Numerical modeling of a full scale reinforced embankment on deep mixing cement piles | |
| Author | Nguyen Hop Minh |
| Call Number | AIT Thesis no.GE-04-06 |
| Subject(s) | Embankments Reinforced concrete Numerical analysis |
| Note | A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. GE-04-06 |
| Abstract | Generally, in design, limit equilibrium method is used to analyze reinforced structures but it only considers the performance of the structures under ultimate condition, hence, information about the interaction mechanism between the reinforced materials and reinforcement as well as working stress condition of the system are not obtained. Furthermore, the consolidation of deep mixing method (DMM) clay-cement piles also cannot be accurately predicted by using the existing solutions, borrowed from PVD and SCP applications, since the permeability of the DMM pile is not as high as that of PVD and SCP. On the other hand, numerical approach not only overcomes these disadvantages but also enables the investigation of various assumptions, predicts the consequences of complex situations, and assesses the viability of conceptual model. Back-analysis using numerical modeling by finite element method or finite different method, if done with appropriate boundary condition, is the best way to obtain realistic in-situ soil parameters. This study concentrates on FEM simulation of the full scale reinforced test embankment in Wangnoi District, Ayuthaya, Thailand with particular attention given to the actual monitored vertical settlements, excess pore water pressures and horizontal displacements. Good agreements between the predicted and observed data have been obtained with the ratio of the permeability of claycement pile over that of surrounding untreated clay, kpile/ksoil, equal to 10, and the modulus of clay-cement material equal to 50 MPa, which is about 135 times of the undrained shear strength of the cement piles. Negative skin friction mobilized on deep mixing pile due to the effect of differential settlement between the pile and surrounding soil was also evaluated through numerical simulations under plane strain and axisymmetric conditions. As the results, a value of , defined as the ratio of skin friction over vertical effective stress, equal to 0.1 and neutral depth of 3.7 m are recommended for analysis of negative skin friction of a single DMM pile, compared to the corresponding values of 0.04 and 2.9 m for and neutral depth, respectively, in case of the plane strain condition. Effects of the DMM pile spacing to the negative skin friction were studied through sensitivity analyses of 1.75 m and 2.0 m DMM pile spacing under axisymmetric condition. Furthermore, effects of subsidence were also considered. It was shown that higher value and lower neutral depth are obtained at greater DMM pile spacing as well as in the case of subsidence due to draw down of the ground water levels. Sensitivity analyses of the lateral movements of vertical facing were carried out with variations of the reinforcement stiffness and reduction factor of interface elements. It is also shown that increasing reduction factor or the strength of the interaction between the reinforcement and backfill material helped to make the embankment more as a rigid body in its behavior. However, this effect is not that strong in case of increasing reinforcement stiffness. Furthermore, the rigid rotation of the embankment due to settlement of the foundation contributed more than 50 percent to the total horizontal displacements and, consequently, the primary source of the embankment horizontal displacement. |
| Year | 2005 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. GE-04-06 |
| Type | Thesis |
| School | School of Engineering and Technology (SET) |
| Department | Other Field of Studies (No Department) |
| Academic Program/FoS | Geotechnical Engineering (GE) |
| Chairperson(s) | Bergado, Dennes T.; |
| Examination Committee(s) | Noppadol Phien-wej; Pham Huy Giao; |
| Scholarship Donor(s) | Asian Institute of Technology Fellowship; |
| Degree | Thesis (M.Eng.) - Asian Institute of Technology, 2005 |