Behavior Of Clay Research Articles

3D Claying: 3D Printing and Recycling Clay

Clay is of great interest as a 3D printing material thanks to its ease of use, recyclability and reusability. This paper analyses the technical aspects of the whole printing process. The behaviour of 3D printing clay is studied with respect to the environment and its specific application as a temporary or definitive formwork system for cement parts. The study addresses the performance of clay and the loss of its properties and characteristics according to the type of protection, whether it is in direct contact with air or cement, or protected with plastics, metal sheets, or combinations of both. A 3D printing system with various printers and 3D models has been considered, observing a direct relationship between the prototype shape, extrusion process and resulting material. The most important variables in 3D printing have been considered: layer height, line thickness, base definition, total model height, overhang angles, overlap between layers, etc. The main technical aspects have been analysed such as raw material properties, kneading, process control, post-treatments and material hardening. As a natural material, clay can be reused indefinitely under certain conditions to be part of a circular economy with low energy consumption and minimal resources. It is concluded that the option of using ceramics in 3D printing for very diverse uses in the architecture, engineering & construction (AEC) sector is very promising due to their ease of implementation, recycling capability and suitability to different environments.

Shear Strength Performance of Electrokinetic Geosynthetics Treated Soft Clay after Water Immersion

The strength aspect of clay soil is a critical concern in practical engineering design. Electroosmosis (EO) has been adopted as a foundation treatment technology in some projects to increase the strength of soft clay. In order to widen the understanding on shear strength performance of EO-treated soil, the behavior of EO-treated soft clay using electrokinetic geosynthetics (EKG) as electrodes under the effect of water immersion was evaluated and compared with that of vacuum preloading (VP) treated soft clay under similar conditions. The main finding was that the EO-treated soil when immersed in water offered more resistance to the change in average water content than VP-treated soil. The average shear strength of EO-treated soil fell by 36.6% during 4 extra days of immersion. When the immersion time was extended to 10 days, the average shear strength fell by 65.4%. In contrast, the immersion time had little influence on the shear strength of VP-treated soil. Hence, if EO-treated soft clays are to be subjected to short-term water immersion, the shear strength of the treated foundations should be reappraised to ensure the safety of the engineering projects.

Application of Hardening State Parameter Constitutive Model for Prediction of Overconsolidated Soft Clay Behavior Due to Embankment Loading

This paper investigates the possibility of the application of the HArdening State Parameter (HASP) constitutive model for numerical modelling of overconsolidated soft clay under embankment loading. The HASP constitutive model is a critical state soil model with a combined hardening rule that uses a state parameter to determine the dilatancy of overconsolidated clay. The model overcomes some shortcomings of the Modified Cam Clay (MCC) model in the prediction of overconsolidated clay’s behavior, while preserving the simplicity and the same set of five parameters. The HASP model was implemented in finite element software. In order to verify the applicability of the model in predicting the behavior of soft overconsolidated clay due to embankment loading, two examples reported in the literature are analyzed. The numerical predictions of the HASP model are compared with the field measurements of ground settlements and pore water pressures, and with the MCC model’s predictions. The results indicate that the HASP model predicts the development of the settlements of the overconsolidated soft clay deposits with a high accuracy from an engineering point of view. There are certain deviations from the field measurements in predicting the pore pressure development, which is often observed for other models as well. For the embankment settlement assessment, as important serviceability issue, the HASP model has an advantage over more complex models that require a large number of parameters. Since the parameters of the HASP model are obtained from standard laboratory tests, it can be easily applied for routine geotechnical analyses.

Sedimentation Behavior of Clays in Response to Pore-Fluid Chemistry: Effect of Ionic Concentration and pH on Its Trends

This study investigates the effect of pore fluid chemistry on the sedimentation trends and liquid and plastic limits within the new fines classification framework for four clayey soils with different specific surface and mineralogy. The sedimentation tests and fall cone tests are performed with seven different ionic concentrations (c = 1 × 10−5 ∼ 1.8 M) and the four target pH values (pH = 3, 5, 7, and 9) for each of the ionic concentrations. Three different sedimentation trends such as flocculated, dispersed, and mixed (at c = 0.0015-to-0.003 M) modes are observed at different ion concentrations and pH conditions of the pore fluids. Three sedimentation parameters named A1, A2 and A3 are defined from the sedimentation curve. The relationship between them implies the salient features of the sedimentation trend for tested clayey soils. These parameters confirm the observed sedimentation modes and the critical ionic concentration; c* ∼ 3 × 10−3 M for AMK and EPK (high specific surface) and c* ∼ 1.5 × 10−3 M for LKW and MI (low specific surface) where notable fabric change occurs. The higher specific surface clays are classified as intermediate electrical sensitive clays whereas the lower specific surface clays are categorized into low electrical sensitivity fines in the new classification chart. A complementary data analysis for the sedimentation parameters and the new fines classification chart reveals that the robust link between distinct sedimentation trends and salient features of clay particles captured in the new fines classification chart can be useful to predict the sedimentation modes of clays with different pore fluid chemistry.

Recent advances in subgrade engineering for high-speed railway

Abstract In the last decade, the design and construction technologies of subgrade in high-speed railway (HSR) developed significantly. This article reviews corresponding development in five aspects, including mechanical properties of fill materials, dynamic performance of subgrade, foundation treatment, retaining structure, and smart construction technologies. It shows that for unbonded granular materials, it is acceptable to use static strength for subgrade design, but for clayey soil it would be more appropriate to base on shakedown theory. The mechanism for lime modified clay has been thoroughly reviewed, and the effect of lime content, curing age, and curing conditions on the behavior of lime-treated clay is discussed. The dynamic response of subgrade, especially the long-term deformation and dynamic stability analysis are important to understanding the behavior of HSR subgrade. The effect of track types, operation speed, etc. on the dynamic response of subgrade are reviewed first. Then, the prediction methods, influencing factors, and corresponding issue for long-term deformation of subgrade are presented, followed by the methods used for dynamic stability analysis. Three types of foundation treatment methods, including geosynthetic-reinforced pile-supported (GRPS) embankment, pile-raft structure, and pile-plate structure are reviewed for the corresponding load transmission mechanism, and application scenario. The static and dynamic behavior of four types of retaining structures are presented, including cantilever retaining wall, geosynthetic reinforced soil retaining wall, anchored retaining structure, and retaining wall reinforced by soil nailing. Finally, a series of new technologies correlated to smart construction are introduced, relating to the survey, design, construction, detection, and management of subgrade.

Geotechnical behavior of high-plastic clays treated with biopolymer: macro–micro-study

Geotechnical behavior of high-plastic clays treated with biopolymer: macro–micro-study

Characterization of Boom Clay anisotropic THM behaviour based on two heating tests at different scales in the HADES URL

Abstract To examine the impact of the heat generated by high-level radioactive waste on Boom Clay, two heater tests have been launched in the HADES underground research facility: the small-scale ATLAS Heater Test and the large-scale PRACLAY Heater Test. The major objective of these tests is to confirm and refine the thermo-hydro-mechanical (THM) constitutive models and associated parameter values obtained from a laboratory characterization programme. This paper presents the observations from the ATLAS and PRACLAY heater tests and the combined numerical modelling of these tests. To characterize the excavation damaged zone in the clay around these tests, a mechanical model with a strain-dependent elastic modulus is introduced for the Boom Clay. The consistency between the observations from laboratory tests and in-situ tests and the outcomes from the numerical models strengthen the confidence in our understanding of the THM behaviour of Boom Clay. They also enabled us to validate the mechanical model and produce a set of anisotropic THM property values for both intact and damaged Boom Clay.

Hybrid numerical modeling of ballistic clay under low-speed impact using artificial neural network

Roma Plastilina No. 1 clay has been widely used as a conservative boundary condition in bulletproof vests, namely to play the role of a human body. Interestingly, the effect of this boundary condition on the ballistic performance of the vests is indiscernible. Moreover, back face deformation should be characterized by measuring the indentation in the deformed clay, which is important for determining the lethality of gunshots. Therefore, several studies have focused on modeling not only bulletproof vests but also the clay backing material. Despite various attempts to develop a suitable numerical model, determining the appropriate physical parameters that can capture the high-strain-rate behavior of clay is still challenging. In this study, we predicted indentation depth in clay using an artificial neural network (ANN) and determined the optimal material parameters required for a finite element method (FEM)-based model using an inverse tracking method. Our ANN-FEM hybrid model successfully optimized high-strain-rate material parameters without the need for any independent mechanical tests. The proposed novel model achieved a high prediction accuracy of over 98% referring impact cases.

Consolidation and swelling behavior of kaolinite clay containing xanthan gum biopolymer

Recently, microbial biopolymer-based soil treatment (BPST) has gained attention for its application in environmentally friendly soil stabilization, particularly for enhancing the strength and stability of fine-grained soils. However, the effects of BPST on clay’s compressibility (consolidation) and expansion (swelling) behaviors remain unclear. This study used xanthan gum, a microbially produced polysaccharide with anionic charges, to stabilize kaolinite clay. The effect of xanthan gum BPST on the consolidation and swelling behavior of cohesive kaolinite clays was assessed through a series of experimental tests, including one-dimensional consolidation tests with elastic wave measurements, swelling tests, environmental scanning electron microscopy, and unconsolidated-undrained triaxial tests. The formation of xanthan gum hydrogels induces pore-clogging, resulting in a delay in the consolidation process, increased energy dissipation, and compressibility. Furthermore, the interaction between kaolinite and xanthan gum improved the undrained shear strength of kaolinite soils, thereby reducing the consolidation time required for a specific bearing capacity. This study demonstrates the possible application of controlling hydraulic conductivity, seismic stabilization, and rapid surface stabilization. However, additional drainage is necessary for in situ applications.

Numerical modelling of the stress strain behaviour of Kuttanad clay.

Numerical modelling of the stress strain behaviour of Kuttanad clay.

Elastoplastic modeling cyclic behavior of natural soft clay with principal stress rotation under traffic loading

Elastoplastic modeling cyclic behavior of natural soft clay with principal stress rotation under traffic loading

Numerical analysis of dynamic behavior of piled embankment under train loading

Piled embankments, which have many advantages, have been widely employed in the construction of railways over soft soil. However, the load transfer mechanism and deformation characteristic induced by train loading, which has great importance for piled embankment design, are not well known and deserve more research attention. In this paper, a three-dimensional numerical model of a piled embankment subjected to train loading is proposed and calibrated by test results, which considers the dynamic behavior of soft clays by a simplified dynamic constitutive model based on bounding surface theory that has been successfully encoded into the ABAQUS. Based on the proposed numerical model, the development of soil arching and accumulative deformation in a piled embankment subjected to train loading is investigated. The load transfer mechanism and deformation characteristics of a piled embankment in terms of the embankment height, velocity of the train, pile spacing and wheel static load are analyzed. The research results can provide some reference for the design of piled embankments under train loading.

Excess pore water pressure behavior of saturated soft clay under cyclic confining pressure with different frequencies

The excess pore water pressure is main factor affecting the dynamic response of saturated soft clay under traffic loads. Recognize that, cyclic triaxial tests with and without cyclic confining pressure were carried out to study the development of excess pore water pressure of saturated soft clay. The impacts of factors, such as cyclic stress ratio (CSR), loading frequency, and cyclic confining pressure, were analyzed. Excess pore water pressure increases with increasing cyclic stress ratios, while decreases with increasing loading frequencies. Nevertheless, with increasing cyclic confining pressures, the maximum excess pore water pressure increases, while the minimum excess pore water pressure remains unchanged. Besides that, the greater CSR and cyclic confining pressure deliver an increment of both maximum and minimum excess pore water pressure rate. However, the excess pore water pressure rate - time curves coincide under different loading frequencies. Meanwhile, both the normalized maximum and minimum excess pore water pressure rates are linearly proportional with time under different test conditions in logarithmic coordinates. Based on that, both maximum and minimum excess pore water pressure prediction models, relating to the above factors, are proposed, and the predicted results accord well with the measured data.

Modelling the Structure and Anisotropy of London Clay Using the SA_BRICK Model

Several constitutive models had been developed by other researchers to cover the main features of mechanical behaviour of natural overconsolidated clays, such as the nonlinear stress–strain response at small and large strains, and the recent stress history effect. Kinematic hardening models include these features to facilitate realistic predictions of soil–structure interaction. This paper presents the further development of a kinematic hardening model BRICK that includes anisotropy and the influence of soil structure on the mechanical behaviour of a natural clay. High quality laboratory tests were used to calibrate the input parameters of the model in a single element configuration, and a documented boundary value problem of tunnel excavation was used to validate the model in finite element calculations. A comprehensive comparative study between the predictions of different kinematic hardening models, using two different software packages, was carried out. It was observed that the SA_BRICK model is in fair agreement with the observed data and gives improved predictions in comparison to other kinematic hardening models, particularly in terms of narrowness of the settlement trough above the tunnel. Advanced predictions of ground deformations caused by tunnel excavations can be effectively used to mitigate possible damage of existing structures affected by tunnelling in an urban environment.

A constitutive framework for the chemo-mechanical behaviour of unsaturated non-expansive clays

Both osmotic and matric suction changes have a significant influence on the mechanical behaviour of clays. Despite the different types of interactions at the microstructural level, both suctions havea relevant effect on the fabric of non-expansive clays. Starting from experimental observations at the laboratory scale, it is possible to identify some common features characterizing the mechanical response of non-expansive clays to salinity and degree of saturation changes. This paper presents an elastoplasticframework to reproduce the behaviour of unsaturated clayey soils upon changes in the salt concentration of the pore fluid. In particular, it presents a strategy to include osmotic suction induced by pore fluid salinity in BBM-like models [1]. The model was implemented in the Thebes code and it was calibrated on experimental data performed on Boom clay [2] and remoulded loess [3].

Molecular insights into the temperature and pressure dependence of mechanical behavior and dynamics of Na-montmorillonite clay.

Sodium montmorillonite (Na-MMT) clay mineral is a common type of swelling clay that has potential applications for nuclear waste storage at high temperatures and pressures. However, there is a limited understanding of the mechanical properties, local molecular stiffness, and dynamic heterogeneity of this material at elevated temperatures and pressures. To address this, we employ all-atomistic (AA) molecular dynamics (MD) simulation to investigate the tensile behavior of Na-MMT clay over a wide temperature range (500 K to 1700 K) and pressures (200 atm to 100 000 atm). The results show that increasing the temperature significantly reduces the tensile modulus, strength, and failure strain, while pressure has a minor effect compared to temperature, as seen in the normalized pressure-temperature plot. Mean-square displacement (MSD) analysis reveals increased molecular stiffness with increasing pressure and decreasing temperature, indicating suppressed atomic mobility. Our simulations indicate temperature-dependent dynamical heterogeneity in the Na-MMT model, supported by experimental studies and quantified local molecular stiffness distribution. These findings enhance our understanding of the tensile response and dynamical heterogeneity of Na-MMT clay under extreme conditions, aiding the development of clay minerals for engineering applications such as nuclear waste storage and shale gas extraction.

Enhancement of Clay Compressibility and Strength Using Nano Magnesium Oxide

In order to satisfy the requirements of environmentally friendly construction projects and minimize greenhouse gas emissions, it was necessary to focus on utilizing nanomaterials instead of conventional materials to enhance clay soils; nano Magnesium Oxide was suggested for this study. The compression and unconfined compressive strength tests were achieved to assess the compressibility behavior and strength of silty clay treated using nano magnesium oxide. Additionally, an investigation into the alteration of the clay microstructure was conducted using field emission scanning electron microscopy (FE-SEM) tests. The silty clay utilized in this research is characterized by a compression index 0.23 and an undrained shear strength of 53 kPa. The soil was treated by adding different percentages of nano-MgO (0.4%, 0.5%, 0.6%, and 0.8%), and the curing period was seven days. The treated soil samples were prepared based on the optimal water content and maximal dry density of the natural soil. The results indicate that utilization of nano Magnesium Oxide leads to a reduction in both values of the index of compression (Cc) and recompression index (Cr), in addition to a decrease in the value of the coefficient of compressibility (av). Also, the test finding for unconfined compressive strength demonstrates a noticeable increase in strength as the percentage of nano-MgO increases, accompanied by a reduction in failure strain. Adding 0.6% (the optimum percentage) of nano Magnesium oxide enhances the strength by about 114% and decreases the value of the compression index by about 36% compared with natural soil.

Strength and compaction behavior of copper slag stabilized soil

Soil is a unique material. This paper helps in identifying the usage of industrial by-product copper slag as a stabilizing agent. The properties of the soils may affect roads built on unstable subgrade with substantial plasticity. Weak sub-grade soils undergo volume changes as a result of variations in the moisture content, which leads to pavement problems such as cracking, settlement, and heaving. It is important to stabilize these weak sub-grade soils in order to prevent its swelling, strength improvement and performance enhancement. The main aim of this research is to study the effect of copper slag (CS) with clay by performing one of the soil stabilization techniques. In this paper, strength and compaction behavior of kaolin clay (KC) stabilized with CS is studied. For strength characteristics, unconfined compressive strength (UCS) and split tensile strength (STS) tests are carried out. Similarly, for compaction characteristics, modified proctor compaction tests are carried out. Total 7 mixes are prepared using different proportions of CS and KC. The first five mixes are of CS and KC with varying content of CS from 0 to 50 % with an increment of 10% in the mix. The remaining two mixes were of 100% CS and 100%KC each. From the test results, it is observed that the inclusion of CS in KC significantly affected its compaction and strength characteristics.

Coupled hydro-mechanical behaviour of a Kaolin Clay in the context of the geothermal use of geotechnical structures

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.

Effect of static pore water pressure on shear behavior of saturated kaolin clay

To study the mechanical properties of sedimentary marine clays in deep seabed, static pore water pressure (SPWP) is often prescribed in triaxial shear tests by applying different back pressure levels (B.P.) corresponding to in-situ position of the water table. In this paper, several undrained and drained triaxial tests have been conducted to study the effect of SPWP on the mechanical behaviors of kaolin clay, which is often used to create artificial marine clay or as a subgrade material in the centrifuge tests of offshore geotechnical engineering. The magnitude of SPWP is found to impact undrained shear strength, initial growth rate of excess pore pressure, friction angle, while has little effect on initial undrained shear stiffness and ultimate excess pore pressure. A new unique line can be determined which is parallel to total stress path by fitting all the critical failure points during undrained shearing. The influence mechanism is considered to be related to a nonuniform distribution of SPWP in different kinds of pores, which makes the clay microstructure changeable under different SPWP. There may exist a "pseudo-suction" when certain SPWP is applied, resulting in a higher friction angle of kaolin clay.