Inadequate subgrade conditions, improper design and construction, and unpredicted increases in traffic demand contribute to premature pavement failures. Particularly when weak subgrades are encountered
and good construction materials become scarce, pavement design becomes a challenge.
The studies at IITH focus on conducting a series of large-scale model experiments to obtain MIF values for different geogrid and geocell-reinforced bases built on various subgrade conditions. Then, MIF-based models were developed for base-layer coefficients for geogrid- and geocell-reinforced pavements when checking the pavement sections for fatigue and rutting failure modes. The MIF values ranged between 1.5 and 3.5 for geogrid-reinforced bases placed over different subgrade conditions.
This study aims at understanding the influence of different geosynthetic reinforcements on the fatigue performance of asphalt layers and the corresponding mechanisms involved. Three different types of geosynthetic reinforcement, a polypropylene geogrid (PP), a coated polyester geogrid and a glass geogrid composite (GGC), were employed to understand the fatigue behavior of asphalt layers via an asphalt beam fatigue test (ABFT) along with the use of digital image correlation (DIC) techniques.
The ABFT results suggest that incorporating geosynthetic reinforcement in the asphalt layers improved the fatigue performance by factors of 11, 27, and 38 for the PP, PET, and GGC specimens, respectively. With the aid of DIC, the mechanisms involved in enhancing the fatigue performance of asphalt layers were effectively evaluated.
Reductions in layer thickness for the geosynthetic-reinforced asphalt layers on the order of 5.9% (PP),
17.6% (PET), and 23.5% (GGC) were established for the geosynthetics evaluated in this study based on
test results adopted in a design example.
This study aims to assess the long-term performance of an alkali-activated fly ash (FA) stabilized reclaimed asphalt pavement (RAP) when utilized as a base course in a full-scale experimental test section. The test results showed that the alkali activation using the liquid alkaline activator significantly improved the mechanical strength, stiffness, and durability of the mixtures.
An experimental test section was designed and constructed on a state highway to evaluate the long-term performance under actual traffic and climatic conditions using horizontal inclinometers and surface profiles. No sign of any distress was observed throughout the monitoring period of 5 years. A comprehensive cost–benefit analysis was performed, which demonstrated that the FRB section could reduce the overall construction cost by approximately 17% while decreasing the total pavement thickness by about 21%. The embodied carbon for the FRB section was estimated to be 30% less than the equivalent cement-treated RAP base for a comparable mechanical strength.
Drainage is one of the primary factors considered during the design of pavements. This study presents the data from large-scale permeameter tests conducted on pavement sections to evaluate the drainage characteristics of geocomposite (GC) embedded GSB layers with and without traffic load. The large-scale permeameter test results indicate that the in-plane drainage capacity of the subbase layer improved by about 12 and 22 fold, respectively, for 2D GC and 3D GC. The GCs can drain infiltrated water at a rate of more than 300 m/day, even if the thickness of the subbase layer is reduced by about 50%. Over the pavement’s design life, long-term in-plane permeability is estimated to decrease by 65–70%. It is estimated that the GC-embedded subbase layers could drain off 50% of the infiltered water from a two-lane pavement system within 2 h, even after reducing the layer thickness by 100 mm. A set of new drainage coefficients for geocomposite improved subbase layers (m3c) were proposed based on the American Association of State Highway and Transportation Officials drainage quality guidelines.
learn moreAutonomous Vehicles (AVs) have stepped up efforts to become the automobiles of the future. In terms of productivity, AVs are superior to Human-driven Vehicles (HVs). Current road infrastructure is believed to be unsuitable for AVs; autonomous vehicles may pose different challenges to pavement structures as they are not engineered to accommodate such novel classes of vehicles. Using a 3D finite element model, the present study simulates the wheel load movement of an autonomous vehicle attempting to maintain its position in the centre of a given lane for safety and fuel efficiency reasons. The 3D model adopts a single wide wheel and takes into account the influence of tyre contact width and the contact tyre pressure on the road with different numbers of wheel passages. The results discuss the influence of speed on the development of road damage stresses and strains at 40 and 80 kmph.
learn moreA landslide can be defined as the movement of a mass of rock, Earth, or debris down a slope. The occurrence and effects of landslides are an issue that affects the entire world and are constantly growing due to unpredictable extreme events and the exposure of people to climatic whims in the mountains. Landslides pose a threat to human life, man-made facilities, property, infrastructure, and the natural environment.
learn more This study investigated the effect of gradation, especially of mean particle size and uniformity of gradation, on the shear modulus degradation of natural marine sands compared to regraded clean sands. A series of fixed-free resonant column tests were performed on graded clean sands and marine sands having similar uniformity coefficient values, Cu. It is observed that the modulus degradation of both clean sands and marine sands increased with the increase in Cu. However, the marine sands have
degraded less than clean sands for the same Cu and effective confining stress. The reasons can be attributed to the non-linearity in the grain size distribution of marine sands above 60% finer and mean particle size, D50 compared to graded clean sands. The overestimation of the modulus degradation of marine sands by the existing empirical equations is demonstrated. A generalized calibrated modulus degradation model for a wide range of clean sands and marine sands is proposed with a high coefficient of determination.
A series of large-scale model experiments were carried out on different geocell reinforced base courses to evaluate realistic base layer coefficients to design flexible pavements. Initially, the modulus improvement factor (MIF) for geocell-reinforced bases were establised for varying subgrade conditions. The MIF values ranged between 1.4 to 5.0 for geocell-reinforced base layers placed over different subgrade conditions. Further, a range of laboratory-produced MIF values and semi-empirical mechanistic design principles were used to analyze the flexible pavements to obtain the base layer coefficients. The traffic was considered from 2 to 150 million equivalent single axle loads, subgrade resilient modulus (Mrs)from 10 MPa to 85 MPa, and MIF from 1.2 to 5.0 for geocells. A new set of base layer coefficients for geocell-supported base layers ranged from 0.175 to 0.425. The proposed models were validated with an as-built pavement section from Montana state and the available design approaches.
learn more Deep soil mixing (DSM) is a ground improvement technique to stabilize weak soils up to intended depths. The traditional binders, lime and cement, pose an environmental concern due to their high energy consumption and CO2 emissions during processing. In this study, an alkali-activated fly ash, as a replacement for cement, was used as a binder.
A scale-model deep soil mixing rig was developed at IITH to simulate the field conditions and different installation patterns. It was demonstrated that the model DSM columns could exactly mimic the full-scale columns and their performance. For more information, please see the published articles.