softened.

Volume change behavior of cement-based repair materials labelled as shrinkage-compensating, shrinkage-compensated or nonshrink

The labels shrinkage-compensating, shrinkage-compensated and nonshrink found in the technical documentation of many proprietary repair materials are all intended in principle to describe systems that exhibit no or little net contraction as a result of shrinkage. In practice, however, these terms are of limited significance in the selection of repair materials without appropriate test data on time-dependent volume changes. This paper provides clarifications on the dimensional behavior of shrinkage-compensating materials and uses experimental findings to emphasize the shortcomings in the information provided in the data sheets of many repair materials labelled as such. In view of a more effective and reliable use of cementitious shrinkage-compensating repair materials, recommendations are made to improve and uniformize the content of the technical data sheets.

An advanced constitutive model for drained and undrained unsaturated soil under different over-consolidation ratios

The soil deposits for general constructions and mining are often under both saturated and unsaturated conditions at different overconsolidation ratios. Within the frameworks of the unified hardening unsaturated model, in this paper, a constitutive model is proposed for the unsaturated overconsolidated soil under drained and undrained conditions. This model is validated against the unsaturated experimental results, and the hydromechanical behavior of soil is thoroughly investigated considering the dilation behaviour under a high overconsolidation ratio. It is found that the prediction results for the volume change, deviator stress, and suction behavior determined by the proposed model agree well with the experimental results, particularly for the dilation behaviour. It can be concluded that this model can predict the hydromechanical behavior of the unsaturated overconsolidated soil under both the drained and undrained conditions.

Assessment of shear strength and compressibility characteristics of a newly developed lunar highland soil simulant (LSS-ISAC-1) for Chandrayaan lander and rover missions

The engineering properties (shear strength and compressibility) of lunar soils influence the design of landers, rovers, and their mobility behavior on the lunar surface. Assessing such properties is important for any lunar-based studies, and it is usually being determined by using suitable lunar soil simulants. This paper explains the shear strength parameters, stress-strain relationships, and volume change behavior of the newly developed lunar highland soil simulant (LSS-ISAC-1), apart from particle size distribution, which have a profound influence on the engineering behavior. In addition, to the above, other engineering properties such as critical state of the angle of internal friction, dilatancy angle, Young's modulus, Poisson's ratio, internal erodibility, small-strain shear wave velocity, and shear modulus have also been evaluated and presented. Mohr-Coulomb and friction-dilatancy theories are considered as a base for the analysis with the use of statistical predictive equations. The relative density and confining pressures are used as functions in the predictive equation to assess the behavior of the LSS-ISAC-1. The comparison of properties with the actual lunar highland soil samples of the Apollo 16 mission reveals a reasonable similarity of LSS-ISAC-1 with the lunar highland soils.