Geosynthetic reinforcements have shown effective performances in basal reinforcement of low volume roads under traffic loads. In recent years, these reinforcements have also been used to improve roads against environmental loading. This study evaluates the performance of geosynthetic-reinforced and lime-treated low volume roads under both traffic loads and environmental conditions. Thirty two test sections were constructed in 2006 over expansive clay subgrade in Grimes County, TX. The sections involved eight different cross sections, including control (unreinforced) sections, subbase lime-treated sections, base geosynthetic-reinforced sections with three geosynthetics types, and combinations of subbase lime-treated with base geosynthetic-reinforced systems. An index of pavement performance was used to compare and rank the overall performance of the road sections. The geogrid reinforced sections were found to significantly enhance the performance of the road sections by preventing the development of longitudinal cracks in paved area. On the other hand, lime treatment showed only limited improvements to the performance of the reinforced sections.

Sanitary landfill provides the most common, economic and aesthetic method among all other solid waste disposal systems around the world. In recent days, addition of moisture and recirculation of leachate back into the waste mass have been a common practice to ensure rapid biodegradation process that enhances landfill gas generation. Methane, the primary end product from the rapid biodegradation process, is captured through a well designed horizontal and vertical collection system to produce electricity. The current practice proposes the horizontal gas collection pipes to be spaced 15 m (50 ft) to 60 m (200 ft) apart at different vertical lifts. The objective of this paper is to investigate the optimum spacing for the collection pipes to ensure maximum gas collection. The investigation was carried out in a municipal solid waste landfill at The City of Denton, Texas. The leachate recirculation and gas collection were conducted through the horizontal recirculation system with the same 0.15 m (6 in) diameter HDPE pipe. Two horizontal leachate recirculation pipes, designated as H2 and H7 were considered to study landfill gas flow rate and gas composition over a period of one year. The horizontal spacing between the pipes were 30 m (100 ft) and 15 m (50 ft) for pipe H2 and pipe H7, respectively. Later, gas generation rate was predicted according to USEPA's first order kinetic gas generation model LandGEM. The field flow rate was compared with the predicted gas flow rate to determine the optimum spacing of the horizontal gas collection system. Based on the preliminary results, the gas collection system with the 15 m (50 ft) spacing was more efficient comparing to the collection system with 30 m (100 ft) spacing.

In this study an empirical formulation to estimate the identification number of transversely isotropic rock β was developed. The empirical formulation is formulated based on a numerical study, using ABAQUS finite element program to model the pressuremeter test, to explore the effect of the cross-anisotropy of geomaterials on β. The FE analysis results were statically analyzed to establish a possible systematical empirical correlation that is capable of predicting the transversely isotropic rock identification number β. the developed formulation shows a superior capability to predict the identification number β. Parametric study has been also conducted to define the significant factors affecting identification number of cross-anisotropy geomaterial β.

The proper engineering of bioreactor landfills requires operation in a manner that maximizes waste decomposition and gas generation with the increased settlement. The landfill settlement occurs due to multiphase interactions of waste components such as solid, fluid and gas phases, with each phase exhibiting variations both in time and space. There are several mathematical models to evaluate the processes of biodegradation, gas generation, gas transport and distribution of moisture within a landfill. However, many existing waste settlement models focus on compression of waste solids but are unable to account for contribution from other phases. An effective model for landfill settlement was developed to consider settlement, gas generation and fluid transport simultaneously. A major obstacle to successful implementation of a multiphase settlement model is the amount of data required to calibrate and validate such a model. This manuscript describes research conducted to collect data from the City of Calgary Biocell Landfill (Calgary Biocell) and validate a multiphase settlement model. Results indicate that the prediction capability of settlement models can be improved by coupling the settlement mechanisms with the generation and dissipation of gas pressure and the moisture distribution.

The Kansas Department of Transportation (KDOT) is currently evaluating Superpave mixture performance with higher percentage of reclaimed asphalt pavement (RAP) materials. Hamburg Wheel Tracking Device (HWTD) tests were done on Superpave mixes with high RAP content sampled from a number projects across the state. Each mixture was subjected to 20,000 repetitions or 20-mm rut depth, whichever came first. The HWTD test results were also correlated with the volumetric parameters and other potentially significant factors. The analysis results showed that the rutting performance was significantly affected by the asphalt source and binder grade regardless of RAP content. The surface mixes with higher percentage of RAP material were not significantly susceptible to rutting compared to the mixes with moderate percentage of RAP material. Volumetric mix design parameters of these mixtures, except voids in mineral aggregate (VMA), were not significant in determining rutting performance. The rut depth decreased with increasing percent VMA for the mixes with moderate percentage (25%) of RAP materials.

Thousands of large diameter drilled shaft foundations are constructed every year to support electric transmission line steel structures. The design of these relatively short, laterally loaded shafts is quite often controlled by performance criteria, i.e. top of shaft deflection and rotation. Traditional design considers possible impacts to overhead conductor and structure performance. Yet, little research has been done to determine how these criteria relate to foundation performance. A study of historic full scale drilled shaft load test results shows a strong relationship between top of shaft rotation and normalized top of shaft deflection (deflection divided by shaft diameter). Test data indicate that lateral loads cannot be maintained without rapid progression to geotechnical failure when top of shaft rotation exceeds about 1 degree. Shaft movement less than this threshold most often exhibits linearly elastic load-deflection and load-rotation behavior, while more plastic movement is generally observed above this level. Evaluating top of shaft rotation/deflection and below ground line deflection results from full scale tests shows short, large diameter reinforced concrete shafts are most accurately modeled assuming rigid body motion with uniform flexure stiffness of the shaft. The paper presents a simplified state-of-practice approach for establishing appropriate performance criteria in relation to drilled shaft diameter.

Water plants annually produce thousands of tons of lime sludge from the water treatment procedures. The lime sludge is usually disposed into landfills as solid wastes. In order to use efficiently lime sludge as subgrade stabilization, proper design procedures for lime sludge introduction need to be followed. The purpose of this study was to evaluate the use of lime sludge as subgrade stabilizer. Experimental study was conducted on five typical types of subgrade soils in Ohio. Lime sludge was found to mildly increase the soil deformation modulus and reduce the plastic behaviors. The data indicated that lime sludge does not significantly improve the unconfined soil strength. Lime sludge however demonstrated the positive effects in improving the freeze/thaw durability.

A compaction quality control (QC) in highway construction in Thailand is typically based on an in-place density measurement using the sand replacement method. Although monitoring compaction quality through a sand cone density test is relatively simple, such method is generally time consuming, labor intensive, less cost-effective, and destructive. This paper presents the laboratory evaluation of an innovative QC tool called the soil density gauge (SDG), which provides rapid and instantaneous measurement of density and moisture content based on the electrical impedance spectroscopy. The SDG was evaluated in a test box. Six highway materials were used in the study. The variation of SDG measurements along with its measurement characteristics was investigated herein. The paper also compared the SDG density and moisture content measurements with other tests such as the nuclear gauge, the soil stiffness gauge, and the sand cone method etc.

A generalized constitutive model for municipal solid waste, based on the framework derived from critical state concepts and incorporating the effects of mechanical creep and time-dependent biodegradation, is presented. The model enables prediction of total landfill compression under incremental loading and with time. To illustrate the applicability of the model, settlements due to incremental loading of waste with time are predicted for typical landfill conditions and are compared with the predicted settlement results using other models reported in the literature. The proposed model predicts the total settlements in a range similar to the reported field-validated models in the literature. Effect of waste lift thickness on landfill settlement is also studied.

Geosynthetics are playing an increasingly more important role in environmental and geotechnical applications as local sources of natural barrier and drainage materials diminish. While much work has already been devoted to comparing the technical effectiveness of geosynthetics to natural soils, there has been relatively little study into the comparative energy efficiencies and sustainability of geosynthetics and soils. This paper presents a quantitative carbon footprint comparison between a traditional compacted soil liner and a geosynthetic clay liner (GCL) for a coal combustion disposal facility constructed in the southeastern United States in early 2011. Because transporting soil material is such a large component of the carbon footprint, the distance to the clay borrow source is a significant parameter in determining equivalency in energy consumption.