ANALYSIS OF INCREASING SHEAR STRENGTH OF SOIL TO SLOPE STABILITY AFTER CONSOLIDATION SETTLEMENT COMPLETED WITH VARIOUS METHOD (original) (raw)
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The shear resistance is very different with different soft soils. Even in same soft soil type, shear resistance have significant difference utilizing different experimental methods. Calculation of embankment stability using these factors would give different results for the same problem. The main objective of this study is to study difference between shear resistances using shear resistance parameters of soft soils from different experiments, and evaluate the difference of stability calculation results of embankments using these parameters. The data was collected in Hai Phong area (Viet Nam) for three types of soft soils such as clay silt, mixed clay silt, and plastic–flow mixed clay. Embankment has been simulated as a section of national highway No.5. Bishop simplified method has ben applied to calculate the stability of embankment. The result shows that safety factor is the highest in the case using parameters from triaxial shear test with C’U’ scheme (Fs = 2.118), followed by triaxial shear test with CU (Fs = 1.628), vane shear test (Fs = 1.226), triaxial shear test with UU (Fs = 0.451), and direct shear test (Fs = 0.334), respectively. Additionally, this study also suggests the selection of suitable parameters in calculating embankment stability for specific cases. The result obtained in this study might be helpful for construction engineers in calculating embankment stability.
The cone penetration test (CPT) has emerged as most widely used for obtaining soil profile and soil properties. In several studies showed that CPT data can also be used for the soil settlement calculation. However these calculations have a different parameter for each location. The main objective of this study was to compare and evaluate the results of settlement using laboratory testing data and consolidation measurement using CPT data of soft clay soil in some area in Indonesia. Furthermore, this study also conducted to find the parameter of CPT settlement (m) that appropriate with the soil condition in this study area and also to analyze the value the horizontal coefficient (Ch) of PVD installation that installed in the field. The Pre-loading with trial embankment of soil subgrade is considered in this study. This study uses a several field soil data CPT test, consolidation laboratory test and settlement plate measurement. The area of study in this research is in access road construction project of Trisakti harbor in Lianganggam, Kalimantan, Indonesia. The results obtained from this study are the horizontal coefficient of PVD (Ch) for the soil in this area is measures as 5 times higher than the vertical coefficient of PVD (Cv) measurement from laboratory data. In addition, the appropriate parameter of settlement using CPT data () is 2.77 obtained by back calculation method in trial embankment and settlement plate result. These results are slightly different from the results of similar research but at a different location in another country.
DEFORMATION ANALYSIS OF EMBANKMENTS
Settlement and stability are the primary geotechnical considerations in the design of embankments founded on soft clay. Settlements are inevitably associated with lateral deformations. Lateral flow in turn is an indirect measure of the stability of embankments. Therefore, a detailed study of different settlement components and lateral deformations and their correlations will provide guidelines for an embankment design. This paper presents a new methodology, termed "Field Deformation Analysis (FDA)," which is based on a simple concept dealing with lateral and vertical deformation characteristics of soft foundations under embankment stage loading. This method is used to delineate and quantify different settlement components, namely, immediate settlement, consolidation settlement, and creep settlement, from the total settlement measured during field observations, for the loading and consolidation stages. Finite element method (FEM) of analysis was performed for comparison with FDA results. The FEM analysis was performed using the CRISP computer program, developed at Cambridge University, which uses many soil constitutive models including the modified Cam-clay model. In 1988, the Malaysian Highway Authority was authorized to build 13 full-scale test embankments at Muar Flats, of which two were constructed without any foundation ground improvements. A comparison study of the results from FDA and FEM, performed for both the untreated full-scale test embankments, revealed very good agreement during loading and consolidation stages. In addition, a consistent relationship between the different settlement components was also observed during the different stages of embankment loading.
2012
Soft soils are not suitable for construction of buildings or facilities without having soil improvements. The soil improvements that are used in the chosen site are Preloading and Prefabricated Vertical Drain (PVD). Analysis of settlement is important to evaluate the site before the construction begins. The objectives of the study are, to predict settlement of an embankment based on Terzaghi OneDimensional Consolidation analysis, to obtain the final settlement by using Asoaka's method based on monitoring data and to compare the soil properties from the lab data with back calculated based on the firn:il settlement. Using Terzaghi One-Dimensional Consolidation Method, prediction of the total settlement is 287mm. The data from monitoring record are used to plot Asoaka's Graph in order to get the actual settlement which is 13mm, then being used to back calculate soil properties. The soil properties those are back calculated based on field settlement are different from those obta...
IPTEK Journal of Proceedings Series
In order to predict the consolidation period in the field, consolidation coefficient in vertical direction (C v) parameter is needed. When vertical drains installed in the compressible layer in order to shortened the consolidation period, it needs consolidation coefficient in horizontal direction (C h). This C h parameter has to be determined from the field settlement that usually obtained from the trial embankment. However, it is very expensive to carry out the trial embankment; therefore, it is usually assumed to be 2 till 5xC v. In this paper, the assumption of the C h value will be proven by using field settlement data taken from the trial embankment at the reclamation area for container yard at Kuala Tanjung, Medan, By choosing the C h value, the compression vs time curves were predicted by adopting the Terzaghi, Asaoka, and Finite Element methods. Afterwards, these predicted settlement curves were plotted with the field settlement curves; from this plotting, it could be figured out the predicted curves which has C h value the same with the field C h value. The results show that from three methods adopted in this study, only the Terzaghi and the Asaoka methods give satisfactory results in settlement prediction. Consequently, only the Terzaghi and Asaoka methods are adopted to determine the C h value. The C h value obtained is about the same, that is 3C v until 5C v. When that C h value used back to predict the settlement, the Asaoka method gives better result than the Terzaghi method.
IJERT-Stability Analysis of Different Soilfil on Embankment Subgrade using Plaxis-2d
International Journal of Engineering Research and Technology (IJERT), 2021
https://www.ijert.org/stability-analysis-of-different-soilfil-on-embankment-subgrade-using-plaxis-2d https://www.ijert.org/research/stability-analysis-of-different-soilfil-on-embankment-subgrade-using-plaxis-2d-IJERTCONV9IS09009.pdf Slope stability analysis is one of the most important topic in geotechnical engineering. For the construction of railways, embankments, canal, road Embankments, earth dams etc. we go for different slopes with different geometric conditions. If the slope is naturally made, the kind of problem is to check the sustainability of slope. If it is manmade type, the problem of choosing soils to build and other conditions which required for stable. The clear idea of this topic is to know the best suitability of locally available fill materials. For this particular analysis done in latest version of plaxis 2D. Evaluation of the stability analysis for road embankment is not only a problem but also a challenge or Geotechnical Engineering. In manmade slope, the problem of choosing soil is an important role for stability condition. The main purpose on this study is to determine the stability of road fill Embankment according to the factor of safety and deformation. In this study, the stability of slope was modelled in scenarios (different fills, different inclination and various level of water table). Finite Element Method by Plaxis 2D was used in numerical analysis of slope. The result of this study showed the suitability of fill soil in embankment construction according to the comparative study of deformations, factors of safety. In collected fill soils, Clayey sand is most suitable for road fill embankment.
A semi-analytical method for the analysis of pile-supported embankments
Journal of Zhejiang University SCIENCE A, 2012
In this paper, a semi-analytical method for the analysis of pile-supported embankments is proposed. The mathematic model describes the cooperative behavior of pile, pile cap, foundation soil, and embankment fills. Based on Terzaghi's 1D consolidation theory of saturated soil, the consolidation of foundation soil is calculated. The embankments with two different types of piles: floating piles and end-bearing piles are investigated and discussed. The results of axial force and skin friction distributions along the pile and the settlements of pile-supported embankments are presented. It is found that it takes a longer time for soil consolidation in the embankment with floating piles, compared with the case using end-bearing piles. The differential settlement between the pile and surrounding soil at the pile top is larger for the embankment with end-bearing piles, compared with the case of floating piles.
Slope Stability of Embankments on Soft Soil Improved with Vertical Drains
Civil Engineering Journal, 2020
The overloads of structures or embankments built on clayey soft ground are generally applied gradually, respecting a specific phasing. This phasing on construction allows the undrained shear strength of clay increasing over consolidation in order to avoid the risk of collapse during loading. In this work, the undrained shear strength of clay over the consolidation was estimated following SHANSEP method of which parameters proposed by eight researchers have been employed, as well as the slope stability analysis of embankments on soft soils during staged construction. Assessment of factor of safety for slope stability was conducted basing on the Bishop method. Additionally, the variations of undrained shear strength and factor of safety were presented. In order to validate the methods discussed in this study, slope stability analysis of five embankments constructed on clayey soft soils improved by the vertical drain technique in a high-speed railway construction project in Morocco was...
Stress and Deformation due to Embankment Widening with Different Treatment Techniques
A two-dimensional (2-D) finite element (FE) model was developed to analyze the deformation and stress of embankment on soft ground due to widening with different treatment techniques. It is found that the embankment widening induces transverse gradient change due to differential settlements and horizontal outward movements at the shoulder of the existing embankment. Embankment widening also increases the shear stress along the slope of the existing embankment, especially at the foot of slope. The failure potential due to embankment widening may increase with the increase of widening width when the widening width is smaller than 8.5 m, but may decrease with the increase of widening width as the widening width is greater than 8.5 m. The effectiveness of four ground and embankment treatment techniques, including geosynthetic reinforcement, light-weight embankment, deep mixed columns, and separating wall were compared. The results indicate that these treatments reduce the differential settlements and improve the stability. The light-weight embankment has the most effectiveness among four treatments. By using the fly-ash backfill material in widening, the transverse gradient change decreases from 0.5%−1.3% to 0.26%−0.8% and the maximum horizontal displacement decreases from 2.76 cm to 1.44 cm.
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.