This paper presents the results of a numerical investigation into the performance of geosynthetic-encased stone columns (GESCs) installed in soft ground for embankment construction. A three-dimensional finite-element model was employed to carry out a parametric study on a number of governing factors such as the consistency of soft ground, the geosynthetic encasement length and stiffness, the embankment fill height, and the area replacement ratio. The results indicate among other things that additional confinement provided by the geosynthetic encasement increases the stiffness of the stone column and reduces the degree of embankment load transferred to the soft ground, thereby decreasing the overall settlement. It is also shown that the geosynthetic encasement has a greater impact for cases with larger stone column spacing and/or weaker soil. Also revealed is that unlike isolated column loading conditions, full encasement may be necessary to ensure maximum settlement reduction when implementing GESCs under...

A geosynthetic reinforced segmental retaining wall was collapsed during a monsoon season in Korea, three months after the completion of wall construction. The circular type global slope failure was the dominant failure mode. The as-built design was examined for its appropriateness in meeting the current design requirements and the global slope stability. A comprehensive stress-pore pressure-coupled finite-element analysis was additionally conducted with due consideration of both positive and negative pore pressures in saturated and unsaturated zones. A number of relevant tests were also carried out on the backfill and the reinforcement collected from the site. The investigation revealed among other things that the inappropriate design and the low-quality backfill were mainly responsible for the wall failure, although the primary triggering factor was the rainfall infiltration. The results of the stress-pore pressure-coupled finite-element analysis provided sound evidences as to the wall performance over t...

This paper presents the results of a comparative study on different finite element modeling approaches for modeling geosynthetic-encased stone column-reinforced ground for use in rapid embankment construction. The specific models considered include: (1) an axisymmetric unit cell; (2) a three-dimensional (3D) column; and (3) a full 3D model. The validity of the unit cell model was tested by comparison with the results from the 3D models. The applicability of continuum elements for modeling the geosynthetic encasement was also investigated. The results show that the 3D column model yielded practically identical results when compared with those of the full 3D model whereas the two-dimensional axisymmetric unit cell model tended to yield results that were 10 to 20% larger in terms of the vertical effective stress and lateral deformation of the stone column. It is also shown that a layer(s) of continuum elements can be used to model the geosynthetic encasement instead of membrane elements which are not readily available in commercial software for geotechnical analysis, provided that the axial stiffness of the geosynthetic encasement is taken into consideration. Based on the results of analysis, the effect of geosynthetic encasement on the performance of stone columns installed in soft ground under embankment loading is also discussed.

The geogrid-encased stone column (GESC) system, which increases the confinement effect, has been developed to improve the load-carrying capacity of stone columns. This paper presents the results of an investigation on improvement in load-carrying capacity and settlement reduction of a GESC using field-scale load tests. Also, the effect of the geogrid encasement length and column strain is investigated. In addition, isolated GESC behaviour was compared to rammed-aggregate pier (RAP) and conventional stone column (CSC) behaviour. The results show that additional confinement provided by the geogrid encasement increased the stiffness of the stone column and reduced the settlement of the soft ground. Also, bulging of the GESC was observed to occur directly beneath the base of the geogrid encasement. The improvement in the performance of GESC was found to be significant, even with partial encasement.

Because of increased public concern regarding the impact of tunneling on surrounding environments, the control of groundwater has become an essential part of the planning, design, and construction of a tunneling project. This paper presents the results of an investigation on interaction mechanism between tunneling and groundwater using a three dimensional stress–pore pressure coupled finite-element model. It is shown that the ground and lining responses are significantly influenced by the relative permeability of the lining, and that the circumferential pregrouting is an effective means for minimizing the tunneling and groundwater interaction. Also highlighted is the importance of the stress–pore pressure coupled analysis in the numerical prediction of tunnel behavior. Practical implications of the findings from this study are discussed in great detail.