Table 4 The friction angle and soil unit weight in each construction stage.
Construction stage | Soil layer | Friction angle (°) | Soil unit weight (kN/m3) | |
|---|---|---|---|---|
3 | Excavate the first soil layer | Plain fill | 15 | 17 |
4 | Erect the first support | Plain fill | 15 | 17 |
5 | Excavate the second soil layer | Completely weathered slate | 18 | 19 |
6 | Erect the second support | Completely weathered slate | 18 | 19 |
7 | Excavate the third soil layer | Strong weathered slate | 32 | 22 |
8 | Erect the third support | Strong weathered slate | 32 | 22 |
9 | Excavate the fourth soil layer | Strong weathered slate | 32 | 22 |
10 | Erect the fourth support | Strong weathered slate | 32 | 22 |
11 | Excavate the fifth soil layer | Medium weathered slate | 38 | 27 |
