Author: Farhana Rahman Publisher: ISBN: Category : Compacting Languages : en Pages : 10
Book Description
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.
Author: Farhana Rahman Publisher: ISBN: Category : Embankments Languages : en Pages : 107
Book Description
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.
Author: Kansas. Department of Transportation. Bureau of Materials & Research Publisher: ISBN: Category : Embankments Languages : en Pages : 106
Book Description
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.
Author: Federal Construction Council. Task Group T-36 on Soil Compaction for Buildings Publisher: ISBN: Category : Soil compaction Languages : en Pages : 64
Author: Farhana Rahman
Author: United States. Army. Corps of Engineers
Author: Jack W. Hilf
Author: Farhana Rahman
Author: 
Author: Santosh S. Salimath
Author: Kansas. Department of Transportation. Bureau of Materials & Research
Author: Shad M. Sargand
Author: Federal Construction Council. Task Group T-36 on Soil Compaction for Buildings
Author: Allan F. Huseth