Influence of transport Layer on Transient Suction Distribution in a Two-Layered Slope

2015 ◽  
Vol 72 (3) ◽  
Author(s):  
Gambo Haruna Yunusa ◽  
Azman Kassim ◽  
Ahmad Safuan A. Rashid
Keyword(s):  
Material Properties ◽  
Slope Failure ◽  
Matric Suction ◽  
Rainfall Infiltration ◽  
Transport Layer ◽  
Residual Soil ◽  
Soil Slope ◽  
Capillary Barrier ◽  
Layered Slope ◽  
Residual Soil Slope

Residual soil slope failure due to rainfall infiltration is one of geotechnical hazards receiving much attention in many tropical climate countries. The infiltrating water eliminates matric suction in the residual soil slope and results in slope failure. A capillary barrier is used to prevent excessive rainfall infiltration and preserve matric suction in the residual soil slope and hence prevent rainfall-induced slope failure. A numerical study to examine the performance of a transport layer in a two-layered slope using capillary barrier principle was presented in this paper. Material properties of tropical residual soils consisting of Grade V (silty gravel) and Grade VI (sandy silt) were used and modelled a two-layered slope. These material properties were obtained from representative soil sample of Balai Cerapan slope in Universiti Teknologi Malaysia, Johor Bahru campus. A granite chips (Gravel) was also incorporated to act as a transport layer in the numerical model. The simulated slope model was then subjected to three different rainfall intensities of 9 mm/h (rainfall 1), 22 mm/h (rainfall 2) and 36 mm/h (Rainfall 3) representing short, medium and high intensity rainfalls, respectively. A total of six numerical schemes were performed by restricting the thickness of the transport layer to 0.1 m. However, to assess the effect of the transport layer thickness on suction distribution; the thickness was increased to 0.2 m. The results of the study show that inclusion of gravelly transport layer enables the top layer of fine sandy silt residual soil to retain the infiltrating water as a result of capillary break developed at the interface and also divert it above the interface towards the direction of the toe of the slope. Similarly the transport layer is found to be effective in preventing water breakthrough occurrence into the underlying coarser soil layer of the two-layered slope, especially when the thickness of the transport layer is optimum.

Monitored and simulated variations in matric suction during rainfall in a residual soil slope

2007 ◽  
Vol 55 (5) ◽  
pp. 951-961 ◽  
Author(s):  
Aurelian C. Trandafir ◽  
Roy C. Sidle ◽  
Takashi Gomi ◽  
Toshitaka Kamai
Keyword(s):  
Matric Suction ◽  
Residual Soil ◽  
Soil Slope ◽  
Residual Soil Slope

NUMERICAL INVESTIGATION OF PERFORMANCE OF CAPILLARY BARRIER SYSTEM WITH TRANSPORT LAYER

2015 ◽  
Vol 77 (12) ◽  
Author(s):  
Gambo Haruna Yunusa ◽  
Azman Kassim ◽  
Zaihasra Abu Talib ◽  
Shabena Jasmin Mohamed Yoosoof
Keyword(s):  
Soil Layer ◽  
Climatic Conditions ◽  
Rainfall Infiltration ◽  
Transport Layer ◽  
Alternative Measure ◽  
Residual Soil ◽  
Capillary Barrier ◽  
Seepage Analysis ◽  
Promising Alternative ◽  
Rainfall Condition

A capillary barrier system is a promising alternative measure for controlling rainfall infiltration into unsaturated residual soil slopes. Although, system with capillary barrier effect has been successfully applied to avert rainfall infiltration in dry and semi-dry climates, its application in humid climates with high precipitation rate is still unsatisfactory. Therefore, this paper evaluates the performance of a modified capillary barrier system with transport layer under humid climatic conditions. The capillary barrier system and the transport layer were simulated with Grade V and Grade VI soils and gravel, respectively. The system was subjected to various rainfall intensities using saturated/unsaturated seepage analysis. When the initial suction of 32 kPa was assigned to the system and subjected to the worst rainfall condition for 24-hour duration, the breakthrough time increases with increase in the thickness of grade VI residual soil layer in the conventional capillary barrier system and the maximum diversion length achieved is less than 2 m. However, when a transport layer was placed at the interface of the grade V and grade VI soils, the diversion length increases to 15 m and avert breakthrough occurrence under the same condition. Therefore, the inclusion of transport layer in a residual soil capillary barrier system improved its performance and prevent breakthrough occurrence.

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.

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.

Comparison of Soil Modulus E50 of Residual Soil Slope Failures in Two Different Rainfall Zones

2014 ◽  
pp. 135-141 ◽  
Author(s):  
M. A. S. N. Mallawarachchi ◽  
E. M. T. M. Ekanayake ◽  
S. S. I. Kodagoda ◽  
A. A. Virajh Dias
Keyword(s):  
Residual Soil ◽  
Soil Slope ◽  
Slope Failures ◽  
Soil Modulus ◽  
Residual Soil Slope

scholarly journals Effect of hysteresis on the stability of residual soil slope

2019 ◽  
Vol 7 (3) ◽  
pp. 226-238 ◽  
Author(s):  
Christofer Kristo ◽  
Harianto Rahardjo ◽  
Alfrendo Satyanaga
Keyword(s):  
Residual Soil ◽  
Soil Slope ◽  
The Stability ◽  
Residual Soil Slope
Sign in / Sign up

Export Citation Format

Share Document