An Integrated Study of Pervious Concrete Mixture Design for Wearing Course Applications

This report presents the results of the largest and most comprehensive study to date on portland cement pervious concrete (PCPC). It is designed to be widely accessible and easily applied by designers, producers, contractors, and owners. The project was designed to begin with pervious concrete best practices and then to address the unanswered questions in a systematic fashion to allow a successful overlay project. Consequently, the first portion of the integrated project involved a combination of fundamental material property investigations, test method development, and addressing constructability issues before actual construction could take place. The second portion of the project involved actual construction and long-term testing before reporting successes, failures, and lessons learned. The results of the studies conducted show that a pervious concrete overlay can be designed, constructed, operated, and maintained. A pervious concrete overlay has several inherent advantages, including reduced splash and spray and reduced hydroplaning potential, as well as being a very quiet pavement. The good performance of this overlay in a particularly harsh freeze-thaw climate, Minnesota, shows pervious concrete is durable and can be successfully used in freeze-thaw climates with truck traffic and heavy snow plowing

Landslides in Shale-Derived Glacial Till

An area in south-east Iowa is notorious for landslides in both cut slopes and embankments. Most of the failed slopes have been modified to lower slope angles as attempted remediation; however in many instances the failure reoccurred. The dominant soil in the cuts and used for borrow material is Kansan age glacial till, while the underlying bedrock is Pennsylvanian shale of the Des Moines series. The till contains significant amounts of the underlying bedrock. In an effort to gain insight into the cause of these failures, an embankment with extensive failures in Monroe County was studied. One slide selected for intensive study was at a 2V:1H slope and 8 meters high. The slide was 16 meters in length. The failure zone was essentially parallel to the original surface at a depth of 0.75 meters. Average strength parameters used in stability analyses produced factors of safety that indicate that failure should not have occurred. X-ray diffraction tests indicate a slightly broader montmorillonite peak in surface soils compared to interior embankment soils, which may indicate the presence of intracrystalline moisture and perhaps a different exchangeable cation in the failure zone soil. This subtle difference could account for a lower shear strength in the soil at the surface of the embankment. It is interpreted that the most likely cause of failure is the reduction of cohesion near the embankment surface after construction. If the reduction of strength is due to weathering and saturation leading to the subsequent swelling of the montmorillonite is the cause of failure, then remediation such as flattening the slope would be ineffective. The use of other soil strengthening techniques such as the use of geosynthetics, minipiles, or chemical stabilization would provide better, long term stability

Economic and Sustainable Evaluation of Fertilizer Application scenarios for Iowa Crop/Livestock

Increased awareness and concern for environmental quality in recent years has increased pressure on farmers to develop and utilize methods to minimize the environmental impact of their production activities. The use of manure produced by livestock enterprises to meet crop nutrient needs is one method that has been used to reach these sustainable environmental goals. The purpose of this study is to evaluate the economic impact on returns of using swine manure to meet crop nutrient needs on a typical midwest crop/livestock farm. An important concern of farmers in a crop/livestock operation such as the one in this study is the lack of sufficient time to apply the manure during labor intensive periods in the crop enterprises: Availability of nutrients in the manure is highest when it is applied in the spring. This is the time when crops also require labor for planting operations. This research evaluates the economic trade-offs of hiring labor to meet labor needis of all the enterprises during these periods, minimize costs and provide a foundation for a sustainable production syste

Durability and Performance of the Pervious Concrete Overlay at MNROAD

This paper presents the results of studies conducted to develop a self-consolidating Portland Cement Pervious Concrete (PCPC) for overlay applications to reduce roadway noise, reduce splash and spray, and to improve friction as a surface wearing course. A variety of mixture variables were characterized for workability to develop a mixture for mechanized placement. During the fall of 2008, a 100 mm (4 in.) thick pervious concrete overlay on traditional concrete was constructed at a test facility. Construction is described as well as results of field tests to characterize the condition of the pavement seven months following construction. Performance testing of the overlay section included bond strength, permeability, skid resistance, and noise generation. The results of these studies show that effective PCPC overlays can be designed for wearing course applications.This paper is published as Kevern, John T., Kejin Wang, and Vernon R. Schaefer. "Durability and Performance of the Pervious Concrete Overlay at MNROAD." Special Publication 282 (2011): 43-54. doi:10.14359/51683641. Copyright 2011 American Concrete Institute. Posted with permission

Slope failure prediction combining limit equilibrium, case histories, and Bayesian Markov Chain Monte Carlo method

This study demonstrates the integration of an analytical geotechnical method and a statistical method to predict the stability of soil slopes using a probabilistic approach. The model utilized Bayesian Markov Chain Monte Carlo re- arametrization, based on prior distributions generated from 104 published case histories, and a synthetic database consisting of 4,032 factor of safety values from limit equilibrium analyses. Validation of the Bayesian model against slope stability case histories showed an area under the receiver operating characteristic curve (AUC-ROC) of 86%, indicating high classification accuracy. The results showed that the Bayesian model performed well when predicting slope stability or instability. It can be used to inform the preliminary design or remediation of slopes by incorporating parameter uncertainties and random effects generally not considered by traditional deterministic studies