Performance Evaluation of Instrumented Geosynthetics Reinforced Paved Test Sections Built Over Weak Subgrade Using Accelerated Load Testing

Weak soil is a common problem in road construction. Whether it is a temporary access road or a permanent road built over a weak subgrade, a large deformation of the subgrade can lead to deterioration of the paved or unpaved surface. Geosynthetics offer a potentially economical solution for stabilizing roads built over weak soil. Three sets of testing programs were be conducted in this study.The first testing program includes conducting accelerated load testing of full-scale geosynthetic reinforced test lanes using rolling wheel load facility; the second program included conducting laboratory cyclic plate loading test on geosynthetic reinforced test sections constructed inside a steel box facility, and the third program included cyclic plate loading test on full-scale test lane sections. An extensive in-situ and laboratory testing was performed before the construction of the test sections and after each stage of pavement construction to assess the strength, stiffness of the pavement layers. Both the full-scale pavement test lane sections and in-box laboratory pavement test sections were instrumented with several sensors to measure the load associated and associated environmental responses. The experimental test results demonstrated that the inclusion of geosynthetics in pavement to reinforce the base and or stabilize the subgrade can significantly enhance the pavement performance in terms of reducing the permanent deformation of pavement layers. The inclusion of geosynthetics in pavement can help redistribute the load and change the stress concentration on top of subgrade layer. The benefits of geosynthetic reinforcement were quantified, within the context of the AASHTOWare Pavement ME Design guide and AASHTO 1993, in terms of increasing the resilient modulus of base course layer and/or reducing the thickness of base aggregate layer in pavement structure.The results for three test experiments showed an increase in traffic benefit ratio when including geosynthetic in pavement.Also, include geosynthetic showed appreciable benefit on reducing the permanent deformation of base layer subgrade in this study. Four empirical models were developed by using nonlinear regression to evaluate and quantify the benefits of using geosynthetics in pavement built over weak subgrade. The first model was developed to quantify the traffic benefit ratio (TBR). The second model was developed to quantify the base course reduction(BCR). The third model was developed to quantify the resilient modulus increase by using the geosynthetics to reinforce the base layer. The fourth model was developed to quantify the increase in resilient modulus by using the geosynthetics to stabilize the subgrade.Furthermore, The developed models were verified with experimental data to predict the amount of each model

Performance of Mortar Incorporating Heat-Treated Drinking Water Treatment Sludge as a Silica-Sand Replacement

This paper examines the possibility of using water purification wastes in the production of mortar. Within the study context, XRD and XRF analyses were performed to obtain the chemical composition of sludge. Moreover, heat-treated sludge at a temperature of 900ºC was used in the preparation of mortar mixes as a partial sand replacement (5, 10, 15, and 20% by sand weight) with a w/c of 0.48. Fresh mortars were tested for workability, and mortar samples with 7, 28, and 90 days curing ages were tested for dry density, absorption, ultrasonic pulse velocity (UPV), and compressive and flexural strengths. Besides, some regression modeling was conducted for each of the measured parameters. In general, the results showed that the use of up to 10% incinerated sludge by sand weight leads to a slight decrease in the workability and density of the mixture and a 10% increase in its strength. Nevertheless, mortars with sludge content of over 10% showed a significant increase in water absorption and a decrease in strength and other properties. Doi: 10.28991/CEJ-2022-08-08-08 Full Text: PD

Seepage Analysis and Optimization of Reservoir Earthen Embankment with Double Textured HDPE Geo-Membrane Barrier

This research paper focuses on conducting a steady state seepage analysis along with the downstream slope factor of safety using the Modified Bishops method in a poorly compacted earthen embankment and optimizing the same reservoir earthen embankment in a case study located near Sadiyavav village in Junagadh district in Gujarat, India. The study site, situated at 21°32'06.5"N and 70°37'26.7"E, is renowned for its Asiatic lions. The analysis and optimization were performed with a double-textured High-Density Polyethylene (HDPE) Geo-membrane barrier. Previously, designs and numerical solutions proposed homogenous embankments and too poorly compacted with no drainage arrangements, which led to anisotropic conditions within the section and water seeping out, cutting the phreatic line. The paper presents the documented improvements in the factor of safety achieved through the seepage analysis and the optimization of the HDPE Geo-membrane barrier. Two improvement techniques were studied using the “Limiting Equilibrium-Finite Element Method” (LS-FEM). The first using (HDPE) Geo-membrane stabilized with gabions, and the second alternative using HDPE Geo-membrane with gabions in addition to rock toe. The study results showed improvements in the downstream slope stability for the two alternatives by 3% and 10%, respectively. Doi: 10.28991/CEJ-2023-09-11-07 Full Text: PD

Using driving simulator to study the effect of crash fact signs on speeding behaviour along freeways

A driving simulator study was utilized to evaluate a potential countermeasure for speeding behaviour in order to reduce speed spillover. The behaviour of 56 subjects was observed. Participants drove a freeway for 5300 metres before exiting onto a three-kilometre urban arterial. Field data from trajectory speed profiles validated the diving simulator results. The impact of the Crash Fact Sign (CFS), a sign that provides information about the number of crashes/fatalities that occurred on that particular road, and Warning Sign (W.S.) on regions affected by speed spillover was investigated. Each subject was asked to drive in four different scenarios: (1) an additional speed limit sign (SLS-2); (2) Warning Sign (W.S.); (3) Crash Fact Sign (CFS); and (4) Crash Fact Sign with Additional Speed Limit Sign (CFS&SLS-2). The study finds CFS&SLS-2 to be the most effective countermeasure because it produces significant average speed reductions, reached 7.8 km, in the area under speed spillover effect. Furthermore, the effect of a traffic signal at the exit urban arterial on speed spillover behaviour was investigated. The speed spillover effect was observed at longer distances when drivers did not stop at the signalized intersection than when drivers stopped