Undrained creep failure of a drainage canal slope stabilized with deep cement mixing columns     

Pitthaya Jamsawang  Phermphorn Boathong  Warakorn Mairaing  Pornkasem Jongpradist 《Landslides》2016,13(5):939-955

This paper presents an analysis of the slope failure of a Suvarnabhumi drainage canal during construction. The Suvarnabhumi drainage canal project includes a large drainage canal with a road on both sides. The width of the bottom of the drainage canal is 48.0 m, the depth of the drainage canal is 3.0 m, and the length of the drainage canal is 10.5 km. Because the project was constructed on very soft Bangkok clay, deep cement mixing (DCM) columns were employed to increase the stability of the excavated canal. The failure of the drainage canal slope occurred 25 days after the end of excavation. The field monitoring data show that lateral movement of the canal slope continuously increased with time, which caused failure due to the instability of the canal slope. The time-dependent deformation and undrained creep behavior of very soft clay was suspected to be the cause of the canal failure. A laboratory investigation of undrained creep behavior and a finite element analysis (FEA) using the soft soil creep (SSC) model were performed to confirm the causes of the canal failure. The results indicate that very soft clay specimens that are subjected to deviator creep stress levels of 70 and 100 % of the peak strength failed by creep rupture within 60 days and 8 min, respectively. The factor of safety for the canal slope, which was obtained from the FEA, shows significant reduction from the initial value of 1.710 to 1.045 within 24 days after the end of excavation due to the effect of undrained creep. This paper also describes a solution method that is applied to a new section of the canal. Field monitoring and an FEA of the new trial section were performed to prove the effectiveness of the solution method.  相似文献   

Performance-based design optimization of embankments resting on soft soil improved with T-shaped and conventional DCM columns     

Phutthananon  Chana  Jongpradist  Pornkasem  Jongpradist  Pattaramon  Dias  Daniel  Jamsawang  Pitthaya  Bergado  Dennes T. 《Acta Geotechnica》2021,16(10):3301-3326

Acta Geotechnica - This paper presents a parametric study of the optimization design for T-shaped deep cement mixing (TDM) and conventional deep cement mixing (DCM) columns improved soft soil for...  相似文献   

Evaluation of rock fracture patterns based on the element-free Galerkin method for stability assessment of a highly pressurized gas storage cavern     

Jukkrawut Tunsakul  Pornkasem Jongpradist  Hyung-Mok Kim  Pruettha Nanakorn 《Acta Geotechnica》2018,13(4):817-832

Reasonable failure paths are crucial in the stability assessment of a highly pressurized gas storage cavern in a rock mass using limit equilibrium analysis. In this study, the fracture patterns in the rock mass around a gas storage cavern are evaluated based on the element-free Galerkin (EFG) method with a cohesive crack model. The proposed analysis method was first validated through scaled-down model testing results before extending to a full-scale problem. Using the current approach, a parametric sensitivity analysis was performed by taking into account the influences of the stress ratio, the depth of the cavern, and the tensile strength of the rock mass. Based on the analysis results obtained, this research showed that the representative failure paths, in which the uplift evaluation is necessary, can be established from the EFG results with careful consideration of crack initiation and the propagation direction. The site having an in situ stress ratio greater than 1.2 is preferred for operation of underground gas storage caverns. By performing the limit equilibrium analyses for stability assessment of the rock mass above the pressurized cavern, we demonstrated that the factor of safety against uplift computed from the failure paths established in this study is higher than or equal to those obtained from analyses with the simplified models in previous studies without considering the influence parameters on the fracture patterns.  相似文献   

Comparative performances of two- and three-dimensional analyses of soil-cement mixing columns under an embankment load     

Pitthaya Jamsawang  Ekkarin Phongphinittana  Panich Voottipruex  Dennes T. Bergado  Pornkasem Jongpradist 《Marine Georesources & Geotechnology》2013,31(7):852-869

Abstract

This research presents measurements and simulations of the full-scale behavior of a test embankment built on a soft marine clay deposit improved using soil–cement mixing (SCM) columns in Bangkok, Thailand, using both two-dimensional (2D) and 3D finite element analyses (FEAs). Fixed SCM columns with two different installation patterns, that is, column groups and column rows, were constructed in the soft clay foundation prior to the construction of the embankment. Three column wall methods, namely, equivalent width, equivalent axial rigidity, and equivalent flexural rigidity approaches, were used to convert the 3D individual columns into 2D plane strain column walls. A comparison of the results obtained through the 3D and 2D FEAs revealed that the 2D analyses provide inaccurate results in terms of the column lateral movements, bending moments, and axial loads induced in the SCM columns in addition to the factors of safety against slope failure. This outcome occurred because the actual columns in the 2D FEA were modeled using extended walls, which essentially prevent the movements of soil between two columns or column rows. Correction factors used to convert the 2D analysis results into 3D analysis results were also proposed in this study.  相似文献   

Effectiveness of deep cement mixing walls with top-down construction for deep excavations in soft clay: case study and 3D simulation     

Jamsawang  Pitthaya  Voottipruex  Panich  Tanseng  Pornpot  Jongpradist  Pornkasem  Bergado  Dennes T. 《Acta Geotechnica》2019,14(1):225-246

This paper presents the observed and simulated effectiveness of deep cement mixing walls created using top-down (DCM-TD) construction techniques for a deep excavation in soft Bangkok clay. The wall system consisted of four rows of 0.7-m-diameter DCM columns, and the bracing system consisted of two 0.25-m-thick basement slabs and seven temporary struts. The effectiveness of the wall system compared to that of other wall systems was evaluated using the measured results of previous case studies. A 3D numerical analysis was performed to calculate forces in the basement slabs and bending moments in the DCM wall. Finally, series of parametric analyses of both DCM-TD and deep cement mixing walls created using bottom-up (DCM-BU) construction techniques were carried out, and their results were compared to highlight the effectiveness of DCM-TD and its applicability to excavations at greater depths. The field and numerical results show that DCM-TD is more effective than DCM-BU in terms of the limitations of lateral wall movement, the bending moment in a DCM wall and the thickness of a DCM wall for various depths because of a larger system stiffness. Therefore, DCM-TD is very effective and suitable for use in potential future deep excavations in urban areas.

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Parameters affecting the lateral movements of compound deep cement mixing walls by numerical simulations and parametric analyses     

Pitthaya Jamsawang  Panich Voottipruex  Pornkasem Jongpradist  Dennes T. Bergado 《Acta Geotechnica》2015,10(6):797-812

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Equivalent void ratio controlling the mechanical properties of cementitious material-clay mixtures with high water content     

Pornkasem Jongpradist  Pitthaya Jamsawang  Warat Kongkitkul 《Marine Georesources & Geotechnology》2013,31(10):1151-1162

Abstract

This research develops a parameter defined as the equivalent void ratio, e?_st, which is able to accurately describe the dependence of the mechanical properties of cementitious material-clay mixtures on the influencing parameters, i.e., the mixing proportion, curing time, and initial state of the mixture, for different types of cementitious materials based on the results of unconfined compression, oedometer, and triaxial tests. Besides Portland cement, cementitious materials, such as fly ash and rice husk ash, are considered supplementary cement with different levels of efficiency. This equivalent cementitious material concept is then adapted for parameter development in conjunction with the effective void ratio proposed from our previous study. The developed single parameter, e?_st, can assess the mechanical properties of cementitious material-clay mixtures with different types of cementitious materials and under different test conditions.  相似文献