scholarly journals Stability analysis of roadway embankments supported by stone columns with the presence of water table under short-term and long-term conditions

2018 ◽  
Vol 162 ◽  
pp. 01013 ◽  
Author(s):  
Shaymaa Tareq Kadhim ◽  
Ziad Bashar Fouad
Keyword(s):  
Water Table ◽  
Factor Of Safety ◽  
Soft Soil ◽  
Stone Columns ◽  
Stone Column ◽  
Stability Factor ◽  
Short Term ◽  
Long Term Conditions ◽  
The Stability

Use of stone column technique to improve soft foundation soils under roadway embankments has proven to increase the bearing capacity and reduce the potential settlement. The potential contribution of stone columns to the stability of roadway embankments against general (i.e. deep-seated) failure needs to be thoroughly investigated. Therefore, a two-dimensional finite difference model implemented by FLAC/SLOPE 7.0 software, was employed in this study to assess the stability of a roadway embankment fill built on a soft soil deposit improved by stone column technique. The stability factor of safety was obtained numerically under both short-term and long-term conditions with the presence of water table. Two methods were adopted to convert the three-dimensional model into plane strain condition: column wall and equivalent improved ground methods. The effect of various parameters was studied to evaluate their influence on the factor of safety against embankment instability. For instance, the column diameter, columns’ spacing, soft soil properties for short-term and long-term conditions, and the height and friction angle of the embankment fill. The results of this study are developed in several design charts.

Numerical Modeling of Horizontally Layered Geosynthetic Reinforced Encased Stone Columns Supporting Embankment on Sabkha Soil

2021 ◽  
Vol 52 ◽  
pp. 164-178
Author(s):  
Imad Eddine Debbabi ◽  
Mohamed Saddek Remadna ◽  
Ahmad Safuan A Rashid
Keyword(s):  
Lateral Pressure ◽  
Soft Soil ◽  
Research Work ◽  
Stone Columns ◽  
Stone Column ◽  
Weak Zone ◽  
Small Areas ◽  
The Stability ◽  
Weak Zones ◽  
Very High

The present research work is concerned with the construction of road embankments on a Sabkha soil in Algeria. This soil is not only soft and very humid during the flooding seasons but also has frequent small areas of very soft soil which are called locally weak zones (LWZ) in the context of this study. LWZ are characterized by low strength and high compressibility. Two-dimensional axisymmetric analyses were carried out using PLAXIS 2D 2017. The study demonstrated that ordinary stone columns (OSC) are ineffective given the nature of these soils due to the excessive bulging caused by the lack of lateral pressure. On the other hand, the reinforced stone columns with external and internal reinforcements called as vertical encasement and horizontal strips (VESC+HRSC) are one of the best improvement methods of locally weak zones (LWZ), especially to increase the stability of embankment on the highway, namely, a much reduced bulging and a reasonable settlement, so that it is possible to build safe and very high embankments (indeed, numerical results showed for a (VESC+HRSC) combination, a vertical settlement of 0.74 m and a lateral deformation of 20.02 mm vs. 1.56 m and 221.16 mm for an OSC). Besides, an extensive parametric study was conducted to investigate the effect of the spacing of the horizontal reinforcing strips and of the column reinforced length. The influence of stone column diameter, depth of locally weak zone, and the effective stiffness of the geosynthetic, on the performance of the (RSC) - embankment composite were also investigated. The computational results are presented in the form of tables and graphs, and compared with previous published results available in the literature.

Remaking Medicare: The Voucher Myth

1998 ◽  
Vol 28 (1) ◽  
pp. 29-46
Author(s):  
Jonathan Oberlander
Keyword(s):  
Consumer Choice ◽  
Baby Boom ◽  
Market Competition ◽  
The Elderly ◽  
Medicare Beneficiaries ◽  
Short Term ◽  
Medicare Program ◽  
The Stability ◽  
Voucher System

There is growing enthusiasm for transforming Medicare into a voucher system. Advocates claim vouchers would increase the health care choices available to Medicare beneficiaries, reduce the regulatory burden on the federal government, and promote the benefits of fair market competition. In addition, some analysts contend vouchers are the only feasible solution to Medicare's short-term financing problems and the long-term “crisis” of the retirement of the baby-boom generation. The author argues against these claims. Vouchers would not work as advertised by proponents because of the limitations of risk-adjustment methods and unrealistic assumptions about consumer choice. Moreover, the elderly and disabled Medicare population is ill-suited to cope in a competitive insurance system. Implementation of vouchers would therefore pose a threat to both the health of beneficiaries and the stability of the Medicare program. The implications of this analysis for Medicare reform are discussed.

scholarly journals A SLR Pre-Processing Algorithm Based on Satellite Signature Effect

2021 ◽  
Vol 11 (19) ◽  
pp. 8880
Author(s):  
Bowen Guan ◽  
Cunbo Fan ◽  
Ning An ◽  
Ricardo Cesar Podesta ◽  
Dra Ana Pacheco ◽  
...  
Keyword(s):  
Mean Value ◽  
Observation Data ◽  
Short Term ◽  
Error Sources ◽  
Effect Model ◽  
The Mean ◽  
The Stability ◽  
First Time ◽  
Satellite Signature Effect

As one of the major error sources, satellite signature effect should be reduced or even erased from the distribution of the post-fit residuals to improve the ranging precision. A simulation of satellite signature effect removal process for normal point algorithm is conducted based on a revised model of satellite response, which fully considers the structural and distribution characteristics of retroreflectors. In order to eliminate both long-term and short-term satellite signature effect, a clipping method for SLR data processing is proposed by defining the clipping location as 5.6 mm away from the mean value of the long-term fit residuals to select effective returns for normal points. The results indicate that, compared to normal points algorithm, the RMS per NP of LAGEOS-1 observation data processed by the clipping method is reduced from 62.90 ± 9.9 mm to 56.07 ± 4.69 mm, and the stability of RMS is improved 53%. This study improves the satellite signature effect model and simulates the fluctuation of normal points caused by satellite signature effect for the first time. The new method based on the simulation of satellite signature effect has stronger robustness and applicability, which can further minimize the influence of satellite signature effect on the SLR production and significantly improve the data property.

Evolutionary Stable Strategies for Supply Chains: Selfishness, Fairness, and Altruism

2018 ◽  
Vol 6 (6) ◽  
pp. 532-551 ◽  
Author(s):  
Caichun Chai ◽  
Hailong Zhu ◽  
Zhangwei Feng
Keyword(s):  
Supply Chains ◽  
Evolutionary Dynamics ◽  
Replicator Dynamics ◽  
Management Strategies ◽  
Individual Preference ◽  
Short Term ◽  
Evolutionary Stable Strategies ◽  
Pure Strategies ◽  
The Stability

Abstract The management strategies of a firm are inevitable affected by individual behavior preferences. The effect of individual preference on the evolutionary dynamics for supply chains is studied by employing replicator dynamics. Each firm has three behavior preferences: selfishness, fairness, and altruism. Firstly, the case that the strategy set of manufacturers and retailers including two pure strategies is considered and the effect of preference parameter on the equilibrium outcome in the short-term interaction is discussed. Secondly, the equilibrium state in the short-term is always disturbed because the change of the environment, firm’s structure, and so forth. Using the replicator dynamics, the evolutionary stable strategies of manufacturers and retailers in the long-term interaction are analyzed. Finally, the extend case that the strategy set of manufacturers and retailers include three pure strategies is investigated. These results are found that the strategy profile in which both manufacturer and retailer choose fairness or altruism, or one player chooses fair or altruistic strategy and the other player chooses selfish strategy may be evolutionary stable, the stability of these equilibria depends on the the preference parameters.

Fabrication of Boron Compensated Hydrogenated Amorphous Silicon Films with Significantly Improved Stability Using Plasma Enhanced Chemical Vapor Deposition Technique

1995 ◽  
Vol 377 ◽  
Author(s):  
Mohan K. Bhan
Keyword(s):  
Chemical Vapor ◽  
Short Term ◽  
Term Stability ◽  
Long Term Stability ◽  
Vapor Deposition Technique ◽  
Improved Stability ◽  
Donor Acceptor ◽  
B Doping ◽  
The Stability

ABSTRACTWe have systematically investigated the effects of addition of sub-ppm levels of boron on the stability of a-Si:H films and p-i-n devices, deposited by PE-CVD technique. The films thus produced with appropriate amounts of boron, show a significant improvement in stability, when soaked under both AM 1.5 (short-term) as well as 10×sun (long-term) illumination conditions. The opto-electronic properties of the films are quite respectable It is concluded that boron compensates the native impurities by forming donor-acceptor pairs, which reduces the “fast” defects and hence the initial degradation of the films. It is also speculated that boron may also be improving the short-term stability, by reducing the recombination of light generated electrons and holes, by converting D° into D+ states. The long-term stability appears to get affected by hydrogen dilution which seems to reduce the amount of “slow” defects. As a result of B doping of i-layer, the initial conversion efficiency of the devices decreases. It is presumed that our devices may contain an enhanced level of boron impurity, than expected, making them as worse material and to degrade less.

scholarly journals Performance of Polyester-Based Electrospun Scaffolds under In Vitro Hydrolytic Conditions: From Short-Term to Long-Term Applications

Nanomaterials ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 786 ◽  
Author(s):  
Oscar Gil-Castell ◽  
José David Badia ◽  
Jordi Bou ◽  
Amparo Ribes-Greus
Keyword(s):  
Molar Mass ◽  
Pure Water ◽  
Phosphate Buffer Solution ◽  
Short Term ◽  
Buffer Solution ◽  
Electrospun Scaffolds ◽  
The Stability ◽  
Short Time

The evaluation of the performance of polyesters under in vitro physiologic conditions is essential to design scaffolds with an adequate lifespan for a given application. In this line, the degradation-durability patterns of poly(lactide-co-glycolide) (PLGA), polydioxanone (PDO), polycaprolactone (PCL) and polyhydroxybutyrate (PHB) scaffolds were monitored and compared giving, as a result, a basis for the specific design of scaffolds from short-term to long-term applications. For this purpose, they were immersed in ultra-pure water and phosphate buffer solution (PBS) at 37 °C. The scaffolds for short-time applications were PLGA and PDO, in which the molar mass diminished down to 20% in a 20–30 days lifespan. While PDO developed crystallinity that prevented the geometry of the fibres, those of PLGA coalesced and collapsed. The scaffolds for long-term applications were PCL and PHB, in which the molar mass followed a progressive decrease, reaching values of 10% for PCL and almost 50% for PHB after 650 days of immersion. This resistant pattern was mainly ascribed to the stability of the crystalline domains of the fibres, in which the diameters remained almost unaffected. From the perspective of an adequate balance between the durability and degradation, this study may serve technologists as a reference point to design polyester-based scaffolds for biomedical applications.

Theoretical bearing capacity of clay under shallow footings: verifying whether it is realistic

1988 ◽  
Vol 25 (1) ◽  
pp. 62-75
Author(s):  
Robert P. Chapuis ◽  
Vincent Silvestri ◽  
Michel Soulié
Keyword(s):  
Bearing Capacity ◽  
Major Influence ◽  
Clay Material ◽  
Short Term ◽  
Rigid Plastic ◽  
Long Term Conditions ◽  
True Value ◽  
Load Tests ◽  
Failure Conditions

Traditionally, the bearing capacity and the settlement of footings on clay are determined independently by theoretical analyses: the bearing capacity for short-term conditions and the settlement for long-term conditions. Bearing capacity methods usually assume that the clay has a rigid-plastic behaviour and they neglect prefailure deformations. Conventional settlement methods ignore failure conditions. However, field load tests give load–settlement curves in which it is impossible to dissociate settlement and bearing capacity.This paper examines whether the calculated theoretical qult is realistic. A long-term load–settlement curve can be easily calculated using an oedometric equation. The curve of soed/B versus load is a good approximation of the true long-term settlement curve and can be used to determine whether the (short-term) bearing capacity qu is realistic: if soed/B has a high value for a load smaller than the computed qu, it means that this qu is not a valid evaluation of the bearing capacity, the true value of which remains unknown. To establish when conventional analyses give erroneous bearing capacities four cases are analyzed, encompassing the influence of the compressibility of the clay material and the influence of downward groundwater gradients on the compressibility. The results show that groundwater conditions have a major influence upon the bearing capacity of highly compressible, slightly overconsolidated clays but practically no influence upon the bearing capacity of clays of low compressibility. Key words: shallow foundations, clay, deformability, bearing capacity, settlement.

scholarly journals Water table evaluation post the construction of canal blocks on peatland in West Kalimantan, Indonesia

2018 ◽  
Vol 195 ◽  
pp. 03016
Author(s):  
Henny Herawati ◽  
Aji Ali Akbar ◽  
Dwi Farastika ◽  
Azmeri
Keyword(s):  
Water Table ◽  
Agricultural Practice ◽  
Short Term ◽  
Stagnant Water ◽  
Tidal Period ◽  
Water Table Fluctuation ◽  
West Kalimantan ◽  
Evaluation Result ◽  
Canal Network

Creating canal network is the first step to do agricultural practice in wetlands that aims to make the wetland dry. The existence of canal network affects the hydrological function of peat ecosystem in West Kalimantan which leads to drought and peatland fires during dry season. Canal network on peatlands causes the previously stagnant water to flow out easily through the canal. Therefore, a repressive effort is required to maintain water table in peatland. A countermeasure that has been applied to restore peat is by constructing canal blocks on the established canals. The objective of this study was to assess and evaluate changes in water table in peatlands after the construction of a canal block in Wajok Hilir Village, Mempawah Regency, West Kalimantan. Based on the water table evaluation result on peatland with and without blocked canal, it is identified that peatland surrounding blocked canal had smaller water table fluctuation than the peatland surrounding unblocked canal during 1 tidal period. This research concludes that the construction of canal block helps retain water longer in peatland so that water table can be maintained in short term and is expected to restore hydrological function of peatland in the long term.

Estimating long-term settlement of floating stone column groups

2014 ◽  
Vol 51 (7) ◽  
pp. 770-781 ◽  
Author(s):  
J.T. Shahu ◽  
Y.R. Reddy
Keyword(s):  
Finite Element ◽  
Soft Soil ◽  
Group Behavior ◽  
Stone Column ◽  
Finite Element Analyses ◽  
Modified Cam Clay ◽  
Single Column ◽  
Foundation Parameters ◽  
Column Group

Design charts for estimating long-term drained settlement of floating stone column group foundations are presented based on three-dimensional, elastoplastic, finite element analyses. In the analyses, the soft soil behavior is represented by the modified Cam-clay model while the stone column and mat are represented by the Mohr–Coulomb model. The finite element predictions are calibrated against model test results. A detailed parametric study of prototype stone column group foundations of various configurations is carried out to evaluate the relative importance of various foundation parameters on the group response. Next, finite element analyses of corresponding unit cells and single columns are performed. Reasonable correlations of load responses are found between single column and group behavior. Group and single column responses are then used to investigate Sg/S1 relationship with different foundation parameters, where Sg and S1 represent the settlement of the group and single column, respectively.

Failure of a Test Embankment On a Sensitive Champlain Clay Deposit

1974 ◽  
Vol 11 (1) ◽  
pp. 142-164 ◽  
Author(s):  
P. La Rochelle ◽  
B. Trak ◽  
F. Tavenas ◽  
M. Roy
Keyword(s):  
Research Program ◽  
Factor Of Safety ◽  
Soft Clay ◽  
New Approach ◽  
Short And Long Term ◽  
Undrained Strength ◽  
The Stability ◽  
Long Term Behavior ◽  
Test Embankment

The present paper reports on the failure of a test embankment built on a soft, sensitive, and cemented clay in Saint-Alban, Quebec. The embankment was built as a first stage of a research program aimed at studying the short and long term behavior of embankments on soft clay foundations.A complete description of the embankment, of the instrumentation, and of the failure is given, followed by the analysis of the failure performed on the basis of different assumptions of fill behavior and of vane strength values mobilized in the clay crust. The analyses show that the assumptions of full mobilization of friction in the fill seems to be the most representative of the fill behavior in the present case and that a suitable factor of safety is obtained only when a reduction of vane strength is assumed to act in the crust.A new approach based on the residual undrained strength is suggested and seems to offer some potential as a valuable means of analyzing the stability of embankments on clay foundations.

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