New Austrian Tunneling Method (NATM) was introduced to Taiwan for the design and construction of rock tunnels in the early 1980s. Experience of utilizing NATM in localized tunneling has been accumulated for more than thirty years. Significant improvement in the implementation of NATM is resulted because of continuous research and development. Suhua Highway
Improvement Project, which involves the construction of several tunnels, further refines the application of NATM in rock tunnels. To select the most qualifying consultants and construction teams for this engineering project, the most advantageous tender and the most economically advantageous tendering method have been employed. Multi-temporal geological data and tunneling records on different scales and resolutions which were obtained in previous construction stages have been integrated to update the geotechnical
characteristics and tunnel behavior. This information would be used for the design of the next construction stage and the the preparation of necessary construction resources for the purpose of risk management. Modern communication software is adopted for timely notification to related personnel. In addition, engineering information is openly disclosed such that timely decision-making is possible, and the design and construction team members would be able to keep abreast of any changes in construction data. By
comparing the construction records of Dongao Tunnel, Yungchuan and New Yungchuan Tunnels, we can clearly see that employing NATM in the construction of rock tunnels has achieved the highest efficiency, relative to the conventional construction method.
Using the mountain section of Suhua Highway as the target study area, we investigate the slope movement patterns and develop mitigation strategies for highway slopes. In this paper, historical disaster events, maintenance records, satellite images, aerial photographs, high-resolution digital surface model for the study area are presented. The digital surface model used in this paper was generated by aerial photographs and unmanned aerial vehicle (UAV). Based on the aforementioned multi-temporal data, we examine the variations in the landform of the study area which are caused by slope movements. The proposed methodology helps in identifying the signs of relatively large-scale landslide, which can be used for life cycle assessment of highway construction, maintenance and management.
The Hepin-Nanao section of Suhua Highway Improvement Project is 20 km in total length. Along this section, Guanin Tunnel and Gufeng Tunnel are connected by Gufeng Bridge. During the design and planning stage, the amount of loose volume could not be accurately estimated. Based on the measurement and data collected during excavation, transportation and backfilling, the remaining earth materials of the Hepin-Nanao section are found to exceed the originally estimated amount by 1.2 million cubic meters. The underestimation is caused by the discrepancy in the estimated bulking factor and estimated swell factor, as well as the uneven excavated surface on the periphery of the tunnel.
Two ways were proposed to reuse the remaining earth materials from the Hepin-Nanao section. The first way is to put the materials into the backfill area so as to re-adjust the slope ratio and height of the backfilling area. After backfilling, there would be 0.7 million cubic meters of the remaining earth materials that still need to be taken care of. Hence, the second way to reuse the materials is to transport them to Xin-Ma station by rail, which would then be used as aggregate materials by the Ilan County Government.
Suhua improvement engineering project is intended to mitigate the potential hazards, such as rockfall, landside, traffic accident etc., along the section between Suao-Yilan and Chongde-Hualien of the Provincial Highway No.9. After more than five years of endeavor, the 9.3km Suao-Dongao section of this project, in which the bridge section occupies about 50%, was finally open to the public in February, 2018. Except for a few sections where spread footing foundations were used, deep foundations were mostly employed owing to adverse geological conditions and environmental factors. The aim of this article is to introduce the selection of foundation type for the bridges in the Suao-Dongao section, as well as the problems encountered and relevant countermeasures employed during the construction stage.
As the critical path along the Suao-Dongao section of the Suhua Highway Improvement Project, Dongao tunnel is a twin-tube highway tunnel located between Suao and Nanao of Yilan county. The tunnel, which is 3.32 km in length and 11.52m in net width, traverses Mt. Houi and Dongao Ridge. The tunnel passes through Suao Formation, Xiaomaoshan Fault, Nansuao Formation, Houishan Fault and Dongao Schist. The largest overburden subjected to the tunnel is 515 m. The construction, which is the most difficult one along the Suao-Dongao section, was started on Dec 15th, 2012. Serious cave-ins and groundwater inflow were encountered during the construction. At the design stage of Dongao tunnel, difficulties encountered during the construction of two nearby railway tunnels were carefully studied. Countermeasures to the construction problems, which were anticipated to occur during the construction of Dongao tunnel, were drawn up. Such countermeasures include geological exploration, forepoling, hindrance of groundwater flow. Besides, pre-reinforcement of tunnel heading was used when there was poor ground. The northbound and southbound of Dongao tunnel were broken through on April 26th and Jul 7th, 2016, respectively, while the tunnels started service on Feb. 5th, 2018. Since the tunnel passes through an area with complex metamorphic rock system and abundant groundwater, the experience presented in this paper serves as a great reference for future tunnel construction in difficult ground.
The total length of the Hepin-Nanao section of Su-Hua Highway Improvement Project is 20km. In this section, Guanin Tunnel and Gufeng Tunnel are connected by Gufeng Bridge, which is 12.6 km in length. According to Lin et al. (1993), the rock formation in this section is Wuta formation, which consists of quartz-mica schist, graphite schist with lenticular chlorite schist, thin-layered marble, chert, metasandstone and thick siliceous schist. Due to complex geological structure and presence of multiple rock types, this area is weak and prone to crushing . Based on the mesoscopic observations of the geological structures which were made during the tunnel construction, we explore the morphology of the geological weakness zone when it is under ductile, ductile-brittle and brittle modes of deformation.
Rock masses at great depths are subject to three highly unfavorable circumstances, which are high ground stresses, high earth temperature and high water pressure. These conditions would drastically increase the difficulty of tunneling. Possible tunneling problems include burst of intact hard rock, severe deformation due to squeezing of fractured rocks, huge amount of high-pressure water inflow, high ground temperature, etc.. In Taiwan, there are many tunnel design and construction case histories that are associated with low to medium overburden. However, there is little experience on tunnel design and construction involving high overburden. In recent years, the construction of Chungren Tunnel along the Hochung-Tachingshwei Section of Suhua Highway Improvement Project with a maximum tunnel overburden of about 1,200m is being executed. In this paper, we present the tunnel design and construction data for the high overburden section of Chungren Tunnel which can be used to assess the influence of the three aforementioned unfavorable circumstances on tunnel construction. This case study can provide a valuable reference for tunnel construction under high overburden condition in Taiwan.
Highway tunnels in operation would need more extensive and expensive maintenance in the long run, if they are not properly maintained during service time. Engineering practice shows that efficient operation and maintenance of highway tunnels rely on strategic life-cycle management.
This paper takes Hsuehshan Tunnel as an example to illustrate its life-cycle maintenance and management strategies. Firstly, we introduce the planning and design considerations of the demands and countermeasures that are
expected for the operation stage. Secondly, the strategy and action plans of safety management under operation are discussed. For Hsuehshan Tunnel, modern techniques related to inspection, monitoring and maintenance, as well as the management information system, have been utilized to enhance the data and information linkage and exchange throughout the entire life cycle. Thirdly, the emergency response plan, which is developed to minimize the occurrence of casualties under emergency conditions, is then briefly reviewed. Lastly, we discuss the development a database of 3D tunnel imaging models, which can be extended to the life-cycle maintenance and management of various types of equipment and resources of the tunnel. This database can provide an effective basis for the decision-making of preventive
maintenance work of highway tunnels in the future.
The purpose of this research is to establish a simplified model to estimate the post-liquefaction settlement of low-rise buildings (i.e. number of storeys less than 5; total building height lower than 15m ) with shallow foundations. This model was developed by using finite difference method (FDM) to simulate the interaction between buildings and liquefiable foundation soil with gradually reducing soil parameters. In this study, we first collected case histories (from 1999 Chi-Chi earthquake and 2016 Meinong earthquake) of which low-rise buildings with shallow foundations were damaged due to liquefaction induced settlement. Then, we developed typical soil profile for each study area. The most critical liquefiable layers would be identified by using simplified procedures for evaluating soil liquefaction potential. The post-liquefaction settlement of the building structures due to liquefaction would then be analyzed by FDM with a parameter reduction approach. The parameters of the liquefiable soil layers would be gradually reduced to a level until the settlement calculation results are comparable to those observed in the field cases. Based on the results of all analysis cases, a simple guide is suggested for determining the appropriate reduced soil parameters.