Browsing by Subject "Gravel"
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Item Dynamic properties of sandy and gravelly soils(2003) Menq, Farn-yuh; Stokoe, Kenneth H.A two-part study was undertaken to evaluate the dynamic properties of nonplastic sandy and gravelly soils. The first part involved the development of a large-scale, multi-mode, free-free resonant column. This device is called the multi-mode device, MMD. Key benefits of this device are: (1) “relatively” large specimens (15 cm in diameter) can be tested, (2) background noise is greatly minimized, and (3) the point of “fixity” in resonance testing is conveniently positioned at the specimen mid-height during the first-mode resonance. With the MMD, three different measurements can be performed. These measurements are: (1) torsional resonance measurements, (2) longitudinal resonance measurements, and (3) direct-arrival, constrained compression wave measurements. These measurements allow linear and nonlinear measurements of shear modulus, G, and material damping ratio in shear, Ds, in addition to measurements of small-strain Young’s modulus, Emax, small-strain material-damping ratio in unconstrained compression, Dc,min, and small-strain constrained modulus, Mmax. These measurements can all be performed sequentially on the same specimen. The second part of the study involved using the MMD to evaluate the dynamic properties of sandy and gravelly soils. A total of 59 reconstituted specimens were tested to systematically investigate the effects of void ratio, e, effective confining pressure, σo', median grain size, D50, and uniformity coefficient, Cu, on modulus and material damping in shear as well as the effects of these parameters on Emax, Dc,min, and Mmax. Some findings are: (1) the large-scale, free-free device works well and is adaptable to construct larger devices, (2) the primary effect of increasing D50 is to increase small-strain shear modulus, Gmax, and decrease small-strain material damping ratio, Ds,min, (3) D50 has a similar effect on Emax and Mmax as on Gmax, (4) Ds,min and Dc,min of dry granular soils are generally lower than 1.0%, (5) σo' has a slightly larger effect on Gmax, Emax, and Mmax of loose, well graded granular materials than dense, uniform materials, and (6) reference strain, γr, (a shearing strain at which G/Gmax = 0.5) is mainly a function of σo' and Cu, while γr increases as σo' increases and Cu decreases.Item Effects of Aggregate Gradation and Angularity on VMA and Rutting Resistance(2001-06) Park, Dae-Wook; Chowdhury, Arif; Button, Joe W.The Superpave system adopted the voids in mineral aggregate (VMA) criteria developed by McLeod using the 75-blow Marshall compactor for conventional dense-graded hot mix asphalt (HMA) mixtures. This VMA criteria is a function of only the nominal size of aggregate regardless of shape, texture, or gradation. The Superpave volumetric mixture design process contains a required minimum value for fine aggregate angularity (FAA) as a function of traffic level and position of the layer within the pavement structure. This parameter is reported as the percentage of uncompacted air voids, with larger values generally indicating increased aggregate angularity and, thus, higher VMA and better resistance to permanent deformation. The purpose of this study was to evaluate the effects of FAA and gradation on the resulting VMA of certain HMA mixtures. The effect of FAA was evaluated using mixtures containing coarse limestone combined with six different fine aggregates. Mixtures with three gradations which pass through, above, and below the restricted zone; three different mineral filler contents; and four different values of FAA were analyzed to evaluate the effects of these parameters on VMA of Superpave mixtures. Based on analyses of these tests, mixtures containing fine granite or limestone showed less permanent deformation than mixtures containing fine river gravel or natural rounded sand. FAA values and permanent deformation did not correlate well. Gradations that pass through the restricted zone did not significantly affect mixture VMA. Mineral filler contents and FAA value did affect mixture VMA significantly. Higher FAA values yielded higher VMA.Item Geology of the fluvial deposits of the Colorado River Valley, Central Texas(1968-08) Weber, Gerald E. (Gerald Eric); Mackin, J. Hoover (Joseph Hoover), 1905-1968Terrace deposits along a 40 mile segment of the Colorado River between Austin and Bastrop, Texas, are mapped in detail. The following deposits have been delineated (lowest to highest): Floodplain, Sixth Street Terrace, Montopolis Terrace, Capitol Terrace, Hornsby Terrace, Asylum Terrace, and Delaney Terrace. The Hornsby Terrace deposits and the Montopolis Terrace deposits were previously unrecognized. A program of mechanical analysis was conducted on samples taken from the terrace deposits and the floodplain. Cumulative frequency curves of grain size from five samples collected up to 15 miles apart from the Asylum Terrace gravel, are distinctively grouped--different from all other samples. Cumulative frequency curves from five samples from the Hornsby Terrace gravel also plot in a close grouping distinct from other samples. Over short distances where abrasion is not a dominant factor it seems that grain size distribution may be useful as a means of correlation of terrace remnants. Analysis of the lithologies of these samples indicate that the Hornsby, Asylum and Delaney Terrace gravels are practically without limestone clasts, in a drainage basin that is, presently, composed dominantly of limestone. This suggests that the Commanche Series in the Edwards Plateau region was not extensively exposed but was covered by the Gulf Series at the time of the formation of these terraces. The Manor lag gravel, an upland gravel in the thesis area, is thought to be the remnant of a high terrace deposit of the Colorado River. All terrace gravels except the Capitol and Montopolis Terrace gravels are thought to be the result of lateral planation by a stream at or near grade. The Montopolis and Capitol Terrace gravels are thought to be the result of a lengthy episode of lateral planation by the Colorado River accompanied by slow degradation.Item Increased Single-Lift Thicknesses for Unbound Aggregate Base Courses(1998-10) Allen, John J.; Bueno, Jaime L.; Kalinski, Michael E.; Myers, Michael L.; Stokoe, Kenneth H.A study was conducted to evaluate the feasibility of compacting unbound aggregate base courses in thicker lifts than currently permitted by state departments of transportation (DOTs). At present, the majority of states allow a maximum lift thickness of 8 inches or less. This project constructed and tested full-scale test sections using a variety of material types. Two test pads were constructed in an aggregate quarry in Texas utilizing crushed limestone. Three crushed granite test sections were built as part of a road widening project in Georgia, and two test pads were constructed of uncrushed and partially crushed gravel with loess fines at a gravel production facility near Memphis, Tennessee. Single-lift thicknesses varied from 6 inches to 21 inches. Moisture contents and densities were evaluated using the Nuclear Density Gauge (NDG). Nondestructive seismic testing, using the Spectral-Analysis-of-Surface-Waves (SASW) technique, was used to evaluate stiffness profiles within the compacted lifts. Cyclic plate load tests were accomplished by means of the Rolling Dynamic Deflectometer (RDD), modified for this static application. Results showed that compaction targets could be attained for lifts up to 21 inches thick. Density and stiffness results for 13-inch thick lifts in the Georgia tests were equal to, or better than, the results for the base placed in two lifts, a 7-inch lift followed by a 6-inch lift. Higher moisture contents during compaction yielded lower shear wave velocity and Young’s modulus values. Seismic results show that the upper 3 inches of the final test pads had lower stiffness values, presumably from lower effective stresses near the surface and possibly from some disturbance caused by the compaction equipment. This zone of lower stiffness and slightly less compaction is less evident in the density measurements.Item Prediction of Working Load Displacements Under Plate Loading Tests from Seismic Stiffness Measurements(1998-10) Myers, Michael L.; Stokoe, Kenneth H.; Allen, John J.A study was conducted to evaluate the feasibility of compacting unbound base courses in thicker lifts than currently permitted by state departments of transportation (DOTs). At present, the majority of states allow a maximum lift thickness of 8 inches or less. This project constructed and tested full-scale test section using a variety of material types. Two test pads were constructed in an aggregate quarry in Texas utilizing crushed limestone. Three crushed granite test sections were built as part of a road widening project in Georgia, and two test pads were constructed of uncrushed and partially crushed gravel with loess fines at a gravel production facility near Memphis, Tennessee. Single-lift thicknesses varied from 6 inches to 21 inches. Moisture contents and densities were evaluated using the Nuclear Density Gauge (NDG). Nondestructive seismic testing, using the Spectral-Analysis-of Surface-Waves (SASW) technique, was used to evaluate stiffness profiles within the compacted lifts. Plate load tests were conducted on the surface of the crushed limestone test pads by means of the Rolling Dynamic Deflectometer specially modified for this fixed site application. Low frequency cyclic loads were applied to determine axial stiffness under transient working loads of varying magnitude. The base courses were tested at to moisture contents. The results were evaluated and compared with small strain seismic tests result. Strain amplitudes in the plate load tests led to a 5% to 25% reduction in measured stiffness as compared to the seismic results.