Methods In Geotechnical Engineering Research Articles

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.

A modeling study of elastoplastic rock failure regime based on finite discrete elements

Numerical simulation has become a pivotal method in geotechnical engineering for analyzing rock failure. However, traditional model lacks comprehensive elastoplastic rock characterization. Therefore, a new finite-discrete element model using the Drucker-Prager criterion and cohesive elements based on a traction-separation law to accurately simulate elastoplastic rock breaking has been built. A scratch test simulation is conducted to describe the mechanical response and failure characteristics of the rock during the cutting process. Rock failure characteristics derived from numerical simulations align closely with experimental observations. These simulations successfully replicate both the ductile and brittle regimes observed during scratch tests. Furthermore, they provide insights into the primary driving factors behind rock failure under different regimes. Variation of cutting force and specific energy obtained from the model are entirely consistent with experimental results, with the specific energy decreasing following a −0.5 power law, thus explaining the energy dissipation rule of the specific energy decrease. In brittle regime, crush zones and the resulting rough shearing surface are observed, plastic damage is also found, revealing that the cutter tip is the key structure influencing them. The model established in this paper holds significant importance for rock mechanical property evaluation and the optimization design of cutter structures.

Generation and Evaluation of CPT Data Using Kriging Interpolation Technique

The cone penetration test (CPT) has been the de facto field exploration method in geotechnical engineering for decades. Variations of CPT can measure parameters for seismic, environmental, and hydrological applications. Analyzing response often requires properties in areas that have little or no data. Therefore, given the limited CPT data, it is critical to understand how to accurately estimate the soil properties at unsampled locations. In this paper, we generated soil shear wave velocity profiles using the kriging interpolation technique and assessed their performance using site response analysis. Four kriging interpolation-based shear wave velocity profiles and four additional CPT-based shear wave velocity profiles defined site conditions for response analysis. We performed a series of 1-D equivalent linear site response analyses using STRATA software. The site response analysis results are presented as amplification factors (AF), peak ground acceleration (PGA) profiles, surface spectral acceleration, and surface acceleration time histories. Compared to CPT-based profiles, the results of kriging interpolation-based profiles were evaluated and discussed. The results confirmed the reliability of the kriging interpolation technique in predicting soil parameters at unsampled locations.

Special Issue on Numerical Modeling in Civil and Mining Geotechnical Engineering

Numerical modeling is a widely used method in geotechnical engineering to understand the interactive responses of infrastructures with soils or/and rocks in both civil and mining engineering [...]

Realization of multi-dimensional random field based on Jacobi–Lagrange–Galerkin method in geotechnical engineering

Geomaterial has spatial variability, which can be described by the random field theory. A powerful tool for realizing random fields is the Karhunen–Loève series expansion (K–L expansion) where the number of random variables depends on the number of K–L expansion terms rather than on the number of grids of geo-structure model. However, the K–L expansion requires the solution of an integral eigenvalue problem whose analytical form exists only in the special case. Hence, the Galerkin method is usually employed to calculate the approximate solution, which especially for multi-dimensional random field inevitably causes the huge computational cost of multi-fold integrals and the approximate error of the solution. For quickly and accurately simulating the random field with fewer random variables, a Jacobi–Lagrange–Galerkin (JLG) method is proposed where the huge amounts of multi-fold integrals are transformed into simple matrix multiplications which are implemented quickly in a MATLAB environment. Furthermore, the discretization error and its influence factors are discussed to determine the parameters of the JLG method, and the procedure of the JLG method is proposed. Finally, a two-dimensional shallow foundation and a three-dimensional slope are employed to demonstrate computational efficiency, accuracy, and applicability of the JLG method.

Life cycle assessment and life cycle cost analysis for geotechnical engineering: review and research gaps

Geotechnical engineering work contributes to the total environmental impact and monetary cost occurring from the construction sector. Decisions made regarding geotechnical engineering aspects have a profound effect on the environmental impact and the monetary cost of the structure during its life cycle. Life Cycle Assessment (LCA) and Life Cycle Cost Analysis (LCCA) are established methods for assessing the environmental impacts and monetary cost from construction works. This paper presents the results from a literature review of 56 published papers regarding the current situation of the use of LCA and LCCA methods in geotechnical engineering. It is found that only limited research has been published in applying LCA and LCCA to geotechnical engineering structures. Further research should focus on developing a framework using LCA and LCCA for geotechnical engineering structures and also identify and fill data gaps in computer software databases. This would help geotechnical engineers in their daily work to reduce the environmental impact and monetary costs throughout the life cycles of the designed structures.

Error Evaluation and Suitability Assessment of Common Reliability Methods in the Case of Shallow Foundations

A geotechnical structure’s reliability index calculated using identical input parameters and assumptions can significantly vary as a function of the used method. The different approaches to solving the reliability problem could result in an error which depends on many factors. The most important error sources are the complexity of the performance function, the number of random variables, their mutual correlations, and marginal statistical distributions. A review of relevant literature in the field of reliability in geotechnical engineering revealed a lack of information on the errors of individual reliability methods for geotechnical problems and general criteria for assessing their suitability concerning the error size. The paper defines the reliability method error and proposes criteria for assessing the suitability of reliability methods in geotechnical engineering. Based on the proposed criteria, the suitability of common reliability methods was evaluated in the example of a shallow foundation, analysed according to Eurocode 7, DA 3, such that Ed=Rd. It is shown that due to the mathematically complex expression of the reliability integral, methods that are easier to use result in a larger error and are not suitable for a reliability analysis of shallow foundations. Sophisticated methods are more accurate but require specific knowledge and resources that are not often used in daily engineering practice.

FEM Simulations of Granular Matter Behaviour Under Triaxial Tests

This article presents the results of a numerical simulation carried out from a series of standard triaxial tests conducted on limestone sand from a quarry situated in Algiers (center of Algeria). The main objective of the investigation is to obtain from a numerical analysis a simple soil model to represent the behaviour of the studied material. The 2D Plaxis program is used in this study with the introduction of a model based on the work of Brinkgreve et al. (in: Benz T, Nordal S (eds) Numerical methods in geotechnical engineering, CRC Press, Boca Raton, 2010). Corrections were made to the formulas used, which are based on the relative density, in order to improve the quality of the results in terms of soil behaviour, mechanical strength and deformation. The comparison of the experimental and numerical results for the Mohr–Coulomb model gives a considerable appreciation on the deformation and resistance. However, it fails to represent properly the stress–strain curve. The use of Duncan and Chang model (Hardening Soil Model-HSM) leads to an underestimation of the resistance characteristics (values of the friction angles) with an overall error of 7.98%. Our work consists of the application of two corrections to the HSM model. The first correction is based on the work of Brinkgreve et al. (2010), which focused on the common parameters between the HSM and the HSSM. An overestimation of the deformations was observed with an overall error of 155.96%. The second step consists of canceling the correction of the elastic modules ( $$E_{50}^{ref}$$ , $$E_{oed}^{ref}$$ ) which reduces the error to 1.53%.

Assessment of basal heave stability for braced excavations in anisotropic clay using extreme gradient boosting and random forest regression

A finite-element analysis considering the anisotropy for the undrained shear strength was performed to examine the effects of the total stress-based anisotropic model NGI-ADP (developed by Norwegian Geotechnical Institute based on the Active-Direct simple shear-Passive concept) parameters on the base stability of deep braced excavations in clays. These parameters included the ratio of the plane strain passive shear strength to the plane strain active shear strength suP/suA, the ratio of the unloading/reloading shear modulus to the plane strain active shear strength Gur/suA, the plane strain active shear strength suA, the unit weight γ, the excavation width B, the wall thickness b, and the wall penetration depth D. According to the numerical results for 1778 hypothetical cases, extreme gradient boosting (XGBoost) and random forest regression (RFR) were adopted to predict the factor of safety (FS) against basal heave for deep braced excavations. The results indicated that the anisotropic characteristics of soil parameters need to be considered when determining the FS against basal heave for braced excavation. XGBoost and RFR can yield a reasonable prediction of the FS. This paper presents a cutting-edge application of ensemble learning methods in geotechnical engineering.

Graphical and Numerical Methods for Stability Analysis in Surrounding Rock of Underground Excavations, Example of Boukhadra Iron Mine N.E Algeria

Underground mining continues to progress to difficult, complex and deeper levels in order to tackle ascending demand of minerals. These deep mining occurs in a very hard conditions, in which right practice must be implemented in order to overcome the technical and safety challenges and reap economic gains. The redistributed stresses, large deformations and creeping behavior in such environments worried engineers and geoscientific researchers. The working technic in Boukhadra iron mine is based on the sublevels slaughtered, with room, pillar workings and roof behaviour. Based on rock mechanics and geotechnical engineering methods, our research adopted geo-mechanical and numerical approaches to predict the rock mass behaviour in Boukhadra underground mine and to deal its stability problem. The results show that plastic deformations and stress points increasingly in pillars. In zones with low cover, the tensile zones develop at the roof, leading to a progressive rupture giving rise to a droop. In some areas, fractures develop in a rather remarkable way; in this case the breaking of the pillars and collapse can occur generalized and brutal. The stability of room-and-pillar mines does not depend only pillars. It involves the determination of critical factors and limits of mining. Our study demonstrates that the use of scientific and technical achievements, have become a necessity in mining.

Study on Cone Penetration Test of Sand Layer along Southwest Coast of Hainan Island

Coastal dunes are widely distributed along the southwestern coast of Hainan Island paralleling to the coastline. Cone penetration test is a commonly used in-situ testing method in geotechnical engineering, it has strong advantage in sand layer which is difficult to obtain undisturbed sample. Through the cone penetration tests and the laboratory test on sand with different densities and grain size distributions, the correlation between in-situ test index and laboratory test index was analyzed. It is found that the hit number of standard penetration test is linearly correlated with the tip resistance of cone penetration test, so the density of sand can be judged by the value of tip resistance. The content of silt and clay in sand has a great influence on side friction and friction ratio of cone penetration test, and the friction ratio is linearly related to the content of silt and clay. For different sand with same geological origin, the particle-size distribution has great impact on the friction ratio, the larger the main particle size is, and the smaller the friction ratio is. For same sand with different geological origin, the content of silt and clay of sand is different, and the cone penetration test curve and the particle-size distribution curve are also different.

A New Contact Formulation for Large Frictional Sliding and Its Implement in the Explicit Numerical Manifold Method

Modelling discontinuous systems involving large frictional sliding is one of the key requirements for numerical methods in geotechnical engineering. The contact algorithms for most numerical methods in geotechnical engineering is based on the judgement of contact types and the satisfaction of contact conditions by the open–close iteration, in which penalty springs between contacting bodies are added or removed repeatedly. However, the simulations involving large frictional sliding contact are not always convergent, particularly in the cases that contain a large number of contacts. To avoid the judgement of contact types and the open–close iteration, a new contact algorithm, in which the contact force is calculated directly based on the overlapped area of bodies in contact and the contact states, is proposed and implemented in the explicit numerical manifold method (NMM). Stemming from the discretization of Kuhn–Tucker conditions for contact, the equations for calculating contact force are derived and the contributions of contact force to the global iteration equation of explicit NMM are obtained. The new contact algorithm can also be implemented in other numerical methods (FEM, DEM, DDA, etc.) as well. Finally, five numerical examples are investigated to verify the proposed method and illustrate its capability.

Assessing effect of dynamic compaction on liquefaction potential using statistical methods – a case study

ABSTRACTThis article is aimed at illustrating the practical use of statistical methods in geotechnical engineering. As an example, the efficacy of dynamic compaction (DC) in the mitigation of liquefaction hazard is studied through a case study of a site in the Chang-Hwa Coastal Industrial Park in Changhua County, Taiwan. Before DC, the soil at the study site, which mainly consists of a layer of hydraulic fill of silty sand to fine sand underlain by recent alluvial plains (Qa), is deemed susceptible to liquefaction. After DC, the soil at the study site is improved such that the liquefaction potential is greatly reduced. The efficacy of DC in reducing liquefaction potential is evaluated quantitatively using the statistical methods, and the effectiveness of these statistical methods, especially when used with visualisation technique, is demonstrated. This provides a basis towards risk-based communication and decision making in the setting of practical applications.

Evaluation of Critical Slip Surface in Limit Equilibrium Analysis of Slope Stability by Smoothed Particle Hydrodynamics

Limit equilibrium methods (LEMs) have been widely used for slope stability analysis in engineering practice. The critical slip surface in LEM, which has the minimum factor of safety (FS), is often assumed as the most likely slip surface and subsequently used as the failure slip surface in the analysis and design of slope stabilization measures, such as soil nails and anchors, for unstable slopes. This assumption has not been validated systematically, probably due to the difficulty in simulating large displacement of soils during landslides. In this study, a new mesh-free, particle-based numerical method in geotechnical engineering called smoothed particle hydrodynamics (SPH) is adopted to simulate the entire process of landslides, including the large displacement of soils after a landslide initiates. A series of comparative studies on the stability analysis of cohesive slopes is performed using both LEM and SPH. The comparative studies show that the assumption is reasonable for stable slopes. However, for unstable slopes in which the location of failure slip surface is critically needed for the design of stabilization measures, the LEM critical slip surface differs substantially from the failure slip surface, and the volumes of sliding soil masses are greatly underestimated by the LEM critical slip surfaces. Using the LEM critical slip surface as the failure slip surface in the design leads to the unsafe design of stabilization measures. A new method was proposed to properly locate the failure slip surfaces for unstable slopes when using LEM. It is found that the failure slip surfaces for unstable slopes is not the slip surface with the minimum FS; instead, it is the one with FS = 1.

Influence of random heterogeneity of the friction angle on bearing capacity factor Nγ

ABSTRACTProbabilistic methods in geotechnical engineering have received a lot of attention during the last decade and different methodologies are used to capture the inherent variability of soil in different geotechnical engineering problems. In this paper, numerical simulations are conducted to obtain the bearing capacity factor, Nγ, for a purely frictional heterogenous soil where the friction angle is modelled as randomly distributed throughout the domain and the effect of its spatial variability on Nγ is investigated. A finite element method, based on the upper bound limit analysis was combined with random field theory and linear programming to develop a probabilistic analysis. Monte Carlo simulations were performed and the effect of the variability of the friction angle defined by statistical parameters on the bearing capacity factor was investigated. Results show that the mean bearing capacity factor Nγ of a footing on a spatially variable cohesionless soil is generally higher than the deterministic Nγ obtained from a constant mean value. Increasing the heterogeneity of the friction angle by an increase in the coefficient of variation generally increases this deviation. This can be explained by the nonlinearity of the relationship between Nγ and the friction angle.

Application of numerical ultimate analysis in identifying the bearing capacity of foundation

Load test is the main method to identify the bearing capacity of foundation in practical engineering. However, some problems are existing in the experiment, such as the scale effect, high cost and long construction period. The newly numerical ultimate analysis can overcome the shortcomings of time-consuming, complicated operation, inaccuracy and so on, which is gradually becoming an effective calculation method in geo-technical engineering. The paper adopts increment loading method and ultimate strain method to simulated the load test numerically. The calculation examples in the paper show that the results of load test can be obtained through numerical ultimate analysis, where the ultimate strain method is better.

On the Global Sensitivity Analysis Methods in Geotechnical Engineering: A Comparative Study on a Rock Salt Energy Storage

The large number of input factors involved in a sophisticated geotechnical computational model is a challenge in the concept of probabilistic analysis. In the context of model calibration and validation, conducting a sensitivity analysis is substantial as a first step. Sensitivity analysis techniques can determine the key factors which govern the system responses. In this paper, three commonly used sensitivity analysis methods are implemented on a sophisticated geotechnical problem. The computational model of a compressed air energy storage, mined in a rock salt formation, includes many input parameters, each with large amount of uncertainties. Sensitivity measures of different variables involved in the mechanical response of the cavern are computed by different global sensitivity methods, namely, Sobol/Saltelli, Random Balance Design, and Elementary Effect method. Since performing sensitivity analysis requires a large number of model evaluations, the concept of surrogate modelling is utilised to decrease the computational burden. In the following, the accuracy levels of various surrogate techniques are compared. In addition, a comparative study on the applied sensitivity analysis methods shows that the applied sensitivity analysis techniques provide identical parameter importance rankings, although some may also give more information about the system behaviour.

Fatores de redução para fluência em geocomposto drenante

A construção civil, muitas vezes considerada atrasada tecnologicamente quando comparada a outros setores, tem buscado incorporar novas tecnologias às suas atividades tradicionais. Na engenharia geotécnica, pode-se destacar o uso crescente dos materiais geossintéticos como evidência. O uso de geocompostos drenantes com a finalidade de captação e condução da água presente no solo tem se tornado cada vez mais frequente. Conhecer e compreender o comportamento deste tipo de material pode representar um dimensionamento mais preciso e, consequentemente, uma maior segurança na aplicação e redução de custos para implementação deste tipo de solução. O estudo busca medir o desempenho de um geocomposto drenante a partir de resultados de ensaios de laboratório para obtenção das características mecânicas, hidráulicas e de durabilidade do geossintético. Com os parâmetros obtidos foi feita uma correlação entre os ensaios de compressão, transmissividade e fluência. Deste modo foi possível fazer a previsão da redução na capacidade de vazão do material em longo prazo, estabelecendo fatores de redução quanto à fluência, específicos para este tipo de material. Baseando-se nos resultados obtidos, o material mostrou um desempenho considerado bastante satisfatório.

Application of Data Analysis Method in Geotechnical Engineering

Geotechnical seismic engineering belongs to the cross field of geotechnical engineering and earthquake engineering. Due to the dual effects of the variability of geotechnical objects and the complexity of dynamic loading, the scientific problems involved in this field have to face more uncertainties. Through the analysis on the status quo of uncertainty analysis methods in geotechnical earthquake engineering in the field of non-deterministic analysis clear difficulties, weak links with all kinds of uncertainty analysis method to solve the inherent weakness of determining geotechnical earthquake engineering uncertainty problem, and can determine the establishment and improvement to provide some ideas and direction analysis model for non.

Calibration of an advanced material model for a shotcrete lining

Proper choice of a constitutive model is an essential part of any successful application of numerical methods in geotechnical engineering. In most cases, attention is paid to the soil constitutive model. For structural elements, such as tunnel linings, retaining structures etc. elastic constitutive models are often used. These material models however do not involve many aspects of a real structural behavior such as limited tensile and compressive strength, strain softening and time dependent behavior during service life of a construction. In the proposed paper, an application of the novel constitutive model for shotcrete (Schädlich, Schweiger, 2014) is presented. The paper is focused at the process of determination of input parameters values of this model based on performed laboratory test. Section of the primary collector network in Brno was chosen for the purpose of obtaining shotcrete lining samples.