In reflection to the changing behaviors of civil engineering and engineers in the last 50 years, geotechnical engineers today face many challenges in today’s fast-paced changing world. This paper discusses the various attributes needed by a geotechnical engineer to meet society’s demands in the new millennium. Attributes include communication, management and leadership skills; international exposure; multi-disciplinary skills; and crisis awareness. Positive attitude and ethical practice in the profession are the basic necessity to attain the attributes. Civil and geotechnical engineering education and continual reforms in the industry laws and practices play a vital role in nurturing such needs.
Most urban basement excavations use diaphragm wall as part of the retaining system. When it comes to design, the diaphragm wall is generally considered to behave in a plane strain pattern no matter the size of excavation. However, experience shows that the diaphragm wall displacements of small/medium size construction sites are much smaller than expected, which is probably a result of the 3-D effect. In other words, the amount of rebar used in diaphragm wall is more than required. This paper studies 5 small/medium excavation sites to delineate the 3-D effects on the wall behavior. It is proposed that the side walls perpendicular to the main section be regarded as buttress walls in resisting wall displacement. The equivalent length of buttress wall is half the length of side walls. Using monitoring results as a basis for comparison, it is found that the proposed design approach can reasonably simulate the excavation behavior of small/medium size construction sites.
Due to the meteorological characteristics, seasonal typhoon, steep topography and fragile geological conditions, the torrential rainfall induced slope failure and sediment-related disaster frequently occur in Taiwan. Using the existing numerical tools, analysis techniques and case history verification, this study established a feasible numerical procedure which consisted of Rainfall-Pore Pressure-Displacement Rate-Factor Safety Numerical Model (or called R-u-v-F Model) and Rainfall-Sediment- Flow Numerical Model (or called R-S-F Model) to perform a immediate evaluation for the possible influence of sediment-related disaster caused by torrential rainfall. Eventually, integrating the calculation results of R-u-v-F Model and R-S-F Model, a series of simplified application charts were generated. Accompanying with simple field investigations, the simplified application charts can be implemented at the sediment-related disaster potential area to evaluate the hazard potential and used as a reference of disaster prevention, warning system and evacuation during torrential rainfall in typhoon season.
Since the bearing capacity of bored piles was greatly affected by the slime around pile tip, the tip grouting was used to solve the problem. However, the whole process of this technique needs to be verified. The study herein provides the numerical results using computer software GeoStudio 2004 to simulate the tip grouting and pile loading test according to the field data, which help us better understand the variation of pile head settlement, load transfer and frictional resistance during the pile loading test.
The main stadium of 2009 World Game is located in Tzou-ying District of Kaohsiung City. The project site is overlain by a 20m thick silty sand layer, followed by a thick silty clay layer of about 26m in thickness. Bedrock is found beneath GL.-46m. The original foundation design calls for the use of raft foundation alone. However, there was great concerns about the detrimental differential settlement that could be induced by factors such as non-uniformly distributed structural loadings, backfills around the stadium, and a 2m excavation within the stadium. It was later concluded by the design team that a pile-raft foundation system is required. Numerical analyses were carried out to study the possible settlement of the main stadium. It was found that the maximum settlement of the pile-raft foundation is about 6cm, while the angular distortion is about 1/567, both satisfied the structural needs.
A case study of damaged piled foundation due to 1995 Kobe earthquake was carried out in this study using a numerical tool. An effective stress analysis was conducted on investigating the failure mechanism of this building during this major earthquake, of which FE-FD staggered solution was adopted in the numerical scheme, AFD model was used to represent the nonlinear behavior of pile, and a cyclic elasto- plastic soil model was used for reproducing the dynamic soil behaviors. This numerical result shows the failure of pile of this building system gathered at pile head and the segment between liquefied and non-liquefied soil layers, which were also observed in the site investigation.
The ground has to be excavated when the railway is buried underground. Consequently, during this excavation period, it will be unavoidable to prevent the train from moving close to the diaphragm wall while keeping the railway traffic running smoothly. This article will study the increasing stress derived from the moving train in proximity of the diaphragm wall and steel support as well as the ground vibration caused by the moving train. The geometry, including the (1) diaphragm wall, (2) steel supporting facilities and (3) surrounding environment is so complicated that a 3D FEM built on the ANASYS must be employed in order to probe into the ground vibration. In this study, the influence of K-18 moving train on the ground vibration is based on the time domain transient analysis. It is expected that the conclusion described in this paper would be helpful for engineers in gaining the ability of the analysis so that a more effective design can be developed for such problems in the future.
City rails (e.g., rapid transit) are always constructed above (via. viaducts) or under (via. tunnels) the existing road systems to reduce conflicts of land use and risks of construction effects on the adjacent buildings. As the network of the rapid transit system becomes well developed, however, the foundation of the viaducts may be constructed on or by the tunnels; such complicated soil-substructure interaction makes numerical simulations an important tool to geotechnical analysis and design. This paper presents a design project for the Circular Line of Taipei Rapid Transit, in which the three-dimensional (3D) model of Midas/GTS is applied to investigate the construction and loading effects of pile foundation on the adjacent shield tunnels, including simulations of soil-pile-tunnel interaction and a series of construction steps. The computed distributions of tunnel deformations can be used as references for monitoring system setup and construction control.
Taipei Mass Rapid Transit Corporation has recently completed the first phase of their network, and the second phase will also be completed in the near future. Besides that, there are several additional routes currently in the planning stage. The continuous increase in the mass rapid transit network expands the complexity in the designing process due to the overlapping in both the stations and routes. Therefore, in terms of geotechnical analysis, the finite element analysis must be more complex to tackle this intricate problem (from 1-dimensional analysis, 2-dimensional analysis to 3-dimentional analysis). Because of the variability in soil and water, the numerical analysis software for geotechnical engineering is not as straightforward as those being used in structural analysis. The key to a successful geotechnical analysis relies on the experiences of the user. In this research, we used a case study to demonstrate how to incorporate experiences to conduct analysis in all the analytical software and compare their results. The information will be highly useful to evaluate the impact on the existing stations from nearby construction.
The island of St. Vincent, located in east Caribbean Sea, was formed by volcanic eruption. There are 3 volcanic centers in the island which raised the terrain abruptly to 1219m high from coast to its middle, narrow ridges with steep gradient and watersheds were then developed. Its volcanic geological formation is complicated, varying from hard lava magmas to weathering pyroclastic debris. The island is only 18km wide, but because of its critical terrain and geological formation, there is yet to have a passage to connect the east and west coast. The St. Vincent Government thus decided to build a Cross Country Road passing through the heavily rainfall and dense forest area.
The Design Work, including the site reconnaissance, topo-survey, geo-survey and investigation, route selection, preliminary and detail design, and contract documentation, had to be completed in 20 months. The Design Group had to apply modern techniques to facilitate the survey and investigation work. On the other hand, based on their profound study, the group had also to work out a 19.71km alignment within the corridor assigned by the Government, to modify the construction methodology and technical requirements to cope their design works with local environment and resource.