Influence of Clay Contents on Drained Shear Strength Parameters of Residual Soil for Slope Stability Evaluation (original) (raw)
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Assessment of Residual Soil Properties for Slope Stability Analysis
International Journal of GEOMATE, 2021
Slope instability is a common natural geological hazard in tropical countries like Malaysia, with abundant residual soil and frequent rainfall. Over the years, these rainfalls have induced instabilities that lead to significant human and economic loss. To reduce the expected disastrous impacts due to rainfall-induced slope failure characterization of residual soil is necessary for evaluation of slope stability assessment. Therefore, this study aims to characterize the residual soil for numerical modelling of rainfall-induced slope failure and preliminary slope stability assessment so that future slope failure can be reduced. A series of experiments involving index properties tests and engineering properties tests were carried out on the residual soil samples collected from a slope located in Universiti Teknologi Malaysia (UTM). Based on the particle size distribution and consistency the soil can be classified as high plasticity silt (MH). The maximum dry unit weight and optimum moisture content are 13.17kN/m3 and 30 %, respectively. Saturated hydraulic conductivity from the falling head test is 2.32055E-07 m/s, while the saturated gravimetric water content was 54%. The effective cohesion and angle of the internal fraction were 8 kPa and 32°, respectively. The average undrained shear strength and unconfined compressive strength were 105 kPa and 43 kPa, respectively. The result obtained in this study was utilized for the preliminary rainfall slope stability assessment in tropical residual soils by simulating rainfall of different intensities and duration on a typical slope profile using PLAXIS 2d. The results show that due to the low hydraulic conductivity and fine-grained nature of the soil, the slopes in the study area are more critical to the low intensity and long duration rainfall events (I≤4Ks). The highly intense and short-duration rainfall (I≥8Ks) has no significant effect on the safety of the soil, as most of the precipitation will contribute to runoff, and only a minor amount of water will infiltrate into the slope.
ANALYSIS OF SLOPE STABILITY ON TROPICAL RESIDUAL SOIL
Tropical residual soil is a product of chemical weathering, thus its characteristics are dependent upon environmental factors such as parent rocks, climate, topography and age. This type of soil can be found in many countries all over the world, especially in the tropical region. Since there are many accident happens due to slope failure, a comprehensive laboratory study need to be conducted in order to determine the properties of soil located at Pahang Matriculation College. Several experiments involving physical index and engineering properties of soil are conducted. The typical tropical residual properties are showed and can be considered as sandy SILT of high plasticity as suggested by previous researchers. The result from CIU testing give 9 kPa of cohesion and 25⁰ of friction angle while unsaturated friction angle was assumed 21⁰. From the slope analysis at Pahang Matriculation College, for a saturated slope (0 kPa suction), the FOS value using Fellenius's method is 1.199 while Bishop's method give 1.262 which the difference is 5.25 %. For an unsaturated slope (20 kPa suction), the FOS using using Fellenius's method is 1.492 while Bishop's method give 1.550 which the difference is 3.89 %. The results concluded that FOS value of slope is always higher if calculated using Bishop's method compare to Fellenius's method.
IRJET, 2020
Moisture content is one of the most crucial factors influencing soil strength. This paper deals with the effect of moisture content and density on the shear strength parameters of WOZEKA-GIDOLE road elastic silt (expansive) embankment soil under dry, wet (partially saturated), OMC and saturated conditions in relation to slope stability analysis. The wide distribution of expansive soil in Ethiopia creates problems in many field of construction such as excavation, slope stability and foundation in understanding their engineering characteristics especially the behavioral changes in dry and saturation condition. In this study, samples were collected from a slope construction road site in WOZEKA-GIDOLE, southern Ethiopia. At a constant grading of a soil its effect on strength, swelling pressure and index properties value has been undertaken, as soils are to be used for making road pavement, embankments. The stability of an embankment will greatly be influence by the shear parameters which are depend upon the degree of compaction. So soil specimen were compacted in the laboratory and the optimum moisture content and dry densities were identified. After compaction soil was tested at the dry side of optimum water content at w = 5%, partially saturate of the optimum at 10%, at 15% OMC and at 20% saturation condition at 1.3 gm/cm 3 , 1.4 gm/cm 3 and 1.55 gm/cm 3 (MDD) dry densities. Parameters of shear strength (C) and (ϕ) were obtained from triaxial shear test (UU) and shows the compacted elastic silt soil behaves like a granular soil on the dry side of optimum water content (5% and 10%) and a reduction in angle of friction and an increase in cohesion are observed as the compaction water contents approach the optimum value. Cohesion shows a slight increase as moisture content increases whereas friction angle highly decreases with increasing moisture content at constant density. The shear strength parameters were used for stability analysis with software GEOSLOPE/W 2018 with Limit equilibrium based methods to calculate the factor of safety (FOS) and locate critical failure arc. The slope stability analysis of elastic silt soil has been done and is used in under different conditions to evaluate slope stability. Analysis of embankment at different heights of the slope with Morgenstern-Price's analysis method. In the present study varying the density and moisture has been affect the properties of expansive soil namely elastic silt soil. Finally constant grading of soil is a technique for modification the geotechnical properties and improving slope stability of embankment and increasing the dry density and decreasing height of embankment, the undrained shear parameters (C & Φ) are improved.
2014
The reduction of shear strength parameters of the soil in the slopes as well as the reduction of suction as the soil become saturated during prolonged rainy seasons are the two main causes of slope failures in Malaysian residual soils. In this study, a total of 227 shear strength parameters were obtained from 29 slope failures in Penang Island and Baling. Both locations are located in Northern Malaysia. In addition, 35 shear strength parameters were also obtained from 10 stable slopes, also at the same locations. Disturbed soil samples were taken at a depth of 100mm from the existing ground surface. Field bulk density tests were carried out at all the location where soil samples were taken. The field bulk density results were later used to re-compact the soil for the consolidated drained shear box tests to be carried out in laboratory. The objective of the research is to determine the threshold values of the effective shear strength parameters of soil taken from both the slope failu...
International Journal of GEOMATE, 2021
Residual shear strength plays a very significant role in geotechnical engineering. This concept has contributed extensively to diverse studies on soil behaviors under the influence of shear failure, both in drained and saturated conditions. In terms of landslides, the assessment of the residual shear strength after an occurrence and the progressive failure risk of slope stability has been very useful. However, information on this shear property in laterite soil appears relatively minimal. This soil type is the most frequently applied embankment for road construction in every Kalimantan region. Therefore, the purpose of this research is to determine the behavior of residual shear strength in laterite soil and the effects of adding coarse sand and clay fractions, using direct shear analysis. Subsequently, the specimens were prepared by compaction tests to obtain the optimum moisture content and uniform density, using coarse sand of varying proportions, termed 5, 10, 15, 20 and 25%, while, the shear strength treatment with wetting and drying cycle conditions was conducted under 2, 4, 6, 8 and 10 days, respectively. The results showed that the addition of the coarse sand and clay (CL) portions was able to increase the residual shear strength parameters (cohesion and internal friction angle) by 4-6%, compared to the pure state. Therefore, the introduction of clay (CL) materials ranging from 20-25% appears suitable in enhancing the residual shear strength of laterite soil. However, the extensive wetting-drying cycle tends to reduce the peak and residual shear strength.
Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis, 2013
Shear strength of soils is highly affected by moisture conditions (i.e. water content), especially if the soil contains clay materials. Usually the laboratory specimen, which are used to determine shear strength of soil are prepared at water content and dry density same as in the field conditions, without respect to the fact, that the conditions in the future might not remain the same. For the purpose of this study soil specimen were compacted and the optimum moisture content was identified. After compaction soil was tested at the dry side of optimum water content at w = 9 %, 10 % and 11 %. Parameters of shear strength were obtained and used for stability analysis with software GEOSLOPE/W 2012. According to referenced literature, it was expected for the shear strength of the soil to decrease with increasing water content. This hypothesis was not proven for clayey soil from Brno region. Development of values of friction angle and cohesion exhibited anomalous behaviour and such develo...
2017
Slope failures always occur in Malaysia especially during the monsoon seasons between October and January every year causing fatalities and damages to properties. The main factors causing the slope failure to occur are reduction of the shear strength parameters and loss of negative suction due to saturation of the slope. The objective of this study is to determine the effective shear strength parameters of the soil taken at slope failure using consolidation drain (CD) shear box and also to determine the factor of safety using SLOPE/W software. The soil samples were tested under submerged condition. The minimum value of effective shear strength parameters obtained from the CD shear box tests were c' = 0 kN/m 2 and ø' = 47.3 0 while the maximum value of c' = 30.2 kN/m 2 and ø' = 35.6 0. The FOS varied from 0.377 to 0.749 with minimum value of factor of safety was 0.377. When using SLOPE/W software on a stable slope cross section having minimum value of effective shear strength parameters, the minimum value of factor of safety was less than 1 indicating that the slope had already failed.
Engineering Properties of Soil from Unstable Slopes in Ranau-Kundasang, Sabah, Malaysia
Transactions on Science and Technology, 2016
A total of five soil samples were collected from different sedimentary rock units namely Trusmadi Formation, Crocker Formation and Pinosouk Gravel in order to analysis the engineering properties of the soils. The soil samples were collected from unstable soil slopes in Ranau-Kundasang, Sabah. The result of analysis shows that the soil moisture content was in the range of 6.94% to 22.70%, the soil organic content range from 0.60% to 1.79%, and the soil specific gravity in the range of 2.49 to 2.65. All samples show the acidity to low alkaline in pH. The average liquid limit of soil samples were from 20.93% to 65.00%, while the plasticity indexes were in the range of 5.67% to 20.98%. The plasticity chart plot of soil found that soils from Trumadi and Crocker Formation were classified as low plasticity soil,while Pinosouk Gravel samples were classified as intermediate to high plasticity. Clay activity analysis showed the existence of illite and kaolinite in soil of Trusmadi and Crocker...
IRJET, 2020
Moisture content is one of the most crucial factors influencing soil strength. This paper deals with the effect of moisture content and density on the shear strength parameters of WOZEKA-GIDOLE road elastic silt (expansive) embankment soil under dry, wet (partially saturated), OMC and saturated conditions in relation to slope stability analysis. The wide distribution of expansive soil in Ethiopia creates problems in many field of construction such as excavation, slope stability and foundation in understanding their engineering characteristics especially the behavioral changes in dry and saturation condition. In this study, samples were collected from a slope construction road site in WOZEKA-GIDOLE, southern Ethiopia. At a constant grading of a soil its effect on strength, swelling pressure and index properties value has been undertaken, as soils are to be used for making road pavement, embankments. The stability of an embankment will greatly be influence by the shear parameters which are depend upon the degree of compaction. So soil specimen were compacted in the laboratory and the optimum moisture content and dry densities were identified. After compaction soil was tested at the dry side of optimum water content at w = 5%, partially saturate of the optimum at 10%, at 15% OMC and at 20% saturation condition at 1.3 gm/cm 3 , 1.4 gm/cm 3 and 1.55 gm/cm 3 (MDD) dry densities. Parameters of shear strength (C) and (ϕ) were obtained from triaxial shear test (UU) and shows the compacted elastic silt soil behaves like a granular soil on the dry side of optimum water content (5% and 10%) and a reduction in angle of friction and an increase in cohesion are observed as the compaction water contents approach the optimum value. Cohesion shows a slight increase as moisture content increases whereas friction angle highly decreases with increasing moisture content at constant density. The shear strength parameters were used for stability analysis with software GEOSLOPE/W 2018 with Limit equilibrium based methods to calculate the factor of safety (FOS) and locate critical failure arc. The slope stability analysis of elastic silt soil has been done and is used in under different conditions to evaluate slope stability. Analysis of embankment at different heights of the slope with Morgenstern-Price's analysis method. In the present study varying the density and moisture has been affect the properties of expansive soil namely elastic silt soil. Finally constant grading of soil is a technique for modification the geotechnical properties and improving slope stability of embankment and increasing the dry density and decreasing height of embankment, the undrained shear parameters (C & Φ) are improved.