Column-supported Embankments Research Articles

Floating stone column-supported embankments on soft soils: numerical study incorporating stability analysis and basal reinforcement with geosynthetic

Floating stone column-supported embankments on soft soils: numerical study incorporating stability analysis and basal reinforcement with geosynthetic

Analytical solutions for the stability of stone column-supported and geosynthetic-reinforced embankment

This study presents a novel prediction model based on the three-wedge method, utilizing a force-based equilibrium model to evaluate the stability of embankments reinforced by stone columns and geosynthetics. The proposed model utilizes six slip surfaces, enabling it to accommodate diverse geometric configurations, shear strength parameters, reinforcement arrangements (i.e., stone columns and geosynthetic), surcharge, water level, and quasistatic seismic coefficients. A constant factor of safety is initially assumed for each slip surface and reinforcement element, although this assumption can be relaxed by varying the strength parameters. The factor of safety is determined analytically through the solution of a polynomial equation. The proposed analytical solutions, which offer a compact form, provide new insights for the three-wedge method and effectively customize the conditions for geosynthetic-reinforced column-supported embankment applications, characterized by wedge interaction between the embankment, clay, geosynthetics, and columns. Validations of the proposed method are performed using the results obtained from the centrifuge test and numerical modelling, demonstrating the reliability of the analytical solution.

Discussion of “Field Experimental and Numerical Studies on Performance of Concrete–Cored Gravel Column-Supported Embankments”

Discussion of “Field Experimental and Numerical Studies on Performance of Concrete–Cored Gravel Column-Supported Embankments”

Stability analysis and optimization of concrete column-supported embankments in soft soil

Stability analysis and optimization of concrete column-supported embankments in soft soil

Evaluation of Critical Length of Encasement for Stone Column-Supported Embankment with Basal Geocell

Evaluation of Critical Length of Encasement for Stone Column-Supported Embankment with Basal Geocell

Numerical study on stability of geosynthetic-encased stone column-supported embankments based on equivalent method

The application of geosynthetic-encased stone column-supported embankments (GESC-supported embankments) has garnered significant attention in geotechnical engineering, with limited investigations into their slope stability. In this paper, an equivalent method was proposed to establish GESC-supported embankment models through three-dimensional finite difference method (3D-FDM). Responses of factor of safety (FS) to arrangement tightness of GESCs (e.g., various column diameters, spacings, and quantities under constant area replacement ratio) and hoop effect of geosynthetic encasements (e.g., various geogrid strengths under different shear strengths of soft soil) were studied. For a given area replacement ratio, FS increased non-linearly with the increasing column quantity or the decreasing ratio of column spacing to diameter at high area replacement ratios. GESCs with smaller diameter and spacing proved to be more effective in improving slope stability, and an optimum ratio of column spacing to diameter was observed for practical use. Besides, FS increased linearly with geogrid strength at low geogrid strength levels, but an extremely lack of the shear strength of soft soils or the column quantity was unfavorable for the application of GESCs. Bending failure was the primary failure feature of GESCs under embankment loading, and the geogrid strength influenced slope stability through the bending capacity of GESCs.

Progressive failure mechanisms of geosynthetic-reinforced column-supported embankments over soft soil: Numerical analyses considering the cracks-induced softening

Cement-based columns in combination with geosynthetic reinforcement is a well-established soft ground improvement technique to enhance embankment stability. This paper aims to present a finite-element (FE) study based on a case history of a geosynthetic-reinforced column-supported (GRCS) embankment over soft soil. In this study, the columns are simulated with an advanced Concrete model to simulate the development of possible cracking and induced strain-softening. Numerical results are compared against published centrifuge tests, giving confidence to the established FE model with the Concrete model. New insights into the progressive failure mechanisms of GRCS embankments over soft soil are then discussed by examining the stress paths, internal forces, and cracks, as well as the plastic failure zones of columns. In addition, the role of columns and geosynthetics on the progressive failure mechanisms (failure loads and sequences) is also examined by an extensive parametric study. The results suggest that provided the optimization of compressive and tensile forces in the columns combined with the tensile stiffness of the geosynthetics is put in place, more columns can be mobilized to resist global sliding failure and to improve the bearing capacity of GRCS embankments.

Numerical analysis of a monitored piled-supported embankment of an airport runway

This paper presents a 3D finite element analysis of deep soil mixing column-supported embankments (CSEs) with a geosynthetic platform. The numerical model simulated the CSE for the expansion (≈1.0 km) of the existing runway at the Salgado Filho International Airport, in the city of Porto Alegre. The numerical model using Abaqus software was calibrated by comparing numerical calculations with good quality instrumentation data. Deep Soil Mixing (DSM) columns were used to improve the soil foundation. A novel approach to modeling the geosynthetic is also presented based on the mechanical properties of this material. The load transfer mechanisms and deformation of the column-supported embankments were analyzed by means of numerical and field results. Additional aspects such as the critical height and the pattern of vertical stress distribution in the columns and embankment as well as the stress distribution in the geosynthetic reinforcement were also investigated. The numerical model reproduces the vertical stress measured by the total stress cells installed above the columns and between the columns. The numerical model shows that the soil reaction of the thick compacted layer used as a work platform reduced the arching and membrane effect in the embankment.

Geosynthetic-Reinforced and Stone Column-Supported Embankments: Numerical and Stability Study

Geosynthetic-Reinforced and Stone Column-Supported Embankments: Numerical and Stability Study

Field tests on partially geotextile encased stone column-supported embankment over silty clay

Various researchers have highlighted that geosynthetic-encased stone columns could be used in place of stone columns (SCs) in very soft soil. In this study, field load tests are performed on individual partially geotextile-encased stone columns (pESCs), individual stone columns (SCs), and a field embankment reinforced with pESCs and SCs in silty clay. Although the material cost of pESCs is designed to be comparable to that of SCs, the tests reveal that pESCs display a higher allowable bearing capacity and stress concentration ratio and less residual settlement than SCs. The embankment reinforced by pESCs is found to incur fewer lateral displacements, while there is no improvement in the drainage performance during the construction period compared to the SCs. For the pESCs, 51–66% of the pressure acting on the top of the column propagates to a depth of z = 1.2 m, wheras, for the SCs, it is only 21–55%. Furthermore, to estimate group behaviour, the ultimate bearing capacity of an individual pile composite ground can be extrapolated. However, individual pESCs achieve much higher stress concentration ratios than the pESC group.

Reliability assessment for serviceability limit states of stiffened deep cement mixing column-supported embankments

Reliability assessment for serviceability limit states of stiffened deep cement mixing column-supported embankments

Numerical Analysis of Arching Behavior of Geosynthetic-Reinforced and DCM Column-Supported Embankment with Geosynthetic Characteristics

Numerical Analysis of Arching Behavior of Geosynthetic-Reinforced and DCM Column-Supported Embankment with Geosynthetic Characteristics

Influence of column position on stability of stiffened deep mixed column-supported embankment over soft clay

Influence of column position on stability of stiffened deep mixed column-supported embankment over soft clay

Limit equilibrium slope stability analysis of column-supported embankment on weak ground

PurposeThe study aims to analyse the stability of embankments over the improved ground with stone column (SC) and pervious concrete column (PCC) inclusions using limit equilibrium method. The short-term stability of PCC-supported embankment system is rarely addressed. Therefore, the factor of safety (FOS) of column-supported embankment system is calculated using individual column and equivalent area models.Design/methodology/approachThe stability analysis of column-supported embankment system is conducted using PLAXIS LE 2D. The various geometrical and shear strength parameters influencing the FOS of these embankment systems such as diameter of columns, spacing between columns, embankment height, friction angle of column material, undrained cohesion of weak ground and cohesion of PCC are considered.FindingsThe critical failure envelope of PCC-supported embankment system is observed to be of toe failure, whereas the failure envelope of stone column-supported embankment system is generally of deep-seated nature.Originality/valueIt is found that for PCC embankment system, FOS and failure envelope are not influenced by the geometrical/shear strength parameters other than height of embankment. However, for stone column-supported embankment system, FOS and failure envelope are dependent on all the shear strength and geometrical parameters considered in this study.

Field Experimental and Numerical Studies on Performance of Concrete–Cored Gravel Column-Supported Embankments

Field Experimental and Numerical Studies on Performance of Concrete–Cored Gravel Column-Supported Embankments

The performance of T-shaped deep mixed soil cement column-supported embankments on soft ground

T-shape deep mixing (TDM) pile is a new method for soft ground improvement, which has an enlarged head at shallow depth, the pile shape analogous to the letter “T”. In this paper, three-dimensional numerical simulation is used to investigate the load transfer mechanism, failure pattern, and settlement behavior of TDM pile-supported embankments by dividing TDM pile into two parts: the enlarged head part and the pile body part and using the concrete model to simulate the TDM piles. The results reveal that the stress arches exist both in the embankment fill and the soil under the flange, and stress concentration will occur at the variable section of TDM piles, resulting in plastic yielding of the pile body, which in turn leads to load transfer to the soil, and additional stresses in the soil will cause additional compression of soft soil between TDM piles. Parameter analysis indicates that the load transfer, plastic zone, and post-construction settlement are related to the height of the enlarged head (H) and pile spacing (S), while pile length (L) only plays an important role in the post-construction settlement.

Influence of Deep-Cement-Mixing Column Rows on Performance of Geosynthetics-Reinforced Column-Supported Embankments

Influence of Deep-Cement-Mixing Column Rows on Performance of Geosynthetics-Reinforced Column-Supported Embankments

Field and 3D Numerical Investigations of the Performances of Stiffened Deep Cement Mixing Column-Supported Embankments Built on Soft Soil

Field and 3D Numerical Investigations of the Performances of Stiffened Deep Cement Mixing Column-Supported Embankments Built on Soft Soil

Internal stability analysis of column-supported embankments: Deterministic and probabilistic approaches

Geosynthetic-reinforced and column-supported (GRCS) embankment is a practical and cost-effective technique for reinforcing soft soils. Internal stability of the column-supported embankment, which is engaged in shearing and bending failure modes, is one of the key issues that geotechnical engineers encounter in the design. To deal with this problem, numerical models are currently used. In this study, a simplified model has been developed for predicting the potential of internal instability in GRCS embankments. The validity of the deterministic model was verified by comparing the predicted safety factors with experimental and numerical observations. The findings show that the proposed model has the potential to accurately evaluate the internal stability of GRCS embankments. Moreover, probabilistic approaches were also used to undertake the reliability and sensitivity studies of column-supported embankments. The bending moment failure mode has a larger impact on the stability of the GRCS embankment than the shear failure mode. It is also found that the safety factor of shearing and bending failure modes is strongly influenced by the undrained soft soil shear strength. Furthermore, the reliability study demonstrates that the embankment height and the number of column rows are important factors in determining the efficiency of GRCS embankments in resisting internal instability.

Geotechnical Engineering Properties of Cement Fly Ash Gravel Mixtures for Application as Column-Supported Highway and Railway Embankments.

Our study investigates the geotechnical engineering properties of cement fly ash gravel mixtures in the laboratory. Gravels with three different size ranges were blended with cement and fly ash. The mixture properties were investigated, including the porosity, density, permeability, unconfined compressive and splitting tensile strengths, cohesion, and friction angle after curing for 28, 50, and 90 days, respectively. The experimental results revealed that the gravel sizes and fly ash contents significantly influenced the strength characteristics. The permeability coefficients of the cement fly ash gravel mixtures were 0.9 to 1.7 cm/s, much higher than a soil-cement column. The unconfined compressive strengths and splitting tensile strengths were found to be from 3.75 to 18.5 MPa and from 0.5 to 2.5 MPa, respectively. The cohesion and friction angle values ranged from 2.2 to 5.3 MPa and 30 to 40 degrees. The mixture strength was 6 to 30 times higher than a soil-cement column. The 15% fly ash provided the best strength characteristics as it exhibited the most significant calcium silicate hydrate contents. Thus, using cement fly ash gravel column-supported embankments is more productive than using a soil-cement column and granular pile to increase the column-bearing capacity and overall stability and accelerate the consolidation process.