Preliminary Investigations and Numerical Simulations of a Landslide Reactivation

Analysis of the Possible Reactivation of the Krbavčići Landslide in Northern Istria, Croatia

Geosciences ◽

10.3390/geosciences10080294 ◽

2020 ◽

Vol 10 (8) ◽

pp. 294

Author(s):

Martina Vivoda Prodan ◽

Željko Arbanas

Keyword(s):

Shear Strength ◽

Rock Mass ◽

Slope Stability ◽

Numerical Simulations ◽

Simulation Software ◽

Residual Shear Strength ◽

Laboratory Test Results ◽

Landslide Reactivation ◽

Flysch Rock Mass ◽

Weathering Grades

The Krbavčići landslide occurred in January 1979 near the town of Buzet, Croatia, after a long period of heavy rainfall. It is located in Northern Istria in the area built of flysch rock mass where numerous mass movements in the past and recent history have been recorded. A flysch rock mass is highly susceptible to weathering, which leads to material disintegration, changes in geotechnical properties, and shear strength decrease, finally resulting in instability processes in flysch slopes. This paper describes existing information about the Krbavčići landslide occurrence, laboratory testing of siltstone samples from a flysch rock mass, and numerical slope stability analyses of a possible landslide reactivation caused by possible long rainy periods and further weathering of the flysch rock mass. Slope stability analysis using the Rocscience, Slide software, as well as landslide numerical simulations using the LS-Rapid simulation software were performed on the basis of the digital elevation model (DEM) and laboratory test results of siltstones with different weathering grades. A DEM of the Krbavčići landslide was obtained on the basis of the unmanned aerial vehicle (UAV) survey conducted in March 2016. The residual shear strength of siltstones to predict a reactivation of landslides is of highest importance and was determined by ring shear and direct shear tests on siltstone samples with different weathering grades. The results of the numerical simulations show that an increase of the groundwater level in the landslide body in combination with the further weathering of the flysch rock material at the sliding surface would have the main influence on a possible landslide reactivation and the further development of the landslide displacement.

Download Full-text

Direct Numerical Simulations of Gas–Liquid Multiphase Flows

10.1017/cbo9780511975264 ◽

2001 ◽

Cited By ~ 151

Author(s):

Grétar Tryggvason ◽

Ruben Scardovelli ◽

Stéphane Zaleski

Keyword(s):

Numerical Simulations ◽

Multiphase Flows ◽

Direct Numerical Simulations

Download Full-text

Saturation mechanism and generated viscosity in gravito-turbulent accretion disks

Astronomy and Astrophysics ◽

10.1051/0004-6361/202038023 ◽

2020 ◽

Vol 640 ◽

pp. A53

Author(s):

L. Löhnert ◽

S. Krätschmer ◽

A. G. Peeters

Keyword(s):

Growth Rate ◽

Numerical Simulations ◽

Accretion Disks ◽

Gravitational Instability ◽

Turbulent Viscosity ◽

Radial Distance ◽

Maximum Growth ◽

Wave Number ◽

Radiative Cooling ◽

Mixing Length

Here, we address the turbulent dynamics of the gravitational instability in accretion disks, retaining both radiative cooling and irradiation. Due to radiative cooling, the disk is unstable for all values of the Toomre parameter, and an accurate estimate of the maximum growth rate is derived analytically. A detailed study of the turbulent spectra shows a rapid decay with an azimuthal wave number stronger than ky−3, whereas the spectrum is more broad in the radial direction and shows a scaling in the range kx−3 to kx−2. The radial component of the radial velocity profile consists of a superposition of shocks of different heights, and is similar to that found in Burgers’ turbulence. Assuming saturation occurs through nonlinear wave steepening leading to shock formation, we developed a mixing-length model in which the typical length scale is related to the average radial distance between shocks. Furthermore, since the numerical simulations show that linear drive is necessary in order to sustain turbulence, we used the growth rate of the most unstable mode to estimate the typical timescale. The mixing-length model that was obtained agrees well with numerical simulations. The model gives an analytic expression for the turbulent viscosity as a function of the Toomre parameter and cooling time. It predicts that relevant values of α = 10−3 can be obtained in disks that have a Toomre parameter as high as Q ≈ 10.

Download Full-text