Geotechnical Engineering Practice Research Articles

Compilation of Consolidation Properties Data of Champlain Sea Clay from Ottawa Region

AbstractEstimation of consolidation settlements in fine-grained soils due to various civil infrastructure loads is traditionally based on results derived from consolidation tests performed on undisturbed soil samples, combined with the data of other soil properties. In many geotechnical engineering applications, consolidation settlements are also estimated using empirical consolidation parameters derived from basic soil properties. This approach relies on correlations from the literature to bypass the time-consuming and expensive sampling techniques, laboratory testing, and other associated expenses. However, these correlations may not provide reasonable consolidation settlement estimations as these correlations are typically developed without considering the influence of stress history, geology, salinity of pore water, gradation, soil fabric, and chemical properties of the soils. This is especially true for Champlain Sea clay deposits from Eastern Ontario region of Canada that are typically with heterogeneous site conditions and exhibit spatial variability of soil properties. In this paper, data from the published literature and industrial and government reports on sensitive Champlain Sea clays were gathered for the Ottawa region. The data collection and clean-up methodology towards enhancing the reliability of the gathered data is comprehensively discussed. The summarized data from this study can be used with a greater degree of confidence towards developing reliable correlations in the estimation of consolidation settlements in geotechnical engineering practice.

Soil-water characteristic curve of expansive soils considering cumulative damage effects of wetting and drying cycles

A novel experimental program was undertaken to explore crack development inside an expansive soil column under cyclic Wetting and Drying (W-D) and its influences on the Soil-Water Characteristic Curve (SWCC). Experimental investigations revealed that in the first drying cycle, fine and evenly distributed cracks developed from initial defects in the upper surface. In the subsequent drying cycles, the unhealed cracks during the wetting cycle further grow in width, length and depth while the initiation zone of new cracks was limited. The crack development characteristics within the soil column were described using fractal dimensions. The cracking degree of soil cross-sections gradually reduced with increasing depth. Also, each W-D cycle process contributed to a similar increment in the crack fractal dimension of soil at the same depth. In addition, the saturated water content, air-entry value and residual suction of cracked expansive soils gradually reduced with an increase in the number of W-D cycles. An obvious bimodal phenomenon was only observed in the SWCC of soil samples after the third W-D cycle. In order to quantify the damage induced by crack development to the soils, the damage variable was proposed based on the crack fractal dimensions. Furthermore, the Damage Impact Factor (DIF), as a function of the volume damage variable and soil plasticity index, was introduced into the traditional Fredlund and Xing (F-X) model to estimate the SWCC of cracked expansive soil. The form of modified F-X model is relatively simple and can be conveniently extended into geotechnical engineering practice applications.

Biopolymers in geotechnical engineering for soil improvement

AbstractSeveral biopolymer applications in geotechnical engineering have been adopted in recent years, notably dust control, soil strengthening, and erosion control. Although biopolymer soil treatment approaches can assure engineering efficiency while satisfying environmental protection standards, this technology requires more validation regarding site adaptability, durability, and economic feasibility. The influence of biopolymers on soil behavior is discussed within geotechnical engineering applications and practices, including soil consistency limits, strength and deformation parameters, hydraulic conductivity, soil-water properties, and erosion prevention.Laboratory studies were performed to confirm the behavior of the treated soil, including Atterberg limits, proctor, and direct shear tests utilizing two types of biopolymers: guar gum and xanthan gum.

Modifying Expansive Soil Characteristics with Xanthan Biopolymer Integration

Abstract: Expansive soils pose significant challenges in various engineering projects due to their tendency to swell and shrink with changes in moisture content. Traditional stabilization methods often come with environmental and economic drawbacks. This research paper explores the potential of xanthan biopolymer, a polysaccharide of microbial origin (Xanthomonas Campestris), as a sustainable and effective alternative for altering the engineering properties of expansive soils. Through laboratory experiments and analysis, the paper investigates the influence of xanthan biopolymer on key soil properties such as swelling behaviour, shear strength, and permeability. The findings provide insights into the feasibility and efficacy of using xanthan biopolymer for soil stabilization, offering a promising avenue for sustainable geotechnical engineering practices.

A framework for estimating the matric suction in unsaturated soils using multiple artificial intelligence techniques

AbstractImplementation of the state‐of‐the‐art understanding of the mechanics of unsaturated soils into geotechnical engineering practice is partly limited due to the lack of quick, reliable, and economical techniques for matric suction measurement. Matric suction is one of the key stress state variables that significantly influences the hydro‐mechanical behavior of unsaturated soils. In this paper, to address this objective, two artificial intelligence (AI) models were developed for estimating matric suction in unsaturated soils based on the particle swarm optimization support vector regression (PSO‐SVR) and multivariate adaptive regression spline (MARS) algorithms. The results suggest that both these models can reasonably estimate matric suction. Compared to the MARS model, the PSO‐SVR model can achieve higher accuracy. Nonetheless, the MARS model facilitates the sensitivity analysis and the selection of essential inputs. A novel integrated framework is proposed and validated, leveraging the strengths, and alleviating the limitations of the PSO‐SVR and MARS algorithms for reliable and rapid estimation of matric suction in the range of 0–1500 kPa for low plastic soils (0 < Ip ≤ 7). Six inputs are required to use this model successfully; some can be measured using conventional laboratory tests, and others can be calculated from mass‐volume relationships.

Forks in the road: decisions that have shaped and will shape the teaching and practice of geotechnical engineering

Geotechnical engineering spans a wide range of applications, including tunnels, foundations, dams, and retaining structures. It deals with a material known to be difficult to model: a particulate material whose mechanical response is affected by all three invariants of the stress tensor, by loading rate, by density and by fabric. New problems and greater complexity in old problems have come about with the effects of climate change. Progress in certain technologies—notably artificial intelligence—also defines the new landscape in which geotechnical engineers must operate. This paper focuses on mechanics-based geotechnical engineering applications. The paper reviews some of the major decisions that were made by the engineers and researchers who developed geotechnical engineering to the point at which it was an identifiable separate discipline and the consequences that these decisions have had on the development of the discipline and on its teaching. The paper identifies some key modelling choices that were made that have had an undeservedly disproportionate impact on the teaching and practice of geotechnical engineering. The focus of the paper is therefore on these decisions and choices, and what should be taught in their place today. Challenges that future geotechnical engineers may face, as well tools that will be available to them, are also discussed in the context of what should be taught in undergraduate and graduate courses.

A review on drainage of dredged marine soils: Advances and prospects

Drainage is a common practice in geotechnical engineering concerning dredged marine soils. Current drainage techniques, including surcharge preloading, vacuum preloading, and combined vacuum-surcharge preloading, have been proven to be effective in soft soil treatment, but are also criticized for their high energy consumption. This paper made a brief review on existing drainage techniques and proposed some prospects for the next-generation techniques in response to the public concern of sustainability. It is found that all conventional preloading techniques have been well studied from tests to modeling, and improved vacuum preloading tends to be used in combination with other techniques. Drainage techniques with lower energy consumption can be realized either by using renewable energy or designing biomimetic devices. The paper is expected to provide a comprehensive while concise report on recent advances in drainage techniques for dredged marine soils and in the meanwhile give an insight into the further development towards a more sustainable future.

Pine cone ash stabilization of expansive soils

<p>The use of appropriate waste materials to stabilize problematic soils, such as expansive soils that are responsible for geotechnical damage, is a common practice in geotechnical engineering. This study presents the use of pulverized ash from the combustion of pine cone (PC) waste as a stabilizing agent to improve the engineering properties of expansive soils. A series of laboratory tests were carried out to examine the effect of different percentages of pine cone ash (PCA) content (3%, 5%, 7%, and 10%) on the Atterberg limits, swelling potential (Sp), linear shrinkage, compressibility, and unconfined compressive strength (qu) of naturally occurring swelling soils and the PC ash-treated soils. The results showed that PC ash contents of 5% and 7% contributed to a significant reduction in the swelling and shrinkage potential and an improvement in the coarsest texture, brittleness behavior, compaction properties, and compressive strength of the treated soils. Conversely, PC ash contents below 3% and above 7% showed minimal changes in the index and engineering properties of the PC ash-treated soils. In particular, the PC ash content of 5% resulted in optimal mitigation of the poor properties of the treated soils. The use of pine cone ash as a stabilizing agent represents a suitable and complementary subgrade soil material for expansive soils on which lightweight structures are built.</p>

Teaching modern soil mechanics

The important role of the critical state theory in the modern soil mechanics is undeniable. It is true that the number of soil mechanics courses that not cover this subject is progressively decreasing. However, when the critical state theory is introduced, this topic cannot be seen as a simple extension of the classic soil mechanics. On the contrary, it is essential that some significant differences between modern and classic soil mechanics are adequately clarified and understood. This subject is a relevant objective of this paper, besides the large benefits brought by the modern soil mechanics. This discipline, like the mechanics applied to other materials, is fundamentally a preliminary learning to prepare for the professional practice of geotechnical engineering. When the main objective is to teach methods to solve the engineering problems (foundations, excavations, embankments, tunnels, etc.), the matters transmitted to the students are sometimes focused on the geotechnical engineering methods, where, nevertheless, soil mechanics, naturally, has an irreplaceable role. It is true that a design is unique in itself. However, all designs must have in common the same theoretical principles of soil mechanics, regardless of the particularities of the geotechnical design. This cannot be neglected in the modern soil mechanics teaching. Brief ideas concerning where and how soil mechanics has been taught, is also introduced. The fundamentals about plastic design of geotechnical structures are highlighted. The article ends calling attention to the outstanding contribution of the critical state theory for a unified understanding of the soil behavior. Its pedagogic benefits are invaluable.

Marine domestication of Sporosarcina pasteurii induces the precipitation of CaCO3 to solidify calcareous sand

The construction of island reef projects using natural seawater, tailored to local conditions, holds significant importance for the advancement of environmentally-friendly geotechnical engineering practices. Previous studies on the application of MICP technology in a seawater environment have been scarce. In this study, Sporosarcina pasteurii were acclimatized to a seawater environment and employed for MICP mineralization reinforcement of calcareous sand, resulting in an enhanced mineralization effect compared to previous attempts under similar conditions. Both direct domestication and gradient domestication methods proved successful in enabling Sporosarcina pasteurii to adapt effectively within a seawater environment. Following domestication, the amount of CaCO3 generated through MICP solidification increased from 2.30% to 4.47%, resulting in a corresponding increase in the Ca2+ conversion rate from 5.19% to 10.02%. Additionally, after domestication, the unconfined compressive strength (UCS) reached up to 309kPa – representing an impressive improvement of 35.53% compared to pre-domestication levels, however, it should be noted that its reinforcement effect still falls short when compared with pure water conditions. The CaCO3 minerals formed after MICP reinforcement using seawater nutrient solution in domesticated Sporosarcina pasteurii predominantly consist of needle-shaped aragonite and granular anorthite minerals, as opposed to the previously observed calcite-type CaCO3 minerals.

Back analysis of cohesion and friction angle of failed slopes using probabilistic approach: two case studies

In general, geotechnical investigations deal with the back analysis of the geotechnical parameters on the basis of the field observation. According to the back analysis method introduced in the present study, geometry of a number of failed slopes have been carefully mapped and then statistical features of the groundwater level, the bulk unit weight and other measurable parameters have been determined. After that, a series of two-dimensional models for back analysis of the failures have been established. Moreover, statistical analyses based on probabilistic approaches have been utilized to estimate the variation ranges of the shear strength variables. The study provided the probabilistic back analysis of the slope failure with the two case studies in the copper mines of Anjerd and Daraloo. Results indicated that the approach to the probabilistic back analysis has been effective in the analysis of the slope failures wherein considerable uncertainty has been observed in the shear strength and other influential variables. Furthermore, the probabilistic back analysis presented a lot of information in comparison to the approach to the deterministic back analysis and thus had more reasonable matching with the practice of geotechnical engineering in the real world. Therefore, this method would be beneficial and practical for stability analysis, redesigning the slopes, designing the new slopes under the same geotechnical conditions and promote the construction safety. The probabilistic back analysis could be also used to estimate the shear parameters and analyze the stability of slopes as a cost-effective and high reliability method.

Testing of tensile properties of two nonwoven geotextiles

The use of geosynthetics has become a common and unavoidable practice in geotechnical engineering, agriculture and environmental engineering. The main disadvantages of earthen construction materials are their insufficient tensile strength and inadequate water permeability or impermeability, depending on the problem to be solved. Such shortcomings are successfully solved by incorporating appropriate geosynthetics (geotextile, geogrid, geocells, geomembrane etc.) into earthen structures. The most used geosynthetic is geotextile, which can provide practically all functions expected from such a product. The aim of this paper was to present and analyse the relative results of multiple tensile tests performed on two nonwoven (NW) geotextiles to provide a realistic insight into the variability of their tensile properties. The obtained results showed a very similar variability of the tensile properties of the tested geotextiles.

Exploring Shear Wave Velocity—NSPT Correlations for Geotechnical Site Characterization: A Review

Shear wave velocity (Vs) is a critical parameter in geophysical investigations, micro-zonation research, and site classification. In instances where conducting direct tests at specific locations is challenging due to equipment unavailability, limited space, or initial instrumentation costs, it becomes essential to estimate Vs directly, using empirical correlations for effective site characterization. The present review paper explores the correlations of Vs with the standard penetration test (SPT) for geotechnical site characterization. Vs, a critical parameter in geotechnical and seismic engineering, is integral to a wide range of projects, including foundation design and seismic hazard assessment. The current paper provides a detailed analysis of the key findings, implications for geotechnical engineering practice, and future research needs in this area. It emphasizes the importance of site-specific calibration, the impact of geological background, depth-dependent behavior, data quality control, and the integration of Vs data with other geophysical methods. The review underlines the continuous monitoring of Vs values due to potential changes over time. Addressing these insights and gaps in research contributes to the accuracy and safety of geotechnical projects, particularly in seismic-prone regions.

A new procedure for characterizing the critical intergranular contact state of non-plastic sand – fines mixed materials

A key and urgent scientific issue is how to characterize the complex intergranular contact state and mechanical behavior evolution of sand–fines mixed materials and then show how this state contributes to the static and dynamic properties of such materials. Both theoretical analyses and experimental data suggest that the mixes have different intergranular contact states as the fines content (FC) increases, and the mixed materials can be classified as sand-like, in-transition, or fines-like. The capability of the Rahman semi-empirical formula to predict the threshold fines content FCth—which distinguishes the regime of “fines in sand” (sand-dominated behavior) from that of “sand in fines” (fines-dominated behavior)—is verified using the basic material and mechanical properties of mixed materials from the literature. Developed from the method for determining the theoretical minimum void ratio, a new method that allows unified characterization of the critical intergranular contact state parameters FCin-min and FCin-max for in-transition soils is established based on the binary packing model, and FCin-min and FCin-max can be determined simply through explicit expressions that use some material physical indices of pure-sand and pure-fines materials. The proposed procedure offers significant advantages for evaluating the critical intergranular contact state and mechanical properties of sand–fines mixed materials in geotechnical engineering practice.

Theory of liquid and plastic limits for fine soils, methods of determination and outlook

Albert Atterberg introduced various consistency limits (state transitions) for fine-grained soil in the 1910s. Of these, the liquid limit (LL) and plastic limit (PL) are ubiquitous in geotechnical engineering practice, including their usage for soil classification and in deducing useful geotechnical parameters through correlations. Given that it is about 110 years since they were first introduced, it seems timely to review critically the current state of play regarding various definitions and theories of these index parameters and their standardised testing methods, as described in majorly used codes worldwide. Because different codes allow different LL apparatus types and employ some dissimilar criteria (e.g. in establishing the end point for the PL test), a change in method or code may produce different consistency limits results for testing the same soil. These differences are rationalised in terms of the controlling soil and test parameters. Some potential pitfalls in consistency limits testing are highlighted. Attention then turns to strength-based approaches, mostly employing fall-cone (FC) set-ups, emphasising their unsuitability for determining Atterberg’s PL. Considering the general poor reproducibility of the PL test, this paper concludes with an alternative way forward, obtaining useful FC index parameters that provide new possibilities for strength predictions and in the classification of fine-grained soils.

Reuse of Waste Materials in Geotechnical Practice

Waste material is an inevitable outcome of most human and industrial activities, lacking enduring value. A significant amount of waste is being generated from various sources such as industrial and domestic activities, driven by population growth and economic expansion. To address these challenges, methods like re-use and recycling are crucial in mitigating the adverse impacts of waste by reducing landfill deposition. Recycling not only helps in conserving natural resources but also diminishes energy consumption. Recently, there has been increasing interest in re-using waste materials as substitutes in geotechnical and geo-environmental applications. For the efficient utilization of waste, it is essential to systematically understand its characterization, various technical aspects, and environmental implications, along with their interrelationships. This study aims to explore the potential of using different by-products and waste materials such as fly ash, shredded waste tires, and recycled concrete aggregates as geomaterials. By doing so, it endeavours to contribute to sustainable practices in geotechnical engineering. Overall, the re-use of waste materials constitutes a significant area of research aimed at fostering sustainability in geotechnical engineering practices.

Macro-micro numerical analysis of granular materials considering principal stress rotation based on DEM simulation of dynamic hollow cylinder test

The granular materials were subjected to the principal stress rotation effect induced by traffic loads, wave loads, and earthquake loads in geotechnical engineering practice. In order to reveal the influence of principal stress rotation on the macro-micro dynamic characteristics, this study proposed a numerical simulation method modeling physical dynamic hollow cylinder tests. Taking the dynamic stress state induced by traffic loading as an example, the numerical test model of the dynamic hollow cylinder was conducted on the subgrade soil, and the influence of principal stress rotation on the macro-micro evolution of dynamic characteristics was analyzed.The results showed that the principal stress rotation accelerated the development of vertical accumulative plastic strain and particle displacement, which aggravated micro-structure destruction of granular material. Moreover, the increase of confining stress declined the variations of normal contact numbers in each direction, which resisted the shear stress induced by principal stress rotation. This study provided a novel method to investigate the macro-micro dynamic characteristics of granular materials subjected to principal stress rotation, which made up for the inability of physical hollow cylinder tests to study microscopic evolution.

Discussion: Development of a Single-Point Method to Determine Soil Plastic Limit Using Fall-Cone Data [Geotech Geol Eng 41:4473–4485, 2023

This discussion article presents a critical appraisal of three empirical correlations developed via multiple regression analysis and presented in the Kayabali et al. [Geotech Geol Eng 41:4473–4485, 2023. https://doi.org/10.1007/s10706-023-02527-0] (the Authors’) investigation for the determination of the soil consistency limits. Specifically, based solely on British Standard (BS) fall-cone (FC) test data, the Authors purport that the correlations given by Equations 2 and 3 of their paper can be used to predict the ASTM rolling-plate plastic limit (i.e., PLRP), while their Equation 4 can be used to predict the BS FC liquid limit (i.e., LLFC). The Authors demonstrated that these correlations gave good predictions of the measured LLFC and PLRP water contents (i.e., wL(FC) and wP(RP), respectively) for 87 fine-grained soils they sourced from different parts of Central Turkey. Employing newly compiled large and diverse consistency limits databases assembled from the published research literature, this discussion article confirms that the Authors’ Equations 2 and 3 generally produce poor wP(RP) predictions for the fine-grained soils comprising these databases, invariably overestimating (often seriously) their measured plastic limit values. Hence, the Discussers recommend that the Authors’ Equations 2 and 3 (being generally unreliable beyond the investigated Turkish soils) should not be used in geotechnical engineering practice. While the Authors’ single-point LLFC method given by their Equation 4 broadly appears as a good wL(FC) predictor for the newly compiled database soils, it is noted that there already exist well-established and standardised single-point LLFC methods.

A Review on Soils Treated with Biopolymers Based on Unsaturated Soil Theory.

Adding different materials to soil can improve its engineering properties, but traditional materials such as cement, lime, fly ash, etc., have caused pollution to the environment. Recently, biopolymers have shown many advantages, such as economy and environmental protection, which make them applicable to geotechnical engineering. This study summarizes the effects of biopolymers on soil's engineering properties and the main directions of current research. Firstly, the advantages and disadvantages of a variety of widely used biopolymer materials and their effects on the specific engineering characteristics of soil (i.e., water retention characteristics, strength characteristics, permeability characteristics, microstructure) are introduced, as well as the source, viscosity, pH, and cost of these biopolymers. Then, based on the theory of unsaturated soil, the current research progress on the water retention characteristics of improved soil is summarized. The key factors affecting the strength of biopolymer-treated soil are introduced. Due to the actual environmental conditions, such as rainfall, the permeability and durability of biopolymer-treated soil are also worthy of attention. In summary, it is necessary to study the variation laws of the engineering properties of biopolymer-treated soil in the full suction range, and to predict such laws reasonably. The relevant results are conducive to the safer and more scientific application of biopolymers in geotechnical engineering practice.

Effect of temperature on the mechanical properties of fine-grained soils - A review

Contemporary geotechnical engineering practice encompasses design and construction of thermo-active geo-structures or structures which would encounter thermal cycles throughout its service life. Therefore, understanding the effect of temperature on soil mechanical properties becomes inevitable. Being a complex and coupled phenomenon it has been quite challenging for the researchers to study experimentally and theoretically the thermo-mechanical behaviour of fine-grained soil. Nonetheless, there are numerous studies which contribute significantly to gain insight about thermo-mechanical behaviour of soils. Incidentally, till date, on this arena of research, no comprehensive review, which provides a holistic development of the subject and its connection with the field application, is available. The prime objective of the present study is to critically appraise the state-of-the-art understanding on thermo-mechanical behaviour of fine-grained soils through a comprehensive literature review. Moreover, this paper also describes the concept of thermo-elasto-plastic strain and thermal creep behaviour of fine-grained soils.