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Showing 4 results for Rutting

Saeed Ghaffarpour Jahromi, Ali Khodaii,
Volume 6, Issue 4 (12-2008)

In this study an empirical model which can be used to predict the rutting parameter (G*/sinδ) for neat and powder rubber modified bitumen describes. The model was developed using 36 unique powder rubber modified bitumen combinations, rubber concentrations were varied at 5% intervals between 5 and 20%. The effects of powder rubber particle size on model accuracy were also studied ultimately a model was produced with the capability of predicting rutting parameter values over a range of temperatures and rubber concentrations. By definition, the upper limit of the performance grade is dependent on the rutting parameter value therefore, the relationship was also considered in terms of high end failure temperature. The Rubber Coefficient for rutting parameter (Rcg) was identified as an important parameter in the estimation of rutting parameter (G*/sinδ) with the addition of powder rubber. This term is a quantitative representation of the increase typically witnessed in rutting parameter values with the addition of powder rubber. Ambient ground powder rubber exhibited higher Rcg values than cryogenically ground particles. Additionally, 95% confidence intervals were generated for the predictive model thus providing a range of accuracy for the model. The resulting confidence intervals were approximately +/-1300 Pa these confidence intervals were seen to capture 92.6% of the 462 data points used. Findings from this research suggest that the differences between cryogenic and ambient powder rubber bitumen are accurately described using the Rcg, furthermore bitumen properties may be predicted using an empirical equation.
H. Ziari, H. Divandari,
Volume 11, Issue 2 (6-2013)

Pavement permanent deformations due to lack of shear strength in mixture are a major reason of rutting. Any simple test to determine mixtures resistance to permanent deformation isn’t distinguished in the 1st level of SUPERPAVE mix design method and prevalent methods for evaluating mixture rut resistance are expensive and time-consuming. Two aggregate types, gradations, asphalt cements and filler types were used in this research to present a prediction model for rutting based on flow number. A mathematical model to estimate flow number of dynamic creep test was developed using model parameters and gyratory compaction slope. The model is validated using Neural Network and Genetic Algorithm and makes it possible to evaluate mixtures shear strength while optimum asphalt content is being determined in laboratory. So not only there is no need to expensive test instruments of rutting or dynamic creep but a remarkable time saving in mix design procedure is achievable.
A. Qadir, A. Qadir,
Volume 12, Issue 3 (9-2014)

Rutting in asphalt concrete is a very common form of distress in asphalt concrete pavement which unfortunately has been incurable to date. One of the prime reasons of rutting is attributed to the behaviour of asphalt binder at elevated temperature. This study has investigated the performance of polypropylene fibres modified asphalt concrete mix against rutting. Two types of asphalt concrete samples were prepared namely control samples (those without polypropylene addition) and modified samples (with polypropylene modification). Marshall Mix Design was used for determining the Optimum Asphalt Content for both sample types. Slab asphalt concrete specimens of dimensions 300 mm length and breadth and 50 mm thickness were prepared for both control and modified samples. These samples were then tested in the Wheel Tracking Device for rutting susceptibility test. The samples were tested at four temperatures i.e. 40°C, 50°C, 55°C and 60°C and under the application of 10 000 load passes of 700N of axle load.. The polypropylene fibres were found to increase the Marshall Stability by almost 25%. The fibres were also determined to be effective against rutting at elevated temperatures while the modification was found to increase the Indirect Tensile strength by stiffening the mix at high temperature however at low temperature, the modification failed to perform effectively.
Changjie Xu, Yuanlei Xu, Honglei Sun,
Volume 13, Issue 2 (6-2015)

In soft soil areas, equal-length piles are often adopted in the retaining system. A decrease in the bending moment value borne by the retaining structure along the pile depth (below the excavation bottom), leads to an inadequate use of the pile bending capacity near the pile bottom. This paper presents retaining systems with long and short pile combinations, in which the long piles ensure integral stability of the excavation while the short piles give full play to bearing the bending moment. For further analysis on pile and bottom heaves deformations and inner-force characteristics, three-dimensional models were built in order to simulate the stage construction of the excavation. The ratio between long and short pile numbers, and the effects on short pile length pile horizontal deformation, pile bending moment and bottom heave are investigated in detail. In the end, a feasible long-short pile combination is established. Obtained results from the simulation data and the field data prove that the long-short pile retaining system is feasible.

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