Rock Tunneling Applied to Steady Water Resources Supply in Taiwan: Challenges and Examples
Chia-Han Lee, Tai-Tien Wang, Shih-Hsien Chang, Shang-Yao Lien and Shih-Wei Huang
ABSTRACT: Increasing soil erosion and slope collapse in some catchment area in Taiwan in the past decade has increased sedimentation rates of reservoirs and reduced their effective capacity, severely affecting the steady water supply. Among multiple measures that have been proposed for stabilizing the water supply, the construction of tunnels for trans-basin diversion and the release of sediment are the most effective and sustainable. Tunneling in a catchment area, even close to a dam, represents serious environmental and engineering risks. This manuscript presents two cases of rock tunneling applied to steady water resources supply. The background of these two projects, relevant geotechnical conditions and tunneling designs are presented. Challenges and some distinctive issues, such as the presence of a high temperature ground, a combustible gas emission ground, and potential instability of rock wedges caused by large underground excavation, are discussed. Associated countermeasures are then presented, associated with a clever design of an elephant-trunk intake pipe to release turbid water from 15 m below tunnel entrance, and related design strategies applied for a huge underground stilling pool and outlet sections. State-of-the-art tunneling through rock and some innovative tunneling technologies are utilized in these two cases.
KEYWORDS: Sedimentation of reservoirs, Rock tunneling, Trans-basin diversion tunnel, Sediment-sluice tunnel
State-of-the Art of the Tunnel Maintenance in Taiwan and Challenges to Sustainable Development
Ya-Chu Chiu, Tai-Tien Wang, Tsan-Hwei Huang
ABSTRACT: Tunnel construction of Taiwan started early in late nineteenth century. Within 125 years, tunnel maintenance in Taiwan went through several stages. In early days, engineers meant tunnel excavation. Tunnel inspections, repairs and reinforcement were performed only when serious damage was observed. As the number of damaged tunnels increased, investigations of the most frequently recurring anomalies revealed that the degradation of tunnels in Taiwan was inevitable and usually occurred in an exceptionally shot period. Frequent earthquakes, a high ground water level and poorly cemented rock masses provides a severe environment for engineering structures. Hence, to adapt more effectively to the environment, tunnel maintenance started to consider the entire life cycle of a tunnel. Recently proposed monitoring technologies and anomaly cause diagnosis methods of Taiwan have been demonstrated to be useful in supporting the sustainable operation of tunnels.
KEYWORDS: Tunnel, Tunnel maintenance, Tunnel inspection, Tunnel repair, Tunnel reinforcement
Tunneling Issues Regarding the Rock Tunnel-Shaft Intersection in Taiwan
Tai-Tien. Wang, Tzu-Tung. Lee, Shun-Min. Lee, Kwei-Shr. Li and Cheng-Hsun Chen
ABSTRACT: The construction of an intersection between a shaft and a rock tunnel is a three-dimensional problem, and requires more complex excavation and support method than those used in conventional two-dimensional tunnel construction, and this fact affects both design and construction. Considering examples of rock tunnelling in Taiwan, this investigation reviews the construction of intersections between shafts and tunnels and related issues. First, cases of construction are collected and reviewed, and the excavation sequences are classified. Challenges to secure construction of the intersections of shafts and tunnels are investigated, including significant scale effects of rock masses on excavations with large cross sections, construction difficulties that are caused by the complicated arrangement of underground excavations, difficulties in controlling rock deformation near the intersections, and groundwater ingress. Strategies and countermeasures applied to overcome these difficulties are introduced with reference to recent projects, and their effectiveness is investigated. Finally, the state-of-the-art design and construction of intersections between shafts and tunnels in Taiwan are presented.
KEYWORDS: Shaft, Rock tunnel, Intersection, Scale effect, Deformation control, Groundwater ingress mitigation.
Assessment of Hard Rock Tunnel Stability: A Note on the Influence of Post-peak Strength Degradation
F. Y. Hsiao, H. C. Kao and S. Y. Chi
ABSTRACT: Tunnelling depth is increasing rapidly in Taiwan. The effect of brittle failure on hard rock tunnelling is, however, rarely studied. For this, in this paper, a study is carried out on the post-peak form of the Hoek-Brown failure criterion and the strength loss experiment, whereby a relationship between strength loss parameter and confining stress is established. Subsequently, a numerical analysis model, so-called strength degradation model, is proposed and applied to predict the impact of the post-peak strength degradation on an actual tunnel. The analysis shows that the effect of the post-peak strength degradation on excavation deformation is becoming more and more pronounced with increasing depth. Severe excavation deformation may endanger tunnel stability during construction in deep overburden. The strength degradation beyond brittle failure shall play an exceptionally important role in the stability of deep tunnelling.
KEYWORDS: Brittle failure, Numerical analysis, Post-peak strength degradation, Tunnel stability
Deep Excavations in Taipei Basin and Performance of Diaphragm Walls
R. N. Hwang, C. H. Wang, C. R. Chou and L. W. Wong
ABSTRACT: Since movements of diaphragm walls are reduced by the presence of existing underground structures in the vicinity of excavation, comparison of the observed wall deflections with the results obtained by using two-dimensional analyses may lead to erroneous conclusions. Similarly, additions to diaphragm walls, such as buttresses, station entrances, ventilation shafts, etc., will also tend to reduce wall deflections. It is thus recommended to compare the results of two-dimensional analyses with the upper envelopes, designated as “reference envelope”, of a family of wall deflection paths of the same geometry of excavation and the same characteristics of the retaining system.
Inclinometer readings obtained at Shandao Temple Station of the Bannan Line of Taipei Metro were studied to establish the relationship between wall deflections and depth of excavations. The results are verified by numerical analyses using computer program PLAXIS. Reference envelopes were developed for the T2 Zone for estimating maximum wall deflections and charts were established for correcting inclinometer readings to account for the movement at diaphragm wall toes. It has been found that the width of excavation has significant influence on wall deflections and toe movements. It has also been found that consolidation of the Songshan Formation due to the drawdown of groundwater in the Jingmei Formation reduce the movements of diaphragm wall toes.
KEYWORDS: Deep excavation, Taipei Basin, Diaphragm wall, Wall deflection, Toe movement, Parametric study, PLAXIS
Hydraulic Characteristics of Jingmei Formation and Dewatering for Deep Excavations in Taipei Basin
G. R. Yang, L. W. Wong and R. N. Hwang
ABSTRACT: The presence of the Jingmei Formation is a unique geological feature of the Taipei Basin. This highly permeable and waterrich stratum was responsible for many failures in underground constructions. The piezometric heads in the Jingmei Formation had to be lowered by pumping for deep excavations to be carried out safely. Discussed herein are the hydraulic characteristics of the Jingmei Formation and the experience gained in large scale dewatering schemes. Attempts have been made to establish the relationship between the progression of tides in the river and the fluctuation of the piezometric levels in the Jingmei Formation.
It has been found that, the transmissivity and storage coefficient deduced from the observed groundwater drawdown are affected by not only the pumping rate, but also the duration of pumping. Therefore, the rates required tend to be overestimated based on the results pumping tests.
KEYWORDS: Jingmei Formation, Taipei Basin, Underground Construction, Deep Excavation, Dewatering
Forensic Investigation of A Subway Tunnel Construction Failure
W. F. Lee, C. C. Wang, K. Ishihara, R. N. Hwang
ABSTRACT: In this paper, the forensic evidences and investigation of a subway tunnel construction failure occurred in Kaohsiung, Taiwan are presented. The studied construction failure occurred during a cross passage excavation of a shield tunnel construction work of the Kaohsiung Mass Rapid Transit System, and resulted in severe tunnel collapse and extensive ground failure that even reached to ground surface 30m above the tunnel depth. Valuable photo images obtained during and post event, as well as results of special geophysical testing methods were presented and compared to verify proposed failure scenario. Information presented in this paper is hoped to be helpful to improve engineers’ knowledge for preventing similar construction risks.
KEYWORDS: Subway, Shield Tunnel, Cross passage, Resistivity Image Profiling Method
Case Study of Renovation on Alishan Route 18 after Typhoon Morakot
Kung-Tai Chou, Wen-Long Wu, Chiao-An Hsiao, Kun-Hsien Chou
ABSTRACT: Typhoon Morakot has brought Taiwan tremendous rainfall in a hundred-year recurrence period. The roads and houses in the middle and southern part of Taiwan have suffered from landslides, debris flows, and floods. Erosion of road foundations, sliding of slopes, and collapse of bridges have paralyzed the road system. Using Alishan Route 18 as an example, this paper discusses different causes, types, and renovation methods of slope disasters for future reference.
KEYWORDS: Typhoon Morakot, Road, Slope, Disaster, Remediation measures
Combining rainfall parameter and landslide susceptibility to forecast shallow landslide in Taiwan
C.F. Lee, C.M. Huang, T.C. Tsao, L.W. Wei, W.K. Huang, C.T. Cheng, and C.C. Chi
ABSTRACT: Catastrophic landslides and debris slides triggered by typhoons such as Typhoon Morakot (2009) have occurred more frequently in the recent years, and caused many casualties and much economic loss in Taiwan. For the purpose of reducing the damage and preventing loss of life resulting from geological hazards, this study collects multiple period landslide inventories which contain the information of occurrence time, location, magnitude, rainfall intensity, accumulated rainfall to establish the rainfall threshold for shallow landslides on a regional scale. This study applies the concept of a hazard matrix which combines the magnitude (landslide ratio of slope units) and the possibility of occurrence (historical disaster records) to set up the early warning thresholds. Accordingly, the critical rainfall thresholds are build up based on the R24 (24 hours cumulated rainfall) and I3 (3-hour mean rainfall intensity) of historical records. A validation result shows the model can predict the possible sediment hazard on the hillslope 2~9 hours before occurrence of landslides. The web-GIS based early-warning system is also developed to display the real-time rainfall data and assess the warning signal immediately for disaster prevention through increasing the response time.
KEYWORDS: Shallow landslide, Landslide susceptibility, Slope unit, Rainfall threshold
Dynamic Analyses for Performance-Based Seismic Design of Geotechnical Structures with Examples in Deep Foundations
D.W. Chang, C.W. Lu, S.S. Lin and J.R. Lai
ABSTRACT: Performance-Based Seismic design (PBSD) of the geotechnical engineering structures can be evaluated by a number of methods taking into account the uncertainties of the designed influence factors. Despite the fact that the seismic force is known to be a significant factor, the static and/or pseudo static analyses seem to be commonly adopted in design practice. This paper briefly discusses alternate approaches with the emphasis on dynamic analysis. Examples are given by the assessments of two deep foundations located in Taiwan. It can be found that dynamic analysis is rather important to the seismic design problems since it can monitor the details of timedependent structural responses incorporating both peak ground acceleration and duration of the earthquake. Other than the 3D finite element analysis, the simplified solution from 1D wave equation analysis can be very effective and convenient for PBSD analysis on deep foundation.
KEYWORDS: Dynamic analysis, Seismic performance, Performance based design, Pile foundation
Time-Dependent Dynamic Characteristics of Model Pile in Saturated Sand during Soil Liquefaction
Chia-Han Chen, Yung-Yen Ko, Cheng-Hsing Chen and Tzou-Shin Ueng
ABSTRACT: In order to quantify the relation between soil stiffness and excess pore water pressure during liquefaction, the test data of a series of shaking table tests on model pile in saturated sand using a large biaxial laminar shear box conducted at the National Center for Research on Earthquake Engineering were analyzed. The pile tip was fixed at the bottom of the shear box to simulate the condition of a pile foundation embedded in a firm stratum. The pile head was mounted with steel disks to simulate the superstructure. In addition, strain gauges and mini-accelerometers were placed on the pile surface to obtain the response of the pile under shaking. Therefore, the model pile can be considered as a sensor to evaluate the changes of dynamic characteristics of soil-pile system during the shaking by using the time-frequency analysis and system identification technique. The results showed that the stiffness of the soil would increase with the dissipation of pore water pressure and the recovery of soil stiffness is directly related to the effective stress ratio of soil specimen.
KEYWORDS: Shaking table test, Soil liquefaction, Excess pore water pressure, Time-frequency analysis, System identification
Geological Investigation and Sliding Mitigation in Jiufen Area
Lee-Ping Shi, Jen-Cheng Liao, Sheng-Hsiung Hung and Chien-Shui Huang
ABSTRACT: Jiufen’s orographic and geological characteristics together with frequent typhoons and heavy rain make it potentially vulnerable to landslides. The landslide problems could be disastrous not only to the 2,300 local residents, but also to the constant flow of tourists visiting the town. After the site investigations, it is concluded that both of the colluvium and groundwater are the most important geological factors to the slope stability problems. According to the long-term groundwater level monitoring result, it varied from 8m to 12m during the period of typhoon and heavy rainfall. And the displacement induced by the groundwater level rising was found. Four underground flow lines were located based on the resistivity image profiling and self-potential investigation. Then five water collection wells were planned to construct according to the locations of underground flow lines. The level lowered down about 15m after the wells completed and the slope became stable. It is suggested that the depth of colluvium in Jiufen area needs to be investigated in more detail.
KEYWORDS: Landslide, Site investigation, Geological survey, Monitoring, Slope stability analysis
Interpretation and Analysis of Potential Fluidized Landslide Slope
H. M. Shu, T. C. Chen, W.C. Yang and Y.X. Luo
ABSTRACT: Fluidized landslide, also called hillslope-type debris flow, often occurs on the village side hillslope in the mountain area during extreme weather condition. Fluidized landslide induces more severe damages than the shallow landslide; however its recognition model is still lacked. In this research a recognition model of the potential fluidized landslide slope was developed using 80 cases occurred in the Kaoping River basin, southern Taiwan. 30 fluidized landslides and 30 shallow landslides are employed for the model development and another 10 events of each landslide are applied for verification. Results show that the recognition model composed of 8 discriminant factors including geomorphology factors, hydrology factors and potential landslide factor predicated by SHALSTAB model provides accuracy rate of 85% of the verification events. Thus the model can be of practical use for fluidized landslide interpretation. The model can be used to identify the potential dangerous slope areas and effectively assist the disaster prevention and early warning of villages in mountain area.
KEYWORDS: Fluidized landslide, Discriminant analysis, Recognition model, SHALSTAB
Interpretation and Analysis of Potential Fluidized Landslide Slope
H. M. Shu, T. C. Chen, W.C. Yang and Y.X. Luo
ABSTRACT: Fluidized landslide, also called hillslope-type debris flow, often occurs on the village side hillslope in the mountain area during extreme weather condition. Fluidized landslide induces more severe damages than the shallow landslide; however its recognition model is still lacked. In this research a recognition model of the potential fluidized landslide slope was developed using 80 cases occurred in the Kaoping River basin, southern Taiwan. 30 fluidized landslides and 30 shallow landslides are employed for the model development and another 10 events of each landslide are applied for verification. Results show that the recognition model composed of 8 discriminant factors including geomorphology factors, hydrology factors and potential landslide factor predicated by SHALSTAB model provides accuracy rate of 85% of the verification events. Thus the model can be of practical use for fluidized landslide interpretation. The model can be used to identify the potential dangerous slope areas and effectively assist the disaster prevention and early warning of villages in mountain area.
KEYWORDS: Fluidized landslide, Discriminant analysis, Recognition model, SHALSTAB
Hosoi Takeshi and Matsushita Shinya
ABSTRACT: Recent technologies for diaphragm wall are highlighted and their technical level is reviewed whether they meet the technical requirement and demand. Then their future views and challenges on the following technologies are discussed: slurry fluids, trench stability, concrete, rebar, slime removal, vertical accuracy control, low headroom machine, and machine for the installation of diaphragm wall underexisting structures.
KEYWORDS: Polymer, Trench stability, High grade concrete, Rebar cage movement, Slime removal, Base grouting, Vertical accuracy, Low-headroom excavator, Existing under-structures.
HISTORICAL NOTE ON “Experiences of Geotechnical Development in Japan and Future Directions”
Masami Fukuoka
ABSTRACT: Geotechnical engineering (Doshitsu-Koogaku in Japanese) was used since Terzaghi’s Erdbaumechanik was translated into Japanese around 1930. The report of the Swedish National Railways about geotechnical engineering was translated into Japanese by the Committee of Geotechnical Engineering, Japanese National Railways, and used as practical reference. The geotechnical engineering was applied effectively for the prevention and restoration of natural disaster and developing food production during 1945-55. Prof. Noboru Yamaguchi presented a paper to the first International Conference in 1936. The Japanese Society of Soil Mechanics and Foundation Engineering was established in 1950, and have been presenting papers and sending delegates to every International Conference. The Soils and Foundation has been issued since 1960. The 9th International Conference of Soil Mechanics & FE was successfully held in Tokyo. Through these activities, geotechnical development in Japan has been published to other countries in the world. Before 1965, we learned a lot from other countries. After 1965, the wave of internationalization has advanced remarkably, and it becomes difficult to extract pure advance of geotechnical engineering in this country. There were many big projects like Seikan Tunnel, Honshu-Shikoku Connecting Bridges, Shinkansen, Highway, Kansai International Airport and Trans-Tokyo-Bay Highway. In connection with these projects, the geotechnical engineering has been developed, and applied to other construction works. There are many important items to be solved. They are environment, energy and labour saving, cost reduction, maintenance, etc. Innovation is necessary to cope with these future problems. Technology transfer to other countries is also important.
