线上学术报告通知
时间：2020年12月11日上午9：00-12：00
会议室：腾讯会议131 311 770
主持人：刘华北
时间安排：
1) 9: 00-9:30 Introduction to ACCP &
“The Engineering of Helical Piles from multi-scale testing approaches”
Dr. Lijun Deng, PEng, Associate Professor, Department of Civil and Environmental Engineering, University of Alberta.
Abstract: Helical piles are becoming popular in renewable energy industry and cold regions of Canada. Unlike conventional driven or cast-in-place piles, this pile type, screwed to the ground, is designed with multiple helical plates that are aimed to increasing the pile resistance. Because of this unique characteristics, the capacity, failure mechanism and ground response to pile installation are to be examined in order to fully understand the interaction between soil and helical piles. This presentation will introduce a series of full-scale helical pile tests and small-scale centrifuge model tests. Results are presented in term of load-displacement curves, group efficiency, and pore pressure measurement and prediction, and so on. The research was intended to investigate the helical pile failure, group behaviour, and pore pressure response to helical pile disturbance.
2) 9:30-10:00 “Effect of structure on the mechanical behavior of loess: implications to flowslides in cemented soils”
Dr. Fangzhou Liu, Assistant Professor, Department of Civil and Environmental Engineering, University of Alberta
Abstract: Loess contains predominately silt-sized quartz grains that are bonded by various cementation agents, that is of significant interest to the understanding of the mechanical properties of lightly cemented soils. Loess is problematic upon wetting as its metastable structure can rapidly transform from a cemented solid body to a fluidized material. The results of series of isotropically consolidated undrained tests compare the large-strain behaviors of intact and reconstituted specimens, that show state-dependent flow instability due to the effect of structure. A constitutive understanding is gained using NorSand model by comparing the computed undrained behaviors of intact and reconstituted loess at the same state parameter. The results confirms the strong effect of structure on flow instability. The experimental data of the centrifuge modelling on loess flowslide induced by the increasing phreatic surface is discussed to further analyze the failure process, with emphasize on the effect of changing slope geometry and pore-water pressure on the flow initiation. The drained-to-undrained transition in the loading path of loess is simulated, and indicates a rapid reduction in strength under such a transition for loess, thereby the triggering mechanism of loess flowslides.
3) 10:00-10:30 “Acquisition, identification, characterization and sophisticated DEM modelling of microstructures of granular soils”
Dr. Bo Zhou, Associate Professor, School of Civil and Hydraulic Engineering, Huazhong University of Science and Technology
Abstract: Microstructures, such as mineral composition, particle shape, fabric, internal flaws, are inherent soil characteristics induced by the geological process and origin, which play significant roles into determining the physical and mechanical properties of granular soils. This presentation reviews the recent progress in acquisition, identification, reconstruction, characterization of the microstructures of granular soils, including river quartz sand, residual sand from highly decomposed granite, and calcareous coral sand, by using the nano-focus X-ray μCT and advanced image processing techniques. Based on the understanding of the microstructures, sophisticated DEM and FDEM modelling techniques for these soils are briefly introduced in the speech. The novelty of the study stems from the pioneering application of the state-of-the-art μCT technology, mathematical characterization and sophisticated DEM methods to the exploration of the microscopic mechanical behaviors of sand particles. The findings from this study may contribute to the advancement of the knowledge frontier in the fundamental mechanism of geomaterials.
4) 10:30-11:00 “Vertical and horizontal deformation of a large pile group supporting an LNG tank”
Dr. Cheng Lin, PEng, Assistant Professor, Department of Civil Engineering， University of Victoria
Abstract: An LNG tank is commonly supported by a large pile group with the number of piles up to >1000. It is well recognized that when subjected to vertical load or horizontal load, a large pile group (the number of piles N>100) behaves significantly different from a small pile group (N<25). However, in general practice, design of the large pile group is still established based on the findings from the small size of pile group. This lecture investigates the vertical and horizontal deformation of a large pile group supporting an LNG tank, with a particular emphasis on the limitations of the prevailing design standards. A series of 3D finite element analyses with the numerical models calibrated against the full-scale load tests was performed to appraise the existing approaches for settlement analysis and lateral behavior analysis. Based on the analyses, some improvements to the deformation analysis of LNG tank foundations are suggested.
5) 11:00-11:30 “Towards Smart Cities: Crowdsensing-based Civil Infrastructure Monitoring”
Dr. Qipei Mei, Assistant Professor, Department of Civil and Environmental Engineering, University of Alberta
Abstract: The deterioration of civil infrastructure systems is a challenge for the development of future smart, sustainable, and resilient cities. Continuous monitoring is a crucial component of smart infrastructure in regard to extending their service lives. In this talk, I will present a novel framework for civil infrastructure monitoring based on crowdsensing. With the involvement of general public who carry smart devices into the monitoring and with the help of artificial intelligence and big data analytics, this framework has the potential to monitor a number of infrastructures simultaneously and can significantly reduce the costs. Two projects under this framework will be presented in this talk. In the first project, a methodology using the vibration data collected from a large number of smartphones in moving vehicles is developed for bridge damage detection. In the second project, deep learning algorithms and cameras mounted in vehicles are used to assess the road surface condition.
6) 11:30-12:00 “Mechanisms of segmental lining damage induced by large water inflow and piping in shield tunneling”
Dr. Huabei Liu, Professor, School of Civil and Hydraulic Engineering, Huazhong University of Science and Technology
Abstract: The accidents of water inflow may be possibly induced by improper construction process during shield tunneling through silty sand layer under high water pressure. Three-dimensional tunneling models were established by employing ABAQUS. The objective was to investigate the influence of water inflow from excavation face or seepage erosion between segment joints on ground settlement and structural damage during shield tunneling. Firstly, the numerical approaches were reliably validated by a series of experimental results from the literatures. And then the influences of large water inflow from excavation face on the ground settlement and structural damage were investigated, followed by the effect of seepage erosion on the ground settlement and structural damage. Lastly, the relationship between the erosion-induced structural damage and lining displacement parameters was established. It was found that the longitudinal bolt force could be identified by the axially deflection angle. The number of yielding bolts could be identified by the average vertical convergence rate of linings, and the maximal lining damage could be identified by the maximal vertical convergence rate.
