Stress-strain Behavior Of Soil Research Articles

Strength behaviour of soil blended with two waste materials-fly ash and tire crumbs with cement

Abstract The rapid development in the economy has led to a growing need for electricity and automobiles, leading to the production of large quantities of fly ash (FA) and discarded tires. The safe disposal of these materials has become a significant problem. FA and scrap tyre derived material has some useful properties which can be beneficially used for enhancing the engineering properties of soil. Therefore, the study investigates the combined impact of FA and scrap tire-derived material on the stress-strain-strength behaviour of a fine-grained residual lateritic soil, incorporating a cementing agent. The research involves compaction tests followed by triaxial compression tests, where FA content added at an increment of 15% starting from 20% by weight of soil. The maximum FA content used in the mix is 50% by weight of soil. Tyre crumb (TC) which is a scrap tire-derived material, is also included in the study, with TC content ranging from 5% to 10% by weight. Additionally, 2% by weight of cement is added to each soil mix as a binding agent. Specimens are compacted in accordance with specific compaction parameters and subsequently cured for duration of up to 28 days. Strength tests are then carried out on those specimens to analyse their strength behaviour. This research primarily examines the shear strength characteristics of soil blended with FA, cement, and TC, emphasizing their geotechnical performance. Addition of 5% TC increases the peak deviator stress of cemented mix having 50% FA content from 1351 kPa to 2710 kPa at 300 kPa confining pressure and 28 days curing period. The inclusion of TC to soil-FA-cement blends is noted to significantly enhance shear strength when compared to mixes without tire crumb. Also, the stress-strain behaviour of soil is significantly influenced by addition of FA and cement in the presence of TC. Therefore, there is an ample scope of utilization of soil-fly ash-cement-TC mixes in geotechnical applications.

Performance evaluation of the Generalized Bounding Surface Model in the simulation of Cajicá clay subjected to monotonic loading

Different constitutive models, based on principles of mechanics and experimental evidence, have been developed over several decades to represent and predict the stress-strain behavior of soils subjected to various loading conditions. The Generalized Bounding Surface Model (GBSM) is one of them and is defined as a fully three-dimensional elastoplastic constitutive model for saturated cohesive soils that employ the bounding surface plasticity in conjunction with a nonassociative flow rule and a soil microfabric-inspired rotational hardening rule. The GBSM has been successfully validated on numerous laboratory reconstituted soils, but not on natural or undisturbed soil samples. Hence, in this paper the predictive capabilities of the GBSM are evaluated in the simulation of the monotonic behavior of an undisturbed cohesive soil called “Cajicá clay” from the high plain of Bogotá in Colombia. In the first instance, an isotropic consolidation test and a set of axisymmetric triaxial compression and extension tests are conducted using an automated triaxial equipment, to experimentally describe the response of the undisturbed soil. From experimental data, the parameters associated with the GBSM model are calibrated to finally evaluate its capabilities in the simulation of a cohesive natural soil. A comparison between experimental data and numerical simulations is presented to show both performance and advantages of the GBSM model.

Comparison of simple stress-strain models in the moderate strain range for fine-grained soils: A review

The prediction of stress-strain behaviour in soils is a problem that can be approached in different ways depending on the design scenario. In some cases, a multi-parameter constitutive model calibrated with non-routine soil tests may be appropriate, for example, where a model has been developed for the relevant soil at a building site subject to complex loading. However, simple characteristic parameters are desirable for examining the variability of soil behaviour especially at regional scales. This paper describes a method of assessing the suitability of simple models for simulating non-linear undrained soil stress-strain behaviour in the moderate strain range. The moderate strain range is defined by a soil strength mobilisation of 20% to 80%. Three simple stress-strain models are compared. A published database of reconstituted triaxial tests is used to evaluate the three models with selected statistical tools that quantify errors associated with the simple model approximation of the relationship between stress and strain. The paper discusses the value of computing the model error and the trade off to make between introducing a greater number of parameters (and tests) for model precision and limiting the complexity of the variability characterisation.

Collapse potential and ultrasonic pulse velocity of loess soils after treatment with expanded perlite and metakaolin

Collapsible soils, including loess, can support heavy loads at their natural humidity but then collapse rapidly and lose a substantial volume when the humidity increases. Soil collapse potential at different immersion stresses was investigated according to ASTM D5333. Different immersion stresses, including 100, 200, 300, 400, and 500 kPa, were used to evaluate the stress-strain behavior of soils before and after saturation. The results indicated that soil collapse potential rose with a raising of immersion stress, resulting in the highest soil collapse potential at 500 kPa immersion stress. Furthermore, the effectiveness of expanded perlite and metakaolin in treating loess soils was examined. The results revealed that the soil collapse potential reduced with an increase in perlite and metakaolin up to 8 %. Also, perlite had a more significant impact on the soil collapse potential than metakaolin. The interlocking force between soil particles was enhanced as the perlite quantity rose, and perlite prohibited soil particles from slipping on each other. Metakaolin decreased the soil collapsibility due to the pozzolanic and chemical reactions which increased particle bonding. The ultrasonic pulse velocity of soils decreased as the percentage of perlite increased. Because the perlite was not spread homogeneously, and the waves can be stuck in the heterogeneities, Metakaolin acted as a filler and increased the ultrasonic pulse velocity of the soils.

PREDICTION OF SOIL SETTLEMENT ON SOFT CLAY SOIL USING NORMALIZED ROTATIONAL MULTIPLE YIELD SURFACE FRAMEWORK (NRMYSF)

Soft clays are highly compressible, high-water content, low shear strength, and have poor permeability, which result in significant settlement under long-term loads. Therefore, one of the most challenging geotechnical engineering problems is to predict the settlement from soft clay soil. Normalized Rotational Multiple Yield Surface Framework (NRMYSF) is developed from the soil stress-strain behaviour and shear strength characteristic. It is able to estimate the stress-strain curve for shear strength in triaxial tests. The consolidated drained (CD) triaxial tests and conventional 1-dimensional consolidation of oedometer has been conducted on soft clay soil. The settlement soil prediction was compared between the NRMYSF and conventional 1-dimensional consolidation under Terzaghi’s principle. The NRMYSF prediction model was smaller than the conventional oedometer by 0.1459m to 0.1431m for Sample A, and by 0.1890m to 0.1398m for Sample B. Therefore, this method has the potential to predict the settlement of soft clay soils.

Factors Influencing Post-Construction Responses of Underlying Tunnel below Excavation Base in Gravelly Clay

This paper investigates the response mechanism behind an existing tunnel subjected to a long and deep collinear excavation in Shenzhen granite residual strata. The maximum excavation depth was 18.0 m and the minimum residual soil depth above the tunnel crown was only 6.3 m, causing appreciable tunnel heave and transverse deformation. Two-dimensional parametric numerical study is adopted to examine the impacts of influential factors (excavation dimensions, ground permeability coefficient, and exposure time of the excavation base) on the tunnel responses. The hardening soil model with small strain (HS-Small) is used to model the soil stress–strain behavior. It is found that the long-term deformation of the tunnel after excavation and unloading cannot be ignored. The soil will continue to consolidate and deform, and the tunnel will continue to heave with soil due to the dissipation of the negative excess pore water pressure. The long-term deformation of the tunnel after excavation and unloading is significantly affected by the excavation geometry. With the increase in excavation width B, the final tunnel heave after excavation and unloading increases first and then tends to be stable. Furthermore, the relative position of the tunnel and the excavation base is also one of the major contributors to the long-term deformation of the tunnel. The growth of tunnel deformation Δf and the exposure time T are exponentially negatively correlated with Ly. The change in the permeability coefficient k has no effect on the final stable tunnel heave and the growth of tunnel deformation Δf, which is exponentially negatively correlated with the exposure time T.

Effect of elevated temperature on geotechnical properties of soils – A review

Land used for construction purposes should have large bearing capability and less squeezability. Soft soils such as clayey soil have low bearing capacity and high compressibility which must be converted or treated before the construction process to meet the requirements. The presence of oil and gas pipe lines, buried high voltage cables, fire accidents, storage of high-level waste could limit the use of conventional methods such as deep cement mixing. Hence, alternate methods are required, heat treatment has been considered to be the efficient technique, if the need of enhancement in characteristics are required. This paper discusses the literature available on thermal treatment. The effect of temperature on various properties of soil like Atterberg limits, free swell, porewater pressure, swelling, shear strength, stress strain behavior of soil and mineralogy is included in this paper. This review paper summarizes the effectiveness of thermal treatment on soft soil.

Calibration of discrete element parameters and experimental verification for modelling subsurface soils

The discrete element method (DEM) has shown considerable advantages for the simulation of soil-tool interaction simulation. To develop reliable DEM simulations, the selection of an appropriate contact model and its parameter calibration are critical. A DEM model of cohesive subsurface soils was established to predict the draught of sweep cultivation by using the Edinburgh elasto-plastic adhesion (EEPA) contact model. Firstly, the DEM parameters were used for calibration, which were significant for the results of the uniaxial confined compression test and the unconfined compressive strength test. Then, the mapping relationship between other DEM parameters and the soil stress–strain behaviour was calculated to obtain a solution matching the stress–strain measurement results. Finally, cone penetration resistance (penetration rate of 8 mm s−1) and the draught of sweep tillage (depth of 200 mm and speed of 1.67 m s−1) were used to evaluate the accuracy of the parameters. The results showed that the penetration resistance in the elastic phase of the simulation was in close agreement (R2 = 0.9964) with the measurements, and the total relative error and the average relative error between the predicted sweep draft and the measurement were 9.4% and 4.77%, respectively. Thus, it was shown that the developed calibration method can effectively predict the development of the sweeping draught and the penetration stress.

Behavior of Residual Soil with High Silt Content Under Low Frequency Cyclic Loading Using Modified Direct Simple Shear Apparatus

This paper presents the experimental work on typical Malaysian silty residual soils in order to evaluate fundamental soil properties in particular its stiffness under low frequency cyclic loading. There has been very little information on local silty residual soils which is very important for local geotechnical design purposes. Lack of such information contributes to the dependency of foreign soil data which might not be representative of local silty residual soils. This study departs from the basis of there have been verified evidences that we are not spared from seismic activity in Malaysia. Hence, it would be misleading if we were to exclude soil properties under cyclic loading for design purposes in Malaysia. This research revolves around the development of simplified device to evaluate the stress-strain behaviour of soils under simple shear strain conditions. The cyclic loading test results on Malaysian sedimentary residual soil sample exhibit increase of drained shear stiffness, GSTIF and gained strength after 30 cycles indicating cyclic hardening behaviour. It is evident that magnitudes of cyclic load and cyclic displacement influences the rate of soil volume change. Nevertheless, the densification of soil samples due to increment of cycles caused reduction in volume change. It is foreseen that the obtained parameters could assist in the practical geotechnical engineering problems related to cyclic conditions.

A Simplified Method for Analysis of Laterally Loaded Piles considering Cyclic Soil Degradation

This paper proposes a simplified method to analyze the bearing behavior of pile undergoing cyclic lateral load. Firstly, a modified strain model is proposed by utilizing the Duncan–Chang model to describe the stress-strain behavior of soils in the strain wedge. Then, a cyclic degradation model of soft clay considering the accumulation of plastic strain and pore water pressure is presented based on the cyclic triaxial test. Combining with the modified strain wedge model and degradation model of soil, a simplified method is established for the cyclic laterally loaded pile. The accuracy of the present method is verified by comparing it with existing model tests. The results show that the pile lateral displacement and strain wedge depth increase with the number of cycles and cyclic load amplitude. It is necessary to consider the effect of cumulative pore water pressure during the analysis of cyclic laterally loaded pile embedded in soft clay.

A review on modelling of the stress-strain behaviour of soil.

Soil has been used as a construction material since antiquity with both success and failure. As the earth material is widely available and relatively economical, it has been found very useful in the construction of foundations, subgrades, embankments and as backfill. The collapsibility of soil is mainly due to the decrease of shear strength and macro-deformation with the increase of moisture content. This can result in some serious problems, such as the differential settlement of the foundation, landslides, and slope instability, resulting in a series of damages of infrastructures and loss of human lives to some degree. In civil engineering, it is very important to make realistic predictions of the behaviour of soil under various conditions. Triaxial tests are to be carried out to study soil behaviour. The results will indicate the shear damage characteristics during the test. The relation of stress and strain of soils can be expressed using constitutive models. It can provide a brief idea about how soil will behave under different conditions. Application of Neural Network can be used to develop a data-driven constitutive modelling of the soil.
 Keywords- Shear strength, Triaxial test, moisture content, constitutive model

Revisiting Hardin’s parameters for the quantification of particle breakage – A statistical entropy approach

It is well recognised that particle breakage in granular materials is affected by stress level, stress path, initial density, and particle size distribution (PSD), amongst others. Furthermore, it has been shown that breakage has a significant influence on the stress-strain behaviour of soils. This paper compares a commonly used breakage parameter with grading entropy coordinates. Such coordinates enable for the representation of any PSD as a single point in a Cartesian coordinate plane. Hence, the evolution of PSD changes may be easily tracked. This paper aims to demonstrate that grading entropy coordinates are as (or more) effective than other breakage parameters, whilst providing additional insight. On the basis of limited data it is shown that grading entropy coordinates are able to capture the dependence of breakage on stress level, stress path and initial PSD.

A sphere packing model for shear bands in dense soils

The rhombic sphere packing can be used to model the biaxial test on granular soils in a very simple way. According to the angle of assemblage, the packing is dilatant or contractive. Correspondingly, overall stresses are transmitted as chains of forces or oblique forces of contact. The connection of the soil stress-strain behaviour and the packing void ratio is achieved by mapping both of the plots. The mapping shows that dense soils are dilatant and loose soils are contractive, separated by the critical state. It also shows that the bifurcation point and the peak strength are features only of dense soils. The band of strain localization is analysed in the elastic regime, and its inclination is found maximizing the intensity of the mobilized stress ratio. The stresses within the shear band are obtained by assuming a partially coaxial packing rotated to reach the full plastic state. The equilibrium of the overall stress at the line of discontinuity reveals a relationship between the peak friction angle and the coefficient of lateral pressure at rest. As long as these parameters are obtained independently of each other, they allow the validation of the theory.

One-step analytical method for required reinforcement stiffness of vertical reinforced soil wall with given factor of safety on backfill soil

The selection of geosynthetic reinforcements in the design of geosynthetic-reinforced soil (GRS) retaining walls has been based on the requirement on the long-term strength. However, the mobilized loads in the reinforcements are related to both the reinforcement stiffness and soil deformation, and the desired factor of safety may not exist in the earth structure if they are not properly considered. Therefore, it is also important to take into account the long-term reinforcement stiffness when designing GRS retaining walls. In this study, a simplistic analytical method is proposed to determine the required reinforcement stiffness with given factor of safety on the backfill soil. The method takes into account soil-reinforcement interaction, nonlinear stress-strain behavior of soil, and soil dilatancy. The reinforcement strains predicted by the proposed method were compared to those analyzed by validated nonlinear Finite Element analyses, and close agreement was obtained.

Application of LSTM approach for modelling stress–strain behaviour of soil

This paper presents a new trial to reproduce soil stress–strain behaviour by adapting a long short-term memory (LSTM) deep learning method. LSTM is an approach that employs time sequence data to predict future occurrences, and it can be used to consider the stress history of soil behaviour. The proposed LSTM method includes the following three steps: data preparation, architecture determination, and optimisation. The capacity of the adapted LSTM method is compared with that of feedforward and feedback neural networks using a new numerical benchmark dataset. The performance of the proposed LSTM method is verified through a dataset collected from laboratory tests. The results indicate that the LSTM deep-learning method outperforms the feed forward and feedback neural networks based on both accuracy and the convergence rate when reproducing the soil’s stress–strain behaviour. One new phenomenon referred to as “bias at low stress levels”, which was not noticed before, is first discovered and discussed for all neural network-based methods.

Fly-by-Pi: Open source closed-loop control for geotechnical centrifuge testing applications

Geotechnical centrifuges are valuable instruments for physical modelling of complex geotechnical problems in a controlled laboratory setting. In comparison to full-scale testing, scaled models are cost effective to construct and instrument and, when tested in a geotechnical centrifuge at increased centrifugal accelerations, are capable of replicating full-scale stress–strain soil behaviour. Centrifuge modellers require specialised hardware and instruments capable of functioning under high accelerations. Such hardware is costly, nearly always purpose built, and often rely on commercial, closed-source data acquisition systems, hardware and control systems.This paper demonstrates a novel and versatile, low cost, open source logger and control system that works in parallel alongside existing centrifuge hardware. This solution, termed Fly-by-Pi, was developed using the Raspberry Pi microcomputer. The system provides closed-loop control of linear actuators with the ability to operate in either cyclic, monotonic, or static load- or displacement-control. The control mechanism can be reprogrammed according to experimental requirements, even during flight in the centrifuge. Three independent experiments are described which included the Fly-by-Pi controller as a key component in their operation. Based on the experience gained during these experiments, the authors encourage wide-spread adoption of open-sourced hardware solutions in extreme testing environments.

Proposed Methods on Enhancement of Dynamic Response of RC Frames and Soil Structure Interaction

In this paper, proposed methods on enhancement of a nonlinear behavior of reinforced concrete frames subjected to cyclic load. A fully nonlinear dynamic analysis is adapted using three-dimensional finite element analysis by means of ANSYS 16.0 code. All structural elements such as footings, columns and girder are simulated in the numerical model. The concrete is assumed to be nonlinear and isotropic. In addition, some proposed methods are investigated to enhance the performance of RC frames under cyclic loading such as, cross bracing steel at the connections and at girder region as well as additional bent bars at the ends of girder. The results of analyses are presented in terms of envelope capacity, load-displacement relationship, stresses and cracks distribution. The results indicated that the provision of additional reinforcement increased the ultimate lateral capacity, ductility and introduce an additional mechanism for shear stresses for RC frame under cyclic loading. The best performance is observed when the cross-bracing is used at the top and bottom column connections whereas, the lateral capacity and displacement is increased by 12.9 % and 27.63% respectively of that computed for Control Frame. In case of cross-bracing steel at beam column connections and case of cross-bracing at beam region, the lateral capacity of RC frames is about 1.09 and 1.04 times that of control frame respectively. Furthermore, the dynamic analysis is carried out under considering the foundation soil whereas the Drucker-Prager model is used to define the stress strain behavior of soil. Besides, some significant observations on the performance of RC frames with change of the values of parametric study are presented in this paper.

Evaluation of the coefficient of earth pressure at rest (K0) of a saturated-unsaturated colluvium soil

To predict the stress-strain behaviour of soils under loading it is relevant the knowledge of its natural stress state, expressed by the coefficient of earth pressure at rest (K0). There are correlations in theliterature for K0determination that comes from researches developed considering sedimentary soils,typically from temperate or cold regions. In dealing with residual and colluvium soils, typical of tropical regions, it is not appropriate to use these correlations, since K0is affected by factors such as degree of weathering, laterization processes and suction, among others that also affect saturated sedimentary soils. This work analysed samples of a colluvium soil from a natural slope at the Pontifical Catholic University of Rio de Janeiro. For the determination of the coefficient of earth pressure at rest of the unsaturated colluvium soil, a flexible wall equipment, with a system of suction control was used. The influence of the net stress level on the value of the coefficient of earth pressure at rest was investigated under a constant suction of 10 kPa, following a loading and unloading cycle of applied vertical stress. The coefficient of earth pressure at rest of the saturated colluvium (null suction) was also determined using a stress-path, Bishop and Wesley type, servo-controlled triaxial equipment. The obtained results are presented and discussed.

Foundation and Pile Interaction with Swelling Soil

The paper provides the results of experimental studies pilot studies of the moisture transfer and clay soil swelling characteristics and their mathematical description. An analytical solution is suggested to determine a stress-strain behavior within a body of soil with non-uniform moisture content interacting with underground structures (foundation, pile, etc.). It is shown that the swelling pressure depends on the type of the stress-strain behavior of soil, and under the compression conditions, exceeds the corresponding swelling pressure under the finite-width foundation base by several times. It was found that the pull-out force of the pile greatly depends on the modulus of deformation of the swelling soil, influence zone and pile diameter.

Immediate and long term effects of compaction on the stress-strain behaviour of soil

This paper explores whether delay in construction after compaction can benefit from the gain in soil’s strength and stability point of view. An experimental investigation has been carried out to examine the gradual development of soil’s shear strength by ageing of mechanically compacted soil at three relative densities. In order to separate the gain in strength due to ageing from that occurring from the reduction in soil moisture, the soil samples prepared in moulds were kept in desiccators for different periods of time (1, 9 and 17 days) before testing unconfined compressive strength test. The soil in densely compacted state is found to gain in strength due to ageing faster than that in medium compacted state. Only due to ageing of 9 days or more, unconfined compressive strength of compacted soil is found about 1.7 to 2.4 times of that attained in day 1 after compaction.