Browsing by Author "Drescher, Andrew"

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Calibration of An Earth Pressure Cell
(2000-09-01) Theroux, Brent; Labuz, Joseph F; Drescher, Andrew
In this study, researchers devised a scheme for calibration of earth pressure cells to observe their response to various loading configurations and to recommend a procedure for field installation. Transducers designed to provide an estimate of normal stress within a soil, earth pressure cells have provided readings that conflict with known loading conditions. Initial calibration tests used hydraulic oil as the pressurizing medium in both hydrostatic and uniaxial pressure conditions, which mimic the manufacturers' procedure for pressure cell calibration. Researchers designed a new testing device to permit the application of uniaxial soil pressure to the earth pressure cells using various types of soil and load configurations. As a result of calibration tests, a field installation procedure was developed and recommended. In the laboratory, a thin-walled steel cylinder with a geotextile bottom was filled with uniform silica sand of a known density, and the earth pressure cell was placed within the sand. The entire apparatus was carried into the field and installed in the desired locations. Once in place, the steel cylinder was pulled up out of the ground, leaving the cell and geotextile behind. Preliminary field data indicate that soil calibration and placement procedure provide reasonably accurate measurements.
Deformability of Shredded Tires
(1999-01-01) Drescher, Andrew; Newcomb, Dave; Heimdahl, Thor
This report describes three separate studies that examine the deformability of shredded tire fill material: The first study determined the response of shredded tires to cyclic loading. These tests were conducted in a load frame on both constrained and unconstrained samples and showed that the material became stiffer with increasing load. The second study focused on the long-term creep settlements of constrained and unconstrained samples. The results indicate that creep exists for a period of up to two years after loading. The third study investigated the possible anisotropic properties of the material. A larger modulus of elasticity was found in directions parallel to the layers than in the direction perpendicular to the layers. However, settlements computed using a representative anisotropic shredded tire fill material indicate that the current settlement analysis, based on isotropic shredded tire layers, predicts maximum settlements conservatively.
Development of Design Guidelines for Use of Shredded Tires as a Lightweight Fill in Road Subgrade and Retaining Walls
(Minnesota Department of Transportation, 1994-01) Drescher, Andrew; Newcomb, David E.
The use of shredded tires as a lightweight fill material over weak soil deposits is gaining popularity as a means of disposing a great quantity of an undesirable waste material in a beneficial manner. This report discusses the production, past applications, and properties of shredded tires with respect to their use in lightweight fills. Shredded tires have the advantages of low bulk density, high permeability, and insensitivity to the presence or state of moisture. However, they possess a high degree of compressibility, and they exhibit a degree of rebound atypical of materials normally used in lightweight fills (e.g., woodchips). Before using shredded tires in a fill, one must consider the layer thickness of the shredded tires, the amount of overburden to be placed on the tires, the type of pavement surface, and the volume of heavy traffic expected to use the roadway. Because of the orientation of shredded tires after placement, the importance of anisotropy as a future research topic is discussed.
Development of Improved Test Rolling Methods for Roadway
(Minnesota Department of Transportation, 2008-02) Hambleton, J.; Drescher, Andrew
Test rolling is a quality assurance test in which penetration of the wheels of a heavy vehicle into subgrade soils is used as a measure of the adequacy of compaction. Current criteria for acceptable test roller penetration are empirical. Two theoretical approaches for modeling test rolling are developed. One is analytic and the other is numerical, based on the finite element code ABAQUS. Both approaches relate wheel penetration to wheel geometry, wheel load, and soil strength parameters (friction angle and cohesion). Elastic soil properties are included in the numerical simulations but play a secondary role. The models accommodate both rigid and flexible wheels. Homogeneous and layered soil structures are considered. Scaled laboratory tests support the theoretical predictions, although full validation requires execution of extensive full scale field testing. The models developed can be used to enhance interpretation of test rolling data and assess the effects of test roller modifications.
Enhancements and Verification Tests for Portable Deflectometers
(2002-02-01) Hoffmann, Olivier; Guzina, Bojan; Drescher, Andrew
In this study, the accuracy of the stiffness estimate from portable deflectometer devices is investigated, based upon the example of a particular device, the Portable Falling Weight Deflectometer PRIMA 100. A laboratory calibration setup, assembly comporting a simply supported steel beam of variable span, is designed to verify the calibration of the device (sensors and data interpretation method). Associated with the tester apparatus, an enhanced setup for the portable device is examined. From verification of the stiffness estimated from the portable device against the known stiffness of the beam the inconsistency of the data interpretation method using peak values of load and displacement time histories is pointed out. An alternative method using Frequency Response Functions, spectral average, Single Degree of Freedom System analog, zero frequency estimates and curve fitting is proposed to extract the static stiffness from PRIMA measurements. Test results show the good agreement between estimates stemming from the modified analysis and true beam stiffness. Baseline for the application of both the alternative method and the enhanced device setup to quality control field measurements is proposed.
Influence of Roofing Shingles on Asphalt Concrete Mixture Properties
(1993-06) Newcomb, David; Stroup-Gardiner, Mary; Weikle, Brian; Drescher, Andrew
It is estimated that the production of new roofing shingles generates approximately 1,000,000 tons of waste annually in the U.S., and about 36,000 tons of this waste is in the Twin Cities Metro Area of Minnesota. With another 8.5 million tons of waste materials which are similar to those used in asphalt concrete, it seems viable that their use in hot-mix would be an attractive alternative to disposing of them in landfills. This report presents the results of an effort to evaluate the use of roofing waste generated by manufacturers and from reconstruction projects. It was shown that up to 5%, by weight of mixture, manufacturing waste roofing shingles could be used in asphalt concrete with a minimum impact on the properties of the mixture. At a level of 7.5%, a noticeable softening of the mixture occurs, and this might be detrimental to pavement performance. The use of shingles from roof reconstruction projects resulted in the embrittlement of the mixture which may be undesirable for low temperature cracking of pavements. The manufactured shingle waste seems to work well in stone mastic asphalt mixtures.
Investigation of Factors Related to Surface-Initiated Cracks in Flexible Pavements
(2003-01-01) Holewinski, Jill M; Soon, Seechew; Drescher, Andrew; Stolarski, Henryk K
This report works to identify potential mechanisms for the occurrence of top-down cracking, as well as to investigate stress patterns and concentrations due to surface load and preexisting transverse (thermal) cracks. It attempts to provide information on surface stresses that derives from both theory and experiments. In particular, contact mechanics solutions are analyzed to gain information on loads that are subsequently used in performing numerical evaluation of surface stresses. Examples of three-dimensional computations using the finite element code ABAQUS illustrate the analysis, and comparisons of stresses for uncracked and cracked pavements are made. The report concludes that the presence of a transverse crack in the AC layer significantly increases the vertical stresses in the base. It also has a noticeable effect on the horizontal stresses in the AC layer. Keywords-longitudianal cracks, transverse cracks, flexible pavements, ABAQUS finite element analysis
Investigation of Recycled Asphalt Pavement (RAP) Mixtures
(2002-02-01) Sondag, Michael S.; Chadbourn, Bruce A.; Drescher, Andrew
This report presents the results of a study on recycled asphalt pavement (RAP) mixtures. The report includes a literature review on RAP and a summary of past research. The research focuses on the use of resilient modulus and complex modulus testing to compare mixtures compacted with only virgin materials to those compacted with varying amounts of RAP. The additional of RAP makes the mixture stiffer, as evidenced by an increase in resilient modulus and complex modulus measurements, according to the research. The addition of RAP also decreases the mixture phase angle, which corresponds to an increase in the elastic properties and a decrease in the viscous mixture properties. The report includes recommendations regarding the proper temperatures and loading frequencies for use in the complex modulus test. It also gives the percentage of RAP and the respective asphalt binder grade necessary to yield the stiffness similar to a virgin mixture.
Moisture Effects on PVD and DCP Measurements
(2006-06-01) Swenson, Joel; Guzina, Bojan; Labuz, Joseph F; Drescher, Andrew
This study deals with the experimental investigation of the effects of moisture and density on the elastic moduli and strength of four subgrade soils generally representing the range of road conditions in Minnesota. The testing approach involved i) reduced-scale simulation of field compaction, ii) field-type testing on prismatic soil volumes, and iii) element testing on cylindrical soil specimens. The field-type testing included: i) the GeoGauge, ii) the PRIMA 100 device, iii) the modified light weight deflectometer (LWD) device, iv) the portable vibratory deflectometer (PVD) and v) the Dynamic Cone Penetrometer (DCP). To compare the Young's modulus values stemming from the field-type and laboratory experiments, cylindrical specimens were extracted from the prismatic soil volumes and tested for the resilient modulus (Mr), small-strain Young's modulus using bender elements.
The results reveal that both moisture and density have a measurable effect on the elastic modulus and strength of all four soils. On the element testing side, the small strain estimates from the bender element tests were in good agreement with the resilient modulus values. In the context of field testing, there was significant scatter of the estimated Young's moduli depending upon the particular testing device.
Reassessment of Diametral Compression Test on Asphalt Concrete
(Minnesota Department of Transportation, 1996-12) Drescher, Andrew; Newcomb, David; Zhang, Wei
This report examines the diametral compression test, as described in ASTM D4123-82 (1987) and SHRP Protocol P07 (1993) procedures. The test helps determine the resilient modulus of asphalt concrete, and less frequently its Poisson's ratio, both mechanical parameters of an ideally elastic material. However, the actual behavior of asphalt concrete is not elastic, but viscoelastic. The viscoelastic behavior of asphalt concrete under traffic-induced loads can be described by the phase angle and the magnitude of the complex compliance or complex modulus. These can be determined from the diametral compression tests that subject the specimen to haversine load history, and from the viscoelastic data interpretation algorithms derived in the current research. To avoid inaccuracies in the data interpretation, the vertical deformation should be measured over a 1/4 diameter central sector of the cylinder by means, for example, of the in-house developed displacement gage. A series of tests on specimens with various asphalt binder viscosity verified the validity of the viscoelastic data interpretation. Specimens from Mn/ROAD materials showed the presence of viscoelastic properties even at temperatures well below freezing.
Small Strain and Resilient Modulus Testing of Granular Soils
(2004-08-01) Davich, Peter; Labuz, Joseph F; Guzina, Bojan; Drescher, Andrew
Resilient modulus, shear strength, dielectric permittivity, and shear and compressional wave speed values were determined for 36 soil specimens created from the six soil samples. These values show that the soils had larger stiffnesses at low moisture contents. It was also noted during testing that some non-uniformity was present within the axial displacement measurements; larger levels of non-uniformity were associated with low moisture contents, possibly due to more heterogeneous moisture distributions within these specimens. Lastly, the data collected during this study was used to recommend a relationship between granular materials' small strain modulus and their resilient modulus. This relationship was given in the form of a hyperbolic model that accurately represents the strain-dependent modulus reduction of the base and subgrade materials. This model will enable field instruments that test at small strains to estimate the resilient modulus of soil layers placed during construction.
The Use of Geosynthetics to Reinforce Low Volume Roads
(2001-01-01) Drescher, Andrew; Erickson, Hans
This report presents the results of a study that investigated the reinforcement function of geosynthetics for typical Minnesota low-volume roadways. Researchers conducted a series of numerical simulations using the finite difference program

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