Health monitoring of bacterial concrete structure under dynamic loading using electro-mechanical impedance technique: a numerical approach

Health monitoring of structures using techniques based on the smart material is an innovative concept that is exploding technological revolutions in the field of civil engineering. The electro-mechanical impedance (EMI) technique is used for structural health monitoring (SHM) and to investigate the damages in the structures. The bacterial incorporation in concrete produces calcite material through metabolism process in presence of moisture and carbon dioxide, which improves the mechanical properties of concrete. Hence, its application in construction of the buildings will improve the health of structures. In this research paper, dynamic behaviour of the bacterial concrete was investigated numerically. The beams of size 700 × 150 × 150 mm of bacterial concrete and control concrete were modelled using finite element-based package ANSYS19. The beam of bacterial concrete was simulated as per the characteristics of the materials produced after the bacterial metabolism reactions. The EMI technique was applied to investigate the health of these beams. Admittance (conductance and susceptance) signatures were determined using piezo-ceramic lead zirconate titanate (PZT) sensors installed at mid-point on the top surface of concrete beams. The beams were exposed to dynamic loading and the intensity of dynamic loading was increased in four sub-steps. For the quantification of strength development in the concrete beam, the root mean square deviation (RMSD) statistical index had been applied. It was observed that the bacterial concrete beam has more resistance to the dynamic loading.

Dynamic response of thickened tailings in shaking table testing

In this study, an instrumented thickened tailings deposit model was designed, built and employed to evaluate the behaviour of layered thickened tailings to dynamic loading by using a shaking table equipment. The thickened tailings were deposited subsequently in three thin layers in a flexible laminar shear box mounted on top of the shaking table. Cyclic loading with a peak horizontal acceleration of 0.13 g and a frequency of 1 Hz was applied to the layered tailings deposit. Different types of sensors were placed to monitor the accelerations, displacements, volumetric water content and pore water pressures at the intermediate depth of each layer. Results indicated that the acceleration for the bottom and middle layers were similar to that of the base of the shaking table; but, this was not the case for the top layer. The measurements of vertical displacements indicated that all layers of thickened tailings experienced initially contraction and subsequently dilation during the shaking. The excess pore water pressure ratios were found to exceed unity through all layers of thickened tailings when the shaking ended. In other words, the results showed that the layered thickened tailings are susceptible to liquefaction under the considered testing conditions. It is also found that upward pore water migration to the top layer and downward pore water flow to the bottom layer occurred in the thickened tailings deposit. This water migration generated additional pore water pressure and also impacted the vertical displacement and liquefaction susceptibility of the thickened tailings material. The results of this study give a better understanding of the dynamic behaviour of thickened tailings, which is crucial for the safety of thickened tailings systems as well as sustainable mining.