Kim GS, et al. J Vet Sci. 2019 Jul;20:e56. https://doi.org/10.4142/jvs.2019.20.e56

This paper summarizes the results and analyses of laboratory and field measurements of the elastic shear modulus of lightly overconsolidated, compressible Chicago clays. These soils are glacially-derived, freshwater ice margin deposits. The laboratory experiments were conducted on twelve high quality block samples obtained from three excavation sites in the Chicago area. The specimens were consolidated to in situ stresses via a recompression technique, and the elastic shear modulus was synchronously obtained from results of bender element tests during consolidation and subsequent creep. Seismic cone penetration and crosshole seismic tests were performed in situ. The results show that the elastic shear moduli from the bender element tests after consolidation and a sufficiently-long creep period are approximately the same as those obtained from the results of the in situ tests. The effects of time on the elastic shear modulus are smaller than the effects caused by soil variability. Evaluation of the laboratory and field data indicates that the elastic shear modulus of compressible Chicago clays can be estimated from the natural water content and mean normal effective stress.

Numerical simulations and calibration of hypoplasticity constitutive parameters for Chicago clays are presented based on laboratory tests conducted on high-quality block samples and field tests from excavations located in the Chicago, Illinois area. The parameters for the hypoplasticity model enhanced with the intergranular strain concept are calibrated from the results of index tests, oedometer tests, and $K_0$ -consolidated undrained triaxial compression and extension tests. Drained stress probes conducted in a triaxial cell after three different preshearing stress paths were used to compare the numerical results with the triaxial test results. One path was applied to study the clay stress-strain behavior at in situ conditions and the remaining two to isolate the effects of recent stress history. The results are shown in terms of the secant shear and bulk stiffness, shear and volumetric stress-strain responses at small and large strains, and stress path reversals.

Tunnel construction workers face many dangers while working under dark conditions, with difficult access and egress, and many potential hazards. To enhance safety at tunnel construction sites, low latency tracking of mobile objects (e.g., heavy-duty equipment) and construction workers is critical for managing the dangerous construction environment. Wireless Sensor Networks (WSNs) are the basis for a widely used technology for monitoring the environment because of their energy-efficiency and scalability. However, their use involves an inherent point-to-point delay caused by duty cycling mechanisms that can result in a significant rise in the delivery latency for tracking mobile objects. To overcome this issue, we proposed a mobility-aware adaptive duty cycling mechanism for the WSNs based on object mobility. For the evaluation, we tested this mechanism for mobile object tracking at a tunnel excavation site. The evaluation results showed that the proposed mechanism could track mobile objects with low latency while they were moving, and could reduce energy consumption by increasing sleep time while the objects were immobile.

This paper presents the theoretical and experimental investigations of the hydraulic conductivity variation of the soil mixture that contains two distinct particle size distributions, coarse and fine soils. A new model for the hydraulic conductivity is introduced that focuses on the relationship between the coarse‐fine soil mixing ratio and the hydraulic conductivity of the mixture. For the model verification, permeability tests were conducted. The glass beads and quality‐controlled standard sand and soils obtained from fields were used for the specimen. The experiment results showed that the hydraulic conductivity of the soil mixture strongly depends on the mixing ratio. As the amount of the coarse soil contained in the fine soil increased, the hydraulic conductivity of the mixture decreased from that for the fine soil until the critical mixing ratio. This ratio is defined as the fine soils perfectly fill the voids between the coarse soils without remains. When the ratio is greater than the critical mixing ratio, the hydraulic conductivity is drastically increased with the mixing ratio up to that of the coarse soil. The comparison between the computed values and the test results shows that the introduced model successfully describes the measurements.