*4.3.2 Increase in the Coulomb's active earth pressure of retaining walls from the shear band tilting effect*

Without the constraint of vertical pressure on the ground surface, a tectonic plate induces a shear-band tilting effect under lateral compression. **Figure 12a** shows the shear-band tilting effect of the shear band on the back of the retaining wall. **Figure 12b** shows the shear-band tilting force *Ps* caused by shear banding shown in **Figure 12a**, the resultant force *R*<sup>s</sup> of the resistance on the shear failure band of the retaining wall, and the increment of the Coulomb's active earth pressure of the retaining wall *Pas* [10].

According to the closed force polygon shown in **Figure 12c** and the sine law, Eq. 17 can be used to calculate *Pas* [10]:

$$P\_{as} = P\_s \frac{\sin\left(\lambda + \phi - \rho\right)}{\sin\left(\rho + a - \phi\right)}\tag{17}$$

*Plasticity Model Required to Prevent Geotechnical Failures in Tectonic Earthquakes DOI: http://dx.doi.org/10.5772/intechopen.107223*

Following the case study of the retaining wall discussed in Section 4.3.1, when the elastic-perfectly plastic model was adopted, the calculated inclination angle of the sliding failure plane was *<sup>ρ</sup>* <sup>¼</sup> <sup>72</sup>*:*83° *:*, the failure block weight was *W* ¼ 228*:*46 kN, and the Coulomb's active earth pressure was *Pa* ¼ 98*:*19 kN.

When one side of the failure block at the back of the retaining wall was uplifted by the shear-band tilting force *Ps*, if *Ps* ¼ 0*:*5*W*, the increment in the Coulomb's active earth pressure of the retaining wall *Pas* can be calculated as 48*:*81 kN. Thus, the increment rate of Coulomb's active earth pressure caused by the shear-band tilting effect was 49.7% [10].
