Displacement of a landslide retaining wall and application of an enhanced failure forecasting approach

Tommaso Carlà,Michael Hendry,Nicola Casagli,Derek Martin,Tom Edwards,Renato Macciotta,Emanuele Intrieri,Trevor Evans,Paolo Farina

doi:10.1007/s10346-017-0887-7

Tommaso Carlà, Michael Hendry + Show 7 more

Open Access

https://doi.org/10.1007/s10346-017-0887-7

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Abstract

The 10-mile Slide is contained within an ancient earthflow located in British Columbia, Canada. The landslide has been moving slowly for over 40 years, requiring regular maintenance work along where a highway and a railway track cross the sliding mass. Since 2013, the landslide has shown signs of retrogression. Monitoring prisms were installed on a retaining wall immediately downslope from the railway alignment to monitor the evolution of the retrogression. As of September 2016, cumulative displacements in the horizontal direction approached 4.5 m in the central section of the railway retaining wall. After an initial phase of acceleration, horizontal velocities showed a steadier trend between 3 and 9 mm/day, which was then followed by a second acceleration phase. This paper presents an analysis of the characteristics of the surface displacement vectors measured at the monitoring prisms. Critical insight on the behavior and kinematics of the 10-mile Slide retrogression was gained. An advanced analysis of the trends of inverse velocity plots was also performed to assess the potential for a slope collapse at the 10-mile Slide and to obtain further knowledge on the nature of the sliding surface.

Highlights

Adequate understanding of landslide behavior is essential for managing associated risks, and substantial information about the evolution and kinematics of a landslide can be obtained by analyzing the deformation of the slope surface (Gili et al 2000; Brückl et al 2006; Baldi et al 2008; Teza et al 2008; Sun et al 2013)
This paper presents the review of the displacement measurements at a railway retaining wall within the 10-mile Slide in Canada
The Tfw approach was applied to the 10-mile dataset in order to account for the implicit uncertainty of INV analyses, to evaluate the risk that was posed by periods of acceleration and to investigate whether false alarms would have been in place; to this aim, the two described phases of acceleration were considered, as these would most likely trigger alarms during monitoring and early warning

Summary

Introduction

Adequate understanding of landslide behavior is essential for managing associated risks, and substantial information about the evolution and kinematics of a landslide can be obtained by analyzing the deformation of the slope surface (Gili et al 2000; Brückl et al 2006; Baldi et al 2008; Teza et al 2008; Sun et al 2013). In relation to the ongoing maintenance of the wall, in the latest part of the monitoring period, a change from Type 2 to Type 1 deformation behavior was observed concerning some of the piles located in proximity of the eastern boundary of the landslide As mentioned preliminarily, this resulted evident in particular in the case of pile 15, which displayed a progressive increase in velocity in July 2016 The smaller distance between Tc and the first Tfw limit in the case of the vertical movements of the second acceleration phase may be attributed to the higher amount of data noise, which leads to an increase in failure prediction uncertainty and to a larger width of the projected failure windows

Discussion and conclusions

Firstacceleration