scholarly journals Influence of Uncertainty of Soil Hydraulic Parameters on Stability of Unsaturated Slopes Based on Bayesian Updating

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-13
Author(s):  
Hsin-Fu Yeh ◽  
Tsien-Ting Huang ◽  
Ya-Sin Yang ◽  
Chien-Chung Ke
Keyword(s):  
Slope Stability ◽  
Water Content ◽  
Confidence Intervals ◽  
Unsaturated Soil ◽  
Bayesian Updating ◽  
Pressure Head ◽  
Volumetric Water Content ◽  
Parametric Models ◽  
Local Factor ◽  
The Impact

In geotechnical engineering, the soil water retention curve (SWRC) is key to solving problems arising from unsaturated soil, and the methodology used to obtain the SWRC parameters is crucial for investigating rainfall infiltration and slope stability. However, on-site measurements of soil data are expensive and time-consuming, and therefore, there is high uncertainty in the SWRC parameters due to the limited amount of data available. This study explores the impact of uncertainty in SWRC parameters on unsaturated soil slope seepage and stability under rainfall conditions. Bayesian updating was initially used to update the posterior distribution of the SWRC parameters of the model and in situ soil. Subsequently, a Markov Chain Monte Carlo (MCMC) method was used to generate random samples, and the uncertainty of the parameters was analyzed. Additionally, SWRC parametric models with different confidence intervals were created, and a hydraulic coupled model was used to evaluate the influence of the SWRC parameters (with different confidence intervals) on slope seepage and stability under rainfall conditions. The results indicated that the parameters α and n affecting the air entry value of the soil and the pore size distribution, respectively, increased as the confidence interval percentile increased. The changes in these two parameters increased the effect of rainfall on the pressure head and volumetric water content of the soil. After rainfall infiltrated the slope, the soil volumetric water content and the internal suction stress of the soil increased, resulting in a reduction in the local factor of safety (LFS) and, hence, a decrease in the stability of the slope. These results show that the predictions for the pressure head and volumetric water content were affected by the uncertainty in the SWRC parameters, leading to errors in the slope stability analysis.

Experimental study on dual capillary barrier using recycled asphalt pavement materials

2014 ◽  
Vol 51 (10) ◽  
pp. 1165-1177 ◽  
Author(s):  
F.R. Harnas ◽  
H. Rahardjo ◽  
E.C. Leong ◽  
J.Y. Wang
Keyword(s):  
Water Content ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Water Storage ◽  
Pressure Head ◽  
Volumetric Water Content ◽  
Capillary Barrier ◽  
Recycled Asphalt ◽  
Fine Grained ◽  
Drainage Rate

The performance of a capillary barrier cover as a cover system is affected by the ability of the capillary barrier to store water. To increase the water storage of a capillary barrier cover, the dual capillary barrier (DCB) concept is proposed. The objective of this paper is to investigate the water storage of the proposed DCB as compared to the storage of a traditional single capillary barrier (SCB). The investigation is conducted using two one-dimensional infiltration column tests under different rainfall conditions. The results show that a DCB stores more water as compared to SCB. The results show that the fine-grained layers of a DCB have higher volumetric water contents during drainage as compared to that of the fine-grained layer of an SCB. The higher volumetric water content is caused by the fact that the thickness of the layers in a DCB corresponds to a pore-water pressure head range where the material has the highest volumetric water content. In addition, a slower drainage rate is resulted from additional layering in a DCB.

The impact of root exclusion on duff moisture and fire danger

2015 ◽  
Vol 45 (8) ◽  
pp. 978-986 ◽  
Author(s):  
Dan K. Thompson ◽  
John Studens ◽  
Chelene Krezek-Hanes ◽  
B. Mike Wotton
Keyword(s):  
Water Content ◽  
Mineral Soil ◽  
Root Water Uptake ◽  
Volumetric Water Content ◽  
Exclusion Experiment ◽  
Stand Type ◽  
Low Levels ◽  
The Impact ◽  
Soil Interface ◽  
Root Exclusion

The impact of root water uptake on duff (both fibric and humic horizons) moisture was investigated at deciduous, mixedwood, and conifer stands in Ontario, Canada. Roots were actively excluded from the duff layer using geotextiles inserted at the duff–mineral soil interface and along the plot edges; liquid and vapour water flow was otherwise not affected by the geotextiles. Root exclusion caused little difference in duff moisture content prior to early June, after which the root exclusion plots remained at 15%–20% volumetric water content, whereas root-intact plots declined to as low as 5% volumetric water content during rain-free periods. Only in the root-intact plots did the duff water content reach sufficiently low levels that duff evaporation was limited by low water content. The net effect of root exclusion was to reduce the cumulative growing season water loss in the duff by 19%–31%, depending on the stand type. Root exclusion also decreased the number of days with a high probability of duff smouldering from as many as 72 days·year−1 to as few as 0 days·year−1. This root exclusion experiment provides a model for short-term duff moisture transitions under thinned forests such as those forests under community wildfire protection.

A Slope Stability Analysis Method Based on Unsaturated Seepage of Slope and its Comparison with Geo-Seep Software

2014 ◽  
Vol 540 ◽  
pp. 177-180 ◽  
Author(s):  
Dong Fang Tian
Keyword(s):  
Stability Analysis ◽  
Slope Stability ◽  
Rigid Body ◽  
Unsaturated Soil ◽  
Limit Equilibrium ◽  
Fem Analysis ◽  
Slope Stability Analysis ◽  
Analysis Method ◽  
The Impact ◽  
Unsaturated Seepage

Based on the FEM analysis of unsaturated slope seepage and strength of unsaturated soil, and adopted the assumption of rigid body limit equilibrium to calculate safe coefficient of landslides, a new slope stability analysis method is promoted and the calculation program called USSP is composed and verified. The method could consider the impact of rainfall and water change to slope stability. Compared with GeoSlope package, it is more practical in rainfall or variation of ground water level condition.

scholarly journals A Modeling Platform for Landslide Stability: A Hydrological Approach

Water ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 2146
Author(s):  
Emadi-Tafti ◽  
Ataie-Ashtiani
Keyword(s):  
Slope Stability ◽  
Water Content ◽  
Water Uptake ◽  
Unsaturated Zone ◽  
Model Verification ◽  
Soil Reinforcement ◽  
Benchmark Problems ◽  
Temporal And Spatial Distribution ◽  
Stability Of Slopes ◽  
The Impact

Landslide events are among natural hazards with many fatalities and financial losses. Studies demonstrate that natural factors such as rainfall and human activities such as deforestation are important causes of triggering a landslide. In this study, an integrated two-dimensional slope stability model, SSHV-2D, is developed that considers various aspects of hydrological effects and vegetation impacts on the stability of slopes. The rainfall infiltration and water uptake of roots change the water content of the unsaturated zone. The temporal and spatial distribution of water content is estimated in the hydrological unit of the developed model. The vegetation unit of the model considers interception loss due to the existence of canopies and trunks, soil reinforcement effect by roots, root water uptake, the impact of root on hydraulic conductivity, and the influence of vegetation weight on slope stability. Benchmark problems with and without vegetation are solved for the model verification. The analyses demonstrate that the consideration of matric suction in the unsaturated zone can increase the safety factor more than 90%. It is also observed that the existence of trees with high density on a slope can increase the factor of safety about 50% and prevent shallow landslides. The present model is a platform for further development of more comprehensive and elaborative slope stability models.

scholarly journals HIRESSS: a physically based slope stability simulator for HPC applications

2013 ◽  
Vol 13 (1) ◽  
pp. 151-166 ◽  
Author(s):  
G. Rossi ◽  
F. Catani ◽  
L. Leoni ◽  
S. Segoni ◽  
V. Tofani
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Slope Stability ◽  
Real Time ◽  
Unsaturated Soil ◽  
Hydrological Model ◽  
Pressure Head ◽  
Stability Model ◽  
Physically Based ◽  
Geotechnical Stability

Abstract. HIRESSS (HIgh REsolution Slope Stability Simulator) is a physically based distributed slope stability simulator for analyzing shallow landslide triggering conditions in real time and on large areas using parallel computational techniques. The physical model proposed is composed of two parts: hydrological and geotechnical. The hydrological model receives the rainfall data as dynamical input and provides the pressure head as perturbation to the geotechnical stability model that computes the factor of safety (FS) in probabilistic terms. The hydrological model is based on an analytical solution of an approximated form of the Richards equation under the wet condition hypothesis and it is introduced as a modeled form of hydraulic diffusivity to improve the hydrological response. The geotechnical stability model is based on an infinite slope model that takes into account the unsaturated soil condition. During the slope stability analysis the proposed model takes into account the increase in strength and cohesion due to matric suction in unsaturated soil, where the pressure head is negative. Moreover, the soil mass variation on partially saturated soil caused by water infiltration is modeled. The model is then inserted into a Monte Carlo simulation, to manage the typical uncertainty in the values of the input geotechnical and hydrological parameters, which is a common weak point of deterministic models. The Monte Carlo simulation manages a probability distribution of input parameters providing results in terms of slope failure probability. The developed software uses the computational power offered by multicore and multiprocessor hardware, from modern workstations to supercomputing facilities (HPC), to achieve the simulation in reasonable runtimes, compatible with civil protection real time monitoring. A first test of HIRESSS in three different areas is presented to evaluate the reliability of the results and the runtime performance on large areas.

Influence of infiltration on Babaoliao shallow landslide in Taiwan using hydro-mechanical coupled model

2020 ◽  
Author(s):  
Ya-Sin Yang ◽  
Hsin-Fu Yeh
Keyword(s):  
Slope Stability ◽  
Water Content ◽  
Soil Layer ◽  
Coupled Model ◽  
Shallow Landslide ◽  
Residual Soil ◽  
Wetting Front ◽  
Element Analysis ◽  
Unstable Slope ◽  
The Impact

<p>Babaoliao landslide is located in Chiayi County of Taiwan. The geological drilling and core interpretation in previous investigation showed that exist 1 to 2 meter depths of residual soil layer above the bedrock. In this area, shallow landslides frequently occur due to the intense rainfall events. An understanding of the hydro-mechanical change under rainfall infiltration within hillslope is critical to capture the slope stability. This study used hydro-mechanical coupled model and finite element analysis to compute the field water content and stress suction, and then assess the field slope stability based on theory of local of factor. Results showed the response of internal hydraulic behavior distribution is related to terrain and the depths of bedrock. The impact of rainfall on slope stability concentrated in shallow residual soil area, since higher permeability of soil cause rainfall infiltrate into hillslope easily and form lateral flow paths, thus limiting the depths of wetting front. The discontinuity of water content distribution within hillslope may accelerate the change of hydro-mechanical behavior and unstable slope development in the hillslope. This study demonstrated the varied distribution of water content, suction stress and LFS over time and space and got the insight into the relativity unstable range of the shallow slope affected by rainfall event.</p>

scholarly journals The impact of agricultural land afforestation on soil water content in Central Bohemia

2021 ◽  
Author(s):  
Jan Vopravil ◽  
Pavel Formánek ◽  
Darina Heřmanovská ◽  
Tomáš Khel ◽  
Karel Jacko
Keyword(s):  
Czech Republic ◽  
Pinus Sylvestris ◽  
Soil Properties ◽  
Water Content ◽  
Scots Pine ◽  
Agricultural Land ◽  
Volumetric Water Content ◽  
Wood Products ◽  
The Czech Republic ◽  
The Impact

In the Czech Republic, the afforestation of agricultural land has been supported by providing subsidies from the government and the European Union. Afforestation of less-productive agricultural land provides many benefits including carbon sequestration, soil erosion control, biodiversity, water retention, cooling, social benefits, decreasing noise and light pollution, increasing air quality, wind speed reduction, oxygen production, wood production and non-wood products. In some aspects, it is possible to produce wood of the same quality on former agricultural land compared to permanent forest land. In this study, we attempted to find out the course of temperatures and volumetric water content as well as some other physical soil properties (at depths of 20, 40 and 60 cm) 9 years after the afforestation of agricultural land (warm, mild dry region of the Czech Republic) with a mixture of broadleaved tree species (Quercus robur L., Quercus rubra L. and Acer platanoides L.) or monospecific Pinus sylvestris L. stand; the study was performed in the period from April to the beginning of November 2020. Concerning the studied physical soil properties, the value of bulk density was higher (and total porosity lower) at a depth of 20 cm in Pinus sylvestris L. compared with agricultural land or the mixture of broadleaves; the water stability of soil aggregates was higher after the afforestation with the mixture of broadleaves. The temperature was lower in the soil of afforested plots (at all studied depths) compared to the agriculturally used land. Differences in rainfall interception, transpiration, soil<br />(and forest floor) properties and other factors could influence the obtained values of water content in the soil of the studied plots. The average volumetric water contents were the highest in the plots with Scots pine (depth of 20 cm) and broadleaves (depth of 40 cm), and on the control plot (depth of 60 cm). The volumetric water content at a soil depth of 20 cm was not significantly (P &gt; 0.05) different when the plot with Scots pine and agriculturally used land were compared. In all other cases and depths, the differences between plots were significant (P &lt; 0.05).

scholarly journals Development of a pore gas pressure transducer used in unsaturated soils at high water content

2019 ◽  
Vol 92 ◽  
pp. 02003
Author(s):  
Rui Chen ◽  
Zhongkui Chen ◽  
Charles Wang Wai Ng ◽  
Jian Liu
Keyword(s):  
Slope Stability ◽  
Water Content ◽  
Unsaturated Soil ◽  
Unsaturated Soils ◽  
Pressure Transducer ◽  
High Water ◽  
Gas Pressure ◽  
Water Infiltration ◽  
High Water Content ◽  
Pore Gas Pressure

Pore gas pressure in soil is an important parameter in many geoscience applications such as evaluating the effects of trapped pore gas pressure on water infiltration through soil mass, optimizing the design of gas extraction wells in landfills and assessing the performance of landfill covers in reducing landfill gas emission. In addition, it has been observed that pore gas pressure affects slope stability in unsaturated soils. However, the pore gas pressure build-up induced by water infiltration is generally ignored in most slope stability analysis by assuming gas pressure to be zero. Therefore, pore gas pressure measurement in soils is crucial to better understand the unsaturated soil behaviour. However, most of current measuring techniques of pore gas pressure are affected by water interruption during the measurement in unsaturated soils, especially at high water content. In this study, a novel gas pressure transducer was developed to measure the pore gas pressure in unsaturated soil within a wide range of water content. The newly developed pore gas pressure transducer mainly consists of an electrical pressure sensor package and an integrated membrane filter which can prevent water leaching through the membrane but allow gas to pass it freely. The performance of the gas pressure transducer was evaluated by a series of permeation tests. The results show that the developed gas pressure transducer has a good repeatability to monitor gas pressure and has a relatively fast response to the gas pressure change in compacted soils. This transducer is able to measure pore gas pressure range of 0~50 kPa of soils within a relatively high range of soil water content.

scholarly journals Roots Affect the Accuracy of Dual-probe Heat-pulse Method for Measuring Water Content in Plant Growth Media

HortScience ◽  
2006 ◽  
Vol 41 (4) ◽  
pp. 970E-971 ◽  
Author(s):  
Susan L. Steinberg ◽  
Gerard J. Kluitenberg ◽  
Soheni Tanzeema
Keyword(s):  
Heat Capacity ◽  
Water Content ◽  
Bulk Density ◽  
Heat Pulse ◽  
Volumetric Water Content ◽  
Maximum Temperature ◽  
Growth Media ◽  
Volumetric Heat Capacity ◽  
The Impact ◽  
Dual Probe

Little attention has been paid to how the presence of roots influences water content measurements obtained with water content sensors. This issue is especially important if sensors are deployed in densely rooted soil or growth media. This work addresses the impact of roots on water content measurements obtained with dual-probe heat-pulse (DPHP) sensors. In the DPHP method, the maximum temperature rise in response to heating (Tmax) is used to calculate volumetric heat capacity, which in turn is used to calculate volumetric water content. The accuracy of DPHP sensors was evaluated in unrooted and rooted 0.25–1 mm baked ceramic aggregate. For both restricted and unrestricted volumes of aggregate the presence of roots caused DPHP sensors to consistently overestimate water content by 0.05–0.09 cm3·cm-3. Measured values of Tmax were lower in the presence of roots, which resulted in overestimation of volumetric heat capacity that was attributed to the high specific heat of water contained in roots in addition to that contained within the aggregate. Differences in water content and aggregate heating between unrooted and rooted aggregate equilibrated to the same matric potential were less distinct in unrestricted volumes, where the decrease in bulk density has the offsetting effect of lowering the heat capacity. Error in water content caused by the presence of roots and changes in bulk density was estimated by developing a theoretical mixing model for volumetric heat capacity that accounted for the heat capacity of all constituents, including aggregate, water, root water, and root tissue. Predicted errors in volumetric water content due to changes in bulk density or changes in heat capacity due to roots agreed well with direct measurement.

scholarly journals Effect of Unimodal and Bimodal Soil Hydraulic Properties on Slope Stability Analysis

Water ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 1674
Author(s):  
Hsin-Fu Yeh ◽  
Tsien-Ting Huang ◽  
Jhe-Wei Lee
Keyword(s):  
Hydraulic Conductivity ◽  
Slope Stability ◽  
Water Content ◽  
Water Retention ◽  
Water Retention Capacity ◽  
Retention Capacity ◽  
Seepage Analysis ◽  
Hydraulic Behavior ◽  
Conductivity Function ◽  
The Impact

Rainfall infiltration is the primary triggering factor of slope instability. The process of rainfall infiltration leads to changes in the water content and internal stress of the slope soil, thereby affecting slope stability. The soil water retention curve (SWRC) was used to describe the relationship between soil water content, matric suction, and the water retention characteristics of the soil. This characteristic is essential for estimating the properties of unsaturated soils, such as unsaturated hydraulic conductivity function and shear strength. Thus, SWRC is regarded as important information for depicting the properties of unsaturated soil. The SWRC is primarily affected by the soil pore size distribution (PSD) and has unimodal and bimodal features. The bimodal SWRC is suitable for soils with structural or dual-porous media. This model can describe the structure of micropores and macropores in the soil and allow the hydraulic behavior at different pore scales to be understood. Therefore, this model is more consistent with the properties of onsite soil. Few studies have explored the differences in the impact of unimodal and bimodal models on unsaturated slopes. This study aims to consider unimodal and bimodal SWRC to evaluate the impact of unsaturated slope stability under actual rainfall conditions. A conceptual model of the slope was built based on field data to simulate changes in the hydraulic behavior of the slope. The results of seepage analysis show that the bimodal model has a better water retention capacity than the unimodal model, and therefore, its water storage performance is better. Under the same saturated hydraulic conductivity function, the wetting front of the bimodal model moves down faster. This results in changes in the pressure head, water content, and internal stress of the soil. The results show that the water content and suction stress changes of the bimodal model are higher than those of the unimodal model due to the difference in water retention capacity. Based on the stability of the slope, calculated using the seepage analysis, the results indicate that the potential failure depth of the bimodal model is deeper than that of the unimodal model.

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