Geotechnical Analysis Research Articles

Probabilistic characterization of soil properties based on the maximum entropy method from fractional moments: Model development, case study, and application

In probabilistic reliability analysis for geotechnical engineering applications, determining the underlying probability distributions of soil properties and corresponding parameters from observed data is a critical initial step because subsequent risk and reliability analyses depend upon these evaluations. Conventionally, the choice of probability distribution is dictated by subjective familiarity with a classical (e.g., normal or lognormal) distribution. This paper proposes an objective and unbiased method to estimate probability distributions of a soil property using the maximum entropy method from fractional moments of observed data. The probability distribution is based on the concept of maximum entropy and is free from the assumptions of classical distributions. A case study is presented for the undrained shear strength of soil in the Nipigon River landslide area, Ontario, Canada. The maximum entropy distributions of the soil property from fractional moments are compared to the frequency histogram, normal and lognormal distributions, and maximum entropy distributions from integral moments. The maximum entropy distribution with two-order fractional moments, almost equivalent to that with four-order integral moments, is verified with the chi-square goodness-of-fit test. Issues related to overfitting/underfitting, minimum sample size, fractional orders, negative moments, and limitations are discussed. Application of the method to geotechnical reliability analysis is illustrated.

Multi-LOD BIM for underground metro station: Interoperability and design-to-design enhancement

Underground metro stations as essential large-scale infrastructures that ease the traffic congestion on the overcrowded urban surface should be thoroughly designed, constructed and maintained. Building information modelling (BIM) has been increasingly employed for project design authoring, construction monitoring and operation management to promote digital engineering. Geotechnical design engaging numerical modelling techniques is an indispensable process for underground construction projects. These cross-disciplinary processes employing heterogeneous applications are yet to be coordinated in an efficient way, and thus improved interoperability can streamline the processes and optimise engineering design. This paper proposes an extension to the primary standard for openBIM data exchange – the Industry Foundation Classes (IFC) to facilitate wider adoption of BIM in underground infrastructure design, construction and management. Then a multiple level-of-detail (LOD) metro station BIM model is introduced to represent information at distinct levels of geometric and semantic richness required for varying application scenarios. Finally, we suggest a workflow underpinned by heuristic techniques, as an intermediate solution, to enhance the interoperability between a BIM authoring tool and a numerical modelling program for geotechnical analysis, and exemplify the workflow with the State Library Station of Melbourne. The proposed workflow offers an automated error-free, design-to-design solution, and hence enables the efficient exploration of design scenarios and construction optimisation before IFC is adopted by geotechnical modelling software.

Geotechnical fragility analysis of monopile foundations for offshore wind turbines in extreme storms

Offshore wind turbines (OWTs) must withstand harsh environmental loads over their 20- to 30-year design life. Fragility analysis investigates the probability of damage over a range of hazard intensities and is integral to a performance-based engineering approach. The focus of this paper is on monopiles, which are widely used to support OWTs in water depths up to around 40m. The paper presents a fragility analysis of monopiles in extreme storms in terms of geotechnical performance, measured by permanent rotation of the foundation. Geotechnical fragility has so far not been comprehensively addressed due to the challenge of predicting soil behaviour under cyclic loading and estimating the probability of extreme responses. On the latter, the paper develops efficient Karhunen-Loeve representations of wind and wave loading that can be combined with inexpensive probabilistic methods to compute fragility. The framework was demonstrated using a representative scenario of a 5 MW OWT installed in clay. Non-linear foundation response was captured by a dynamic 3D finite element model. Fragility curves were generated using subset simulation for storms with return periods (RPs) from 1 to 100 years. Fragility during extreme storms (with 50- and 100-year RPs) was significantly higher than storms with RPs of 10 years or less.

The initial fabric of undisturbed and reconstituted fluvial sand

High-quality undisturbed samples of fluvial sand were obtained from the field using the ground freezing technique. In the laboratory, the in situ void ratio of these high-quality undisturbed frozen samples was replicated using four different reconstitution methods: dry deposition, moist tamping, water sedimentation (by spooning) and slurry deposition. The initial fabric of the specimens was evaluated using X-ray micro-computed tomography and advanced image analysis. Initial fabric features were assessed in terms of the particle orientation, anisotropy, void ratio distribution and particle sizes within the specimens. Fabric analysis results suggest that none of the laboratory reconstitution techniques used captures the true three-dimensional initial fabric of undisturbed fluvial sand. However, the slurry deposition method managed to reproduce the inherent particle orientation, anisotropy and the variations of void ratio and particle sizes of the undisturbed fluvial sand. This observation explains why previous rigorous studies on the macro-mechanical behaviour of sands deposited under water have systematically demonstrated that slurry deposition is the most suitable method to reconstitute in the laboratory natural sands deposited under water. This has major implications for geotechnical testing and analyses of liquefaction of sands deposited under water such as fluvial, offshore and tailings sands.

Geotechnical Analysis of a Mat Foundation Supporting a Wellhead Platform

China National Offshore Oil Corporation (CNOOC) currently is developing a mat-supported wellhead production platform concept as an alternative solution to conventional jacket platforms in shallow-water oil fields. The platform is towed to the site with the mat foundation elevated. The mat then is lowered and embedded in the seabed as the hull is jacked out of the water. Steel pipe piles subsequently are driven through the tubular legs of the platform. After grouting the connection, the pile foundations provide permanent support for the platform. The mat foundation therefore provides only temporary support to the platform. This paper presents a case study focusing on the installation behavior of the mat foundation in a soft soil site as part of the platform concept development and suitability evaluation. The study determined (1) the expected penetration depth under the platform’s self-weight considering its irregular geometry and soft over stiff clay stratigraphy; (2) the target center of gravity to achieve even penetration and the potential for tilt development in the case of offset from the target position; (3) the effectiveness of using ballast tanks to correct the tilt; and (4) settlement after the installation due to dissipation of pore pressure and creep. Advanced large-deformation finite-element simulations featuring a strain softening soil model and analytical analyses were performed. A dedicated lab testing program geared was designed and executed to provide the necessary soil parameters for the analyses. This paper presents the techniques and considerations that were applied in this study and insights gained into the installation and subsequent postinstallation behavior of large-area mat foundations.

Numerical modelling of large deformation problems in geotechnical engineering: A state-of-the-art review

Many problems in geotechnical engineering involve large movements or rotations, examples include natural processes such as landslides, and man-made processes such as earthmoving and pile penetration. While the use of numerical modelling, primarily the finite element method (FEM), is now routine in geotechnical design and analysis, the limitations of conventional FEMs soon become apparent when attempting to model large deformation problems. For this reason, the search for alternatives remains a key goal of many geotechnical researchers, both to find accurate methods but also to develop efficient ones. In this review paper, prompted by Technical Committee 103 of the International Society for Soil Mechanics and Geotechnical Engineering (ISSMGE), we survey the current state-of-the-art in numerical modelling techniques aimed at large deformation problems in geotechnics. The review covers continuum and discontinuum methods and provides a clear picture of what is and is not currently possible, which will be of use to both practitioners seeking suitable methods and researchers developing existing or new methods.

Geotechnical engineering analysis of material modeling and earthquake coefficient effect on NMR mine area

Waste management issue in mining industry has become increasingly important. In this regard, construction of tailings embankment or dams play an important role. Most of the tailings dams require some kinds of remedial actions during their operational life time, wherein PT Newmont Minahasa Raya (NMR), a mine company in North Sulawesi, Indonesia, has established a new forest covering 215 ha aimed at functioning as a rainwater catchment area to recharge associated groundwater systems. Two different material models were utilized during the finite element computations, comparing the performance of the more advanced constitutive Soft Soil material model, (Soft Soil Model, SSM) against the Mohr-Coulomb material model (Mohr-Coulomb Model, MCM) commonly used today. Practical geotechnical analysis of the stability of embankment construction is done by using a program Plaxis calculations based on the Finite Element Method for analyzing the value of deformation with Earthquake Coefficient obtained value safety factor 1.9085 as MCM and 1.9078 as SSM.

A study of the soil-water reliability model in the whole matric suction range

Soil–water characteristic curves (SWCCs) are considered as a basis for analyzing fluid–solid coupling of unsaturated soil. How to estimate the SWCC over the whole region with matric suction based on the limited local datasets is challenging. Laboratory test is separately carried out on the ranges with low and high matric suctions of the undisturbed residual soil widely distributed in southeast China. With the test data, a model for SWCCs of soil in the whole range with matric suction is established by applying the reliability analysis method. Through analysis and verification based on the test data and data of 52 samples of three types of soil (sand, silt-loam and clay) obtained from UNSODA, it is found that the model parameters involved in the model show significant physics meaning. The model can be used to estimate the SWCC of soil within the whole range with matric suction according to part of the data (in the low or high matric suction part). Compared with the other models, the model is robust and is applicable for acquiring SWCCs of different types of soil within the whole range matric suction with R2>0.98. In addition, the model provides an important method to obtain SWCCs of soils with different texture, and is of the reference significance to the geotechnical AI analysis.

Assessment on strength reduction schemes for geotechnical stability analysis involving the Drucker-Prager criterion

Assessment on strength reduction schemes for geotechnical stability analysis involving the Drucker-Prager criterion

Geologic and geomorphologic study of the Terra Murata and Centane-Panoramica sites (Island of Procida, Naples Bay, Southern Tyrrhenian sea) aimed at solving some applied geological and geotechnical problems

A geologic and geomorphologic study aimed at solving some geological and geotechnical problems, regarding the massive seepage of meteoric waters in the coastal cliffs of the Island of Procida (Naples Bay, southern Italy), composed of both tuffs and loose pyroclastic deposits, has been carried out in the geosites of Terra Murata (Middle Ages village and coastal cliff towards the Corricella Bay) and Centane-Panoramica (coastal cliff facing on the Tyrrhenian sea). A detailed geologic and geomorphologic survey has allowed to suggest solutions to the applied geological and geotechnical problems related to the occurrence of massive seepages of waters at the physical interface between pyroclastic rocks and loose pyroclastic deposits, characterized by different density, permeability and porosity and also controlled by a dense network of fractures, involving the pyroclastic deposits cropping out in the selected areas. Field sampling and geotechnical laboratory analyses have been carried out to calculate the values of main geotechnical parameters of the yellow tuffs cropping out at the Terra Murata promontory. At the same time, a detailed monitoring of the seepages of waters has been carried out through a detailed geological survey of the tuff outcrops of the promontory. The obtained results have suggested a strong control from both the geomorphologic instability of the coastal cliff and tectonic setting. At the Centane-Panoramica geosite the geological survey, coupled with geotechnical analyses and standard penetrometric tests, has accordingly evidenced that the geomorphologic instability was mainly concentrated in the sectors of the tuff coastal cliffs facing seawards towards the Tyrrhenian sea.

Geologic and geomorphologic study of the Terra Murata and Centane-Panoramica Sites (Island of Procida, Naples Bay, Southern Tyrrhenian Sea) aimed at solving some applied geological and geotechnical problems

A geologic and geomorphologic study aimed at solving some geological and geotechnical problems, regarding the massive seepage of meteoric waters in the coastal cliffs of the Island of Procida (Naples Bay, Southern Italy) composed of both tuffs and loose pyroclastic deposits, has been carried out in the geosites of Terra Murata (Middle Ages village and coastal cliff towards the Corricella Bay) and Centane-Panoramica (coastal cliff facing on the Tyrrhenian Sea).A detailed geologic and geomorphologic survey has allowed to suggest solutions to the applied geological and geotechnical problems related to the occurrence of massive seepages of waters at the physical interface between pyroclastic rocks and loose pyroclastic deposits, characterized by different density, permeability and porosity and also controlled by a dense network of fractures, involving the pyroclastic deposits cropping out in the selected areas.Field sampling and geotechnical laboratory analyses have been carried out to calculate the values of main geotechnical parameters of the yellow tuffs cropping out at the Terra Murata Promontory. At the same time, a detailed monitoring of the seepages of waters has been carried out through a detailed geological survey of the tuff outcrops of the promontory. The obtained results have suggested a strong control from both the geomorphologic instability of the coastal cliff and tectonic setting. At the Centane-Panoramica geosite, the geological survey, coupled with geotechnical analyses and standard penetrometric tests, has accordingly evidenced that the geomorphologic instability was mainly concentrated in the sectors of the tuff coastal cliffs facing seawards towards the Tyrrhenian Sea.

Development of Subsurface Geological Cross-Section from Limited Site-Specific Boreholes and Prior Geological Knowledge Using Iterative Convolution XGBoost

AbstractThe delineation of vertical geological cross-sections is an essential task in geotechnical site characterization and has a profound impact on subsequent geotechnical designs and analyses. I...

Analysis and Stabilization of Slopes Using Geo5 Software

Abstract: With the development of technology and software, it has become easy to solve difficult problems in every field which use to take a lot of time. The use of software in the field of civil engineering has grown since the last decade. GEO5 is one such software which may be used to solve many geotechnical problems. GEO5 consists of wide range of powerful programs based on analytical method sand the Finite Element Method such as Stability Analysis, Excavation Design, Retaining, Wall Design, Foundation Design, Soil Settlement Analysis, Digital Terrain Model, Geotechnical Finite Element Analysis like analyzing and design of slope, design of retaining walls, settlement analysis, foundation design and much more .It is a very simple and powerful tool for solving geotechnical problems based on traditional analytical methods and Finite Element Methods (FEM).The easy-to-use suite consists of individual programs with a unified and user-friendly interface. Each program is used to analyze a different geotechnical task but all modules communicate with each other to form an integrated suite. In this project modules related to slope stability have been studied in details and then used them for analysis of slope stability. Using GEO5 software the geometry of problems were created in GEO5 and the analysis were carried out considering the stability and economic considerations. Also, the costs of different types of reinforcing methods were determined and compared. It is found that soil nailing is most economical. Keywords: GEO5software, Analysis, Soil nailing, Anti-slide Piles, Anchors, Reinforcemet

Machine learning of geological details from borehole logs for development of high-resolution subsurface geological cross-section and geotechnical analysis

ABSTRACT The subsurface geological cross-section is indispensable before design and construction of a geotechnical structure can commence. The development of geological cross-sections often requires significant manual efforts for simplification of stratigraphic boundaries. For example, straight lines are commonly used to connect stratum boundaries at adjacent boreholes, and soil layers with small thicknesses are often ignored. Such a simplification heavily relies on practitioners’ experience and may induce great uncertainties in the developed geological cross-sections and subsequent geotechnical analysis and design (e.g. slope stability analysis). In this study, a Bayesian supervised machine learning method, multiple-point statistics, is adopted to automatically generate high-resolution subsurface geological cross-section with proper incorporation of prior geological knowledge and all details observed from limited borehole logs. Locations and number of boreholes are automatically determined with due consideration of slope failure mechanism. The proposed method is demonstrated using an illustrative example. It is shown that the proposed method successfully captures geological details and local stratigraphic variations within a slope and quantifies the associated interpretation uncertainties. The geological details and local stratigraphic variations have great effects on the slope failure mechanism. There is a risk of overestimating overall slope stability if an over-simplified geological model is adopted for slope design.

Investigation and analysis of groundwater-derived damage to the Shahe ancient bridge site in Xi\u2019an, China

Earthen cultural ruins and their subsurface environments act as carriers or support for aboveground cultural heritage artefacts, and groundwater has been identified as the most important factor accelerating the destruction of ruins. In this paper, a wooden structure on the site of the Xianyang Shahe ancient bridge is taken as the research object. Through geotechnical surveys and site sample analyses, the relationship between the environment and cause of damage at the site is explored. Fluctuations in groundwater level are found to affect the movement of water and salt, thereby accelerating deterioration and allowing microbes and other soil inhabitants and plants to erode the ruins. Furthermore, strong correlations are revealed between the stratigraphy of the area and both ruin status and sample analysis results. Geotechnical investigation data are used to predict the effects of various damaging factors on long-term preservation and the underlying mechanisms and to propose feasible, long-term countermeasures for preservation studies.

Hydrofracturing in situ stress measurements of itabirite in the Brazilian Ferriferous Quadrangle and their limitations

This article presents a first attempt to carry out in situ stress measurements (magnitudes and orientations) of the itabirite in the Brazilian Ferriferous Quadrangle by hydraulic fracture testing at a depth of 399 m. Previous studies on this rock have considered estimated values of the k index (ratio between the horizontal effective stress Sh, generally controlled by tectonism, and the vertical effective stress Sv, generally controlled by gravity), and it is not a common practice to carry out in situ stress tests in this region and rock type to support geotechnical analysis. The area of study was located at a depth of 500 m in a pit because the determination of the in situ stress distribution is very important to assess the stability of the open-pit mine. The planning, execution and results of the tests are presented. The studied rock mass exhibits different geological structures, such as banding and foliation, which resulted in difficulties with performing the tests, and only 12.5% of the tests were successful. The results can help interpret the strains and stresses induced by mining activities in slopes in the Brazilian Ferriferous Quadrangle and their impacts on the surrounding structures. For a better determination of the regional in situ stresses in the rock of the Brazilian Ferriferous Quadrangle, hydraulic tests on pre-existing fractures are recommended.

Korelasi Point Load Index dan Uniaxial Compressive Strength pada Satuan Batupasir dan Batulempung Formasi Latih untuk Penentuan Koefisien Kekuatan Batuan di Pit X Tambang Batubara PT Berau Coal, Kalimantan Timur

Physical and mechanical properties of rock for engineering purposes are indispensable for any civil/construction, mining and other engineering requirment. The results of the uniaxial compressive strength (UCS) test are very much needed in various geotechnical analyzes or engineering, in particular in the mining industry in relation to the calculation of the pit slope design and other mining infrastructure. Rock samples used in this study were obtained from the results of geotechnical drilling (full core drilling). The rock engineering properties test to obtain UCS and PLI values was carried out in the laboratory. Testing the rock hardness index using the point load index (PLI) can be done more quickly, cheaply, practically and can use rock samples with a variety of sample shapes. The focus and object of the research are mudstone and sandstone units as part of the Lati Formation. These two types of layers are the most dominant rock types as a constituent of the pit slopes in the research area. To ensure that the correlation results are in accordance with the rules of scientific research, the distribution of UCS and PLI data from laboratory test results is verified using a statistical approach / testing. Correlation and analysis between the two rock engineering properties test results are very useful for geotechnical analysis data input. The coefficient or constant values obtained can be used to determine the rock strength values used in various geotechnical analyzes so that the analysis can be carried out more efficiently, effectively and quickly and can support geotechnical engineering work.

Estimating drained cross-anisotropic elastic parameters in saturated clays using the undrained properties

The accurate determination of anisotropic small-strain stiffness properties in natural soil deposits is of crucial importance in many geotechnical and geological engineering analyses. Accordingly, the main objective of this study is to propose an approach for evaluating the drained elastic stiffness parameters in saturated clays using the undrained properties. To attain this objective, by assuming cross-anisotropy in clayey soils, it is shown that two measured anisotropic components of shear moduli and the vertical component of Young's modulus in the undrained conditions possess the main contributions. They were then combined with a series of theoretical equations and empirical assumptions in the literature representing the relationships between the drained and undrained elastic parameters to yield the estimated values for the anisotropic drained Young's moduli. To verify the reliability of the suggested approach, the anisotropic elastic properties of 51 clayey soil specimens from 21 different soil types relating to 15 various sites in 4 countries were collected based on the experimental laboratory tests reported in literature. The anisotropic drained Young's moduli in each specimen were estimated through the proposed technique and then compared with directly measured ones with satisfactory agreement. The findings of this study may serve as the convenient references for economic and precise determination of in-situ elastic stiffness parameters in cohesive soil deposits using the non-invasive seismic surveying.

Results of Application of Artificial Neural Networks in Predicting Geo-Mechanical Properties of Stabilised Clays—A Review

This study presents a literature review on the use of artificial neural networks in the prediction of geo-mechanical properties of stabilised clays. In this paper, the application of ANNs in a geotechnical analysis of clay stabilised with cement, lime, geopolymers and by-product cementitious materials has been evaluated. The chemical treatment of expansive clays will involve the development of optimum binder mix proportions or the improvement of a specific soil property using additives. These procedures often generate large data requiring regression analysis in order to correlate experimental data and model the performance of the soil in the field. These analyses involve large datasets and tedious mathematical procedures to correlate the variables and develop required models using traditional regression analysis. The findings from this study show that ANNs are becoming well known in dealing with the problem of mathematical modelling involving nonlinear functions due to their robust data analysis and correlation capabilities and have been successfully applied to the stabilisation of clays with high performance. The study also shows that the supervised ANN model is well adapted to dealing with stabilisation of clays with high performance as indicated by high R2 and low MAE, RMSE and MSE values. The Levenberg–Marquardt algorithm is effective in shortening the convergence time during model training.

A maximum entropy method using fractional moments and deep learning for geotechnical reliability analysis

A maximum entropy method using fractional moments and deep learning for geotechnical reliability analysis