The underground railway system extended towards perimeter of the city as the city gradually expands. It eliminates the noises and vibration cause by trains’ moreover it clears the corridor of railway crossings in the city place as result of better traffic flows and development in the city. The key for planning underground railway system is to focus on reducing levy upon private land and houses, moreover increases traffic flow and maintain operational safety during reconstruction period. The range of the construction project starts from the existing railroad on the west side of Keelung road to Huling street, where reconstruction of cut and cover tunnel has taken place. The restriction of land use forces the engineers to give up conventional method of building a new retaining wall for the tunnel excavation. To retaining for the tunnel excavation face engineers design to use the existing retaining wall implemented with soil improvement method. The tunnel reconstruction process includes demolition of existing tunnel before new tunnel is constructed, space limitation for the machineries, change construction procedures, demolish and prop up techniques for the reconstruction. The article summaries several design and construction features for the project.
In this article, a case study is introduced to the application of ground freezing method on cross passage. Various studies are conducted in this paper, including ground freezing design, construction risk assessment and management, and further discussion after final construction. Feed-back analysis is also performed based on well-documented monitoring data. This case study can be as a reference for future ground freezing design on cross passage.
Rapid transit system is developed in order to provide the required transportation for urban area. The cut and cover construction method is applied for most of the Taipei Rapid Transit System stations, which are founded on the wide and major roadway, in the initial stage. However, the new routes are arranged on narrow road for the 2nd stage of the transit system. The large scale and complicated utilities existed under the narrow road restrict the flexibility to build a cut and cover station. As mined stations are adopted in many major cities around the world to enhance the flexible of service route, and reduce the land acquire, a different concept to planning a mined station in Taipei will needed in order to reduce the impact of traffic and environmental, shorten schedule, less cost and excavation deposit, etc. The challenges and their counter measures of mined station are invested to guide a different station concept for the rapid system in Taipei Transit System.
According to the design route, one shield tunnel in the Songshan Line of Taipei MRT shall pass underneath the underground parking lot at Tacheng Park and may conflict with 6 reinforced concrete piles with 1.5m in diameter. Since the shield machine is incapable of cutting through piles with such a large size, the piles in conflict have to be demolished manually before tunneling. Detailed monitoring plans and automatic monitoring systems are introduced, following a series of structural simulations and geotechnical engineering safety analyses and evaluations. Ground improvement is first applied around the piles from the bottom slab of the parking lot. Miners are then sent out of the shield machine to demolish the sections of piles in conflict. This paper illustrates structural analyses and safety assessments of the underground parking lot, demolition procedures, and setup of the automatic monitoring systems. It is hoped that this case study can provide as a reference for similar projects in the future.
This paper describes the essential concerns for the barrette installation and the adaptability study for the construction equipments. The causes resulting in unattainable ultimate(failure) capacity under proposed testing load are addressed as well. To verify the behaviors of skin friction and end bearing for circular bored piles and barrette, two case histories using t-z and q-w curves for comparison are presented. The article also introduces a record-breaking load testing project in which had hit 6000T mark using anchor barrettes as reaction system.
Cities have been upgrading their functions for pursuing the convenience in human life and production activities. This pursuit is appeared to take the form of constructing structures and related facilities. Structures, such as buildings, roads, railways, river banks, drinking water, sewerage facilities and etc., were constructed to meet the human needs at times, however, the necessities to compensate problems, such as the aging of those facilities, the shorting due to population increase, the threat of earthquakes or floods, have repeatedly demanded the restructuring of those facilities.
Today, reconstruction seems to have at grade land fully occupied with structures, and therefore, the utilization of underground space is further anticipated. The improvement in construction technologies, construction equipment, and the development of new materials have been enabling to work in underground spaces.
This report addresses the changes and methods of soil improvement technologies primarily demanded by underground utilization in relation to recent city renaissance projects that the author was involved.
It has been more than two decades since the first tunneling construction was implemented in Taipei MRT system. Reviewing the over 20-year evolution of the underground tunneling, we actually found that the said design and construction have been much progressing. However, we have encountered with a number of difficulties in the structures and shield tunnel when we performed the construction of the Taipei MRT successive routes which pass through the satellite cities around Taipei with narrow streets and crowded buildings. The gist of the article is to introduce the underpinning method which has been adopted recently in the design and construction of the shield tunneling of the MRT construction. By means of the case study, the readers will understand the underpinning procedure how the piles are partly cut, the new foundation is implemented, the stress is transferred, and the monitoring is carried out, and finally the double tube passes through the tunnel smoothly. The case study is served as a reference for the similar construction in the future.
In recent years, cross walls and buttresses are extensively used in deep excavation projects to reduce the lateral deformation of diaphragm wall. In certain projects, diaphragm wall trenching machine was used to construct barrettes to replace drilled shafts, which is a practice that helps to reduce construction interfaces. This paper introduces a case history that incorporates cross walls, buttresses and barrettes to optimize the design in minimizing the excavation induced deformation and foundation settlement.
Design and construction issues related to the cross wall and buttresses, such as the joint type between perimeter diaphragm wall and buttresses, construction sequence of the barrettes, etc., were fully addressed for this project. As verified by the monitoring results, lateral deformation of the diaphragm wall was within the design limit.
This site is located at Xizhi District, New Taipei City. An area of more than 20,000 m2 was excavated to the depth of 9.2 meters by using 20.5-meter diaphragm walls with several types of buttresses and periphery top-down method. A 3D geotechnical numerical method was adopted to analyze the stability and deformation of the retaining system. A 1D numerical method was also used by simplifying the 3D behavior. By comparing the results, uncertainties still remained. Therefore, emergency measures were planed in advance in order to handle the unpredictable situation. Afterward, the excavation had been done smoothly. The actual maximum deformations of diaphragm walls were smaller than the predicted values. After reviewing the excavation procedures and their caused behaviors, suggestions were made to the future similar cases.