Observed Performance and FEM-Based Parametric Analysis of a Top-Down Deep Excavation in Soil-Rock Composite Stratum

Table 1

Summary of the main construction activities.

Stage	Construction activities	Duration (days)
1	Excavate to top slab, construct columns and top slab, and backfill and restore traffic	78
2	Construct end-suspended piles, excavate to 2 m BGS	59
3	Install ground anchors YMG1 and YMG2, apply prestress of 200 kN	17
4	Excavate to 5 m BGS	14
5	Construct temporary support	9
6	Excavate to 7 m BGS	12
7	Install ground anchors YMG3, apply prestress of 100 kN	19
8	Excavate to 8 m BGS	22
9	Install ground anchors YMG4, apply prestress of 310 kN	16
10	Excavate to 9.5 m BGS	13
11	Install ground anchors MG1	7
12	Excavate to 12 m BGS	15
13	Install ground anchors MG2	23
14	Excavate to 13.5 m BGS, cast middle slab	17
15	Install ground anchors MG3	26
16	Excavate to 15.5 m BGS	11
17	Install ground anchors MG4	18
18	Excavate to 17.5 m BGS	29
19	Install ground anchors MG5	21
20	Excavate to 20 m BGS	10
21	Cast base slab	19