## 4 CEL Modelling
### Simulation of Pile Installation on Deep Mixing Soil  
For the ground improvement, secondly, the deep mixing method is reviewed to identify the feasibility of that. In this analysis, the self-standing of pile equipment on deep mixing soil and the overturn of pile equipment during pile installation caused by the settlement are comprehensively investigated using CEL technique. It is assumed that the deposit of deep mixing soil is constructed from 0.0 m to 5.0 m. The analysis cases are divided into three cases such as (1) self-standing of pile equipment; (2) effect of pile jacking; and (3) effect of pile driving. Figure 12 represents a CEL model and boundary conditions for the simulation of pile installation on deep mixing soil. The dimensions of the domains are composed of about 16 times the pile equipment length (\(P_{l}\)) and a height of 16.0 m, to minimize the wave reflecting effect caused by the pile driving. At the sides of the domains, a zero flow velocity normal to those planes is prescribed, and a zero follow velocity in the vertical direction is imposed at the base of the domains [6; 13]. The pile domain and soil domain are imposed on the Lagrangian coordinate and Eulerian coordinate, respectively. The input parameters for analyses are summarized in Table 2, based on the geotechnical investigation. Also, the contact pressure of pile equipment is considered as 183.7 kN/m\({}^{2}\), according to the design report [28]. For the pile jacking, the velocity of pile jacking is considered as 1 m/sec. For the pile driving, discrete hammer blows are imposed by a time-load curve applied at the reference point of the pile, as shown in Figure 13[13], and the pile driving energy is considered as 100 kN\(\cdot\)m.  
Figure 11: Results of simulating forced replacement method (\(H\) = 3.0 m). Figure 10: Results of simulating forced replacement method (\(H\) = 2.0 m): (a) Replacement depth, range and height of heave soil; (b) replacement angle. Figure 14 illustrates the results of simulating pile installation on deep mixing soil. As shown in Figure 14, the pile equipment could not be self-standing, also, in the cases of pile jacking and driving, the pile equipment during pile installation settle and overturn, because of being not enough bearing capacity of pile equipment to resist overturning. To investigate the behavior of pile equipment, the vertical displacements at each edge of pile equipment are checked, as shown in Figure 15. For the self-standing of pile equipment, the vertical displacements at all of the edges are similar. However, the differential vertical displacements at each edge occurs during the pile installation, especially, the vertical displacements in the front of the pile equipment are larger than those of the rear. In addition, the vertical displacements during the pile installation are larger than those in case of self-standing of pile pile. Figure 12: CEL model and boundary conditions for the simulation of pile installation on deep mixing soil: (**a**) 3D view; (**b**) front view; and, (**c**) side view. Figure 13: Pile driving load with time for one hammer blow (modified from [PERSON] et al. [13]). pile equipment. It is indicated that the behavior of pile equipment is influenced by the pile installation loading such as pile jacking and driving. The deep mixing method has a disadvantage of expensive costs for construction. Also, the soil conditions composed of very deep soft soil in this site is unfavorable to economic feasibility. Thus, the extremely expensive costs for construction would be expected in order to ensure enough bearing capacity for constructability using deep mixing methods. Based on this point, it is hard to consider the deep mixing method in this site.