To study and predict the behavior of flexible pavement over expansive soils, a pavement structure... more To study and predict the behavior of flexible pavement over expansive soils, a pavement structure was subjected to different laboratory and fieldwork experiments. The existing pavement was replaced and designed based on California Bearing Ratio (CBR) method, with a new one, and subjected to the traffic from various number of load cycles from 12.1 up to 155.52 kcycles of standard axle load (80 kN) through dual wheel assembly over a 6-month period. As the preliminary step, the deflection measurements were taken at the asphalt surface layer, using a Total station at different distances as function of truckload applications. The numerical analysis is carried out with the Finite Element software package PLAXIS version 2012. In the new model, the calculation of the transferred pressure to the pavement through contact area of tires is 3D it was turned into a 2D problem, and the pavement was subjected to a static loading using a ratio factor of dynamic additional charge. The materials' behavior was simulated with nonlinear models: Mohr-Coulomb (MC) for pavement layers and soft-soil model (SSM) for the expansive subgrade, in saturated drained and undrained conditions. The results indicate that displacements under static loading in saturated drained conditions and when non-linear materials are present are the closest to field measured deflections.
Predicting the swelling pressure (Ps) in subgrades constitutes a new approach in pavement structu... more Predicting the swelling pressure (Ps) in subgrades constitutes a new approach in pavement structural design. It is shown, however, that current conventional testing programs could lead to erroneous results. Several approaches to estimate Ps have so far been proposed; yet, no universally accepted method has been suggested. In this study, 40 subgrade soil samples taken from a route in Tebessa city (Algeria) were subjected to different laboratory tests. Values of free swelling pressure were measured by using an odometer. A statistical model capable of indirectly estimating Ps is provided. The model is based on a correlation of Ps with dry density ($$\rho _{\mathrm{d}})$$ρd), water content (w) and plastic limit, and has been checked by variance inflation factors method to examine multicollinearity. The proposed equation demonstrates a high correlation coefficient ($$R^{2})$$R2) of 0.887 when compared to the direct laboratory results. Excellent estimation capability was achieved using th...
This investigation discusses the findings on analysis results of a pavement structure constructed... more This investigation discusses the findings on analysis results of a pavement structure constructed on a relatively expansive material consisting mainly of brown clayey silt in Tebessa, Algeria. Cores were taken to laboratory from a piece of roadwork. Remolded samples were taken from subgrade of a deteriorated road. The soils were generally found to be of medium plasticity and of a medium to high expansion potential. Oedometer test for free swell indicated a constant volume pressure that produced stress in excess of 350 kN/m2. The following involves description of the behavioral characteristics of expansive soil as it relates to flexible pavements. Computer code Plaxis 8.2 was used for numerical simulation to check the behavior of structure pavement with three models in pavement structure, and free expansion test was performed to calibrate the soil subgrade with Soft-Soil Model. The results showed that the combined model Mohr-Coulomb in the pavement structure and the Soft-Soil in subgrade accord perfectly with deformations taken on the existing pavement. To stabilize the swelling character of subgrade, an adequate surcharge pressure is used according to the procedure described in the paper. It showed that after 9 months, the deformations have been stabilized at -0.007 m without any cracks in the pavement.
To study and predict the behavior of flexible pavement over expansive soils, a pavement structure... more To study and predict the behavior of flexible pavement over expansive soils, a pavement structure was subjected to different laboratory and fieldwork experiments. The existing pavement was replaced and designed based on California Bearing Ratio (CBR) method, with a new one, and subjected to the traffic from various number of load cycles from 12.1 up to 155.52 kcycles of standard axle load (80 kN) through dual wheel assembly over a 6-month period. As the preliminary step, the deflection measurements were taken at the asphalt surface layer, using a Total station at different distances as function of truckload applications. The numerical analysis is carried out with the Finite Element software package PLAXIS version 2012. In the new model, the calculation of the transferred pressure to the pavement through contact area of tires is 3D it was turned into a 2D problem, and the pavement was subjected to a static loading using a ratio factor of dynamic additional charge. The materials' behavior was simulated with nonlinear models: Mohr-Coulomb (MC) for pavement layers and soft-soil model (SSM) for the expansive subgrade, in saturated drained and undrained conditions. The results indicate that displacements under static loading in saturated drained conditions and when non-linear materials are present are the closest to field measured deflections.
Predicting the swelling pressure (Ps) in subgrades constitutes a new approach in pavement structu... more Predicting the swelling pressure (Ps) in subgrades constitutes a new approach in pavement structural design. It is shown, however, that current conventional testing programs could lead to erroneous results. Several approaches to estimate Ps have so far been proposed; yet, no universally accepted method has been suggested. In this study, 40 subgrade soil samples taken from a route in Tebessa city (Algeria) were subjected to different laboratory tests. Values of free swelling pressure were measured by using an odometer. A statistical model capable of indirectly estimating Ps is provided. The model is based on a correlation of Ps with dry density ($$\rho _{\mathrm{d}})$$ρd), water content (w) and plastic limit, and has been checked by variance inflation factors method to examine multicollinearity. The proposed equation demonstrates a high correlation coefficient ($$R^{2})$$R2) of 0.887 when compared to the direct laboratory results. Excellent estimation capability was achieved using th...
This investigation discusses the findings on analysis results of a pavement structure constructed... more This investigation discusses the findings on analysis results of a pavement structure constructed on a relatively expansive material consisting mainly of brown clayey silt in Tebessa, Algeria. Cores were taken to laboratory from a piece of roadwork. Remolded samples were taken from subgrade of a deteriorated road. The soils were generally found to be of medium plasticity and of a medium to high expansion potential. Oedometer test for free swell indicated a constant volume pressure that produced stress in excess of 350 kN/m2. The following involves description of the behavioral characteristics of expansive soil as it relates to flexible pavements. Computer code Plaxis 8.2 was used for numerical simulation to check the behavior of structure pavement with three models in pavement structure, and free expansion test was performed to calibrate the soil subgrade with Soft-Soil Model. The results showed that the combined model Mohr-Coulomb in the pavement structure and the Soft-Soil in subgrade accord perfectly with deformations taken on the existing pavement. To stabilize the swelling character of subgrade, an adequate surcharge pressure is used according to the procedure described in the paper. It showed that after 9 months, the deformations have been stabilized at -0.007 m without any cracks in the pavement.
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