Conference Agenda

Asphalt pavements lose their bearing capacity when rainwater infiltrates the base course through cracked and damaged areas in the surface course and binder course. The decrease in base course bearing capacity causes progressive damage because of base course defor-mation, resulting in early deterioration of the entire pavement structure. Major pavement repairs have been limited to cutting overlays because the cost of pavement maintenance and repair notably drops with increased road stock volume. Thus, an experimental study was conducted to improve the base course durability of asphalt pavement by laying geo-textiles to extend the long life of road pavements. As a result, geotextile was found to suppress the reduction of base course bearing capacity even when rainwater infiltrated the pavement.

Plate load test (PLT) is used frequently to evaluate the elastic modulus (EPLT) of soils; however, this test is cumbersome, time-consuming and requires huge setup for reaction force. While Light Weight Deflectometer (LWD) devices are emerging in earthwork quality control to swift evaluate the deformation modulus (ELWD) and non-destructive in nature. ELWD play a vital role as an input parameter for the design of infrastructure projects. It is decisive to comprehend the effect of plate contact pressures on the measurements of ELWD for the considered two plate contact pressures and elastic modulus (EPLT) from PLT for both unreinforced and reinforced sandy soil cases is the focus of this study. To successfully implement the use of LWD testing to replace plate load test (PLT), the correlations were proposed in terms of modulus improvement factors (MIF) of reinforced sandy soils and both test results are in good agreement.

<p>Construction of transport structures on a weak base causes a lot of problems for designers and builders. It is always associated with high costs and significantly increases the production time. The methods for design and construction of high embankments on weak bases of geocell mattresses using geogrids have been developed and are successfully used in Ukraine. During construction of the road embankment near the bridge over the railway in Reni, Ukraine, geocell mattresses were used over the section of more than 5 km. The silted marshland, overgrown with reeds, could not serve as a good foundation for the 11 m high embankment. Difficult hydrogeological conditions and the threat of constant floods prompted to use the geocell mattress technology, which made it possible to reduce the cost and time of construction. Using the program "TensarSlope" version 1.13, the following types of calculations were performed: calculation of the overall stability of the embankment with the geocell mattress at its base with and without the seismic impact; calculation of the settlement of the foundation with reinforcement with the geocell mattress; calculation of consolidation of the base of the embankment reinforced with the flat mattress, etc. The total settlement of the soil layers No. 4 and No. 5 was 0.9 cm/year, which made it possible to build the 11 m high road embankment made of geocell mattresses in accordance with requirements of the building codes in force in Ukraine. After the embankment was reinforced with the geocell mattresses, the following was achieved: the total settlement of the embankment base was reduced by 30%; the calculated resistance of the base soil was increased by 25%; the bearing capacity of the base was increased by 33%. This effect was obtained due to reinforcement of the embankment soil with geocell mattresses and their interaction with the embankment soil.</p>

<p>Geosynthetic reinforcement of asphalt layers has been used for almost several decades but to this day a proper evaluation of influence of these materials on pavement fatigue life is still challenging task, especially for new types of geogrids composites. This paper presents the evaluation of fatigue performance of large sized asphalt concrete beams reinforced with new type of geogrid composite in which hexagonal (multiaxial) polypropylene stiff monolithic paving grid with integral junctions is bonded to the polypropylene non-woven paving fabric. Non reinforced samples were used as a reference. Fatigue testing was per-formed in the scheme of four-point bending test (4PB-PR) in the controlled strain mode at the constant temperature of +13°C and frequency of 1Hz. The specimens width (170 mm) was selected on the assumption that asphalt layers should cover at least 2 full hexagon pitches of multiaxial geogrid. The distance between axes of the end supports equalled to 740 mm. The distance between axes of the loading supports equalled 247 mm. Test results were analysed in several aspects, including the standardized approach based on stiffness reduction but also with the use of critical strain at one million cycles. The effect of the notch on the fatigue life and the ability of the reinforcement to crack propagation delay was also analysed. Based on the ε6 critical strain, reinforced samples result in an increase of the critical strain from 30% (notched) to 40% (un-notched).</p>

<p>Road cave-ins associated with hidden cavities are one of key issues in road maintenance. Field model tests were carried out to develop and improve methods of detection, diagnosis, and repair of hidden cavities at the prototype scale test road, 30 m long and 6 m wide, constructed in the Saitama University campus. The test road consisted of 100 mm surface course (straight asphalt), 250 mm upper base course with M-30 graded crushed stones, 100 mm lower base course with C-40 graded crushed stones, and 200 mm subgrade with decomposed granite sandy soil. Hidden cavities were made artificially by burying bags filled with fine gravel in well-compacted base course layers. Fine gravel was removed by a vacuum cleaner after the completion of the surface course. FWD tests and plate loading tests were carried out to investigate stability of hidden cavities in base course. This paper reports stability of hidden cavity in base course layer. Factors affecting the stability of cavity, such as pavement structure, depth of cavity, and temperature, are discussed.</p>

<p>A series of laboratory model tests were also carried out to investigate the effect of type of geosynthetics and their depth in the base course on the stability.</p>

The incorporation of geosynthetic interlayers during the asphalt overlay construction has proven successful in mitigating the reflective cracking and enhancing the pavement structural capacity. However, milling an asphalt layer reinforced with geosynthetic interlayer is a huge concern, since there is a possibility of geosynthetic interlayers compromising the reclaimed asphalt pavement (RAP) quality and characteristics. On the other hand, inclusion of RAP into the hot mix asphalt (HMA) is a common practice. Hence, it is important to understand the characteristics of RAP collected from geosynthetic-reinforced asphalt layers (referred herein as GRAP) and their influence on the performance of asphalt mixtures. The objective of this study is to understand the characteristics of GRAP and subsequently, investigate the performance of asphalt mixtures with 15 % and 30 % GRAP contents. Additionally, the performance of asphalt mixtures with 15 % and 30 % RAP contents, and 100 % virgin aggregates (referred as control mixture) was evaluated for comparison with that of asphalt mixtures combining GRAP. The characterization of GRAP and RAP included particle size gradation and binder extraction tests, while the performance evaluation of the asphalt mixtures included indirect tensile strength, and moisture susceptibility tests. Comparison of binder extraction test results revealed that the GRAP samples had binder content slightly higher than that of the RAP samples. While the comparison of indirect tensile strength and moisture susceptibility test results indicated the performance of asphalt mixtures with GRAP similar to that with RAP, where both mixtures out-performed the asphalt mixtures made solely of virgin aggregates. This indicates the potential of incorporating GRAP and RAP up to 30 % into the asphalt mixtures without compromising the performance of asphalt mixtures.

<p>Geogrids are used to reinforced and stabilise the roads and improve the bearing capacity of pavements on soft subgrades. Additionally, geogrids installed within granular layer of a pavement formation are frequently used to control environmental distress and limit longitudinal cracking due to expansive subgrades by providing the stiffening, known as the new function of geosynthetic material to control deformations in the soil-geosynthetic composite.</p>

<p>In order to quantify the effect of geogrid reinforcement / stabilisation, a full-scale pavement field trial was established upon a soft and expansive subgrade in 2018. Sections with variable geogrid arrangements were constructed in order to allow the quantitative assessment of geogrid reinforcement/stabilisation; both in terms of their initial contribution to composite insitu stiffness parameters and their benefit to the long-term performance of a pavement.</p>

<p>On site testing was completed within all trial sections during the project’s construction phase, such that the initial state (strength and stiffness) of the subgrade and each pavement layer was adequately characterised. Post construction, ongoing performance monitoring has included the use of embedded pressure cells.</p>

<p>An analysis of the first 3 years of monitoring of this full-scale field trial was conducted, with selected results presented herein. The data demonstrates that the inclusion of geogrids successfully improves the bearing capacity of the pavement profile by reducing the traffic imparted vertical pressures being exerted upon the underlying materials. The results also demonstrate that the presence of two geogrid layers (with one placed at the subgrade-subbase interface and one at the subbase-base interface) offer a greater improvement of the bearing capacity than the installation of a single geogrid at the interface of subgrade-subbase materials. Additional observations relate to longitudinal cracking of the pavement, where greater control of cracking has been initially achieved in the test sections where geo-reinforcement was installed.</p>

<p>Pervious pavements are similar to conventional pavements with no fine or little content of fine aggregate. Pervious pavements are considered as sustainable pavements as it controls storm water runoff, mitigate urban heat island effect. The construction of pervious concrete pavement on soft soil subgrade is not feasible unless subgrade soil specially treated with some strengthening material. Geocell is a three-dimensional geosynthetic product that is a promising material to reinforce the soil, there are no prominent studies in the past on application of geocell in the pervious concrete pavement. The present research is focused on the pervious concrete pavement performance using geocell base under the static loading. The series of static plate load tests on geocell reinforced and unreinforced pervious pavements as per the Indian Road Congress standards. In addition to the above tests, studies were also conducted by placing nonwoven geotextile at the interface of the pervious slab, geocell base, and at interface of the geocell base and subgrade. The test results have shown that the vertical deformation, was reduced when the pavement is reinforced with geocell, the separation, filtration and drainage functions enhanced by non woven geotextile.</p>

<p>Spatial variability of the base and subgrade layers has been proven to induce adverse impact on the structural response of pavement. However, few studies have assessed the effect of the spatial variability of the asphalt layer on pavement performance. This study aims to explore the impact of spatial variability of the Young’s modulus in the asphalt layer on the critical pavement strain by using Random finite difference methods (RFDM). As geogrid reinforcement has become a common practice in flexible pavement engineering, the role of geogrid reinforcement in the statistical effect of asphalt spatial variability is especially focused on in this study. Several key conclusions are drawn. (1) The assumption of the asphalt heterogeneity can induce an underestimation of the critical pavement strain. (2) Geogrid helps to mitigate the negative impact of spatial variability by reducing the mean value and standard deviation of the critical strain. (3) The low-modulus dominating effect not only makes the mean strain in probabilistic case higher than the deterministic strain but also make the geogrid be mobilized more fully than the deterministic situation. </p>

<p>The problem of construction of the Big Almaty Ring Road (BAKAD) in conditions of the possibility of flooding by ground and external waters is considered. The hydrogeological conditions of this site and general constructive solutions of the embankments, according to the working project, were considered. In this area, groundwater during the survey period was discovered at depths of 0.6-16.0 m. When designing structures on these collapsible soils, one should take into account the possibility of increasing their moisture content by soaking the soil from above from external water sources. Taking this into account, it is necessary to provide for a set of measures, including the elimination of subsidence properties (water protection and constructive measures). Having studied the experience of road construction in Kazakhstan and the CIS countries, as well as the design data and geological conditions of the project "BAKAD", as well as analyzing the results of laboratory soil studies and the results of field stamp tests. The following decision was made: 1) Loess-like clayey soil of brown color, light, hard, subsidence can be used as an artificial embankment with good compaction and preventing large amounts of water from entering the body of the soil embankment. 2) It is necessary to protect the embankment slopes from the ingress of water by establishing a layer of geosynthetics. 3) It is necessary to pay attention to the compaction of the central part and the slopes of the embankment, which will provide protection from the influence of melt water into the body of the embankment, the penetration of which will lead to a deterioration. 4) In some areas where the water table is near the base of the embankment, install a geogrid with an aggregate to resist the loads from the higher roadbed. The research results are theoretically substantiated and graphically interpreted.</p>