This case, a three stories reinforced concrete building located at Yuan-Lin Township in the middle of Taiwan, tilted as a result of the Chi-Chi Earthquake on September 21, 1999. Differential settlement of the ground floor slab was 17.3cm and building tilting between 1/110 to 1/150. After using low-pressure cement-water grass mixture grout to restore the tilted building, the maximum differential settlement of the ground floor was reduced to 2.5cm, while the maximum differential settlement of structural frame was reduced to 1.4cm and 1.5cm in the transverse and longitudinal directions, respectively.
This paper describes the restoration plan, including layout of micro piles and jet grout piles serving as curtain wall, and layout of grouting locations. The restoration construction activities, including quality control and survey datum during grouting to restore the tilted building, are also addressed. We hope the experiences gained in this project will provided useful guides for readers.
Shield tunnels have been completed more than 100km since been introduced in 1970 and quite lots of experiences have been accumulated in Taiwan. The safety of shield tunnel relies on lining structures that are designed to sustain the dead load, water pressure and construction load. However, the deterioration of lining structure in the early shield tunnel is unavoidable after operation more than 30 years. To maintain the early stage tunnel in its normal function, an appropriate measure for the maintenance management has to be taken into account.
From life extension and reducing life cycle cost point of view, different stages, such as planning, design, construction, examination, maintenance and reinforcement, cannot divided into apart. They shall be in consistency. To reduce the cost of the future maintenance and management, this study proposes special topics and strategies to be taken into account in the planning design and construction stages. The checking items and methods for maintenance management, ways of safety evaluation, maintenance reinforcement measures and case studies have also included in this paper. It is expect that the concepts and suggestions described in this paper would be helpful for engineers in gaining a further ability of shield tunnel maintenance and management so that more durable tunnel and safety operation can be developed for such problem in the future.
Some of Taiwan’s existing bridges have not been well maintained for years. In addition, frequent natural disasters such as earthquake, typhoon, and torrential rain have worsened the condition of the existing bridges seriously. The rehabilitation of old bridges has to be performed as soon as possible. After the revision of the Bridge Seismic Design Code after 921 earthquakes, the safety evaluation and rehabilitation of existing bridges have commenced step by step. The rehabilitation work will inevitably face the foundation retrofit problem. This paper aims to discuss the causes of bridge foundation retrofit, the decision making flowchart, and the selection of retrofit measures for later foundation retrofit design reference.
A seismic retrofit method, PRISM method, for piers in water without expensive dry-up process is introduced in the paper. Pre-cast panels, including reinforcement steel plates, are used to surround the piers for retrofitting. Subsequently, mortar is used to fill the gap between the pier and the panels.
Experiences gained after some applications prove the workability and quality of the PRISM method. One application is also introduced in the paper to verify the superiority of the construction process and the low construction cost, comparing to other retrofitting methods.
The amount and scale of slope damages in Taiwan mountainous region have drastically increased and expanded since 921 earthquake struck in 1999. Up to date, whenever typhoons or torrential rains attack, landslides would easily cause a great loss of lives and properties and become one of the frequent natural disasters in Taiwan. In particular, numerous landslides in the upper reaches along the Tachia River after the 921 earthquake not only resulted in uplift of the riverbed, but also endanger the safety of structures, roads and dams along the river bank. This study firstly explicates the principle of emergency and long term measures undertaken and the investigation methods employed for the structures on the hillsides. It further analyzes the applicability of each slope stabilization and remedy method. Finally, it gives a general description and an overall review of the slope remedial work and rehabilitation in the vicinity of Kukuan and Techi dam upstream of the Tachia River implemented after the 921 earthquake and heavy rainfall.
The total length of the existing water Transport main, from Chin-Tan weir to the junction box in the Chang-Hsin plant, is about 8,811m. There are only 5 manholes available along the route. The allowable time for rehabilitation is only two months in accordance with the water stoppage for the Chin-Mei Chi pipeline downward re-profiled project. Considering the available time is tight, the simple megascopic inspection method was adapted. The rehabilitation method should comply with the following requirements, such as easy to mobilization, use of non-toxic material, handy equipment, and fast installation, etc. Prior to repairing, the defects and cracks were categorized into five types accordance to with the repairing methods： (a) surface repairing with silicate based chemicals, (b) water sealing injection along the construction joint, (c) water sealing injection along the crack, (d) refilling the holes on the lining, surface finishing and water sealing injection, (e) repairing honeycomb and defects. By means of intensive mobilization of manpower and equipment, this project was completed successfully not only on schedule but also with good quality.
The concept of influence of adjacent underground construction on existing structures are briefly introduced in this paper. Construction works that may commonly induce ground movement are diaphragm wall, pile, deep excavation, shield tunneling and dewatering etc. The process for classifying the extent of influence and uncertainty involved are discussed. Japanese experiences on this subject and local case histories are cited as examples for dealing with this difficult problem.
Constructing shield tunnels near existing structures such as passing underneath buildings, bridges or railways has become more and more common in metropolitan rapid transit projects. For these works it is quite essential to assess the construction impact level, adjust drilling parameters by feedback analysis, arrange monitoring systems based on the behaviors of the existing structure and perform protection countermeasures such as ground improvement. The approaches adopted for shield tunnel construction near existing structures in Kaohsiung Metropolitan Rapid Transit project will be introduced in this article as a reference for similar projects in the future.
Due to the density of MRT lines in Taipei, some new-alignment construction must be driven through the existing wall bodies, and this environmental limitation and safety concern have made the construction even more challenged. The construction of bored tunneling between the Songjiang-Nanjiang station(O12) and Zhongxiao-Xinsheng station(O13) in the Xinzhuang line of Taipei MRT was driven through the underground structure of six panels of the retaining wall beneath the existent tunnels of the Taiwan Railway（TR）and the Taiwan High Speed Rail（THSR）system, including the irregular continuous walls and non-continuous base of foundation piles.
The article states the difficulties to drive through underground wall bodies and shares the countermeasure adopted in the case; it’s expected to provide the similar cases with some reference.