Effect of FWD Testing Position on Modulus of Subgrade Reaction

2014 ◽  
Vol 518 ◽  
pp. 53-59 ◽  
Author(s):  
S.N. Shoukry ◽  
G.W. William ◽  
M.Y. Riad ◽  
J.C. Prucz
Keyword(s):  
Temperature Gradient ◽  
Early Morning ◽  
Slab Thickness ◽  
Positive Temperature ◽  
Falling Weight Deflectometer ◽  
Subgrade Reaction ◽  
K Value ◽  
Modulus Of Subgrade Reaction ◽  
Late Evening ◽  
Falling Weight

This paper discusses the variation of the Modulus of subgrade reaction (k) backcalculated from slab deflection basins, interactive with the location of the Falling Weight Deflectometer (FWD) load pulse, and curling of slabs due to daily temperature variations. The k-value was calculated following the AASHTO design guides procedures, while deflection basins were recorded at an interval of 3 to 4 hours along the day on an instrumented concrete pavement test section in West Virginia. The state of deformation of the slabs are continuously monitored, through dowel bar bending measurements and records of the temperature gradient profiles through the slab thickness, as well as joint openings every 20 minutes. The results indicated that the backcalculated k-values are greatly affected by the positive temperature gradient, and the least variation in (k) was found in the slab center. In order to minimize errors in back-calculations of k-values, it is recommended to perform the FWD test for recording deflection basins in the interior of the slab during late evening or in the early morning.

DIPLOBACK: Neural-Network-Based Backcalculation Program for Composite Pavements

1997 ◽  
Vol 1570 (1) ◽  
pp. 143-150 ◽  
Author(s):  
Lev Khazanovich ◽  
Jeffery Roesler
Keyword(s):  
Neural Network ◽  
Winkler Foundation ◽  
Multilayer Composite ◽  
Falling Weight Deflectometer ◽  
Subgrade Reaction ◽  
Elastic Parameters ◽  
The Neural Networks ◽  
Elastic Layers ◽  
Falling Weight ◽  
Moduli Of Elasticity

A neural-network-based backcalculation procedure is developed for multilayer composite pavement systems. The constructed layers are modeled as compressible elastic layers, whereas the subgrade is modeled as a Winkler foundation. The neural networks are trained to find moduli of elasticity of the constructed layers and a coefficient of subgrade reaction to accurately match a measured deflection profile. The method was verified by theoretically generated deflection profiles and falling weight deflectometer data measurements conducted at Edmonton Municipal Airport, Canada. For the theoretical deflection basins, the results of backcalculation were compared with actual elastic parameters, and excellent agreement was observed. The results of backcalculation using field test data were compared with the results obtained using WESDEF. Similar trends were observed for elastic parameters of all the pavement layers. The backcalculation procedure is implemented in a computer program called DIPLOBACK.

Analytical Solutions and Derivation of Relative Permeabilities for Water-Heavy Oil Displacement and Gas-Heavy Oil Gravity Drainage Under Non-Isothermal Conditions

2016 ◽  
Vol 19 (01) ◽  
pp. 181-191 ◽  
Author(s):  
F. J. Argüelles-Vivas ◽  
T.. Babadagli
Keyword(s):  
Temperature Gradient ◽  
Relative Permeability ◽  
Heavy Oil ◽  
Variable Temperature ◽  
Spontaneous Imbibition ◽  
Analytical Models ◽  
Gravity Drainage ◽  
Positive Temperature ◽  
Relative Permeability Curves ◽  
Isothermal Gas

Summary Analytical models were developed for non-isothermal gas/heavy-oil gravity drainage and water-heavy oil displacements in round capillary tubes including the effects of a temperature gradient throughout the system. By use of the model solution for a bundle of capillaries, relative permeability curves were generated at different temperature conditions. The results showed that water/gas-heavy oil interface location, oil-drainage velocity, and production rate depend on the change of oil properties with temperature. The displacement of heavy oil by water or gas was accelerated under a positive temperature gradient, including the spontaneous imbibition of water. Relative permeability curves were greatly affected by temperature gradient and showed significant changes compared with the curves at constant temperature. Clarifications were made as to the effect of variable temperature compared with the constant (but high) temperatures throughout the bundle of capillaries.

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