Damage Evolution of Underground Structural Reinforced Concrete Small-Scale Static-Loading Experiments
Small-scale RC models of both piles and tunnel duct s were produced as mockups of reality and loaded under soil confinement conditionsto investigate the damage evolution of structural RC interacting with soil. Experimental v erifications usinga 3D nonlinear FE analysis program called COM3D, which was developed at the University of Tokyo, are introduce d. This analysis has been used in practice for seismic performance a ssessment of underground ducts and in-ground LNG storage tanks in consideration of soil-structure interactionunder static and dynam ic loading. Varying modes of failure of RCpilessubjected to different m agnitudes of soil confinement were successfully reproduced in the proposed small-scale experiments and numerically simulated as well. Analytical simulation was applied to RC tunnel mockups under a wide variety of depth and soil confinement conditions, and reasonable matchin g was confirmed.
Seismic analysis of underground reinforced concrete structures considering elasto-plastic interface element with thickness
Abstract Since underground reinforced concrete (RC) structures interact with the surrounding soil medium, the behavior of the interfacial zone between the RC structure and the surrounding medium of the underground RC structure should be considered for accurate seismic analysis. In this paper, an averaged constitutive model of concrete and reinforcing bars for the RC structure and the path-dependent Ohsaki’s model for the soil are applied, and an elasto-plastic interface model which considers the thickness of the interface is proposed for seismic analysis of underground RC structures. A finite element analysis program is developed and verified by predicting both static and dynamic behaviors of underground RC structures. Then, the effects of the interface on the behavior of underground RC structures are analyzed. The effect of stiffness of the RC structure due to different reinforcement ratios of underground RC box structures to the behavior of the structures is also analyzed. Finally, failure mechanisms of underground RC structure under seismic action are simulated through seismic analysis of an underground RC station structure.
Parboiled rice effluent: A wastewater niche for microalgae and cyanobacteria with growth coupled to comprehensive remediation and phosphorus biofertilization
Abstract The potential of microalgae and cyanobacteria for bioremediation of wastewater by nutrient uptake combined with simultaneous biomass production is a well recognized perception of today's world. The present study illustrates the treatment of a highly polluted wastewater generated during parboiling of paddy in rice mill industries, widely operational in developing countries where rice is the staple food crop, with the help of microalgal and cyanobacterial isolates capable of growing at high rates in parboiled rice mill effluent (RME). This endeavor leads to comprehensive bioremediation of the said effluent and subsequent use of the harvested biomass as slow release phosphorus biofertilizers and the treated effluent for crop irrigation. The RME-acclimatized algal consortium demonstrated highest growth in terms of fresh weight and greatest remediation efficiency at the end of 36 days' treatment of RME, with 93.9% phosphorus and 100% ammonia-nitrogen removal, 98.7%, 91.6% and 93.5% reduction in biological oxygen demand, chemical oxygen demand and total dissolved solid, respectively, and an increment of 186 ± 0.3 mg L − 1 dissolved oxygen, bringing down the pollutants level well below the discharge limits suggested by Central Pollution Control Board, India. Additionally, microalgae in the consortium aggregated in clumps spontaneously in presence of the filaments of Phormidium sp. facilitating easy harvest. The RME-acclimatized algal consortium demonstrated highest accumulation of polyphosphate (poly-P) (0.76 ± 0.01% of dry weight) as well as highest release of phosphorus in non-sterile soil emphasizing the essential role of soil phosphorus solubilizing organisms to leach soluble phosphorus from the insoluble poly-P present in the biomass. The rice seedlings watered with treated RME also showed improved growth effect on shoot height and leaf width. The study results establish the suitability of RME as an excellent growth media for microalgae and cyanobacteria.