Modelling the control of groundwater on landslides triggering: the respective role of atmosphere and rainfall during typhoons

Abstract. Landslides are often triggered by catastrophic events, among which earthquakes and rainfall are the most depicted. However, very few studies have focused on the effect of atmospheric pressure on slope stability, even though weather events such as typhoons are associated with significant atmospheric pressure changes. Indeed, both atmospheric pressure changes and rainfall-induced groundwater level change can generate pore pressure changes with similar amplitude. In this paper, we assess the respective impacts of atmospheric effects and rainfall over the stability of a hillslope. An analytical model of transient groundwater dynamics is developed to compute slope stability for finite hillslopes. Slope stability is evaluated through a safety factor based on the Mohr-Coulomb failure criterion. Both rainfall infiltration and atmospheric pressure variations, which impact slope stability by modifying the pore pressure of the media, are described by diffusion equations. The models have then been forced by weather data from different typhoons that were recorded over Taiwan. While rainfall infiltration can induce pore pressure change up to hundred kPa, its effects is delayed in time due to diffusion. To the contrary, atmospheric pressure change induces pore pressure changes not exceeding a few kPa, but its effect is instantaneous. Moreover, the effect of rainfall infiltration on slope stability decreases towards the toe of the hillslope and is cancelled where the water table reaches the surface, leaving atmospheric pressure change as the main driver of slope instability. This study allows for a better insight of slope stability through pore pressure analysis, and shows that atmospheric effects shouldn’t always be neglected.

Download Full-text

Atmospheric pressure compared to rainfall as landslide triggering factors along a hillslope

10.5194/egusphere-egu21-12658 ◽

2021 ◽

Author(s):

Lucas Pelascini ◽

Philippe Steer ◽

Laurent Longuevergne

Keyword(s):

Slope Stability ◽

Pore Pressure ◽

Water Table ◽

Atmospheric Pressure ◽

Pressure Change ◽

Unconfined Aquifer ◽

Air Pressure ◽

Water Infiltration ◽

Landslide Occurrence ◽

Pressure Changes

Landslides are one of the sources of natural hazards that cause damages and losses but also shapes the landscape. A better understanding the factors triggering or pre-conditioning landslide occurrence is therefore critical for risk assessment, with implications for hillslope erosion and landscape dynamics Triggering of catastrophic landslides is generally associated with events such as earthquakes or intense rainfalls. In Taiwan, a minimum of 22,705 landslides were reported during the typhoon Morakot in 2009 (Lin et al., 2011). Landslides triggered during storms are generally associated to the intensity and cumulated amount of rainfall, as water infiltration destabilize slopes (Iverson, 2000). However, a correlation has also been reported between slope stability and the change in atmospheric pressure (Schulz, 2009). Indeed, a change in air-pressure can lead in a readjustment in pore pressure, and cause fluid movements normal to the surface. The aim of this study is to characterize the effect of atmospheric pressure changes and define its specific contribution on slope stability when combined with rainfallA 2-dimensional analytical model has been developed based on diffusion equations to describe the destabilization induced by water infiltration and atmospheric pressure changes induced by typhoons. As both mechanisms are function of pore pressure, and especially groundwater pore pressure, the water table within a finite-length hillslope is modelled using Townley&#8217;s (1995) analytical expression of water flow in a unconfined aquifer. The hillslope itself is a simple tilted half-space with a water divide at the top and a river at the toe forcing the water table to the surface. Slope stability is inferred through a safety factor computed using the coulomb criterion. Both rainfall infiltration and air pressure modify pore pressure through a diffusion process. While rainfall increases water table height and induce large increases in pore pressure within days or hours, , we show that atmospheric-induced pore pressure change is instantaneous and can occur even if the hillslope is fully saturated.The model allows to separate the hillslope response into two regimes, upslope or downslope, where the destabilization is mainly linked to rainfall or to atmospheric pressure change, respectively.&#160; Our results suggest that landslide occurring during storms in the downstream part of the hillslope are likely candidate for being triggered by atmospheric pressure change, in particular if the storm occurs with a humid initial condition. We show that the effect of atmospheric pressure changes is not negligible. On contrary, it is crucial to define the amplitude, timing and geometry of the hillslope instability, especially when combined to rainfall.

Download Full-text

The impact of atmospheric pressure change and rainfall for triggering landslides during weather events

10.5194/egusphere-egu2020-5423 ◽

2020 ◽

Author(s):

Lucas Pelascini ◽

Philippe Steer ◽

Laurent Longuevergne ◽

Dimitri Lague

Keyword(s):

Pressure Drop ◽

Slope Stability ◽

Atmospheric Pressure ◽

Weather Conditions ◽

Pressure Change ◽

Weather Events ◽

Pressure Changes ◽

The Impact ◽

Landslide Triggering

Landslides are a complex phenomenon which triggering depends on both intrinsic properties of soils and rocks and external influences such as the action of weather conditions, or earthquakes. Around 6,000 landslides failed the 6th of September 2018 during the Mw 6.6 Hokkaido Eastern Iburi earthquake (Japan), one day after the typhoon Jebi hit the region. If the ground acceleration induced by the seismic waves likely played a major role in the triggering of these landslides, it is unclear how it compares to the respective role of rainfall and atmospheric pressure drop induced by the typhoon. The aim of this work is therefore to investigate the influence of weather conditions on landslide triggering, and more specifically to characterize the relative contributions of rainfall and atmospheric pressure changes on slope stability.For this purpose, a simple model is developed to describe the two mechanisms and to compare their respective impact on slope stability. The model considers a homogeneous isotropic tilted infinite half-space in one dimension. Slope stability is estimated using a safety factor and a Mohr-Coulomb criterion. In the static case, groundwater is accounted for by adding an unconfined aquifer into the model. Analytical models based on diffusion equations have been used to describe the impact of rainfall and atmospheric pressure changes on slope stability (Iverson, 2000; Schulz, 2009). Extracting a response function from these models allows us to compute the stability change due to any rainfall or pressure time series. The model parameters are taken for a typical slope in Taiwan tilted with a 25&#176; angle and with characteristics of a fully saturated loamy soil at 4 m depth and put under conditions similar to the Morakot typhoon, with more than 240 mm of rain on a 24 h period and an associate atmospheric pressure drop of 4 kPa.Atmospheric pressure change and rainfall impacts the media in a very different way despite being associated to the same physical phenomenon, pressure diffusion. The atmospheric effect is instantaneous and directly affects the effective stress with a maximum of 4 kPa. This effect decreases over time while the pore pressure is adjusted to the atmosphere. The rainfall effect is delayed in time but has a greater impact on the effective stress, reaching 11.7 kPa almost 2 days after the end of the rainfall event. While atmospheric pressure does not change significantly the safety factor, it can exacerbate the effect of rainfall and advance the failure in time because of the respective temporal lag between the 2 processes. &#160;Therefore, this study may lead to a better understanding of the effect of weather events such as typhoons on landslide triggering and slope stability. Our results call for revisiting in a more systematic approach the role of atmospheric pressure change on landslide triggering during extreme weather events. Because a 1D model may hide some effects associated to hillslope geometry, we then consider 2D numerical models which allow us to offer some first insights on slope stability during weather events, accounting for topography.

Download Full-text

Revealing seasonal crustal seismic velocity variations in Taiwan with single-station cross-component analysis

10.5194/egusphere-egu21-7010 ◽

2021 ◽

Author(s):

Kuan-Fu Feng ◽

Hsin-Hua Huang ◽

Ya-Ju Hsu ◽

Yih-Min Wu

Keyword(s):

Pore Pressure ◽

Seasonal Variations ◽

Seismic Velocity ◽

Pressure Change ◽

Temporal Variations ◽

Air Pressure ◽

Weather Data ◽

Single Station ◽

Seismic Velocity Changes ◽

Velocity Changes

Ambient noise interferometry is a promising technique for studying crustal behaviors, providing continuous measurements of seismic velocity changes (dv/v) in relation to physical processes in the crust over time. In addition to the tectonic-driven dv/v changes, dv/v is also known to be affected by environmental factors through rainfall-induced pore-pressure changes, air pressure loading changes, thermoelastic effects, and so forth. In this study, benefiting from the long-term continuous data of Broadband Array in Taiwan for Seismology (BATS) that has been operated since 1994, we analyze continuous seismic data from 1998 to 2019 by applying single-station cross-component (SC) technique to investigate the temporal variations of crust on seismic velocity. We process the continuous waveforms of BATS stations, construct the empirical Green&#8217;s functions, and compute daily seismic velocity changes by the stretching technique in a frequency band of 0.1 to 0.9 Hz. We observe co-seismic velocity drops associated with the inland moderate earthquakes. Furthermore, clear seasonal cycles, with a period of near one-year, are also revealed at most stations, but with different characteristics. Systematic spectral and time-series analyses with the weather data are conducted and show that the rainfall-induced pore-pressure change is likely the main cause to the seasonal variations with high correlations. The strong site-dependency of these seasonal variations also precludes air pressure and temperature which varies smoothly in space from being dominant sources and suggests spatially-varying complex hydro-mechanical interaction across the orogenic belt in Taiwan.

Download Full-text

Mechanics of machine milking: I. Pressures in the teatcup assembly and liner wall movement

Journal of Dairy Research ◽

10.1017/s0022029900018240 ◽

1964 ◽

Vol 31 (3) ◽

pp. 303-313 ◽

Cited By ~ 9

Author(s):

C. C. Thiel ◽

P. A. Clough ◽

D. N. Akam

Keyword(s):

Strain Gauge ◽

Atmospheric Pressure ◽

Pressure Change ◽

Rate Of Change ◽

Inertia Effects ◽

Machine Milking ◽

Wall Movement ◽

Opening And Closing ◽

Pressure Changes ◽

Pulsation Cycle

SummaryA method is described of measuring pressures in a teatcup assembly using strain gauge transducers and simultaneously following movement of the liner wall by means of a cine camera. In preliminary experiments with a narrow bore type liner it was found that pressures below the teat could vary during a single pulsation cycle from a few inches of mercury below atmospheric pressure (inHg vacuum) to as high as 25 inHg vacuum in the absence of an airbleed. Bleeding air into the barrel of the liner or into the clawpiece considerably reduced fluctuation in pressure, and the vacuum barely rose above the nominal milking vacuum of 15 inHg. Reducing the rate of change of pressure in the pulsation chamber did not greatly affect the maximum vacuum obtained. Opening and closing of the liner by pressure change in the pulsation chamber was under some conditions considerably delayed by the pressure conditions existing inside the liner.It is suggested that inertia effects of milk in the cluster and the natural frequency of the system are largely responsible for the observed pressure changes under the teat.

Download Full-text

The Effect of Rainfall Infiltration Time to the Unsaturated Soil Slope Stability

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.71-78.4864 ◽

2011 ◽

Vol 71-78 ◽

pp. 4864-4867

Author(s):

Guang Hua Cai ◽

Hai Jun Lu ◽

Wei He ◽

Long Guan ◽

Wei Qi Xu

Keyword(s):

Slope Stability ◽

Pore Water ◽

Pore Water Pressure ◽

Limit Equilibrium ◽

Water Pressure ◽

Rainfall Infiltration ◽

Soil Slope ◽

Soil Permeability ◽

Rainfall Condition ◽

Pressure Changes

Rainfall infiltration is currently one of the important factors in studying the soil-slope stability. By using saturated-unsaturated seepage theory, the traditional limit equilibrium method and so on, analyze the water content and the pore-water pressure changes under the rainfall condition, then analyze the influence mechanism of the slope stability. Through the Seep/W and the Slope/W of the GEO-Slope software, do the numerical simulation of the slope stability under the rainfall condition, to seek the distribution of pore-water pressure on the rainfall situation and the influence of the seepage field from various parameters such as rainfall intensity and the soil permeability coefficient, thus to study the slope stability.

Download Full-text

Stability analysis of unsaturated clay slope based on the coupled effect of temperature and saturation

Quarterly Journal of Engineering Geology and Hydrogeology ◽

10.1144/qjegh2021-009 ◽

2021 ◽

pp. qjegh2021-009

Author(s):

Zizhen LIU ◽

Xiaogang WANG ◽

Yue YIN ◽

Jiwei LI ◽

Guotao SHAO

Keyword(s):

Slope Stability ◽

Rainfall Infiltration ◽

Slope Instability ◽

Effect Of Temperature ◽

Coupling Equation ◽

Content Type ◽

Coupled Effect ◽

Unsaturated Clay ◽

Matrix Suction

In view of the clay slope instability caused by environmental temperature and rainfall infiltration in summer and autumn, the mechanism of the effect of temperature and saturation on unsaturated clay slope stability was discussed. To achieve this objective, this study uses the theoretical and numerical methods. Based on the theory of unsaturated clay and the law of heat conduction, the relationship between cohesion and matrix suction of unsaturated clay was derived considering the influences of temperature and saturation. Considering the effect of temperature and saturation, the coupling equation of shear strength of unsaturated clay was constructed under conditions of rainfall infiltration. The coupling equation of temperature and saturation was used in the strength reduction method, and the slope stability was analysed by FLAC software. The results show that the cohesion of unsaturated clay slope increases with the increase of depth, and the safety factor considering the coupled effect of temperature and saturation is smaller than that without considering the temperature effect; the clay slope is unstable considering the coupled effect of temperature and saturation, but stable without considering the coupled effect when the saturation of soil reaching 80%.Thematic collection: This article is part of the Role of water in destabilizing slopes collection available at: https://www.lyellcollection.org/cc/Role-of-water-in-destabilizing-slopes

Download Full-text

Study on the Relationship between Hongmiao Mine Gas Emission and Atmospheric Pressure Change on

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.524-527.739 ◽

2012 ◽

Vol 524-527 ◽

pp. 739-742

Author(s):

Xi Hua Zhou ◽

Jian Yuan Zhao ◽

Xian Wei Xu

Keyword(s):

Coal Mine ◽

Atmospheric Pressure ◽

Pressure Change ◽

Emission Source ◽

Return Flow ◽

Gas Emission ◽

Production Safety ◽

Mine Gas ◽

Pressure Changes ◽

The Relationship

Atmospheric pressure changes on the fully mechanized top-coal caving has very significant effect to gas emission produce, through discussion to the mine gas emission source,and analysis the actual measured data.Get the result:with the rise of the ground atmospheric pressure ,the mine gas emission is absolutely reduced,and gas changes in return flow is after atmospheric pressure changes 0.5-1h later. Summarized measures to the gas emission suddenly increased.To the coal mine has guiding significance for production safety.

Download Full-text

Heart Rate Signal Decomposition

Methods of Information in Medicine ◽

10.1055/s-0038-1634264 ◽

2000 ◽

Vol 39 (02) ◽

pp. 200-203

Author(s):

H. Mizuta ◽

K. Yana

Keyword(s):

Blood Pressure ◽

Heart Rate ◽

Pressure Change ◽

Normal Subjects ◽

Signal Decomposition ◽

Large Individual ◽

Heart Rate Fluctuations ◽

Type Pattern ◽

Signal Cancellation ◽

Pressure Changes

Abstract:This paper proposes a method for decomposing heart rate fluctuations into background, respiratory and blood pressure oriented fluctuations. A signal cancellation scheme using the adaptive RLS algorithm has been introduced for canceling respiration and blood pressure oriented changes in the heart rate fluctuations. The computer simulation confirmed the validity of the proposed method. Then, heart rate fluctuations, instantaneous lung volume and blood pressure changes are simultaneously recorded from eight normal subjects aged 20-24 years. It was shown that after signal decomposition, the power spectrum of the heart rate showed a consistent monotonic 1/fa type pattern. The proposed method enables a clear interpretation of heart rate spectrum removing uncertain large individual variations due to the respiration and blood pressure change.

Download Full-text