3 D Computer Modeling Of Subsurface Conditions For Bridge Foundations
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3-D Computer Modeling of Subsurface Conditions for Bridge Foundations
A study was conducted to evaluate the potential for using three-dimensional (3-D) computer modeling to assist Missouri Department of Transportation Soils and Geology personnel and Bridge Division personnel in developing accurate and realistic understanding of subsurface conditions for bridge structures. Secondary objectives of the study included developing a preliminary procedure for development of 3-D geologic models of bridge sites and identifying key issues to be addressed for more widespread use of 3-D modeling activities. The site of a proposed new bridge across the Missouri River near Lexington, Missouri was selected as a demonstration case study for 3-D geologic modeling. Several separate models of this site were developed during the project to demonstrate the different levels of abstraction for a 3-D model of a particular site. The computer models developed are presented and described in this report.
Modeling of Seismic Wave Scattering on Pile Groups and Caissons
This report documents practical modeling procedures adopted in the bridge engineering community involving seismic dsigns and retrofits of long span bridges relative to treatment of wave propagation problems. It also discusses wave scattering issues arising from irregular foundation boundaries affecting seismic loading of the bridges, which is not explicitly considered in th current design practice. Wave scattering is generally implemented in the nuclear power plant industry for seismic designs of various containment systems often using frequency domain computer programs. To examine the subject of wave scattering for application to long span bridge foundations, systematic modeling is exercised using a time domain based computer program and verification is made against a frequency domain computer program. For present day seismic designs of major bridges, nonlinear time history analysis is a common procedure to examine seismic loading of the structure permitting plastic hinging and ductility to be implemented. Thus, the current trend is to adopt time domain based computer programs for performing wave scattering analyses which can also serve as a common platform to be used by both geotechnical and structural engineers for the global bridge model. A major benefit is to minimize the amount of work for data transfer and potential error arising from two different groups (geotechnical and structural engineers) working on different computer codes requiring different input/output. By using the same computer code by both geotechnical and structural engineers, many problems are eliminated. Typically, wave scattering analyses are conducted in the frequency domain. This report presents studies of wave scattering using a time domain computer program. The same computer program can be used by structural engineers to proceed with coding the superstructure model, directly using the results from the wave scatterings analysis. The report presents various sensitivity analyses in order to minimize wave reflection and refraction at the model's side boundaries. Numerical integration schemes and implementation of Rayleigh parameters are discussed. Careful examination of waves traveling the bottom boundary allows proper modeling of the half-space below the region of interest. The studies explore the effects from wave scattering on large pile groups and soft ground conditions, and findings on the frequency ranges where significant scattering is observed are reported. Large caissons are know to affect seismic wave scattering due to the large wave length implied by the dimensions of the foundation embedded in soil. Parametric studies are performed to examine the shaking level that is altered by the wave scattering mechanism. From the current findings, it appears that the wave scattering tends to reduce the shaking level, especially in the high frequency range, and hence is beneficial to the bridge design
Rock Mechanics: Achievements and Ambitions
Rock Mechanics: Achievements and Ambitions contains the papers accepted for the 2nd ISRM International Young Scholars’ Symposium on Rock Mechanics, which was sponsored by the ISRM and held on 14–16 October 2011 in Beijing, China, immediately preceding the 12th ISRM Congress on Rock Mechanics. Highlighting the work of young teachers, researchers and practitioners, the present work provides an important stimulus for the next generation of rock engineers, because in the future there will be more emphasis on the use of the Earth’s resources and their sustainability, and more accountability of engineers’ decisions. In this context, it is entirely appropriate that the Symposium venue for the young scholars was in China — because of the rock mechanics related work that is anticipated in the future. For example, in the Chinese Academy of Sciences report, “Energy Science and Technology in China: A Roadmap to 2050”, it is predicted that China’s total energy demand will reach 31, 45, 61 and 66 x 108 tce (tonnes of coal equivalent) in 2010, 2020, 2035, 2050. The associated per capita energy consumption for the same years is estimated at 2.3, 3.1, 4.1 and 4.6 tce. This increasing demand will be met, inter alia, by the continued operation and development of new coal mines, hydroelectric plants and nuclear power stations with one or more underground nuclear waste repositories, all of which will be improved by more modern methods of rock engineering design developed by young scholars. In particular, enhanced methods of site investigation, rock characterisation, rock failure understanding, computer modelling, and rock excavation and support are needed. The topics in the book include contributions on: - Field investigation and observation - Rock constitutive relations and property testing - Numerical and physical modeling for rock engineering - Information technology, artificial intelligence and other advanced techniques - Underground and surface excavation and reinforcement techniques - Dynamic rock mechanics and blasting - Predication and prevention of geo-environmental hazard - Case studies of typical rock engineering Many of the 200 papers address these topics and demonstrate the skills of the young scholars, indicating that we can be confident in the continuing development of rock mechanics and rock engineering, leading to more efficient, safer and economical structures built on and in rock masses. Rock Mechanics: Achievements and Ambitions will appeal to professionals, engineers and academics in rock mechanics, rock engineering, tunnelling, mining, earthquake engineering, rock dynamics and geotechnical engineering.