Performance of Flexible Pavements over Two Subgrades with Similar CBR but Different Soil Types (Silty Clay and Clay) at the FAA's National Airport Pavement Test Facility

2008 ◽  
Author(s):  
Navneet Garg ◽  
Gordon F. Hayhoe
Keyword(s):  
Flexible Pavements ◽  
Test Facility ◽  
Soil Types ◽  
Silty Clay ◽  
Airport Pavement

Subgrade stress ratios as airfield pavement rutting performance indicators

2007 ◽  
Vol 34 (2) ◽  
pp. 189-198
Author(s):  
Kasthurirangan Gopalakrishnan ◽  
Marshall R Thompson
Keyword(s):  
Transfer Functions ◽  
Flexible Pavements ◽  
Federal Aviation Administration ◽  
Flexible Pavement ◽  
Test Facility ◽  
Airport Pavement ◽  
Study Results ◽  
The Us ◽  
Stress Ratios ◽  
New Generation

Rutting is a major distress in airport flexible pavements. Subgrade vertical strain criteria are used in many airport flexible pavement design procedures to consider the development of rutting. Several research studies have identified the limitations associated with these criteria. Design criteria based on subgrade stress ratios (SSRs) are being considered for evaluating subgrade rutting in airport flexible pavements. In this paper, the SSRs based on measured vertical subgrade stresses are related to surface rutting in flexible pavements subjected to repeated trafficking of Boeing 777 and 747 simulated test gears at the US Federal Aviation Administration (FAA) National Airport Pavement Test Facility (NAPTF). The results indicated overstressing of the subgrade in two test sections, and this was confirmed by trench study results. A good correlation was obtained between the SSRs and the surface rut depths, supporting the validity of developing SSR-based rutting transfer functions for airport flexible pavements serving the next generation of aircraft.Key words: rutting, subgrade stress ratio (SSR), National Airport Pavement Test Facility (NAPTF), pressure cell (PC), new generation aircraft, airport flexible pavement.

scholarly journals PREDICTING CAPACITIES OF RUNWAYS SERVING NEW LARGE AIRCRAFT

Transport ◽  
2008 ◽  
Vol 23 (1) ◽  
pp. 44-50 ◽  
Author(s):  
Kasthurirangan Gopalakrishnan
Keyword(s):  
Functional Performance ◽  
Flexible Pavements ◽  
Evaluation Methodology ◽  
Test Facility ◽  
Simplified Approach ◽  
Pavement Surface ◽  
Airport Pavement ◽  
Surface Deflections ◽  
Non Destructive ◽  
Large Aircraft

This paper presents a simplified approach for predicting the allowable load repetitions of New Large Aircraft (NLA) loading for airfield runways based on Non‐Destructive Test (NDT) data. Full‐scale traffic test results from the Federal Aviation Administration's National Airport Pavement Test Facility (NAPTF) were used to develop the NDT‐based evaluation methodology. Four flexible test pavement sections with variable (unbound layer) thicknesses were trafficked using six‐wheel and four‐wheel NLA test gears until the test pavements were deemed failed. Non‐destructive tests using a Heavy Weight Deflectometer (HWD) were conducted prior to the initiation of traffic testing to measure the pavement surface deflections. In the past, pavement surface deflections have been successfully used as an indicator of airport pavement life. In this study, the HWD surface deflections and the derived Deflection Basin Parameters (DBPs) were related to functional performance of NAPTF flexible pavements through simple regression analysis. The results demonstrated the usefulness of NDT data for predicting the performance of airport flexible pavements serving the next generation of aircrafts.

scholarly journals Antioxidant and phytochemical activities of Amaranthus caudatus L. harvested from different soils at various growth stages

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Muhali Olaide Jimoh ◽  
Anthony Jide Afolayan ◽  
Francis Bayo Lewu
Keyword(s):  
Biological Activity ◽  
Biological Activities ◽  
Antioxidant Properties ◽  
Clayey Loam ◽  
Soil Types ◽  
Growth Stages ◽  
Silty Clay ◽  
Clay Loam ◽  
Amaranthus Caudatus ◽  
Different Soils

Abstract This study aimed at profiling the biological activities of Amaranthus caudatus cultivated on different soils in a glasshouse experiment. Five soil types namely; sandy clay loam, silty clay loam, clayey loam, loam and control (unfractionated soil) were experimentally formulated from primary particles of clay, sand and silt following the United State Department of Agriculture’s (USDA) soil triangle technique. After harvesting at pre-flowering (61 days after planting), flowering (71 days after planting) and post-flowering (91 days after planting) stages, crude extracts were obtained with water and ethanol. Total flavonoids, phenolic and proanthocyanidin contents of the extracts, as well as their biological activities, were determined using 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), 2,2 diphenyl-1-picrylhydrazyl ethanol (DPPH), nitric oxide and phosphomolybdate assays. It was observed that biological activity of A. caudatus varied with soil types, stages of maturity and solvents of extraction. The highest phytochemical yield was recorded in ethanolic extracts of clayey loam harvested prior to flowering and the same trend was replicated in the antioxidant properties of the plant. For optimal biological activity, it is recommended that clayey loam soil should be used for cultivation of A. caudatus and harvest should be made near flowering to capture high phytochemical yield from the species.

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