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14 pages, 4944 KiB

Open AccessArticle

Analysis of a Bending-Stressed Pile in Interaction with Subsoil

by Norbert Jendzelovsky and Katarina Tvrda

Buildings 2023, 13(6), 1497; https://doi.org/10.3390/buildings13061497 - 09 Jun 2023

Cited by 1 | Viewed by 940

This study explored reinforced concrete piles located in a flexible half-space and loaded with external loads, considering various contact elements and the connection between the pile and the ground massif. Piles are mainly solved as axially loaded elements stressed by a vertical force. [...] Read more.

This study explored reinforced concrete piles located in a flexible half-space and loaded with external loads, considering various contact elements and the connection between the pile and the ground massif. Piles are mainly solved as axially loaded elements stressed by a vertical force. However, there are also several cases in the construction industry where a pile is stressed by a horizontal force or by a bending moment, producing a bending loaded pile. A static model of a pile and the surrounding subsoil was constructed using software based on FEM. The pile was modelled from 3D finite elements that were rotationally symmetric around the vertical axis of the pile. Additionally, the flexible half-space was modelled from 3D elements that were rotationally symmetrical around the piles. The boundary conditions were applied on the surfaces around the perimeter and at the bottom of the ground massif. The flexible half-space was modelled up to the area where there was zero deformation. The presented analysis focused on the description of different types of contact elements between the surface of the reinforced concrete pile and the surrounding ground mass. This interaction was modelled as a fixed connection or as point-to-point contact, and a contact surface. In the next part, different boundary conditions on the pile bottom were considered. Floating piles, supported by joints or firmly woven into the ground massif, were considered. All these outputs based on FEM were compared with the analytical solution of the bent pile that was published in the 1980s. The deformations and internal forces during different modelling of the contact between the edge of the concrete pile and the surrounding ground mass were compared. The higher values of the studied quantities were for rigid connections, which is logical. For contact elements, the property of the contact was considered. This property introduces less stiffness, and thus, the resulting values were lower compared to those for a fixed connection. The presented analysis of the FEM analytical and numerical solution is also very valuable for engineers working in construction. Full article

(This article belongs to the Special Issue Advances in Soils and Foundations)

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17 pages, 6183 KiB

Open AccessArticle

Nonlinear Settlement Calculation of Composite Foundation Based on Tangent Modulus Method: Two Case Studies

by Yonghua Li, Lei Yao, Gaoxiang Chen, Weijian Zhao and Xiangang Liu

Buildings 2023, 13(4), 892; https://doi.org/10.3390/buildings13040892 - 28 Mar 2023

Cited by 1 | Viewed by 1252

Abstract

The tangent modulus method of undisturbed soil is a new method in settlement calculation, which is mainly applied to hard soil with a strong structure, such as silty clay, completely weathered rock, and granite residual soil with an SPT blow count greater than [...] Read more.

The tangent modulus method of undisturbed soil is a new method in settlement calculation, which is mainly applied to hard soil with a strong structure, such as silty clay, completely weathered rock, and granite residual soil with an SPT blow count greater than 8. The tangent modulus is mainly obtained from a field plate load test, which can consider the influence of the soil stress level and reflect the nonlinear characteristics of the foundation settlement. In a multi-layer soil foundation, since the deep plate loading test is difficult, a method was proposed to determine the tangent modulus of deep soil. It is assumed that the ratio of the initial tangent modulus to the deformation modulus is equal to the ratio of the unloading–reloading modulus

E_{ur}^{ref}

to the secant modulus

E_{50}^{ref}

obtained by triaxial unloading–reloading test. Since there are corresponding empirical formulae for SPT counts and the deformation modulus of different types of soils in many regions, the initial tangent modulus can be derived by the above method. In two cases of a composite foundation, the compression modulus and tangent modulus were used to calculate the settlement of the foundation, which is then compared with the measured results. The results show that the proposed method for determining the tangent modulus of deep soil is feasible in theory, and the calculating accuracy of the tangent modulus is significantly higher than that of the traditional compression modulus. Full article

(This article belongs to the Special Issue Advances in Soils and Foundations)

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18 pages, 36353 KiB

Open AccessArticle

Responses of Structural Components of a Full-Scale Nailed Retaining Structure under the Influence of Surcharge Loading and Nail Head Configuration: A Numerical Study

by Meen-Wah Gui and Ravendra P. Rajak

Buildings 2023, 13(2), 561; https://doi.org/10.3390/buildings13020561 - 18 Feb 2023

Cited by 1 | Viewed by 974

Abstract

Soil-nailing is a simple and economical method of stabilizing cut slopes and retaining excavation. Most of the soil-nailing related studies, in particular the experimental work, were conducted in idealized or homogeneous ground, but such a result might not necessarily be representative. Thus, for [...] Read more.

Soil-nailing is a simple and economical method of stabilizing cut slopes and retaining excavation. Most of the soil-nailing related studies, in particular the experimental work, were conducted in idealized or homogeneous ground, but such a result might not necessarily be representative. Thus, for a more representative study, instead of treating the ground as homogeneous it should be treated as a system of horizontal layers. This study assessed the performance of a full-scale nailed retaining structure for a foundation pit of a 20-storey building through a series of numerical analyses. The influence of full-face facing thickness, nail head geometrical configuration (size and thickness) and surcharge loading on the response of the structural components of the soil-nailing system adopted is the main concern. The results were evaluated in terms of axial force, shear force and bending moment of the structural facing element and the horizontal displacement of the soil retained behind the facing element. In both cases, the distribution of nail axial (tensile) force in each nail reinforcement was also compared and evaluated. It was found that the thickness of full-face facing affected the facing shear force and bending moment, while the surcharge loading influenced the facing axial force and the horizontal displacement of the retained soil and that the magnitude of the axial force registered at the fixed end was governed by the size of the discrete nail head. Full article

(This article belongs to the Special Issue Advances in Soils and Foundations)

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19 pages, 3713 KiB

Open AccessArticle

Dynamic Stress Path under Obliquely Incident P- and SV-Waves

by Mingyuan Wang, Linfeng Song, Xinglei Cheng, Jianxin Zhang, Liqiang Lu and Wenqian Li

Buildings 2022, 12(12), 2210; https://doi.org/10.3390/buildings12122210 - 13 Dec 2022

Viewed by 1269

Abstract

This study derives the expression of dynamic stress components of the soil element in the semi-infinite elastic space under obliquely incident P- and SV-waves, and obtained the corresponding dynamic stress path. The effects of some factors including the incidence angle, Poisson’s ratio, frequency, [...] Read more.

This study derives the expression of dynamic stress components of the soil element in the semi-infinite elastic space under obliquely incident P- and SV-waves, and obtained the corresponding dynamic stress path. The effects of some factors including the incidence angle, Poisson’s ratio, frequency, wave velocity, phase difference, and soil depth on the dynamic stress path are analyzed. It is found that the dynamic stress path in the (σ_y − σ_x)/2 − τ_xy plane is an oblique ellipse, and the above factors have significant effects on that. The maximum dynamic stress level for Poisson’s ratio of 0.3 is about twice that for 0.48. The maximum dynamic stress level for 2.5 Hz is about six times that for 1 Hz. In general, the maximum dynamic stress level is about 40 kPa, no matter how the wave velocity changes. Compared with other phase difference, the dynamic stress level for the phase difference of 60° is largest with a value of 43 kPa. The dynamic stress level becomes greater as the soil depth increases, and the maximum value at 30 m depth is about 40 kPa. The variation trend of the three characteristic parameters with the incident angle exhibits the double-peak or triple-peak curves for different influencing factors. The research findings can provide some guidance for the site seismic dynamic response analysis and structural seismic design. Full article

(This article belongs to the Special Issue Advances in Soils and Foundations)

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19 pages, 6532 KiB

Open AccessArticle

Application of the Coupled Markov Chain in Soil Liquefaction Potential Evaluation

by Hsiu-Chen Wen, An-Jui Li, Chih-Wei Lu and Chee-Nan Chen

Buildings 2022, 12(12), 2095; https://doi.org/10.3390/buildings12122095 - 29 Nov 2022

Cited by 1 | Viewed by 1315

Abstract

The evaluation of localized soil-liquefaction potential is based primarily on the individual evaluation of the liquefaction potential in each borehole, followed by calculating the liquefaction-potential index between boreholes through Kriging interpolation, and then plotting the liquefaction-potential map. However, misjudgments in design, construction, and [...] Read more.

The evaluation of localized soil-liquefaction potential is based primarily on the individual evaluation of the liquefaction potential in each borehole, followed by calculating the liquefaction-potential index between boreholes through Kriging interpolation, and then plotting the liquefaction-potential map. However, misjudgments in design, construction, and operation may occur due to the complexity and uncertainty of actual geologic structures. In this study, the coupled Markov chain (CMC) method was used to create and analyze stratigraphic profiles and to grid the stratum between each borehole so that the stratum consisted of several virtual boreholes. The soil-layer parameters were established using homogenous and random field models, and the subsequent liquefaction-potential-evaluation results were compared with those derived using the Kriging method. The findings revealed that within the drilling data range in this study, the accuracy of the CMC model in generating stratigraphic profiles was greater than that of the Kriging method. Additionally, if the CMC method incorporated with random field parameters were to be used in engineering practice, we recommend that after calculating the curve of the mean, the COV should be set to 0.25 as a conservative estimation of the liquefaction-potential interval that considers the evaluation results of the Kriging method. Full article

(This article belongs to the Special Issue Advances in Soils and Foundations)

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19 pages, 3431 KiB

Open AccessArticle

Cost-Based Optimization of Isolated Footing in Cohesive Soils Using Generalized Reduced Gradient Method

by Muhammad Naqeeb Nawaz, Agha Shah Ali, Syed Taseer Abbas Jaffar, Turab H. Jafri, Tae-Min Oh, Mirvat Abdallah, Steve Karam and Marc Azab

Buildings 2022, 12(10), 1646; https://doi.org/10.3390/buildings12101646 - 10 Oct 2022

Cited by 4 | Viewed by 2282

Abstract

This study presents a cost-based optimization model for the design of isolated foundations in cohesive soils. The optimization algorithm not only incorporates safety requirements in the form of ultimate limit state (ULS) and serviceability limit state (SLS) criteria but also deals with the [...] Read more.

This study presents a cost-based optimization model for the design of isolated foundations in cohesive soils. The optimization algorithm not only incorporates safety requirements in the form of ultimate limit state (ULS) and serviceability limit state (SLS) criteria but also deals with the economics simultaneously. In that regard, the generalized reduced gradient (GRG) method is used for the optimization purpose to achieve the least construction cost of an isolated foundation along with the integration of design parameters as optimization variables. The optimization technique is elaborated using a design example in silty clayey soil and the results of the optimized design are compared with those of the conventional design. The optimization model shows that the optimized design can reduce the construction cost by up to 44% as compared to the conventional design cost for the particular example. Moreover, a sensitivity analysis is also performed to evaluate the quantitative impact of cohesive soil properties, design load, and groundwater table on the construction cost. The results indicate that the construction cost majorly depends on the combined effect of four key parameters: Young’s modulus, recompression index, design load, and groundwater table. Full article

(This article belongs to the Special Issue Advances in Soils and Foundations)

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15 pages, 3559 KiB

Open AccessArticle

Study Using Machine Learning Approach for Novel Prediction Model of Liquid Limit

by Muhammad Naqeeb Nawaz, Sana Ullah Qamar, Badee Alshameri, Steve Karam, Merve Kayacı Çodur, Muhammad Muneeb Nawaz, Malik Sarmad Riaz and Marc Azab

Buildings 2022, 12(10), 1551; https://doi.org/10.3390/buildings12101551 - 27 Sep 2022

Cited by 8 | Viewed by 1848

Abstract

The liquid limit (LL) is considered the most fundamental parameter in soil mechanics for the design and analysis of geotechnical systems. According to the literature, the LL is governed by different particle sizes such as sand content (S), clay content (C), and silt [...] Read more.

The liquid limit (LL) is considered the most fundamental parameter in soil mechanics for the design and analysis of geotechnical systems. According to the literature, the LL is governed by different particle sizes such as sand content (S), clay content (C), and silt content (M). However, conventional methods do not incorporate the effect of all the influencing factors because traditional methods utilize material passing through a # 40 sieve for LL determination (LL₄₀), which may contain a substantial number of coarse particles. Therefore, recent advancements suggest that the LL must be determined using material passing from a # 200 sieve. However, determining the liquid limit using # 200 sieve material, referred to as LL₂₀₀ in the laboratory, is a time-consuming and difficult task. In this regard, artificial-intelligence-based techniques are considered the most reliable and robust solutions to such issues. Previous studies have adopted experimental routes to determine LL₂₀₀ and no such attempt has been made to propose empirical correlation for LL₂₀₀ determination based on influencing factors such as S, C, M, and LL₄₀. Therefore, this study presents a novel prediction model for the liquid limit based on soil particle sizes smaller than 0.075 mm (# 200 sieve) using gene expression programming (GEP). Laboratory experimental data were utilized to develop a prediction model. The results indicate that the proposed model satisfies all the acceptance requirements of artificial-intelligence-based prediction models in terms of statistical checks such as the correlation coefficient (R²), root-mean-square error (RMSE), mean absolute error (MAE), and relatively squared error (RSE) with minimal error. Sensitivity and parametric studies were also conducted to assess the importance of the individual parameters involved in developing the model. It was observed that LL₄₀ is the most significant parameter, followed by C, M, and S, with sensitivity values of 0.99, 0.93, 0.88, and 0.78, respectively. The model can be utilized in the field with more robustness and has practical applications due to its simple and deterministic nature. Full article

(This article belongs to the Special Issue Advances in Soils and Foundations)

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23 pages, 4921 KiB

Open AccessArticle

Two Novel Vlasov Models for Bending Analysis of Finite-Length Beams Embedded in Elastic Foundations

by Feng Yue, Ziyan Wu, Zhiqiang Fan and Haokai Li

Buildings 2022, 12(8), 1122; https://doi.org/10.3390/buildings12081122 - 29 Jul 2022

Viewed by 1411

Abstract

The issue of soil–structure interaction (SSI) is essentially to analyze the influence of complex media on the mechanical behavior of supported structures. With the development of underground space, geological structures and space constraints put forward higher requirements for foundations and buildings. In this [...] Read more.

The issue of soil–structure interaction (SSI) is essentially to analyze the influence of complex media on the mechanical behavior of supported structures. With the development of underground space, geological structures and space constraints put forward higher requirements for foundations and buildings. In this paper, the effects of soil heterogeneity and embedment depth on the bending of finite-length beams embedded in two novel Vlasov elastic foundations are investigated. Firstly, the constitutive relations of subsoil are simulated by Gibson and transversely isotropic soils, and the type of elastic foundation is described by the modified Vlasov model. Then, based on variational principles, the governing differential equations for the deformation and attenuation parameters of beams embedded in elastic foundations are derived by taking the variation of the minimum potential energy of the system, and the characteristic coefficient related to the embedment depth is introduced. Finally, the mechanical performance of the beam and foundation is obtained by an iterative technique and the Fourier series method, and an extensive parametric study is performed to examine influence of some basic parameters on the deformation and internal forces of the system. The results show that the mathematical expressions of two refined elastic models are in good agreement with those of the traditional Vlasov foundation after degradation. The iterative technique based on the principles of solid mechanics can be employed to obtain more reliable model parameters. More importantly, with the increase in the embedment depth, the mechanical responses of the beam and subgrade forces decrease. The main reason is that the restraint effect of the soil media around structures, which leads to the reduction of the characteristic coefficient affecting the displacement of beams. Moreover, the heterogeneity of soil, including Gibson characteristics and transverse isotropy, should be considered according to specific working conditions in civil engineering. Full article

(This article belongs to the Special Issue Advances in Soils and Foundations)

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17 pages, 3507 KiB

Open AccessFeature PaperArticle

Role of Subgrade Reaction Modulus in Soil-Foundation-Structure Interaction in Concrete Buildings

by Ali Khosravifardshirazi, Ali Johari, Akbar A. Javadi, Mohammad Hassan Khanjanpour, Behnaz Khosravifardshirazi and Mohammad Akrami

Buildings 2022, 12(5), 540; https://doi.org/10.3390/buildings12050540 - 24 Apr 2022

Cited by 6 | Viewed by 2886

Abstract

One of the key issues in structural and geotechnical engineering is that most parts of buildings are usually analysed separately and then the outputs are used in foundation designs. In this process, some effects are neglected. In this study, the soil–structure interaction (SSI) [...] Read more.

One of the key issues in structural and geotechnical engineering is that most parts of buildings are usually analysed separately and then the outputs are used in foundation designs. In this process, some effects are neglected. In this study, the soil–structure interaction (SSI) in foundations of concrete buildings was evaluated using the direct finite element method (DFEM). 3D models were developed and used to analyse concrete buildings with different stories constructed on soft soil. Foundation settlement, deformation of foundation, soil pressure diagram, and weight of reinforcement in the foundation were considered as the main parameters. Deformation of the foundation was analysed using the finite element method considering the effect of combined loadings (combinations of dead load, live load, and earthquake load). It is shown that by changing values of subgrade reaction modulus (Ks) in foundation design, the effects of SSI on tall buildings can be considered automatically. The results also show that the soil–structure interaction can cause changes in the pattern of foundation settlement, foundation deformation, and the weight of reinforcement used in foundation design. Furthermore, dishing deformation in foundation appeared in terms of SSI effects. An equation is provided to simplify considering SSI effects in foundation design. This method is practical for civil (especially structural) engineers, and they can conveniently consider these effects in foundation design without using DFEM. Full article

(This article belongs to the Special Issue Advances in Soils and Foundations)

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21 pages, 6825 KiB

Open AccessFeature PaperArticle

Neural Network-Based Prediction Model for the Stability of Unlined Elliptical Tunnels in Cohesive-Frictional Soils

by Sayan Sirimontree, Suraparb Keawsawasvong, Chayut Ngamkhanong, Sorawit Seehavong, Kongtawan Sangjinda, Thira Jearsiripongkul, Chanachai Thongchom and Peem Nuaklong

Buildings 2022, 12(4), 444; https://doi.org/10.3390/buildings12040444 - 05 Apr 2022

Cited by 21 | Viewed by 2027

Abstract

The scheme for accurate and reliable predictions of tunnel stability based on an artificial aeural network (ANN) is presented in this study. Plastic solutions of the stability of unlined elliptical tunnels in sands are first derived by using numerical upper-bound (UB) and lower-bound [...] Read more.

The scheme for accurate and reliable predictions of tunnel stability based on an artificial aeural network (ANN) is presented in this study. Plastic solutions of the stability of unlined elliptical tunnels in sands are first derived by using numerical upper-bound (UB) and lower-bound (LB) finite element limit analysis (FELA). These numerical solutions are later used as the training dataset for an ANN model. Note that there are four input dimensionless parameters, including the dimensionless overburden factor γD/c′, the cover–depth ratio C/D, the width–depth ratio B/D, and the soil friction angle ϕ. The impacts of these input dimensionless parameters on the stability factor σ_s/c′ of the stability of shallow elliptical tunnels in sands are comprehensively examined. Some failure mechanisms are carried out to demonstrate the effects of all input parameters. The solutions will reliably and accurately provide a safety assessment of shallow elliptical tunnels. Full article

(This article belongs to the Special Issue Advances in Soils and Foundations)

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16 pages, 1834 KiB

Open AccessTechnical Note

Development of a New Uplift Pile with Prestressed Semi-Bonded Composite Anchor

by Zongyuan Mao, Hao Guo, Yongkang Wu, Enzhi Wang and Xu Li

Buildings 2022, 12(9), 1478; https://doi.org/10.3390/buildings12091478 - 17 Sep 2022

Cited by 3 | Viewed by 3819

Abstract

This paper introduces a new type of prestressed uplift pile that adopts the semi-bonded composite anchor as the main reinforcement. An in-situ experimental study was carried out to investigate the new pile’s deformation, stress, bearing capacity, and cracking characteristics, which were then compared [...] Read more.

This paper introduces a new type of prestressed uplift pile that adopts the semi-bonded composite anchor as the main reinforcement. An in-situ experimental study was carried out to investigate the new pile’s deformation, stress, bearing capacity, and cracking characteristics, which were then compared with the conventional piles. Results show that although the reinforcement ratio of the new pile is only 0.75%, much less than that of the conventional pile (i.e., 3.84%), it achieves similar or even better mechanical properties under uplift loads. The cost of the pile’s anchorage system is reduced by 43.8%, and the total cost of a single pile is reduced by 33.6%. Compared with the conventional pile, the new pile makes better use of the lateral friction resistance of the lower pile body, and the uplift bearing capacity and the uplift resistance of the pile are improved correspondingly. In addition, the cracking resistance of the new pile is significantly improved, with the cracking load increased by 88.2% and the cracking area reduced by 48.3%. In addition, the multi-layer structure of the composite main bar provides better protection for the load-bearing steel strands against corrosion. As such, the new type of pile is expected to gain much better durability than the conventional ones. Full article

(This article belongs to the Special Issue Advances in Soils and Foundations)

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