Rainfall-induced slope sliding behavior in Taiwan: Constraints by continuous GPS observations

Abstract

The aim of this research was to investigate the spatial-temporal evolution of the slope deformation and its causes through long-term observation from continuous Global Position System (CGPS) We observed seasonal slow motion and short-term fast displacement from CGPS sites on the slope in the Central Range of Taiwan The direction of seasonal slow motion can be distinguished from the dry and wet season where the direction of wet season is consistent with the slope direction Short-term fast displacement is mainly triggered by extreme rainfall with the displacement recorded by CGPS is up to 349 mm To better understand the slope movement we established a CGPS network on a deep-seated gravitational slope in northern Taiwan The targeted slope with the Huafan University campus built on top of it is a translational deep-seated gravitational slope with a dip-slope of about 10°-20° toward southwest and a potential sliding surface located at 10-40 m depth composed of early Miocene alternations of sandstone and shale in northern Taiwan We setup 13 single-frequency and 2 dual-frequency CGPS stations on and outside the campus sliding area since April 2016 During the observation period the slope creeps slowly with velocity of about 13 mm/year toward southwest to south and the angle of the movement vector is steeper than the angle of the sliding surface which suggest that the movement is not associated with sliding surface but plastic deformation of the slope mass We found that four noticeable displacement events with the maximum 68 1 mm displacement occurred in September 2016 June 2017 October 2017 and October 2018 respectively These fast displacements concur with four apparent rainfall events which accumulated 661、365、435 and 384 mm The surface displacements are synchronous with slip on the sliding surface for the rainfall events rainfall infiltration to sliding surface is main factor to trigger the slope failure The movement pattern of fast displacement is changed by different rainfall patterns short-term extreme rainfall cause larger displacement in short time otherwise long-term rainfall with low intensity cause a longer displacement time

Date of Award	2020
Original language	English
Supervisor	Ruey-Juin Rau (Supervisor)