An advanced technology for measuring track substructure conditions has been developed by Sol Solution in France. This technology, referred to as the PANDA® and Geo-Endoscopy® technique, comprises driving a variable energy cone penetration device into the track substructure using an instrumented anvil to collect strength (and modulus by correlation) profile with depth. Condition monitoring of the track substructure layers is accomplished through insertion of a camera into the same hole, also called Geoendoscopy®. The tests are commonly faster than Dynamic Cone Penetration (DCP) testing and cause negligible damage to the track substructure with the use of light and portable devices. This paper presents data from PANDA® and Geo-Endoscopy® testing efforts recently carried out under the scope of an ongoing research study at the University of Illinois. The primary objective was to relate the substructure layer properties to plastic layer deformations measured through advanced geotechnical instrumentation. Combined analysis of the PANDA®, Geo-Endoscopy®, and field instrumentation data has been used to highlight the reliability of this innovative technique towards improved evaluation of track substructure layer conditions
Abstract. The transient hot-wire (THW) technique is widely used for measurementsof the thermal-conductivity of most fluids and some attempts have also been carried out for simultaneous measurements of the thermal-diffusivity with the same hot wire. This technique was also tried to determine thermal properties of soils by the mean of probes which can be considered as wire with some assumptions. The purpose of this paper is to validate the thermal conductivity measurement by the THW technique in geomaterials, composed of compacted sand + clay mineral that can be used for earth construction (Compacted Earth Brick). The thermal transfer behaviors are mainly governed by the texture and moisture of the geomaterials. Thus the investigations were performed (1) in media made of glass beads of different diameters in dry and saturated state in order to observe the role of grain sizes and saturation state on the wire temperature (∆t) measurements and (2) in the compacted clay-geomaterial at different moisture states. The ∆t / ln(t) diagrams allow the calculation of two thermal conductivities. The first one, measured in the short time acquisition (< 1s), characterizes the microtexture of the material and its hydrated state. The second one, measured for longer time acquisitions, characterizes the mean thermal conductivity of the material.
Abstract. X-ray Computed Tomography (X-ray µCT) was employed to characterize vertical variations of structural porosity of a soil profile (pore dimension higher than 5.10 3 µm3 ). Three distinct horizons of a Cambisol have been studied for a total depth of 75 cm: L, S 1 /S 2 and S 2 /S Fe horizons. Samples have been cored in situ by driving in PVC tubes (inner diameter 10 cm). From reconstructed and filtered volumes, pores segmentation allows to study variations of structural porosity within the profile. Two kinds of porosity were identified: biological pores (tube-like) and physical pores (fracture-like). Structural porosity content varies strongly according to the horizons: from 5.48% in the L horizon to 6.48% in the S 1 /S 2 horizon. The 3D connectivity of both of these pore types was also assessed. During sampling, soil shearing induced damages around the cores. Identification and quantification of the damaged zone was performed from the calculation of porosity profile from core surface to core heart. In average, the damaged zone reaches a depth of 1 cm. Porosity loss (compaction) or porosity increase (fracturing) was observed according to the studied profile.
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