Clarifying the effectiveness of drainage tunnels in landslide controls based on high-frequency in-site monitoring
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CASE HISTORY
Clarifying the effectiveness of drainage tunnels in landslide controls based on high-frequency in-site monitoring Zhen-lei Wei 1 & Dong-fei Wang 2 & Hao-di Xu 1 & Hong-yue Sun 2 Received: 19 August 2019 / Accepted: 6 March 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract An increase in groundwater table is a critical trigger for a deep-seated landslide. An effective way of improving the stability of the deep-seated landslide is to reduce the groundwater table through drainage works. This study aims to clarify the effectiveness of drainage tunnel systems in preventing and controlling deep-seated landslides based on high-frequency field-monitoring data. In the study, we measured depth of groundwater table data and the deformation process of a deep-seated landslide before and after construction of a drainage tunnel. Our study shows the drainage tunnel improved the stability of the landslide significantly. Furthermore, the depth of groundwater table increased rapidly, and there was a significant reduction of surface displacement and crack width of the slope after construction of the tunnel. The results of numerical modeling also showed that the safety factor increased from 0.92 to 1.063 after the tunnel’s construction. The variation of the safety factor before and after the construction of drainage tunnel induced by different return period storms was also estimated. Keywords Drainage tunnel . Groundwater . Surface displacement . Crack width
Introduction Precipitation plays an important role in triggering landslides. For shallow landslides, the infiltration of rainfall changes the pore water pressure, which leads to reduced soil strength and consequently increased slope instability (Iverson 2000). The stability of unsaturated soil slopes subject to transient infiltration and seepage has been investigated in detail through the use of numerical modeling and experiments (Yang et al. 2019). At sufficiently high rainfall intensities, a perched water table can form above the main water table, potentially reducing stability where landslides may be triggered in certain circumstances (Take et al. 2015). For deep-seated landslides, rainfall often causes an increase in the groundwater table. The impact of increased groundwater table on deep-seated landslides usually leads to the increases in pore water pressure and decreases the effective strength of potential slip surfaces
* Hong-yue Sun [email protected] 1
College of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058, China
2
Ocean College, Zhejiang University, Hangzhou 310058, China
(Corominas et al. 2005; Conte et al. 2018; Rosone et al. 2018; Zhi et al. 2016; Wei et al. 2019a). Based on 3 years of monitoring recording, Rosone et al. (2018) investigated the mechanical influence of pore water pressure on the stability of a deep-seated landslide and pointed out the effect that the passage of time had on the displacement of the pore water pressure variation induced by rainfall. Sun et al. (2019b) investigated the c
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