The northern part of the Central Range in area north of Hoping River exposes many kinds of metamorphic rocks including two slate-dominated strata namely Suao Formation and Nansuao Formation, three schist-dominated strata namely Tungao Schist, Nanaoling Schist and Wuta Schist, four metamorphosed igneous bodies namely Fongshushan Amphibolite, Yuantoushan Gneiss, Fanpochienshan Gneiss and Tachoshui Gneiss, and Hanpen Marble. This paper introduce main lithologies of these strata and discuss the structural characteristics of metamorphic rocks applied to engineering purpose. Among that, secondary foliations such as slaty cleavage and schistosity are the main weak planes in metamorphic terrane, and therefore it needs more concern during engineering construction.
The Tananao Schist exposed in the eastern slope of the Central Range is the oldest rock of Taiwan and formed under many tectonic events. The original contact relationships are overprinted that resulted from metamorphic events and associated deformations, and therefore is difficult to carry out structural analysis. In addition, the ambiguous and disordered outcrops are insufficient to establish the deformation history of the Tananao Complex. In this study, we first focus on the preserved complex geometries of structures to correlate the overprinting folds throughout the whole area, and second correlate these different structures with the geological characteristics and investigations in area south of the Hoping river of Taiwan.
In-situ stress state plays an important role of underground construction design, natural resources development and underground waste disposal. Anelastic strain recovery (ASR) method of retrieved cores can be used to quickly evaluate the three-dimensional stress state, including directions and magnitudes of stresses, by measuring relaxed strain on a single core, which are its strong advantages. The purpose of this article is to briefly introduce the principles, experimental procedures and data analysis of ASR. One case study in the retrieved meta-granitic core of Hoping, Hualien is also illustrated the application of ASR in Taiwan.
This study adopts a non-conventional maintenance approach, including statistical analysis for correlation between historical repairing costs, international roughness index (IRI) along a road and the critical precipitation that causes instability for highway neighboring slopes, to examine the geotechnical characteristics along the eastern section of the central-cross island highway and associated influences on its maintenance tasks. The critical precipitation is relatively low, indicating that the highway has poor resistance to nature disaster. Hazard types for the highway are mainly affected by its relative location to a slope and geotechnical characteristics, and can be classified into three major types: 1) Roadbed disaster caused by rock sliding or debris fall with a creak-side slope neighboring to the highway, 2) traffic blocked caused by rock sliding or debris fall with slopes next to the highway, and 3) rock fall from a hill-side slope neighboring to the highway. Geotechnical factors accounting for these highway hazards include the freezing and thawing effect in high elevation mountain area, foliation and associated dip slopes, well-developed folding and schistosity, differential erosion in boundary of schist and marble stratum and associated weak zone, and regressive erosion on upstream of Liwu River and its branches. Additionally, the IRI can estimate smoothness along the highway, and also has relations with creak-side slope instability. Application of IRI for disaster presentation and mitigation, such as describing roadbed disaster and its relation to critical precipitation for various sections of the highway, are worth further study.
Suhua Highway was first reclaimed from the Houshan in Taiwan as the northern trail in Qing dynasty, and then built as seaside path in Japanese colonial rule period. It has taken almost half century for highway improvement after Taiwan restoration, the highway was opened for double lanes’ usage. However, suffered from nature hazards frequently, the Suhua Highway has become one of the most regularly blocked highways in the past two decades in Taiwan. There are always broken ridges and steep cliffs along the highway. The stratum are crimped and bulged due to highly activated plate movement, resulting in obverse folds and close faults that mixed up with competent and incompetent rocks. The difficulty for construction and maintenance of the highway are obvious. This study reviews the construction history of the Suhua Highway and associated major issues for maintenance at various temporal stages, and the influence of geological and geotechnical characteristics on highway maintenance. Additionally, the adopted short-term monitoring and early warning system and long-term reroute strategies are also introduced. The lessons learned from the Suhua Highway may provide valuable experience for life-cycle based highway construction and maintenance.
The construction and maintenance of a highway are significantly affected by topographical and geological conditions along the highway, and must take account for environmental protection and impact on landscaping. This study reviews the historical construction stages and maintenance works for the Tai 11 eastern costal highway. Based on the second-stage improvement project launched at 1990’s and focusing on representative sections featured in frequently maintenance and traffic bottlenecks in northern part of the highway, the geotechnical characteristics near these sections and associated maintenance issues are investigated. Countermeasures adopted to improve stability and service level of these sections, and compromising with highway construction and maintenance over environmental protection and landscaping maintenance as well, are also discussed and commented.
Metamorphic hard rock extensively exists in Eastern Taiwan. Hard rock can sustain high stress and high elastic strain. Underground excavation in hard rock is normally stability. However, hard rock exhibits a strength loss feature beyond brittle failure when they were subjected to high overburden stresses. Such situation may endanger the opening stability. According to the comparison of numerical analyses and experiential formula, the evaluation of failure depth surrounding an opening could be underestimated and the estimation of opening stability is possibly incorrect when the elastic-ideally plastic model was adopted. The post-peak strength degradation for hard rock is quite important in the stability of deep excavation. In this paper, the tri-axial compression tests of marble were performed and other past experiments were reviewed to establish the relationship between the strength loss parameter and the confining pressure. It provides a further knowledge for underground designing and construction in Eastern Taiwan.
In order to verify the influence of blasting vibrations on the sliding of the metamorphic rock slope that occurred at a quarry in eastern Taiwan, a series of blasting vibration monitoring was conducted near and around the land sliding site. A least square linear regression method was used to obtain the geological parameters of the blasting vibration attenuation formula. These geological characteristic parameters were then used to evaluate the possible maximum vibration value and verify the influence of vibrations on the land sliding site. According to the test results acquired, the peak particle velocity of 27 mm/sec was recorded at the front end of the slope, which is much lower than the threshold value of 220 mm/sec that may trigger a land slide. A peak particle velocity of 3.47 mm/sec was also measured at the crevice located on the top of rock slope. According to the analysis results found in this study, it can be concluded that the blasting conducted at the quarry will not affect the slope stability of the land sliding site. The finding of this study can also be used as a reference for evaluating the influence of blasting on the stability of the rock slope.
No. 9 highway improvement project is one of 12 major love-Taiwan infrastructure projects. It is expected to offer a long-term safe and reliable highway for the public between the northern region and the eastern part in Taiwan. It is also expected to be a sustainable engineering and environmental construction. The alignment of this project is cross the western Central Range belt and eastern Central Range belt. There are totally eight tunnels for this project. Guanyin tunnel is the longest one with 7.9 kilometers long. Guanyin tunnel and the following Gufeng tunnel is critical path for the whole plan. In accordance with the special geology of the tunnel, special consideration for the assessment and proposed response strategies of the tunnels is carefully reviewed in this paper. The optimization of tunnel construction risk, green construction, sustainable development and full lifecycle management concepts are considered to meet the needs of the environment, ecology and landscape during the plan and design stages of this project. It is expected to reach the "low environmental impact, save energy and reduce carbon emissions," and "to extend lifecycle of the highway ". This paper is hopeful as the references for engineering and construction.
Aiming to investigate underground configuration of the Chihshang Fault, this study carries out four resistivity image profiles in Yuli area. Field investigation results show that the stratum east to the Chihshang Fault in Yuli area is the Lichi Formation with a resistivity of 1~30 Ω-m, and west to the Fault is alluvium formation with a resistivity of 100~800 Ω-m. The fault zone dips 60°~80° to the east, and is covered by an alluvium layer that is not active recently. In the Lichi Formation a sliding surface that may be correlated with the disturbed zone shown in ground surface. The creeping zone observed in ground surface, moved along a single plane, locates in the boundary of the alluvium and Lichi Formation with a strike of NS direction approximately in north Yuli area , turned to west slightly near the Chuanzai Mountain and disturbed along the east side of the river, and turned to east toward NS direction on the east side of location where RIP-3 is performed. The terrain scarp on the west side of Chuanzai Mountain may be the faulty scarp resulted from the regressive erosion after the creeping effect of the fault. The alluvium west to the fault sediments from the elevation of about 0 m to 120-150 in the east part and form a boundary plane with the Lichi Formation dipping to the west. This configuration may result from the east movement of the river and lead to current appearance.