Deep Cement Mixing Columns Research Articles

Enhancing the seismic performance of highway embankments on soft soils: a comparative study of conventional and T-shaped deep cement mixing columns

Enhancing the seismic performance of highway embankments on soft soils: a comparative study of conventional and T-shaped deep cement mixing columns

Laboratory modelling of stiffened deep mixing columns with variable diameter under vertical load in loose sand

ABSTRACT The T-shaped deep mixing column (TDM) is a new proposed technique used to increase the ultimate load of the deep mixing column in loose sand. Enlarging the column diameter at a certain depth provides additional bearing area beneath the column under the enlarged part, which leads to an increase in the ultimate load. In this study, a series of laboratory tests were conducted to study and analyse the behaviour of stiffened deep cement mixing columns in loose sand under compression loading. The impact of different parameters such as stiffening methods, embedment ratio, TDM cap length ratio, TDM cap diameter ratio, and the position of the T-shape were studied. It is found that all stiffening methods significantly enhance the load-settlement response of the deep cement mixing (DCM) columns. The stiffening technique of reinforcement bars with a T-shape gives the greatest improvement, increasing the ultimate load by 191.1% compared with the conventional column.

A nonlinear optimization method for calibration of large‐scale deep cement mixing in very soft clay deep excavation

AbstractThis work proposes a novel technique to conduct back‐analysis of lateral displacement of deep cement mixing (DCM) columns in deep excavation construction. For the first time, we propose a process to investigate both soil and underground structure end‐to‐end automatically. The novel technique is a complex combination of three crucial factors: (1) a nature‐inspired optimization algorithm (O), (2) a three‐dimensional PLAXIS Geotechnical Engineering software (P) and (3) a modern Python language programming (P), hereinafter called the a nature‐inspired optimization algorithm (O), a three‐dimensional PLAXIS Geotechnical Engineering software (P) and a modern Python language programming (P) (OPP) technique. The novel meta‐heuristic algorithm simulated the co‐evolved partnership behavior of shrimps and goby fishes, termed Shrimp and Goby Association (SGA), which plays an important role in complex analyses. A series of exams to determine the SGA's performance is conducted on 38 benchmark test functions (IEEE Congress on Evolutionary Computation 2017 and 2019) and three real‐world engineering design problems to showcase its applicability. The metaheuristic and PLAXIS 3D analysis work well together, which makes the back‐analysis technique powerfully to determinate stiffness parameters instead of the traditional approaches. Based on the optimized parameters, the lateral deflection of DCM and soil are well predicted for excavation. This study proposes a technique to estimate efficiently the stiffness parameter for very soft soil. As a consequence of the optimization process, an equation to determine the stiffness parameter of DCM columns from laboratory test is also proposed. Based on the obtained results, this research provides a comprehensive methodology for predicting risk, enhancing safety, saving time and money, and effectively designing and constructing underground structures.

Simplified analytical solution for time dependent deformation of soft soil improved with pervious column considering load transfer between column and soil

This paper presents a simplified analytical solution to analyse the coupled excess pore water pressure dissipation and deformation response of a composite stone column – soft soil foundation. The mathematical formulation is derived considering the combined radial – vertical flows of excess pore water pressure in stone column and soft soil areas (orthotropic permeability for each area), and adopting the settlement pattern for the composite ground suggested by an existing study in the literature. The homogeneous consolidation formulations are solved first to develop Green’s function for final excess pore water pressure solutions, employing the method of separation of variables and eigenfunction expansion technique. Then, the final solutions for excess pore water pressure corresponding to the nonhomogeneous consolidation formulations are derived in terms of Green’s formula, which can be expanded readily into a double series solution. The obtained analytical solutions can be used to examine the variation of excess pore water pressure against time at any point in the composite foundation. Thus, the consolidation settlements of stone column and soft soil areas and the differential settlement between them can be captured. The average differential settlement between the soil and column areas is used to compute the shear strains and shear stresses in the composite ground during the consolidation process. The proposed analytical solution is validated via a worked example in conjunction with a verification exercise against finite element simulation. The analytical predictions are presented in terms of the total vertical stress variations and excess pore water pressure dissipations against depth and time, the settlements and average degrees of consolidation for stone column and surrounding soft soil, and the shear stress distribution in the soil region. The capability of proposed analytical solution is also verified against field measurements of a full-scale test of soil - column composite ground (pervious column). The verifications show that the obtained analytical solution can predict the coupled excess pore water pressure dissipation – deformation response of soft soils improved by pervious columns such as stone columns and soil- deep cement mixing columns reasonably well.

Embankments Reinforced by Vertical Inclusions on Soft Soil: Numerical Study of Stress Redistribution

Constructing embankments over soft soils is a challenge for geotechnical engineers due to large settlements. Among diverse ground-improvement methods, combining piles and geosynthetics (e.g., geosynthetic-reinforced piles, deep cement mixing columns, geotextile-encased columns) emerges as a reliable solution for time-bound projects and challenging ground conditions. While stress distribution within pile-supported embankments has been extensively studied, the load transfer efficiency of piled solutions with geosynthetic reinforcement remains less explored. The novelty in this study lies in the investigation of three different inclusion solutions from a common control case in the numerical model considering the role of geosynthetic reinforcement. This study investigates the load transfer mechanisms in embankments supported by various techniques including geosynthetic-reinforced piles, deep cement mixing columns, and geosynthetic-encased granular columns. Two-dimensional axisymmetric finite element models were developed for three cases of embankments supported by vertical inclusions. Numerical findings allow clarification of the soft ground and embankment characteristics which influence the arching and membrane efficiencies. Rigid piles outperform deep cement mixing (DCM) columns and geotextile-encased columns (GEC) in reducing settlements of soft ground. Geosynthetic reinforcements are particularly helpful for rigid pile solutions in high embankments due to their load transfer capability. Additionally, physical properties of fill soil can impact the inclusion solutions, with high shear resistance enhancing the arching effect and lower modulus subsoils showing better arching performance.

Research on Vertical Bearing Performance of Precast Concrete Pile Reinforced with Cement-Treated Soil under Different Loading Modes

Precast concrete pile reinforced with cement-treated soil (PCRC) is a composite pile formed by inserting a precast concrete (PC) pile into a deep cement mixing (DCM) column. It has become widely recognized and used for soft soil ground treatment. Despite its extensive application, the cooperative bearing mechanism of PCRC has not been fully investigated under diverse loading conditions. This paper presents the results of finite element analysis, comparing the bearing performances of the PCRCs under two loading forms: load applied solely to the PC pile (Form 1) and the entire cross-section (Form 2). The results reveal that the inner and outer cores of the PCRC loaded under Form 2 can synergistically work together, exhibiting a 13.2% higher ultimate bearing capacity than the PCRC with Form 1. The load sharing ratio, μ, of the inner core of the PCRC loaded under Form 2 ranges from 0.86 to 0.93, while μ of the inner core under Form 1 remains stable at approximately 0.96. Increasing the loading plate size improves the DCM column’s load sharing capacity. Furthermore, axial load tests in Form 1 underestimated the bearing capacity of PCRC to a certain extent. It is, therefore, recommended in engineering design that the top of the DCM column be positioned higher than that of the PC pile to achieve the actual force mode of Form 2.

Shielding effects of deep cement mixing column rows on an anchored sheet pile quay in soft clay: three-dimensional centrifuge and numerical modeling

Shielding effects of deep cement mixing column rows on an anchored sheet pile quay in soft clay: three-dimensional centrifuge and numerical modeling

Behaviour of anchored sheet pile quay stabilized with deep cement mixing columns in soft soil: Centrifuge and numerical modelling

This paper describes research on the behavior of anchored sheet pile quay stabilized by deep cement mixing (DCM) columns in soft soil through a centrifugal test investigation to understand excavation-induced soil-structure interaction mechanisms. By employing an advanced soil constitutive model, three-dimensional (3-D) finite element (FE) simulations were subsequently performed to back-analyze the centrifuge test. Moreover, a numerical comparison analysis between this case and a null DCM columns case was performed to describe the shielding effect of the DCM columns composite foundation in the anchored sheet pile quay in terms of lateral earth pressure, bending moment, lateral deflection of the quay wall, and quay ground settlement induced by excavation. Finally, a parametric study was carried out to investigate the effect of DCM column arrangement and geometry on the quay wall lateral deflection. Results showed that the presence of DCM columns reduced the adverse effects on the quay wall in excavations, and they could effectively enhance the stability of the anchored sheet pile quay in soft soil, such as the shielding effect. In addition, the parametric study results indicate that length and the elastic modulus of the column are two critical factors affecting the shielding effect of DCM columns. This research provides reasonable explanations and valuable insights to understand the soil-structure interaction mechanism in anchored sheet pile quay and is of use in the preliminary design of sheet pile quay structures in soft soil.

Influence of deep-cement-mixing column rows on the performance of geosynthetics-reinforced column-supported railway embankment

Knowledge regarding the stability of geosynthetics-reinforced column-supported railway embankment (GRCSE) on soft foundation is of great significance for transportation infrastructure safety design, and deep-cement-mixing (DCM) columns constructed under the toe of an embankment is used to improve the performance of GRCSEs. This study conducted two centrifuge model tests to simulate the failure of a constructed embankment in a 40-g environment. The failure mechanism of each component in the GRCSE system and the effect of additional DCM column rows near the embankment toe on the GRCSE performance were analysed. The particle image velocimetry (PIV) technique was used to draw further insights from the results. The tests revealed that a failed column within the GRCSE system led to the progressive failure of adjacent columns, coupled with the progressive and retrogressive propagation of shear strains in the soft soil, which resulted in embankment collapse. The addition of DCM column rows near the embankment toe reduced the local shear strain accumulation in the soft foundation and thus improved the overall stability. The incremental tensile strain of the geosynthetic reinforcement in various phases was different in the cases with and without additional DCM column rows. Moreover, the effects of various factors of DCM rows, including row number and length, on the GRCSE stability were numerically analysed.

Optimization of fiber-reinforced deep cement-fly ash mixing column materials

The flexural and compressive strength requirements of deep cement mixing (DCM) columns subjected to lateral loading have brought forth the demand to specify how the incorporation of fiber and fly ash improves these properties and the mixture quality, including the construction design characteristics of segregation and swelling. The paper addresses this issue considering the experimental results from the extensive parametric study in which various lengths and content of carbon fiber (4-, 6-, and 12-mm lengths and 0.1, 0.4, 0.8% by volume of the mixture) are incorporated into the cement-based mixtures with and without the optimized fly ash content. Along the strength parameters, the effects of mixture quality responses on the performance of DCM columns are also investigated. The segregation results of the fresh mixtures, unconfined compression strength (UCS), flexural strength, and swelling values from the 28-day cured specimens are presented. The novel version of the Goal Attainment Method is used for the optimizations, in which the procedures of high-order regression equations and the multi-objective desirability contents are included to obtain more accurate optimization results in terms of the controlling parameters of segregation, swelling, UCS, and flexural strength. The setting time and workability results from the mixtures having the optimized parameters are also presented to demonstrate the fluidity of the optimized mixtures. The addition of carbon fiber led to significant improvements in the segregation and swelling ratios, with gains of up to 35%. Moreover, the three-point flexural strength and unconfined compressive strength were enhanced by 278% and 54%, respectively. The paper specifically reveals that the incorporation of carbon fiber significantly improves the mixture quality characteristics of segregation and swelling as well as the parameters of flexural strength and UCS.

Soft clay improved by deep cement mixing column technique

Soft clay improved by deep cement mixing column technique

Ultimate Bearing Capacity of Soft Soil Improved by DCM Columns: A Comparative Review

The use of deep cement mixing (DCM) columns for soil stabilization is an economical and reliable ground improvement technique that has been studied extensively. The aim of this article is to review the ultimate bearing capacity (UBC) of soft soils improved by DCM columns in a series of 1 g physical modelling tests. Reliable databases of 35 stabilized tests using end-bearing DCM columns and 42 stabilized tests using floating DCM columns are analyzed. The effects of the influencing parameters of undrained shear strength of the soil (Cus) and DCM columns (Cuc), and the area improvement ratio (α) on the UBC and bearing capacity (Nc = UBC/Cus are discussed. The failure modes of the improved soil have been compared. The review results show that, for end-bearing and floating DCM columns, the role of α and the strength ratio between the columns and soil, respectively, are vital. The effect of the average end-bearing factor for DCM columns (Nc = 15.27) on the UBC was found to be higher than for floating DCM columns (Nc = 8.08). The experimental results were used to develop four computational models to estimate the UBC of stabilized soil improved by end-bearing and floating DCM columns.

A case study of a dcm column-supported embankment over soft clay

ABSTRACT This paper investigates a case study of a highway embankment in Thailand constructed over Deep Cement Mixed (DCM) column improved ground. The case study was simulated using a 2D plane-strain model adopting the equivalent area approach for columns. Field measurements for deformations and excess pore pressures are compared with the finite element results to verify the numerical model, and to understand the load transfer mechanism. The most likely failure mode of the embankment was investigated by computing the Factors of Safety (FOS) against the bearing failure and bending failure of individual DCM columns, and the overall stability of the embankment. Results show that the most likely failure mode for this embankment is the bending failure of attached columns underneath side slopes. In the case study, attached columns are used to control the lateral deformations. In the paper, three other approaches used in practice for lateral deformation control are investigated: (i) Load transfer platform (LTP) with a geosynthetic layer above DCM columns with single columns near the side slopes (ii) T-shaped single columns near the side slopes and (iii) Reinforced single columns near the side slopes. Results show that in this particular case, due to the presence of a relatively deep fill layer above the soft clay deposit, lateral deformation control measures applied closer to the column heads such as LTP or T-shaped columns are not effective. However, the use of double columns with increased bending stiffness throughout the soft clay layer or increasing the length of columns underneath the embankment is the most effective solution in reducing lateral deformations.

Seismic response of pile groups improved with deep cement mixing columns in liquefiable sand: shaking table tests

A series of shaking table model tests were performed to examine the effects of deep cement mixing (DCM) columns with different reinforcement depths on the seismic behavior of a pile group in liquefiable sand. Due to the DCM column reinforcement, the fundamental natural frequency of the model ground increases noticeably. The excess pore pressure of soils reduces with the increase of reinforcement depths of the DCM columns. Before liquefaction, the acceleration response of soils in the improved cases is obviously lower than that in the unimproved case, but the acceleration attenuation is greater after liquefaction in the unimproved case. Moreover, the lateral displacement of the superstructure, the settlement of the raft, and the bending moment of the piles in the improved cases are significantly reduced compared with those in the unimproved case, and the reduction ratios rise with the increase of reinforcement depth of the DCM columns. However, reinforcement by the DCM columns may result in the variation of the location of the maximum moment that occurs in the pile.

Study on Stress Distribution in Soft Ground Consolidated with Deep Cement Mixing Columns under Road Embankment

Soil consolidation using deep mixing method (DMM) is commonly used to protect soft ground in alluvial stratum in deltas such as Mekong Delta. In this study, the finite element method (FEM) using PLAXIS software is adopted to analyze the stress distribution on columns and ground base of the deep cement mixing (DCM) columns system combined with geotextiles in the consolidation of soft ground under road embankment in Tien Giang Province. With this method, the behavior of the DCM columns in soft ground treatment is examined by the distribution of stress and settlement of the DCM columns and soft soil layers. Simultaneously, the settlement of road base construction is monitored. The stress distribution on DCM columns and their settlement are also given from the analysis of FEM. The FEM models simulating the soft ground consolidated with DCM columns combined with geotextile under the road embankment in Tien Giang with the DCM columns of 0.6 m diameter, 11.2 m length and 1.0m center –to- center spacing show the largest settlement of 0.120 m and the stability coefficient of 1.679.

QA/QC PLAN AND EVALUATION OF FIELD STRENGTH AND PERMEABILITY VALUE FOR DEEP CEMENT MIXING

Deep Cement Mixing (DCM) is widely used to improve the strength and stiffness of soil by mixing it with cement. When DCM is used as a low permeability barrier for water cut off, permeability must be tested in addition to the usual strength values. One concern in DCM construction is the quality assurance and quality control (QA/QC) of this technique to ensure uniformity along the DCM column. It is even more crucial when low permeability is required for the DCM column to be used as a seepage cut-off in an earth bund, in addition to its strength requirement. In this application, the DCM columns require low permeability and adequate strength. In this paper, two QA/QC aspects will be evaluated: the operational control and the evaluation of the treated DCM column. The operational control in terms of mixing time, cement content, rotation speed and mixing energy will be studied to gain an understanding of how strength and permeability changes with the variability of the soil with depth. A rational QA/QC plan will be briefly proposed to ensure a consistent and rational method is developed for the evaluation of the strength and permeability variation of the treated soils over the area and the depth. These will help in the development of acceptable characteristic value for the geotechnical parameters of soils treated with DCM (in line with Eurocode 7).

Intelligent modelling and design of soft soil improved with floating column-like elements as a road subgrade

The use of stone columns (SC) and deep cement mixing (DCM) columns to stabilize road subgrades are economical and reliable ground improvement techniques that have been extensively studied. The current study used an adaptive neural fuzzy inference system (ANFIS) hybridized with a particle swarm optimization (PSO) algorithm to develop models for estimating the ultimate bearing capacity (UBC) of soft soil improved with floating SC or DCM columns. A database of 86 physical modelling tests was used to create and train the ANFIS-PSO models. The input parameters used were the undrained shear strength of soft soil, area improvement ratio, and length-to-diameter ratio of the floating SC and DCM columns. The performance of the proposed ANFIS-PSO model has been validated using the testing data and a decision-making model for the design of the geotechnical properties of the floating SC and DCM columns has been proposed. The results show that the accuracy of the proposed ANFIS-PSO model in terms of the performance indices was satisfactory. The R2, VAF, and MSE values were obtained for the testing sets of the optimized ANFIS-PSO predictive model. This ANFIS-PSO model can be used by geotechnical engineers for the design of floating DCM and SC columns that increase the UBC of a road subgrade.

Evaluating the environmental impact of contaminated sediment column stabilized by deep cement mixing

Deep cement mixing (DCM) method is a widely used geotechnical technique for increasing ground stabilization before construction works. However, the environmental influence of stabilized ground on the surrounding area remains a concern. A physical model experiment of DCM-treated sediment column was conducted to investigate both geotechnical and environmental effects on the surrounding sediment. The DCM column contained the cement-stabilized contaminated sediment and surrounded by uncontaminated sediment. The physical behaviour, including settlement, pore water pressure, and total pressure were measured under different loadings. Simultaneously, the migration of the major ions into seawater, and leaching of potentially toxic elements into the surrounding sediment were evaluated. The results revealed that the leaching of major ions from the DCM column followed the dissipation of excess pore water and migrated to the seawater above the sediment surface. Nevertheless, the leaching behaviour of potentially toxic elements into the surrounding sediment and variation of pH value after the DCM treatment were within an acceptable level. Therefore, the contaminated marine sediment could be effectively stabilized and solidified by in-situ remediation with minimal secondary pollution to the surrounding environment.

Laboratory investigation of the properties of cement fly ash gravel for use as a column-supported embankment

Deep cement mixing (DCM) columns are used to support embankments built on soft clay, but these columns have limitations in terms of their engineering properties such as low column strength and low column permeability. Therefore, the use of cement fly ash gravel (CFG) instead of DCM columns has been introduced. The objective of this paper is to present an experimental investigation of the properties of CFG. Gravels with sizes of 4.76 to 12.70 mm were mixed with ordinary Portland cement (OPC) Type 1 and fly ash (FA) to create CFG materials. OPC was partially replaced by FA at levels of 0 to 25% by weight of OPC. The engineering properties of the CFG materials were studied through the porosity, compressive strength, flexural strength, modulus of elasticity, and permeability coefficient after curing for 28, 50, and 90 days. The microstructures of the OPC-FA pastes were examined by using X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. Finally, preliminary guidelines for selecting a suitable porosity of CFG columns were proposed. Test results show that the porosity of the CFG materials ranged from 25.8 to 31.1% and affected the strength and permeability. The strength of CFG was 6 to 13 times greater than that of a DCM column, and the permeability of CFG was 9 to 17 mm/s, which was much higher than that of a DCM column, indicating that the use of a CFG column-supported embankment built on soft clay was more effective than the use of a DCM column in terms of the column bearing capacity and acceleration of consolidation settlement. The replacement of 15% of the OPC with FA exhibited the highest strength and smallest porosity because it provided the greatest amount of calcium silicate hydrate. Preliminary guidelines show that small-sized gravel with medium porosity is proper for generating column-supported embankments on soft clay to carry medium loads and to accelerate the consolidation process.

Parametric analysis and optimization of T-shaped and conventional deep cement mixing column-supported embankments

Abstract The aim of this article was to optimize the shape and modulus of T-shaped deep cement mixing (TDM) and conventional deep cement mixing (DCM) columns for supporting embankment over soft soil. Objective of optimization is minimizing the column costs and differential settlement while maximizing the stress efficacy. A 2D axisymmetric numerical modelling was employed to investigate the behavior of TDM and DCM column-supported embankments. The influence of each parameter of the column-embankment system (CES) on differential settlement and stress efficacies is presented and discussed. The optimization approach using a genetic algorithm (GA) combined with a response surface method (RSM) was used to find an optimal solution. The numerical optimization results show that the use of optimal TDM column can provide lower differential settlement and higher stress efficacies compared to the conventional DCM column under the same or even lower column construction costs.