Browsing by Author "Labuz, Joseph F"
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Item Calibration of An Earth Pressure Cell(2000-09-01) Theroux, Brent; Labuz, Joseph F; Drescher, AndrewIn 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.Item Earth Pressure Behind A Retaining Wall(2005-03-01) Bentler, Joseph G; Labuz, Joseph F; Schultz, Arturo EEarth pressure cells, tiltmeters, strain gages, inclinometer casings, and survey reflectors were installed in fall 2002 during construction of a 26-ft (7.9-m) high Minnesota Department of Transportation (Mn/DOT) reinforced concrete cantilever retaining wall. A data acquisition system with remote access monitored some 60 sensors on a continual basis. Analyses of the data indicated the development of active earth pressure at the end of backfilling, with a resultant at about one-third of the backfill height. Translation of 0.45 in. (11 mm), or about 0.1% of the backfill height, was responsible for development of the active condition. The wall also rotated 0.03 degrees into the backfill as a rigid body, while the top of the stem deflected 0.16 in. (4 mm) away from the backfill. Sensor readings showed the earth pressure distribution to be quite complex during the backfilling process. Evidence was found for residual lateral stresses from compaction. Translation of the wall overnight following the construction workday reduced the compaction-induced lateral stresses. Changes in earth pressure and wall deflection weeks after backfilling were attributed to changes in temperature and rainfall. The data showed that the wall design, while reasonable, could be made more efficient by removing the shear key, which was ineffective.Item Experimental data on pore moduli of porous rock(2018-04-06) Tarokh, Ali; Labuz, Joseph F; jlabuz@umn.edu; Labuz, Joseph F; Rock Mechanics Laboratory, Department of Civil, Environmental, and Geo- Engineering, University of MinnesotaThese data address two key questions: (i) is Ks'' a constant and (ii) under what conditions does Ks'' = Ks hold. We present unique laboratory experiments that enable the direct measurement of Ks'', for the first time, for ideal and natural porous solids.Item Experimental data on poroelastic moduli of transversely isotropic rock(2021-12-25) Tarokh, Ali; Labuz, Joseph F; jlabuz@umn.edu; Labuz, Joseph F; Rock Mechanics Laboratory, Department of Civil, Environmental, and Geo- Engineering, University of MinnesotaThese data present volumetric and deviatoric poroelastic moduli from a series of drained, undrained, and unjacketed tests in uniaxial, hydrostatic, and axisymmetric compression for a porous sandstone. These data enable the direct and independent measurement of all eight parameters that fully describe the mechanical response of a transversely isotropic rock.Item Moisture Effects on PVD and DCP Measurements(2006-06-01) Swenson, Joel; Guzina, Bojan; Labuz, Joseph F; Drescher, AndrewThis 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.
Item Small Strain and Resilient Modulus Testing of Granular Soils(2004-08-01) Davich, Peter; Labuz, Joseph F; Guzina, Bojan; Drescher, AndrewResilient 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.