scholarly journals Performance Analysis Of “Toga” Foundation With Cap On Thick Soft Soil Based On Laboratory Models And Finite Element Analysis

UKaRsT ◽  
2020 ◽  
Vol 4 (2) ◽  
pp. 222
Author(s):  
Melissa Kurnia ◽  
Paulus Pramono Rahardjo
Keyword(s):  
Soft Soil ◽  
Soil Conditions ◽  
Deep Foundations ◽  
3D Analysis ◽  
Element Analysis ◽  
Soil Layers ◽  
The Right ◽  
Laboratory Models ◽  
Deformation Relationship ◽  
Plaxis 3D

Various alternative foundations are offered depending on soil conditions from the results of soil investigations. In difficult soil types such as thick, soft soil layers, pile foundation is generally used to avoid the excess settlements, but deep foundations for small buildings are not the right solution when viewed from a cost perspective. One of the more economical foundations is to use the” toga” foundation, with a plate on top and a caisson underneath where the caisson can be inserted into the soil with an open end. Through this study, the carrying capacity of the” toga” foundation will be analyzed. Then the foundation will be made on a laboratory scale and tested with axial load. The load and deformation relationship were analyzed using PLAXIS 3D analysis. It can be concluded the performance of the ”toga” foundation on thick, soft soil can be used for two-floored buildings

Consolidation in Soft Soil – Case Study on Prefabricated Vertical Drains (PVDs)

2021 ◽  
Vol 15 (1) ◽  
pp. 310-319
Author(s):  
Nadarasa Kuganeswaran ◽  
Afikah Rahim ◽  
Nazri Ali
Keyword(s):  
Ground Improvement ◽  
Soft Soil ◽  
3D Analysis ◽  
Prefabricated Vertical Drains ◽  
Vertical Drains ◽  
Vertical Drain ◽  
Prefabricated Vertical Drain ◽  
Improvement Method ◽  
Plaxis 3D

Background: Constructing on soft ground is one of the challenges of geotechnical engineering. The unpredictable behaviour and characteristics of soft soil can cause much damage resulting in high maintenance costs in the post-construction phase. Objective: The purpose of this study is to analyse the consolidation process and ground improvement method using surcharge and a prefabricated vertical drain by measuring the accuracy of the prediction settlement value with the actual site settlement results. Methods: An effective ground improvement method is the application of a surcharge and prefabricated vertical drains (PVDs). Various methods can be used to predict the settlement effectively, one such method being PLAXIS 3D simulation. A case study on ground improvement works was selected for this research, where PVDs were constructed and implemented at the site. A few undisturbed samples were collected from the site to generate the parameters based on the lab test conducted in the simulation process. This parameter was carefully studied and representing the principal input for the 3D model, which is generated and represents the actual ground improvement method for the selected case study. The analysis was performed using a borehole and soft soil model to generate the diagram. The prediction settlement value was generated from the PLAXIS 3D analysis as the baseline comparing to the actual results. The factors that influence the settlement value, such as the length and spacing of the prefabricated vertical drain, construction method, and soil characteristics, are also discussed. Results: A predicted settlement of 2553 mm was generated by the simulation, while the actual settlement outcome at the site was 2096 mm, a difference of 457 mm, and a prediction accuracy of 82.1%. Conclusion: The study found that the combination of surcharge and prefabricated vertical drain in the ground improvement worked well. Also, discussed were the factors that influenced the accuracy of the prediction and the site results.

scholarly journals Feedback of the behaviour of a silo founded on a compressible soil improved by floating stone columns

2018 ◽  
Vol 149 ◽  
pp. 02008
Author(s):  
Ramdane Bahar ◽  
Omar Sadaoui ◽  
Fatma Zohra Yagoub
Keyword(s):  
Soft Soil ◽  
Limit State ◽  
Soil Improvement ◽  
Stone Columns ◽  
Soil Conditions ◽  
Deep Foundations ◽  
The Stability ◽  
Compressible Soil ◽  
The City ◽  
Ongoing Monitoring

The coastal city of Bejaia, located 250 kilometers east of the capital Algiers, Algeria, is characterized by soft soils. The residual grounds encountered on the first 40 meters usually have a low bearing capacity, high compressibility, insufficient strength, and subject to the risk of liquefaction. These unfavorable soil conditions require deep foundations or soil improvement. Since late 1990s, stone columns technique is used to improve the weak soils of the harbor area of the city. A shallow raft foundation on soft soil improved by stone columns was designed for a heavy storage steel silo and two towers. The improvement of 18m depth have not reached the substratum located at 39m depth. The stresses transmitted to the service limit state are variable 73 to 376 kPa. A rigorous and ongoing monitoring of the evolution of loads in the silo and settlements of the soil was carried out during 1400 days that is from the construction of foundations in 2008 to 2012. After the loading of the silo in 2010, settlement occurred affecting the stability of the towers due to excessive differential settlements. Consequently, the towers were inclined and damaged the transporter. This paper presents and discusses the experience feedback of the behavior of these structures. Numerical calculations by finite elements have been carried and the results are compared with the measurements.

scholarly journals Seismic Response of Long-Span Triple-Tower Suspension Bridge under Random Ground Motion

2017 ◽  
Vol 2017 ◽  
pp. 1-16 ◽  
Author(s):  
Chang-ke Jiao ◽  
Xin Dong ◽  
Ai-qun Li ◽  
Guang-dong Zhou ◽  
Xiao-ping Wu
Keyword(s):  
Finite Element ◽  
Soft Soil ◽  
Nonlinear Dynamic Analysis ◽  
Suspension Bridge ◽  
Soil Conditions ◽  
Suspension Bridges ◽  
Random Response ◽  
Element Analysis ◽  
Long Span ◽  
Random Responses

Multitower suspension bridge is of different style compared to the traditional suspension bridge with two towers, and consequently the dissimilarity of static and dynamic behaviors is distinct. As a special case of multitower suspension bridge, two long-span triple-tower suspension bridges have been constructed in China and the seismic random response of triple-tower suspension bridges is studied in this paper. A nonlinear dynamic analysis finite element model is established in ABAQUS and the Python language is utilized to facilitate the preprocess and postprocess during the finite element analysis. The procedure for random response calculation of structures based on the pseudoexcitation method is presented, with the initial equilibrium state of structure considered, which may be ignored for long-span bridges during calculating of stochastic response. The stationary seismic random responses of triple-tower suspension bridge under uniform excitation in firm, medium, and soft soil conditions and under spatially varying excitation in soft soil are investigated. The distribution of RMS of random responses of displacements and internal forces of the stiffening girder and towers is presented and discussed in detail. Results show that spatially variable ground motions should be considered in the stochastic analysis of triple-tower suspension bridge.

scholarly journals Influence of granular material characteristics in the behaviour of “Bouregreg Valley” soft ground improved with stone columns

2018 ◽  
Vol 149 ◽  
pp. 02020
Author(s):  
Noura Nehab ◽  
Khadija Baba ◽  
Latifa Ouadif ◽  
Lahcen Bahi
Keyword(s):  
Finite Element ◽  
Constitutive Model ◽  
Granular Material ◽  
Complex Geometry ◽  
Soft Soil ◽  
Permanent Deformation ◽  
Stone Columns ◽  
Soil Conditions ◽  
Natural Soil ◽  
Element Analysis

The use of finite element analysis has become widespread in geotechnical practice as means of optimizing engineering tasks; it can be easily applied to the treated areas by stone columns, which are a method of improving the soil having low geotechnical properties and likely to deform significantly under load action, by incorporating granular material (commonly called ballast) compacted by remounting passes, so they act mainly as inclusions with a higher stiffness, shear strength than the natural soil. Moreover the stone columns are highly permeable and act as vertical drains facilitating consolidation of the soft soil improving the performance of the foundation. However the characteristics of this granular material influence the behavior of soft soils treated by the stone columns technique, especially: the friction angle, the cohesion, the modular ratio and the constitutive model. The choice of the constitutive model depends on many factors but, in general, it is related to the type of analysis that we intend to perform. Numerical modeling must consider the diversity of the materials nature, the complex geometry of structures-land and the behavior of materials generally nonlinear (permanent deformation). It is a simple and effective alternative to approach the real behavior of soils reinforced by stone columns and the influence of materials characteristics, it allows settlement analysis, lateral deformation, vertical and horizontal stresses in order to understand the behavior of columns and soil. It also has the advantage of integrating the settlements of the underlying layers. This paper aims to study the mechanisms of functioning and interactions of stone columns with the surrounding ground, and vis-à-vis the various parameters characterizing the granular material "ballast" and the surrounding soil, which influence the behavior of the improved soil, The paper presents, in the first part, soil conditions and the parameters associated with columns, is then presented 3D finite element analyses, so the parametric study was carried out varying several properties especially granular material properties.

scholarly journals Ultimate capacity of piles penetrating in weak soil layers

2018 ◽  
Vol 162 ◽  
pp. 01025
Author(s):  
Ahmed Al-Obaidi ◽  
Pinar Mahmood
Keyword(s):  
Soft Soil ◽  
Soil Layer ◽  
Vertical Direction ◽  
Deep Foundations ◽  
Elastic Model ◽  
Ultimate Capacity ◽  
Weak Soil ◽  
Soil Layers ◽  
Dense Sand ◽  
Pass Through

A pile foundation is one of the most popular forms of deep foundations. They are routinely employed to transfer axial structure loads through the soft soil to stronger bearing strata. Piles generally used to increase the load carrying capacity of the foundation and reduce the settlement of the foundation. On the other hand, many cases in practice where piles pass through different layers of soil that contain weak layers located at different depths and extension, also some time cavities with a different shape, size, and depth are found. In this study, a total of 96 cases is considered and simulated in PLAXIS 2D program aiming to understand the influence of weak soil on the ultimate pile capacity. The piles embedded in the dense sand with a layer of weak soil at different extension and location. The cross section of the geometry used in this study was designed as an axisymmetric model with the 15-node element; the boundary condition recommended at least 5D in the horizontal direction, and (L+5D) in the vertical direction where D and L are the diameter and length of pile, respectively. The soil is modeled as Mohr-Coulomb, with five input parameters and the behavior of pile material represented by the linear elastic model. The results of the above cases are compared with the results found in a pile embedded in dense soil without weak layers or cavities. The results indicated that the existence of weak soil layer within the surrounding soil around the pile decreases the ultimate capacity. Furthermore, it has been found that increase in the weak soil width (extension) leads to reduction in the ultimate capacity of the pile. This phenomenon is applicable to all depth of weak soil. The influence of weak layer extension on the ultimate capacity is less when it is presentin the upper soil layers.

scholarly journals ANALISIS KAPASITAS DAYA DUKUNG PADA RAGAM PONDASI BETON BULAT MENGGUNAKAN STANDARD PENETRATION TEST (SPT)

Pondasi ◽  
2021 ◽  
Vol 26 (1) ◽  
pp. 38
Author(s):  
Undayani Cita Sari ◽  
Moh. Nur Sholeh ◽  
M. Mirza Abdilah Pratama ◽  
Ivan James Aritonang ◽  
Febi Danu Prasetya
Keyword(s):  
Bearing Capacity ◽  
Soft Soil ◽  
Physical And Mechanical Properties ◽  
Soil Classification ◽  
Standard Penetration Test ◽  
Empirical Method ◽  
Gis Mapping ◽  
Soil Conditions ◽  
Deep Foundations ◽  
Penetration Test

ABSTRACT One of the field investigations to determine the characteristics of the soil is Standard Penetration Test (SPT). In the SPT test, soil samples can also be obtained, then it can be used to determine the physical and mechanical properties of a soil. Meanwhile, the value of SPT (N-SPT) can be used to determine the bearing capacity of deep foundations. Deep foundations are usually used in high-rise buildings that have large loads with hard soil conditions that are relatively deep. This study analyzes the bearing capacity of spherical concrete pile with various diameters of 70 mm, 80 mm, 90 mm, and 100 mm. In this study, the pile depth was determined at 20 meters. The analysis was carried out using empirical methods and Allpile programming. The location of this study was in the northern part of Semarang. The results show that the diameter has an effect on increasing the bearing capacity. Mapping of the results of the bearing capacity was also presented using GIS. Based on the map, it is found that the lowest bearing capacity is located in the northern part (location of Tanjung Mas Semarang) with soft soil classification. Meanwhile, the highest carrying capacity is shown in Central Semarang with medium soil classification.Keywords: spherical pile, bearing capacity, N-SPT, empirical method, Allpile, GIS mapping  ABSTRAK Salah satu investigasi dilapangan untuk mengetahui karakteristik tanah adalah menggunakan Standard Penetration Test (SPT). Pada pengujian SPT juga dapat diperoleh sampel tanah yang selanjutnya dapat digunakan untuk mengetahui propertis fisik dan mekanis dari suatu tanah. Sementara itu, nilai SPT (N-SPT) dapat digunakan untuk mengetahui kapasitas daya dukung pondasi dalam. Pondasi dalam ini biasanya digunakan pada bangunan bertingkat yang memiliki beban besar dengan kondisi tanah keras yang relatif cukup dalam. Pada studi ini menganalisis hasil kapasitas daya dukung pondasi bulat beton dengan berbagai variasi diameter dari 70 mm, 80 mm, 90 mm, dan 100 mm. Pada studi ini, kedalaman pondasi ditentukan pada 20 meter. Analisis dilakukan menggunakan metode empirik dan pemrograman Allpile. Lokasi tinjauan studi ini adalah pada wilayah Semarang bagian Utara. Hasil menunjukkan diameter pondasi berpengaruh terhadap peningkatan kapasitas daya dukungnya. Pemetaan hasil dari kapasitas daya dukung juga ditampilkan dengan menggunakan GIS. Berdasarkan pemetaan yang dibuat, diperoleh bahwa kapasitas daya dukung terendah terletak di bagian utara (lokasi Tanjung Mas Semarang) dengan klasifikasi tanah lunak. Sedangkan, kapasitas daya dukung tertinggi ditunjukkan adalah di Semarang Tengah dengan klasifikasi tanah sedang. Kata kunci: pondasi bulat, kapasitas daya dukung, N-SPT, metode empirik, Allpile, pemetaan GIS 

scholarly journals Water Table Effects on the Behaviors of the Reinforced Marine Soil-footing System

2021 ◽  
Vol 2 (3) ◽  
pp. 296-305
Author(s):  
Ramin Vali
Keyword(s):  
Finite Element Analysis ◽  
Water Table ◽  
Soft Soil ◽  
Reinforced Soil ◽  
Qeshm Island ◽  
Element Analysis ◽  
Soil Layers ◽  
System A ◽  
The Finite Element Analysis ◽  
Geotechnical Tests

This study evaluates the effects of a water table on the behaviors of a geogrid reinforced soil-footing system on marine soft soil layers in Qeshm Island, Iran. The main aim of this research is to recommend the optimum specification of the reinforced soil-footing system. A series of geotechnical tests were adopted to measure the properties of the soil profile. The impacts of the water table and the geogrid layer specifications were evaluated by the finite element analysis to investigate the system’s behaviors. Finally, the optimal reinforced soil-footing is suggested. Doi: 10.28991/HEF-2021-02-03-09 Full Text: PDF

scholarly journals Checking the site categorization criteria and amplification factors of the 2021 draft of Eurocode 8 Part 1–1

2021 ◽  
Author(s):  
Roberto Paolucci ◽  
Mauro Aimar ◽  
Andrea Ciancimino ◽  
Marco Dotti ◽  
Sebastiano Foti ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Shear Wave ◽  
Ground Motion ◽  
Shear Wave Velocity ◽  
Soft Soil ◽  
Site Amplification ◽  
Soil Conditions ◽  
Eurocode 8 ◽  
Site Specific ◽  
Amplification Factors

AbstractIn this paper the site categorization criteria and the corresponding site amplification factors proposed in the 2021 draft of Part 1 of Eurocode 8 (2021-draft, CEN/TC250/SC8 Working Draft N1017) are first introduced and compared with the current version of Eurocode 8, as well as with site amplification factors from recent empirical ground motion prediction equations. Afterwards, these values are checked by two approaches. First, a wide dataset of strong motion records is built, where recording stations are classified according to 2021-draft, and the spectral amplifications are empirically estimated computing the site-to-site residuals from regional and global ground motion models for reference rock conditions. Second, a comprehensive parametric numerical study of one-dimensional (1D) site amplification is carried out, based on randomly generated shear-wave velocity profiles, classified according to the new criteria. A reasonably good agreement is found by both approaches. The most relevant discrepancies occur for the shallow soft soil conditions (soil category E) that, owing to the complex interaction of shear wave velocity, soil deposit thickness and frequency range of the excitation, show the largest scatter both in terms of records and of 1D numerical simulations. Furthermore, 1D numerical simulations for soft soil conditions tend to provide lower site amplification factors than 2021-draft, as well as lower than the corresponding site-to-site residuals from records, because of higher impact of non-linear (NL) site effects in the simulations. A site-specific study on NL effects at three KiK-net stations with a significantly large amount of high-intensity recorded ground motions gives support to the 2021-draft NL reduction factors, although the very limited number of recording stations allowing such analysis prevents deriving more general implications. In the presence of such controversial arguments, it is reasonable that a standard should adopt a prudent solution, with a limited reduction of the site amplification factors to account for NL soil response, while leaving the possibility to carry out site-specific estimations of such factors when sufficient information is available to model the ground strain dependency of local soil properties.

Evaluation of web reinforcements in prestressed concrete box girders through shear-transverse bending domains

2020 ◽  
pp. 136943322098170
Author(s):  
Michele Fabio Granata ◽  
Antonino Recupero
Keyword(s):  
Analytical Model ◽  
Prestressed Concrete ◽  
3D Analysis ◽  
Box Girders ◽  
Element Analysis ◽  
Cross Sectional ◽  
Interaction Domains ◽  
Global And Local ◽  
Resultant Forces

In concrete box girders, the amount and distribution of reinforcements in the webs have to be estimated considering the local effects due to eccentric external loads and cross-sectional distortion and not only the global effect due to the resultant forces of a longitudinal analysis: shear, torsion and bending. This work presents an analytical model that allows designers to take into account the interaction of all these effects, global and local, for the determination of the reinforcements. The model is based on the theory of stress fields and it has been compared to a 3D finite element analysis, in order to validate the interaction domains. The results show how the proposed analytical model allows an easy and reliable reinforcement evaluation, in agreement with a more refined 3D analysis but with a reduced computational burden.

Sensitivity Analysis of Smoothed Particle Hydrodynamics in PAM-CRASH for Modeling of Soft Soils

2013 ◽  
Author(s):  
Ranvir Dhillon ◽  
Moustafa El-Gindy ◽  
Rustam Ali ◽  
David Philipps ◽  
Fredrik Öijer ◽  
...  
Keyword(s):  
Smoothed Particle Hydrodynamics ◽  
Soft Soil ◽  
Strength Criterion ◽  
Model Parameters ◽  
Rapid Progression ◽  
Element Analysis ◽  
Particle Modeling ◽  
Modeling Techniques ◽  
Particle Hydrodynamics ◽  
Smoothed Particle

The rapid progression of computational power and development of non-mesh particle modeling techniques provides solutions to problems which are not accurately modeled using traditional finite element analysis techniques. The field of soft soil modeling has been pressing on in recent years and the smoothed particle hydrodynamics (SPH) modeling method in PAM-CRASH provides opportunity for further advancement in accuracy. This research focuses on the development of soft soil models using SPH with verification using pressure-sinkage and shear strength criterion. Soil model parameters such as geometry and contact model are varied to determine the effect of the parameters on the behaviour of the soft soil and relationships are developed. The developed virtual soil models are compared against existing soils to determine which soils are accurately modeled and further refinements are made to validate the models with existing empirical data.

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