scholarly journals CALCULATION OF VERTICAL DEFORMATIONS OF THE FOUNDATIONS ON THE SOFT SOIL IMPROVED BY GEOTEXTILE ENCASED STONE COLUMNS

2020 ◽  
Vol 11 (3) ◽  
pp. 64-76
Author(s):  
R. I Shenkman ◽  
A. B Ponomaryov
Keyword(s):  
Numerical Modeling ◽  
Soft Soil ◽  
Experimental Studies ◽  
Elementary Cell ◽  
Stone Columns ◽  
Soil Conditions ◽  
Good Convergence ◽  
Engineering Technique ◽  
Calculation Results ◽  
Vertical Deformations

The article provides information on research in the field of improving weak clay bases by installing vertical soil piles in a shell of geosynthetic materials (geotextile encased stone columns). This method has proven to be effective for strengthening the foundations of large areal objects in certain soil conditions, but has not become widespread as a method for improving the foundations of building foundations, which, among other things, is due to the lack of simple engineering methods for calculating the improvement parameters. The article presents an engineering technique for determining the settlement of shallow foundations on a weak clay base which is improved by the geotextile encased stone columns. The technique is based on considering the elementary cell of the improved foundation for which the pressure distribution in the weak soil and the improvement element is determined by the iterative enumeration process. This distribution should ensure equality of the vertical deformations of the improvement element and the soft soil, which should be the same due to the stiffness of the foundation of the building or structure. The calculation of the deformations of a geotextile encased stone columns is carried out by solving the Lamé problem and the deformations of soft soil by standard methods presented in the regulatory literature. Comparison of the calculation results by the proposed method with the data of numerical modeling in an axisymmetric setting is presented. In the numerical modeling of the soil, the Mohr-Coulomb elastic-plastic model was used. Geosynthetic reinforcement was modeled using a special element that only accepts tensile stresses. The rigidity of the foundation of the base is taken to be infinitely large. The analysis of the presented simulation results showed good convergence of the calculations with the data of experimental studies and the data of numerical simulation using the finite element method.

scholarly journals METODE VACUUM CONSOLIDATION DENGAN PRELOADING UNTUK MEMPERCEPAT KONSOLIDASI TANAH PADA PERUMAHAN DI TANGERANG

2021 ◽  
Vol 4 (1) ◽  
pp. 171
Author(s):  
Jason Sastilaya ◽  
Gregorius Sandjaja Sentosa
Keyword(s):  
Pore Water Pressure ◽  
Water Pressure ◽  
Soft Soil ◽  
Drainage System ◽  
Soil Condition ◽  
Soil Improvement ◽  
Soil Conditions ◽  
Soil Plasticity ◽  
Calculation Results ◽  
Long Time

The expansion of housing in big cities cannot be denied given the rapid population growth in Indonesia. One of the areas that is currently expanding housing is Kosambi City, Tangerang. Soil conditions in Kosambi City are soft soil with high moisture content and soil plasticity, low permeability and soil bearing capacity, and high pore water pressure. This soft soil condition makes the consolidation decline take a very long time. To overcome the problem of the length of time for this consolidation settlement, it is necessary to improve the land. Soil improvement is being carried out, namely the method of vaccum consolidation with preloading. The combination of these methods is carried out by installing a vertical drainage system in the form of prefabricated fabricated drain (PVD) in soft soil, then the initial load is given in the form of preloading on the soil. The calculation results show that the amount of consolidation reduction that occurs when clay soil is loaded with a stockpile of 1.2 m high, a water surcharge of 1.3 m and a vaccum load is 0.3929 m and 0.6968 m for 85 years. The combined method of preloading and PVD is proven to be able to accelerate the time of consolidation, where Preloading and PVD are installed in a triangle pattern between 0.80 m to a depth of 12 m, capable of achieving a consolidation degree of 90% within 8 weeksPerluasan perumahan di kota besar tentu tidak dapat dipungkiri mengingat pesatnya pertumbuhan penduduk di Indonesia. Salah satu daerah yang sedang dilakukan perluasan perumahan yaitu Kosambi City, Tangerang. Kondisi tanah di Kosambi City merupakan tanah lunak dengan kadar air dan plastisitas tanah yang tinggi, permeabilitas dan daya dukung tanah yang rendah, serta tingginya tekanan air pori. Kondisi tanah lunak ini membuat penurunan konsolidasi membutuhkan waktu yang sangat lama. Untuk mengatasi masalah lamanya waktu penurunan konsolidasi ini, perlu dilakukan perbaikan tanah. Perbaikan tanah yang dilakukan yaitu metode vaccum consolidation dengan preloading. Kombinasi pada metode ini dilakukan dengan cara memasang sistem drainase vertikal berupa prefabricated fabricated drain (PVD) di dalam tanah lunak, kemudian diberikan beban awal yaitu berupa timbunan (preloading) pada tanah tersebut. Hasil perhitungan menunjukkan besar penurunan konsolidasi yang terjadi jika tanah lempung dibebani dengan timbunan setinggi 1,2 m, water surcharge setinggi 1,3 m dan beban vaccum  adalah 0,3929 m dan 0,6968 m selama 85 tahun. Metode kombinasi preloading dan PVD terbukti mampu mempercepat waktu konsolidasi, dimana Preloading dan PVD dipasang dengan pola segitiga berjarak 0,80 m hingga kedalaman 12 m, mampu mencapai derajat konsolidasi 90% dalam waktu 8 minggu. 

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 Geosynthetic Encased Columns Supporting Rail Infrastructure – Perspectives on Research and Case Studies

2020 ◽  
Author(s):  
Erol Guler ◽  
Cihan Cengiz ◽  
Oliver Detert
Keyword(s):  
Case Studies ◽  
Ground Improvement ◽  
Soft Soil ◽  
Academic Research ◽  
Major Effect ◽  
Economic Benefits ◽  
Shaking Table ◽  
Stone Columns ◽  
Soil Conditions ◽  
Rail Network

Significant investments are being made towards enhancing the reach of the railway infrastructure due to the vast economic benefits it brings. An inevitable consequence of the expansion of the rail network is the soft soil conditions encountered in the alignment. Geosynthetic encased columns (GEC) is a proven ground improvement technology which can be adapted as soil remediation technique for such conditions. In this paper, first an introduction to the concept of GECs will be given. Then the recent advances in the academic research on the GECs will be elaborated. As it is known, earthquakes are one of the most devastating disasters and certainly also have a major effect on transportation infrastructure. In this paper results of shaking table tests to compare ordinary stone columns and GECs behavior under earthquake loading conditions will also be presented. The brief recap of the state of the art on the geosynthetic encased columns including their earthquake behavior will be followed by case studies on three major projects where the site conditions and project requirements will be discussed. The significant benefits of geosynthetic encased columns in relation to project requirements will also be elaborated.

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 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.

Reducing Settlement of Foundation on Soft Soil Ground Using Structural Piles and Stone Columns

2017 ◽  
pp. 537-541
Author(s):  
C. Zhou ◽  
J. H. Yin ◽  
T. L. Chen ◽  
S. S. Chen ◽  
J. P. Ming
Keyword(s):  
Soft Soil ◽  
Stone Columns

scholarly journals Research of transient processes in case of single-phase insulation faults in low-voltage ship power grids, taking into account the resistance at the fault point

2020 ◽  
pp. 49-54
Author(s):  
И.Е. Кажекин
Keyword(s):  
Single Phase ◽  
Low Voltage ◽  
Experimental Studies ◽  
Power Grids ◽  
Transient Processes ◽  
Safety Issues ◽  
Physical Experiments ◽  
Marine Industry ◽  
Calculation Results ◽  
Constant Potential

В работе рассмотрены вопросы безопасности бортовых электросетей объектов морской индустрии, показано влияние перенапряжений на их основные показатели, которыми определяются опасности смертельных электротравм, опасности возникновения пожаров и взрывов. Представлены результаты математического моделирования электрического разряда по уравнению Майра с учетом особенностей переходного процесса при однофазных замыканиях на корпус. Показана роль напряжения смещения нейтрали по постоянному потенциалу, наибольшие значения которого формируются при неустойчивом контакте фазы с корпусом судна. Описаны результаты экспериментальных исследований переходных процессов, сопровождающихся возникновением неустойчивыми искровыми разрядами. Сравнение результатов расчета по предложенной методике с результатами физических экспериментов показало весьма удовлетворительную сходимость. Предложенная модель может быть использована для уточнения показателей, характеризующих безопасность судовых электросетей. The paper deals with the safety issues of on-board power grids of the marine industry facilities, shows the influence of overvoltages on their main indicators, which determine the dangers of fatal electrical injuries, the risk of fires and explosions. The results of mathematical modeling of an electric discharge according to the Mayr equation, taking into account the features of the transient process in single-phase short circuits to the case, are presented. The role of the bias voltage of the neutral at a constant potential is shown, the highest values ​​of which are formed during unstable contact of the phase with the ship's hull. The results of experimental studies of transient processes accompanied by the appearance of unstable spark discharges are described. Comparison of the calculation results by the proposed method with the results of physical experiments showed a very satisfactory convergence. The proposed model can be used to refine the indicators characterizing the safety of ship power grids.

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