| 1 | Unconfined compressive strength of MICP and EICP treated sands subjected to cycles of wetting-drying,freezing-thawing and elevated temperature:Experimental and EPR modelling显示文摘Microbial-induced carbonate precipitation(MICP)and enzyme-induced carbonate precipitation(EICP)are two bio-cementation techniques,which are relatively new methods of ground improvement.While both techniques share some similarities,they can exhibit different overall behaviours due to the differences in urease enzyme sources and treatment methods.This paper presented 40 unconfined compressive strength(UCS)tests of MICP and EICP treated sand specimens with similar average calcium carbonate(CaCO3)content subjected to cycles of wetting-drying(WD),freezing-thawing(FT)and elevated temperature(fire resistance test e FR and thermogravimetric analysis e TG).The average CaCO3 content after a certain number of WD or FT cycles(ACn)and their corresponding UCS(qn)reduced while the mass loss increased.The EICP treated sand specimens appeared to exhibit a lower resistance to WD and FT cycles than MICP treated specimens possibly due to the presence of unbonded or loosely bonded CaCO3 within the soil matrix,which was subsequently removed during the wetting(during WD)or thawing(during FT)process.FR test and TG analysis showed a significant loss of mass and reduction in CaCO3 content with increased temperatures,possibly due to the thermal decomposition of CaCO3.A complete deterioration of the MICP and EICP treated sand specimens was observed for temperatures above 600C.The observed behaviours are complex and theoretical understanding is far behind to develop a constitutive model to predict qn.Therefore,a multi-objective evolutionary genetic algorithm(GA)that deals with pseudo-polynomial structures,known as evolutionary polynomial regression(EPR),was used to seek three choices from millions of polynomial models.The best EPR model produced an excellent prediction of qn with a minimum sum of squares error(SSE)of 2.392,mean squared error(MSE)of 0.075,root mean square error(RMSE)of 0.273 and a maximum coefficient of determination of 0.939. | Isaac Ahenkorah Mizanur Rahman Rajibul Karim Simon Beecham | 2023 | Journal of Rock Mechanics and Geotechnical Engineering2023，15，5： | 2 |
| 2 | Self-centring segmental retaining walls—A new construction system for retaining walls显示文摘This paper reports on an experimental study on a new self-centring retaining wall system.Four post-tensioned segmental retaining walls(PSRWs)were experimentally tested.Each of the walls was constructed using seven T-shaped concrete segments with a dry stack.The walls were tested under incrementally increasing cyclic lateral load.The effect of the wall height,levels of post-tensioning(PT)force,and bonded versus unbonded condition of PT reinforcement on the structural behavior of the PSRWs was investigated.The results showed that such PSRWs are structurally adequate for water retaining structures.According to the results,increasing the wall height decreases initial strength but increases the deformation capacity of the wall.The larger deformation capacity and ductility of PSRW make it a suitable structural system for fluctuating loads or deformation,e.g.,seawall.It was also found that increasing the PT force increases the wall’s stiffness;however,reduces its ductility.The residual drift and the extent of damage of the unbonded PSRWs were significantly smaller than those of the bonded ones.Results suggest that this newly developed self-centring retaining wall can be a suitable structural system to retain lateral loads.Due to its unique deformation capacity and self-centring behavior,it can potentially be used for seawall application. | Mehdi JAVADI Reza HASSANLI Md Mizanur RAHMAN Md Rajibul KARIM | 2021 | Frontiers of Structural and Civil Engineering2021，15，4： | 0 |
| 3 | Behaviour of self-centring shear walls——A state of the art review显示文摘The application of unbonded post-tensioning (PT) in structural walls has led to the development of advanced self-centring (rocking) shear wall systems that has significant advantages, including accelerated construction due to the incorporation of prefabricated elements and segmental construction for different materials (e.g., concrete, masonry, and timber), reduced residual drifts, and little damage upon extreme seismic and wind loads. Concrete, masonry, and timber are often used for the construction of unbonded PT structural wall systems. Despite extensive research since the 1980s, there are no well-established design guidelines available on the shear wall configuration with the required energy dissipation system, joint’s locations and acceptance criteria for shear sliding, confinement, seismic performance factors, PT loss, PT force range and residual drifts of shear walls subjected to lateral loads. In this research a comprehensive state-of-the-art literature review was performed on self-centring shear wall system. An extensive study was carried out to collect a database of 100 concrete, masonry, and self-centring shear wall tests from the literature. The established database was then used to review shear walls’ configurations, material, and components to benchmark requirements applicable for design purposes. The behaviour of concrete, masonry and timber shear walls were compared and critically analysed. The general behaviour, force-displacement performance of the walls, ductility, and seismic response factors, were critically reviewed and analysed for different self-centring wall systems to understand the effect of different parameters including configurations of the walls, material used for construction of the wall (concrete, masonry, timber) and axial stress ratio. The outcome of this research can be used to better understand the behaviour of self-centring wall system in order to develop design guidelines for such walls. | Mehdi JAVADI Reza HASSANLI Md Mizanur RAHMAN Md Rajibul KARIM | 2023 | Frontiers of Structural and Civil Engineering2023，17，1： | 0 |
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