Climatic effects on pore-water pressure, deformation and stress mobilization of a vegetated volcanic soil slope in Hong Kong

2015 ◽  
pp. 63-82
Author(s):  
C. W.W. Ng ◽  
A.K. Leung
Keyword(s):  
Hong Kong ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Soil Slope ◽  
Volcanic Soil ◽  
Climatic Effects

scholarly journals Numerical Analysis of the Effects of Crack Characteristics on the Stress and Deformation of Unsaturated Soil Slopes

Water ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 194 ◽  
Author(s):  
Liuxin Yang ◽  
Enlong Liu
Keyword(s):  
Pore Water ◽  
Unsaturated Soil ◽  
Crack Width ◽  
Evaporation Rate ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Infiltration Rate ◽  
Soil Slope ◽  
Soil Slopes ◽  
Stress And Deformation

Cracks induced by evaporation or rainfall have a great influence on the stability of unsaturated soil slopes, which can lead to landslides during the rainfall process. In order to study the effect of crack characteristics on the evolution of stress and deformation of unsaturated soil slopes, a series of numerical analyses under different conditions were performed using a coupled elastoplastic finite element program that we developed for unsaturated soil. When carrying out the numerical analyses, the effective stress for unsaturated soil proposed by Bishop and an elastoplastic double-hardening constitutive model for the soil skeleton were employed. The varying parameters, including the crack location, the discharge speed, evaporation rate, infiltration rate, and tensile strength, were investigated to study the coupling process of pore water pressure and deformation in the process of evaporation and rainfall infiltration. The numerical results showed that the minimum pore water pressure of the soil slope at the end of evaporation/rainfall decreased gradually and the crack width increased gradually as the crack set closer to the slope; the larger the discharge speed of pore air, the greater the crack width. With the increase in the evaporation rate, the pore water pressure of the soil slope reduced and the crack initiated earlier and became wider. As the infiltration rate increased, the pore water pressure of the soil slope and the crack width increased, but the decreasing duration became shorter. The change of tensile strength had little effect on the pore water pressure, but the development of the crack width changed with evaporation and rainfall infiltration.

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

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.

Use of recycled crushed concrete and Secudrain in capillary barriers for slope stabilization

2013 ◽  
Vol 50 (6) ◽  
pp. 662-673 ◽  
Author(s):  
H. Rahardjo ◽  
V.A. Santoso ◽  
E.C. Leong ◽  
Y.S. Ng ◽  
C.P.H. Tam ◽  
...  
Keyword(s):  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Coarse Grained ◽  
Residual Soil ◽  
Soil Slope ◽  
Capillary Barrier ◽  
Concrete Aggregates ◽  
Crushed Concrete ◽  
Residual Soil Slope

A capillary barrier is a two-layer cover system having distinct hydraulic properties to minimize water infiltration into the underlying soil by utilizing unsaturated soil mechanics principles. In this study, a capillary barrier system was designed as a cover system for a residual soil slope to maintain stability of the slope by minimizing infiltration during heavy rainfalls in the tropics. The capillary barrier system (CBS) was constructed using fine sand as the fine-grained layer and recycled crushed concrete aggregates as the coarse-grained layer. The coarse-grained layer is commonly constructed using gravels or granite chips. However, due to scarcity of aggregates and in consideration of environmental sustainability, recycled crushed concrete aggregates were used as the coarse-grained layer in this project. The suitability of recycled crushed concrete aggregates as a material within the coarse-grained layer of a CBS is subject to the hydraulic property requirement. For comparison, another CBS was constructed using fine sand as the fine-grained layer and a geosynthetic (Secudrain) as the coarse-grained layer. The performance of each constructed CBS on the residual soil slope was monitored using tensiometers installed at different depths — from 0.6 to 1.8 m below the slope surface — and a rainfall gauge mounted on the slope. An adjacent original slope without the CBS was also instrumented using tensiometers and piezometers to investigate the performance and effectiveness of the CBS in reducing rainwater infiltration and maintaining negative pore-water pressures in the slope. Real-time monitoring systems were developed to examine pore-water pressure, rainfall, and groundwater level in the slopes over a 1 year period. Characteristics of pore-water pressure distributions in the residual soil slope under a CBS with recycled crushed concrete aggregates and in the original slope during typical rainfalls are highlighted and compared. The measurement results show that the CBS was effective in minimizing rainwater infiltration and therefore, maintaining stability of the slope.

Response of a residual soil slope to rainfall

2005 ◽  
Vol 42 (2) ◽  
pp. 340-351 ◽  
Author(s):  
H Rahardjo ◽  
T T Lee ◽  
E C Leong ◽  
R B Rezaur
Keyword(s):  
Water Content ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Residual Soil ◽  
Soil Slope ◽  
Pore Water Pressures ◽  
Pressure Water ◽  
Water Contents ◽  
Residual Soil Slope

Rainfall-induced landslides are a common problem in residual soil slopes of the tropics. It is widely known that rainfall-induced slope failures are mainly caused by infiltration of rainwater; however, the response of a residual soil slope to infiltration is not fully understood. The difficulties lie in the quantification of the flux boundary condition across the slope surface with respect to infiltration and its effect on the pore-water pressure conditions in the slope. Therefore, it is important to understand the response of a slope to different rainfall conditions and the resulting changes in pore-water pressures and water contents. A residual soil slope in Singapore was instrumented with pore-water pressure, water content, and rainfall measuring devices, and studies were carried out under natural and simulated rainfalls. Results indicate that significant infiltration may occur in a residual soil slope during a rainfall. Small total rainfalls can contribute a larger infiltration percentage than large total rainfalls. The percentage of infiltration usually decreases with increasing total rainfalls. The study has indicated the existence of a threshold rainfall of about 10 mm for runoff generation to commence. Infiltration during wet periods may lead to the development of positive pore-water pressures as a consequence of a perched water table condition. Matric suctions are recovered gradually during dry periods due to redistribution. Soil water contents tend to be higher near the toe of the slope than at the crest irrespective of rainfall events, indicating subsurface movement of water in the downslope direction. The study has also indicated a correlation between rainfall amount and relative increase in pore-water pressure. The results can be used to quantify the flux boundary conditions required for the seepage analyses associated with rainfall-induced slope failures.Key words: infiltration, pore-water pressure, water content, residual soil, rainfall-induced slope failures.

The Analysis of Soil Slope Transient Seepage Consider the Change of Permeability Coefficient in Rainfall Condition

2012 ◽  
Vol 446-449 ◽  
pp. 1888-1892
Author(s):  
Zhong Ming He ◽  
Yan Qi Qin ◽  
Zhong Xin Cai
Keyword(s):  
Pore Water ◽  
Permeability Coefficient ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Rainfall Infiltration ◽  
Water Infiltration ◽  
Soil Slope ◽  
Seepage Field ◽  
Finite Element Software ◽  
Transient Seepage

In order to study the transient seepage field of soil slope when the saturated permeability coefficient changes under rainfall infiltration condition, the finite element software is used to build the numerical analysis model, the influence of slope seepage field and pore water pressure caused by the change of saturated permeability coefficient are emphatically discussed. The results show, under the condition of the certain sustained rainfall strength and rainfall duration, the rain water infiltration rate and infiltration depth are proportional to slope soil saturation permeability coefficient; Pore water pressure along the elevation direction shows the characteristic of “two big heads, among small” under the influence of rainfall infiltration.

Consolidation modelling of soils under the test embankment at Chek Lap Kok International Airport in Hong Kong using a simplified finite element method

2001 ◽  
Vol 38 (2) ◽  
pp. 349-363 ◽  
Author(s):  
Guofu Zhu ◽  
Jian-Hua Yin ◽  
James Graham
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Hong Kong ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
International Airport ◽  
Geological Conditions ◽  
Test Embankment ◽  
Element Method

This paper models consolidation of the foundation soils under a test embankment at the new Chek Lap Kok International Airport in Hong Kong. The modelling used a simplified finite element method and material parameters derived from results in the original site investigation report. Various features that need to be considered in applying the simplified method are illustrated through this case study. Good predictions of settlement results are obtained. Relatively large discrepancies in pore-water pressure predictions suggest that the nonlinear nature of hydraulic conductivity needs to be taken into account when large compressions are likely to occur. Geological conditions are shown to be a key factor in successful modelling of consolidation behaviour.Key words: consolidation, pore-water pressure, case modelling, finite element method, vertical drains, settlement.

Effect of rainfall on matric suctions in a residual soil slope

1996 ◽  
Vol 33 (4) ◽  
pp. 618-628 ◽  
Author(s):  
T T Lim ◽  
H Rahardjo ◽  
M F Chang ◽  
D G Fredlund
Keyword(s):  
Slope Stability ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Matric Suction ◽  
Residual Soil ◽  
Soil Slope ◽  
Field Instrumentation ◽  
Pore Water Pressures ◽  
Residual Soil Slope

A slope stability study involving shallow slip surfaces should include the effect of negative pore-water pressures in a slope. A field instrumentation program was carried out to monitor negative pore-water pressure (i.e., in situ matric suction) in a residual soil slope in Singapore. Variations in matric suction and the matric suction profiles under (1) a canvas-convered grassed surface, (2) a grassed surface, and (3) a bare ground surface, in response to rainfalls were investigated. Changes in matric suction due to changes in climatic conditions decrease rapidly with depth. The change was found to be most significant in the bare slope and least significant under the canvas-covered slope. The amount of decrease in matric suction after a rainstorm was observed to be a function of the initial matric suction just prior to the rainstorm. Positive pore-water pressures were observed above the groundwater table, suggesting the development of a perched water table within the slope. These observations are also typical of other regions experiencing high seasonal rainfalls. The field monitoring program presented can be adopted for investigating rainfall-induced landslides in other parts of the world. Key words: matric suction, negative pore-water pressure, field instrumentation, rainfall, residual soil, slope stability.

TIME TO THE END OF PRIMARY CONSOLIDATION (EOP) OF SOFT CLAYEY SOILS: CONCERNING THE EFFECT OF ATTERBERG’S LIMIT AND CYCLIC LOADING HISTORY

2019 ◽  
Vol 128 (2B) ◽  
pp. 29-41
Author(s):  
Trần Thanh Nhàn
Keyword(s):  
Cyclic Loading ◽  
Pore Water ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Clayey Soils ◽  
Loading History ◽  
Cyclic Shear ◽  
Wide Range ◽  
Primary Consolidation ◽  
Time Required

In order to observe the end of primary consolidation (EOP) of cohesive soils with and without subjecting to cyclic loading, reconstituted specimens of clayey soils at various Atterberg’s limits were used for oedometer test at different loading increments and undrained cyclic shear test followed by drainage with various cyclic shear directions and a wide range of shear strain amplitudes. The pore water pressure and settlement of the soils were measured with time and the time to EOP was then determined by different methods. It is shown from observed results that the time to EOP determined by 3-t method agrees well with the time required for full dissipation of the pore water pressure and being considerably larger than those determined by Log Time method. These observations were then further evaluated in connection with effects of the Atterberg’s limit and the cyclic loading history.

Conjectures, Hypotheses, and Theories of Drumlin Formation (In memory of Stanislaw Baranowski)

1981 ◽  
Vol 27 (97) ◽  
pp. 503-505 ◽  
Author(s):  
Ian J. Smalley
Keyword(s):  
Shear Strength ◽  
Pore Water ◽  
Stress Level ◽  
Critical Stress ◽  
Pore Water Pressure ◽  
Water Pressure ◽  
Glacial Till ◽  
Forming Process ◽  
Stress Levels

AbstractRecent investigations have shown that various factors may affect the shear strength of glacial till and that these factors may be involved in the drumlin-forming process. The presence of frozen till in the deforming zone, variation in pore-water pressure in the till, and the occurrence of random patches of dense stony-till texture have been considered. The occurrence of dense stony till may relate to the dilatancy hypothesis and can be considered a likely drumlin-forming factor within the region of critical stress levels. The up-glacier stress level now appears to be the more important, and to provide a sharper division between drumlin-forming and non-drumlin-forming conditions.

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