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Environmental & Engineering Geology Division
The Sanyi Fault in the vicinity of a railway tunnel on the northern bank of Tachiahsi.
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Environmental and engineering geology is an important aspect of applied geology. Before construction of any
highways, reservoirs, or housing on hill slopes and other engineering objects, one should carefully
investigate and plan according to the geology of the construction site: otherwise improper construction
can cause fatal disasters and property damage. The Environmental & Engineering Division performs
investigation in environmental and engineering geology relying on both geological principles and advanced
laboratory techniques to prevent geological disasters. The approach used combines site sampling with testing
and analysis of engineering materials to understand the potential geological problems and mechanical
characteristics of the rock mass at the site. The results contribute to implementation of proper policy,
prevention of geologic disasters, and lowering of engineering costs.
The Environment and Engineering Geology Division conducts research related to major construction projects
and developing social needs ongoing in Taiwan. Many research projects have been completed and a geologic
data bank established. The current research has focused on the subsurface geology of metropolitan areas,
environmental engineering safety evaluation, and geologic hazards, etc.
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STUDY SUBSURFACE GEOLOGY AND ENGINEERING CHARACTERISTICS OF THE TAIPEI METROPOLITAN AREA
Locations of deep holes drilled by CGS in the Taipei Basin.
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In July 1991, the Central Geological Survey initiated the first 5-year project on the subsurface geology
and engineering characteristics of the Taipei Basin. Every year drilling sites have been selected and drill
cores recovered for both geological investigations and engineering tests. Monitoring instruments have also
been installed in the boreholes. Furthermore, a GPS net and several high precision level profiles have been
set around the basin to monitor neotectonic movement and activity of faults.
The program has drilled 10 deep boreholes in the basin, and 8 of them penetrated the Quaternary sediments
and into the Tertiary strata. It has been found that the deepest part of the Tertiary basement is 500m below
sea level in the Kuando-Luchou-Wukou area near the northwestern margin of the basin while the depth of the
basement in the southeastern part of the basin decreases to less than 100 meters.
The upper most Quaternary sediments belong to the Sungshan Formation consisting of soft sand-silt-mud
deposits 30 to 100 meters in thickness. The Chingmei Gravel that underlies the Sungshan Formation has
long been considered as a foundation for construction project in the basin by civil engineers.
This gravel unit is composed of fine matrix-supported gravel of thickness less than 10 meters in the
eastern part of the basin. It is not strong enough to support high-rise buildings in that area.
The program is still ongoing. It is expected that after the program is complete, the geologic history and
origin of the basin, together with the sedimentary environment and the engineering characteristics of the
Quaternary formations will be fully established, which will be beneficial to the city development, land
utilization, and construction safety in the Taipei Metropolitan area.
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Improper construction on slopes often causes fatal disasters.
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INVESTIGATION OF THE GEOLOGICAL HAZARDS
Geologic hazards are widely distributed in Taiwan because of the rugged topography and complicated geologic
setting. Landslides and debris flows during typhoon have destroyed traffic routes in mountainous area and
damaged dwellings on hill slopes. The investigation of landslides has attracted public attentions and become
a major task of the Central Geological Survey in recent years.
The ongoing landslide investigation related project includes the investigations of landslide distributions
and analysis using remote sensing and aerial photography. These tools provide preliminary information on
landslide distributions and properties, such as position, size, volume, type, and cause of landslide.
The data are useful for land-use planning and development, and landslide prevention. In addition, the
Division studies the effect of neo-tectonic movement on engineering construction. Case studies include
geologic hazards, surface uplift and subsidence, crust deformation, fault activity, earthquakes and mass
movement.
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