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Mixing cement and soil is a traditional technique used to improve their mechanical properties. Other studies proposed a rational dosage methodology for soil-cement mixtures. This method is based on the void-cement ratio and aimed at obtaining a particular strength level. The present study evaluated the validity of the void-cement ratio (η/Civ) and analysed the stress – strain – strength behaviour of aeolian dune sand from Natal, Brazil, mixed with cement. Isotropically consolidated drained triaxial compression tests (CID-C) were conducted with moulded samples containing 0.0, 2.5, 5.0 and 7.5% cement by weight of dry soil. Void ratios corresponded to three conditions of relative density: loose, medium and dense, with confining stresses of 50, 100, 200 and 300 kPa. The effect of void ratio, cement content and void-cement ratio on the stress-strain-strength behaviour of the mixtures was determined. The results showed that the void-cement ratio is an appropriate parameter to assess the effective strength of the cement-sand mixture studied. [ABSTRACT FROM AUTHOR]

A novel robust method for estimating equivalent tunnelling Mohr–Coulomb strength parameters in elastic–plastic or elasto–brittle–plastic media satisfying Hoek–Brown failure criterion is proposed. Based on the best uniform approximation technique, this method consists of explicit and closed-form formulae in terms of elementary functions, making the estimation of equivalent parameters more convenient than other methods. A simple code is provided and a series of benchmark test cases are performed for validation. When the tunnel support is accurately known, the performance estimates of this method are better than estimates of best fitting in an artificial stress range and best fitting in the existing range methods, but not as accurate as the performance of equating model responses method and that proposed by Jimenez et al. However, when the estimation of support pressure is poor, this method is the most robust among all methods. In elasto–brittle–plastic rock mass, the advantage of robustness of this method is even more obvious. Considering both accuracy and robustness, this method can be employed as a preferable alternative. [ABSTRACT FROM AUTHOR]

The present study examines the three-dimensional hygric and mechanical behavior of oak wood. The moisture equilibrium state, characterized by the sorption isotherms, was obtained from measurements taken during adsorption and desorption cycles. Sorption behavior was analyzed with the Dent theory and compared considering the sorption direction (adsorption/desorption cycle). Sorption parameters were provided for possible numerical applications in hygric material models. The corresponding swelling and shrinkage behavior was examined and characterized by the moisture expansion parameters for all anatomical directions. Orthotropic mechanical material behavior was characterized by determining the elastic engineering (Young's moduli, shear moduli, and Poisson's ratios) and the bending, compressive and compressive shear strength material parameters. Influence of moisture content (MC) on the mechanical material properties was studied using Young's moduli, Poisson's ratios, and the investigated strength parameters. A significant difference between the sorption behavior in adsorption and desorption, known as the hysteresis effect, could be proved. Furthermore, swelling and shrinkage behavior did not show any dependency on the adsorption/desorption cycle. The results confirm the significant influence of MC on the Young's moduli and the strength properties, however, did not validate an influence on the Poisson's ratios. [ABSTRACT FROM PUBLISHER]