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Mechanistic pavement design procedures based on elastic layer theory require characterization of pavement layer materials including subgrade soil. This paper discusses the subgrade stiffness measurements obtained from a new compaction roller for compaction control on highway embankment projects in Kansas. Three test sections were compacted using a single, smooth steel drum intelligent compaction (IC) roller that compacts and simultaneously, measures stiffness values of the compacted soil. Traditional compaction control measurements such as, density, in-situ moisture content, stiffness measurements using a soil stiffness gage, surface deflection tests using the light falling weight deflectometer (LFWD) and falling weight deflectometer (FWD), and penetration tests using a dynamic cone penetrometer (DCP), were also done. The results show that the IC roller was able to identify the locations of lower soil stiffness in the spatial direction. Thus, an IC roller can be used in proof rolling. IC roller stiffness showed sensitivity to the field moisture content indicating that moisture control during compaction is critical. No universal correlation was observed among the IC roller stiffness, soil gage stiffness, back-calculated subgrade moduli from the LFWD and FWD deflection data, and the California bearing ratio obtained from DCP tests. The discrepancy seems to arise from the fact that different pieces of equipment were capturing response from different volumes of soil on the same test section.
Mechanistic pavement design procedures based on elastic layer theory require characterization of pavement layer materials including subgrade soil. This paper discusses the subgrade stiffness measurements obtained from a new compaction roller for compaction control on highway embankment projects in Kansas. Three test sections were compacted using a single, smooth steel drum intelligent compaction (IC) roller that compacts and simultaneously measures stiffness values of the compacted soil. Traditional compaction control measurements such as, density, in-situ moisture content, soil stiffness measurements using soil stiffness gage, surface deflection tests using the Light Falling Weight Deflectometer (LFWD) and Falling Weight Deflectometer (FWD), and penetration tests using a Dynamic Cone Penetrometer (DCP), were also done. The results show that the IC roller was able to identify the locations of lower soil stiffness in the spatial direction. Thus the IC roller can be used in proof rolling. IC roller stiffness showed sensitivity to the field moisture content indicating that moisture control during compaction is critical. No universal correlation was observed among the IC roller stiffness, soil gage stiffness, backcalculated subgrade moduli from the LFWD and FWD deflection data, and the California Bearing Ratio (CBR) obtained from DCP tests. The discrepancy seems to arise from the fact that different equipment were capturing response from different volumes of soil on the same test section. Analysis using the newly released Mechanistic-Empirical Pavement Design Guide (M-EPDG) shows that pavement rutting, roughness and asphalt base thickness are significantly influenced by the subgrade strength. "Target" modulus for compaction quality control can also be obtained by this analysis.
TRB's National Cooperative Highway Research Program (NCHRP) Report 676: Intelligent Soil Compaction Systems explores intelligent compaction, a new method of achieving and documenting compaction requirements. Intelligent compaction uses continuous compaction-roller vibration monitoring to assess mechanistic soil properties, continuous modification/adaptation of roller vibration amplitude and frequency to ensure optimum compaction, and full-time monitoring by an integrated global positioning system to provide a complete GPS-based record of the compacted area--
The book comprises selected proceedings of the 2016 annual conference of the Indian Geotechnical Society. The technical papers presented on the theme “Geotechnical Characterisation and Geoenvironmental Engineering” highlight the modified geotechnical properties of soil admixed industrial waste and also the characteristics of soil with different pore fluid under varying test conditions. The major topics covered are (i) characterisation of soils, rocks and synthesised materials and (ii) geoenvironmental engineering and behaviour of unsaturated soil. This book will prove a valuable reference for researchers and practicing engineers alike.
This book is a compilation of selected papers from the 1st Indo-China Research Series in Geotechnical and Geoenvironmental Engineering held in May 2020 online. The webinar series was held at a time of COVID-19 pandemic, when there is lack of physical connectivity. The cutting-edge research topics in Civil and Environmental Engineering ranging from bio-geotechnology, methane gas hydrates, frozen soils, rock testing, and related high-rise buildings response under wind loading will be covered. The contents make valuable contributions to academic researchers and engineers in the industry and provide a platform for demonstrating joint research between scientists from India and China. These are the first proceedings of its kind to demonstrate and motivate more joint research cooperation in Civil and Environmental Engineering between two countries. It was done mainly to motivate youth research scholars to understand each other and develop long-term cooperation.
This book is one out of 8 IAEG XII Congress volumes and deals with education and the professional ethics, which scientists, regulators and practitioners of engineering geology inevitably have to face through the purposes, methods, limitations and findings of their works. This volume presents contributions on the professional responsibilities of engineering geologists; the interaction of engineering geologists with other professionals; recognition of the engineering geological profession and its particular contribution to society, culture, and economy and implications for the education of engineering geologists at tertiary level and in further education schemes. Issues treated in this volume are: the position of engineering geology within the geo-engineering profession; professional ethics and communication; resource use and re-use; managing risk in a litigious world; engineering and geological responsibility and engineering geology at tertiary level. The Engineering Geology for Society and Territory volumes of the IAEG XII Congress held in Torino from September 15-19, 2014, analyze the dynamic role of engineering geology in our changing world and build on the four main themes of the congress: Environment, processes, issues and approaches. The congress topics and subject areas of the 8 IAEG XII Congress volumes are: Climate Change and Engineering Geology. Landslide Processes. River Basins, Reservoir Sedimentation and Water Resources. Marine and Coastal Processes. Urban Geology, Sustainable Planning and Landscape Exploitation. Applied Geology for Major Engineering Projects. Education, Professional Ethics and Public Recognition of Engineering Geology. Preservation of Cultural Heritage.
Compaction of embankment soils is a key factor influencing premature pavement distresses and bridge approach settlement. The current specifications of the Kansas Department of Transportation (KDOT) address embankment compaction in terms of density and moisture content. However, the implementation of performance-based specifications would require measuring mechanical properties of soil, such as stiffness, in addition to density. This is needed because soil stiffness is the parameter used to characterize the embankment soil in the design of pavement structures. The objectives of this study were to investigate the use of the Light Falling Weight Deflectometer (L-FWD) to measure in-situ soil stiffness and to investigate the feasibility of developing a stiffness-based specification for embankment soil compaction quality control. To achieve these objectives, soil stiffness values were measured at multiple locations along nine KDOT embankment projects using the Prima 100 L-FWD. Concurrent density and moisture measurements were also taken at select locations. Bulk soil samples were collected and remolded soil samples were used to measure the resilient moduli of the soils in the laboratory at varying density and moisture contents. For each soil, and at each combination moisture content and dry density level used in the laboratory tests, a constitutive model was derived from the laboratory resilient modulus data to capture the stress-dependent behavior of the soil. The constitutive model was then implemented in a finite element model of a semi-infinite soil half-space to compute the deflection at the surface of the half-space for a circular load. An equivalent elastic modulus for the soil half-space was back-estimated with the Boussinesque formula, for each combination moisture content and dry density. A regression model was then developed to relate the equivalent elastic modulus of the soil half-space to the dry density and moisture content of the soil. The regression model was used to predict the equivalent elastic moduli for the in-situ moisture contents and dry density values recorded during the field L-FWD tests. The predicted equivalent moduli were then compared to the moduli measured by the L-FWD. It was found that the equivalent moduli predicted from the results of the laboratory resilient modulus tests do not correlate with the in-situ soil stiffness measured with the L-FWD. This prevented the development of a quality control scheme based on laboratory measured resilient moduli. The high degree of spatial variability obtained for the in-situ moduli measured with the L-FWD prevented the development of a quality control scheme based on a control test strip.