Abstract
Abstract. The investigation results of large-scale landslides in the central part of Taiwan from Central Geologic Survey identified a new, largescale landslide in the Chashan Village of Alishan Township, Chiayi County (ID: D160) which has the potential to influence the safety of Chashan Village residents. In coordination with the surface geological survey, Chashan site can be divided into three potential sliding areas (zones A, B and C). The paper uses GeoStudio for evaluating the stability of different hydrological and seismic scenarios. The results of scenario simulation show that: (1) In the normal and high water level scenarios, the safety factor obtained in zone A is greater than 1.0, and the initial judgment belongs to the stable state; (2) In the earthquake scenarios, the A4 potential sliding mass in zone A will be collapsed; (3) Through the scenario simulation, when the water level in zone A rises more than 25 meters or the PGA exceeds 160 gal, it is possible to cause the collapse of A4 potential sliding mass. The result of the study will contribute that the complex phenomenon between the stability of landslides and hydrogeological conditions can be revealed and clarified through the detailed study on the hydrogeological investigation, observation and the numerical simulation.
Highlights
Taiwan is an active mountain belt created by the oblique collision between the northern Luzon arc and the Asian continental margin
The CGS concluded that a potential large-scale landslide in the Chashan Village of Alishan Township, Chiayi County, (ID: D160, hereby called the Chashan site, Figure 1) may impact the safety of the Chashan Village
The monitoring system set up in the Chashan site included: one set of rain-gauge (D160), two sets of soil moisture meter installed nearby AH-01 and BH-03, two observation wells installed in AH-02 and BH-03, two time-domain reflectometers (TDR) installed in AH-01 and BH-02, and five sets of strong motion recorders installed in CS-01~CS-05
Summary
Taiwan is an active mountain belt created by the oblique collision between the northern Luzon arc and the Asian continental margin. The increase in the frequency and intensity of extreme natural events due to climate change brought significant large-scale landslides in the mountain area of Taiwan. Because of the extreme volume of material mobilized in a large-scale landslide, other natural disasters can be triggered by the large-scale landslide including debris flows and landslide dams. Large-scale landslides can severely impact and pose a significant hazard to nearby villages. Through a long term project implemented by the Central Geological Survey (CGS, 2010-2012; 2013-2015), the location of potential large-scale landslides and villages more susceptible to large-scale landslide hazards have been mapped. The CGS concluded that a potential large-scale landslide in the Chashan Village of Alishan Township, Chiayi County, (ID: D160, hereby called the Chashan site, Figure 1) may impact the safety of the Chashan Village. According to household registration office census data in January, 2018 (data source: https://chuchihro.cyhg.gov.tw), there were a total of 112 households and 297 people in the Chashan Village
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