mag

Malaysia Water Research Journal
The factor of safety sliding may be expressed by Eq. [2] below, which generally
a minimum factor of safety of 1.5 is required:
[2]
where,
∑R V
= sum of the vertical resisting forces
∑R H
= sum of the horizontal resisting forces
δ = angle of friction between the soil and base slab k = the range between 1/3
to 2/3
c = cohesion of soil R = resistance force B = bottom length of structure
Option
Table 1. Overturning check on coastal block structure at point 0
Ɵ
Moment at 0
ΣM+
(kNm)
ΣMkNm)
Remark
1 30° 58.2 18.88 3.1 Ok
2 45° 18.1 7.58 2.4 Ok
3 60° 8.74 7.64 1.14 No (redesign 3a)
3a 60° 14.71 7.64 1.9 Ok
Table 2. Sliding check on coastal block structure at point 0
Angle (°) ƩRV (kN) ƩRH (kN) B (m) FS Remark
30 68 18.45 1.85 3.7 Ok
45 40.2 15.36 1.2 2.8 Ok
60 31.75 12.34 1.05 2.9 Ok
The result of analysis is given as above. Table 1 showed the moment acting
on coastal block for stability analysis on overturning check. The factor of safety
for overturning is more than 1.5. The force acting on coastal block for stability
analysis on sliding check are summarised as shown in Table 2. The stability of
coastal block is analysed using full scale data collected from site and secondary
data where necessary.
The structure is exposed to both forces from the wave action and lateral
earth action specifically active earth pressure. As the block moves away from
the backfill, there is a decrease in the pressure on the wall. The decrease
continues until a minimum value is reach after which there is no reduction in the
Institut Penyelidikan Hidraulik Kebangsaan Malaysia (NAHRIM)
33
National Hydraulic Institute of Malaysia (NAHRIM)