Influence of Fouling and Water Content of Ballast on Railway Substructure Bearing Capacity

2017 ◽  
Author(s):  
A. K. Rohrman ◽  
H. F. Kashani ◽  
C. L. Ho
Keyword(s):  
Slope Stability ◽  
Bearing Capacity ◽  
Water Content ◽  
Strength Properties ◽  
Triaxial Tests ◽  
Repeated Loading ◽  
Layered System ◽  
Modes Of Failure ◽  
Track System ◽  
Track Substructure

The performance of ballasted railway systems is commonly compromised by the infiltration of fine material into the voids of the ballast. This sand and finer grained materials in the ballast is known as fouling. Increased fouling can cause decreases in hydraulic conductivity and shear strength of the ballast, as well as reduce stiffness and resilient modulus of the overall track system. These problems can cause gradual deterioration of the track, which could eventually require maintenance. One of the largest source of fouling comes from ballast breakdown resulting from abrasion caused under repeated loading. This study aims to investigate the effects of fouling from ballast breakdown on the bearing capacity of the substructure that supports the rail superstructure. Previous investigations at the University of Massachusetts Amherst utilized large scale 10-inch (25.4 cm) diameter triaxial tests on granitic ballast with fouling from ballast breakdown. The tests were run with fouling contents of 0% (clean ballast), 15%, and 30% and at water contents varying from dry ballast to field capacity. Confining pressures of 5 psi (34.5 kPa), 10 psi (68.9 kPa) and 15 psi (103.4 kPa) were used in this series of tests. Using the results from these tests, the Mohr-Coulomb strength properties can be determined for each case. This study will make use of the strength properties obtained from the results of these tests and apply them using two commonly used bearing capacity analyses. The first model is the Meyerhof and Hanna Method which considers the track as a continuous footing over a layered system. This model considers two modes of failure; punching of an individual sleeper, and track system bearing. The second model applied is the slope stability method, which uses a two-dimensional limit equilibrium approach and the method of slices to determine a factor of safety against slope stability. This analysis is commonly performed using various software programs. In this study, SLOPE/W from the GeoStudio software package is utilized for analysis. The factors of safety resulting from the bearing capacity analysis using these two methods will be compared for each of the test configurations performed, which will help to confirm the results of the analyses. Since the Mohr-Coulomb strength properties change with the degree of fouling and the water content of the ballast, it is expected that this will have some effect on the bearing capacity of the track substructure. The results of these analyses showing the effects of water content and fouling of ballast on overall track substructure bearing capacity are presented in this paper.

scholarly journals The Influence of Segregation Size of Peat and Pre- Consolidation Pressure on the Effective Shear Strength Properties

2018 ◽  
Vol 250 ◽  
pp. 01013
Author(s):  
Norhaliza Wahab ◽  
Mohd Khaidir Abu Talib
Keyword(s):  
Shear Strength ◽  
Water Content ◽  
Peat Soil ◽  
Confining Pressure ◽  
Strength Properties ◽  
Triaxial Tests ◽  
Consolidation Pressure ◽  
Sieve Size ◽  
Preconsolidation Pressure ◽  
Fiber Size

The degree of composition for peat soil in geotechnical engineering may affected the shear strength of the peat soil based on their types (sapric, hemic and fabric). The strength was affected by many factors such as its origin, water content, organic matter and arrangement of peat fibric. The aims of this paper was to investigate the influence of segregation peat sizes and preconsolidation pressure on the effective shear strength properties of reconstituted peat 1.000 mm (<RS1.00) and reconstituted peat 2.360 RS2.36). All the reconstituted peat samples were segregated through passing opening sieve size 1.00 mm and 2.36 mm with the aid of water to obtain homogeneous reconstituted peat slurry and were preconsolidated with 50 kPa, 80 kPa and 100 kPa pressure to obtain samples for triaxial tests. The Triaxial Consolidated Undrained Test was selected to test the shear strength properties of the reconstituted peat samples by using confining pressure 25 kPa, 50 kPa and 100 kPa. Both of the effective shear strength properties result such as cohesion and angle of friction obtained recorded <RS2.36 has higher strength than <RS1.00. The main factors that contribute to the differences shear strength value between two size reconstituted peats were segregation of peat size which affected by peat size (fiber size) and also pre-consolidation pressure applied which reduced the voids, water content and also improved the stiffness and strength of the specimen. All specimen and testing was conducted at RECESS, UTHM.

Behavior of Mexico City clay subjected to undrained repeated loading

1989 ◽  
Vol 26 (1) ◽  
pp. 159-162 ◽  
Author(s):  
J. Abraham Diaz-Rodriguez
Keyword(s):  
Water Content ◽  
Mexico City ◽  
High Water ◽  
Elastic Behavior ◽  
Triaxial Tests ◽  
High Water Content ◽  
Repeated Loading ◽  
Silty Clay ◽  
Undisturbed Soil ◽  
Very High

This note describes a series of cyclic triaxial tests on undisturbed soil samples of Mexico City clay, obtained near the SCT building. The site is a silty clay deposit of a very high water content and soft consistency. The material exhibits elastic behavior in spite of its very high water content. Three empirical relationships describing an equivalent Young's modulus, an equivalent damping ratio, and a cyclic stress level, associated with cyclic strain level, were obtained. Test results define two different patterns of strength loss. Key words: undrained strength, repeated load, clay, modulus, damping, Mexico City.

scholarly journals Shear strength properties of Hong Kong soils for slope stability

2020 ◽  
Vol 27 (1) ◽  
pp. 48-54
Author(s):  
Hong Yau Wong
Keyword(s):  
Shear Strength ◽  
Hong Kong ◽  
Slope Stability ◽  
Triaxial Compression ◽  
Quantitative Relationship ◽  
Site Investigation ◽  
Standard Penetration Test ◽  
Strength Properties ◽  
Triaxial Tests ◽  
Soil Shear Strength

With the recent advancement in technology, the method, accuracy and speed of slope stability analysis have been vastly improved. Nevertheless, the reliability and appropriateness of such analysis can be very much in doubt if the soil behaviour, in particular the shear strength behaviour, is not fully understood. The objective of this paper is therefore to evaluate the shear strength behaviour of various soil types in Hong Kong. This comprises the collection, processing and analysis of the laboratory and field works carried out in the past few decades, in particular the triaxial compression testing in the laboratory and standard penetration test (SPT) in the field. For correlating SPT with soil shear strength, a fairly large number of carefully controlled site investigation works with SPT are carried out both above and below any Mazier sampling. Laboratory triaxial tests are then carried out in these Mazier samples. Finally, it is hoped that a basically quantitative relationship between soil shear strength and SPT can be obtained as this would enable a soil shear strength profile to be established once the corresponding SPT profile has been determined on site by carrying out SPT in adequate number of drill holes.

Test Study on the Compressive Strength Properties of Compacted Clayey Soil

2016 ◽  
Vol 703 ◽  
pp. 380-385
Author(s):  
Han Bing Liu ◽  
Hu Zhu Zhang ◽  
Jing Wang
Keyword(s):  
Compressive Strength ◽  
Stress State ◽  
Bearing Capacity ◽  
Water Content ◽  
Clayey Soil ◽  
Triaxial Compression ◽  
Quadratic Function ◽  
Confining Pressure ◽  
Strength Properties ◽  
And Function

In order to study the effect of water content, degree of compaction and stress state on bearing capacity of subgrade, the engineering compacted clayey soil was taken as the subject investigated, regulation of compressive strength changing with water content, degree of compaction and confining pressure were analyzed through triaxial compression test, and function relationships between compressive strength and water content, degree of compaction and stress state were fitted based on the test data. Results show that effects of water content, degree of compaction and confining pressure on compressive strength properties of subgrade compacted clayey soil are all remarkably. The compressive strength decreases according to a quadratic function with the increase of water content, as well as increases in accordance with a quadratic function with the increase of the degree of compaction, and increases linearly with the increase of confining pressure. Improving the construction compaction standard properly, adopting the essential lateral confinement measure and keeping a lower water content of the subgrade in service can improve the bearing capacity and stability of the highway subgrade.

scholarly journals Research of the Behavior of Clay Materials with Double Porosity

2021 ◽  
Vol 13 (6) ◽  
pp. 3219
Author(s):  
Hynek Lahuta ◽  
Luis Andrade Pais
Keyword(s):  
Double Porosity ◽  
Strength Properties ◽  
Triaxial Tests ◽  
Building Structures ◽  
Foundation Soil ◽  
Problematic Use ◽  
The North ◽  
Static Liquefaction ◽  
Confinement Stress ◽  
Clay Materials

This contribution presents results from a series of compression and undrained triaxial tests to study the mechanical behavior of dump clay from the north of Bohemia. The use of these materials as a foundation for construction can’t be achieved without the adoption of some precautions. This comes from embankment, formed by digging the ground (altered claystone), up to the level of coal mining which is in a sub horizontal stratigraphic layer. A potential static liquefaction behavior was observed in undrained tests for high confinement stress. A structural collapse was noticed with the results obtained in the triaxial test. This collapse is characterized by an unexpected large decrease in deviator and mean effective stress. The soils formed have strength properties that are potentially dangerous. These concepts can improve the use of these kinds of soils in geotechnical engineering work. It continues and expands the results obtained in previous research, especially the future problematic use of these materials as the foundation soil for line or building structures.

Slope stability and bearing capacity of landfills and simple on-site test methods

2017 ◽  
Vol 35 (7) ◽  
pp. 730-738 ◽  
Author(s):  
Atsushi Yamawaki ◽  
Yoichi Doi ◽  
Kiyoshi Omine
Keyword(s):  
Slope Stability ◽  
Bearing Capacity ◽  
Test Methods ◽  
Site Test

scholarly journals Probability Assessment of Slope Instability in Seasonally Cold Regions under Climate Change

2021 ◽  
Author(s):  
Yulong Zhu ◽  
Tatsuya Ishikawa ◽  
Tomohito J. Yamada ◽  
Srikrishnan Siva Subramanian
Keyword(s):  
Climate Change ◽  
Slope Stability ◽  
Water Content ◽  
Air Temperature ◽  
Climate Changes ◽  
Slope Instability ◽  
Climate Factors ◽  
Cold Regions ◽  
The Past ◽  
Assessment Approach

Abstract This paper proposes an effective approach for evaluating the influences of climate change on slope stability in seasonally cold regions. Firstly, to semi-quantitatively assess the effects of climate changes on the uncertainty of climate factors, this study analyzes the trend of the two main climate factors (precipitation and air temperature) by the regression analysis using the meteorological monitoring data of the past 120 years in different scales (e.g., world, country (Japan), and city (Sapporo)), and the meteorological simulation data obtained by downscaling the outputs of three different regional atmospheric models (RAMs) with lateral boundary conditions from three different general circulation models (GCMs). Next, to discuss the effects of different climate factors (air temperature, precipitation, etc.) and to determine the key climate factors on the slope instability, an assessment approach for evaluating the effects of climate changes on slope instability is proposed through the water content simulation and slope stability analysis using a 2-dimensional (2D) finite element method (FEM) homogeneous conceptual slope model with considering freeze-thaw action. Finally, to check the effectiveness of the above assessment approach, assessment of instability of an actual highway embankment slope with the local layer geometry is done by applying the past and predicted future climate data. The results indicate that affected by global warming, the air temperature rise in some cold cities is more serious. The predicted future weather will affect the shape of the normal density curve (NDC) of the distribution of slope failures in one year. The climate changes (especially the increase in precipitation) in the future will increase the infiltration during the Spring season. It will lengthen the time that the highway slope is in an unstable state due to high volumetric water content, thereby enhancing the instability of the slopes and threatening more slopes in the future.

scholarly journals Settlement and bearing capacity of water-saturated soils of foundations of finite width under static impact

Vestnik MGSU ◽  
2021 ◽  
pp. 463-472
Author(s):  
Zaven G. Ter-Martirosyan ◽  
Armen Z. Ter-Martirosyan ◽  
Ahmad Othman
Keyword(s):  
Bearing Capacity ◽  
Strain State ◽  
Water Saturation ◽  
Strength Properties ◽  
Finite Width ◽  
Stress Strain ◽  
Linear Deformation ◽  
Stress Strain State ◽  
Linear And Nonlinear ◽  
Water Saturated

Introduction. In case of brief exposure to static loads or dynamic loads, in conditions of absence of drainage, distribution of total stresses between the skeleton of soil and pore gas-containing water should be taken in account. The situation of the stress-strain state of the base is further complicated when we consider the degree of water-saturation of soil of the foundation (0.8 < Sr ≤ 1). The aim of the study is to pose and solve problem of the stress-strain state of a water-saturated soil massif, Including settlement and bearing capacity of a water-saturated base of a foundation of finite width, depending on the degree of water saturation of soils, taking into account the linear and nonlinear properties of the skeleton of soil and the compressibility of pore gas-containing water. Materials and methods. Henckyʼs system of physical equations are used as a calculation model to describe the relationship between deformation and stresses of soil, which takes into account the influence of the average stress on the deformation and strength properties of the soil. This system allows us to represent the linear deformation of the soil as the sum of the volumetric and shear components of the soil of this deformation. In addition allows us too to determine the deformation of the layer of soil, as part of the compressible thickness of the base of foundation with finite width under conditions of free deformations. Results. Depending on the linear and nonlinear deformation parameters, the settlement can be developed with a damped curve (S – p) and stabilize, and can be developed with a non-damped curve (S – p) and moved to the stage of progressive settlement. Conclusions. Solutions have been made for cases when the water-saturation of the base soils changes in the range of 0.8 to 1.0. It is shown that the settlement and bearing capacity of a water-saturated base significantly depends on the degree of water saturation of soils.

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