Hydraulic Conductivity and Pore Water Pressures in a Clayey Landslide: Experimental Data

Abstract

To analyze the response to hydrological conditions of an instable slope in a structurally complex clay formation, the hydraulic conductivity of the subsoil was estimated and pore water pressures were monitored. Two types of field tests were carried out: falling head tests in the Casagrande piezometers and localized seepage measurements in test boreholes. The experimental data show that in a narrow band around the slip surface, the hydraulic conductivity is higher—more than two orders of magnitude—than that of the landslide body and of the stable formation. Furthermore, the data of a long-term monitoring by Casagrande piezometers and vibrating wire cells show that the response of pore water pressures to the site hydrological conditions along the shear band is far faster than in the landslide body and in the stable formation. The slip band seems largely connected to the atmosphere, and the water pressures in the band are correlated with the deep displacement rates of all the inclinometers crossing the active slip surface.

Mechanics of coseismic and postseismic acceleration of active landslides

“…The shear zone is likely to be less permeable than the adjacent layers due to its compacted state 45 . There is, however, some field evidence showing that it can also be more permeable 46 . In this study they are modelled with the same permeability, which allows for reduction in the number of model parameters.…”

“…It is rather questionable whether a homogeneous clayey layer of 30 m thickness with a permeability of k = 10 −10 m s −1 can be encountered in a real landslide. However, thinner layers with such a permeability are indeed realistic 45,46 , and can lead to postseismic movements over a period of several years.…”

Processes and factors controlling the groundwater flow in a complex landslide: A case study in the northern Italy

“…Looking at the rapid hydraulic response to precipitation in piezometers located mainly in the landslide body (P2, P3, P4 and P5), it is easy to understand that, in the case study, preferential flow-paths play an important role in the infiltration processes, differently to other similar landslides (e.g., Di Maio et al, 2020). Various authors identify fast infiltration of precipitation into the fractured media through macropore patterns in the topsoil (Beven & Germann, 1982) pipe network (Uchida, 2004), cracks and sharp vertical discontinuities (Debieche et al, 2012;Hencher, 2010;Shao et al, 2016) as one of the most important aspects for landslide hydrogeological behaviour.…”

A Review on Past Cases of Geophysical Explorations for Assessment of Slope Stability

“…-지하수의 분포 토양의 함수비 및 수문학적 모델을 구성하는 경우도 있 는데, 이 경우 활동면(slip surface)을 파악하게 될 수 있 다. 집중호우시에 사면에서 무너질 가능성이 있는 구간 을 파악하는 것이 목적으로, 사면의 3D 지질모델을 구성 하는 경우도 있다 (Maio et al, 2020). 사면의 수문학적 3D 지질모델을 구성하게 되면 산사태 조기경보 시스템 을 구성할 수 있으며, 이 경우 전기비저항 탐사가 유용 하게 사용된다 (Maio et al, 2020) (Kamiński et al, 2021) Polar plots are plotted in the same color scale, with spectral amplitude normalized to f1 spectral value at S7.…”

“…집중호우시에 사면에서 무너질 가능성이 있는 구간 을 파악하는 것이 목적으로, 사면의 3D 지질모델을 구성 하는 경우도 있다 (Maio et al, 2020). 사면의 수문학적 3D 지질모델을 구성하게 되면 산사태 조기경보 시스템 을 구성할 수 있으며, 이 경우 전기비저항 탐사가 유용 하게 사용된다 (Maio et al, 2020) (Kamiński et al, 2021) Polar plots are plotted in the same color scale, with spectral amplitude normalized to f1 spectral value at S7. In each plot, frequency values and related vibration directions are highlighted in red for f1, in green for f2, and in red for f3 (Colombero et al, 2017).…”