top down construction case2
DESCRIPTION
The table details the load combinations used for "Case 2", in compliance with LTA's design criteria for underground tunnels/stations.TRANSCRIPT
I) II)Box SDL excavt
Self Wt top 1.5m
Self-
wei
ght o
f Hul
l & In
t Mem
bers
SDL
incl
udin
g 1s
t & 2
nd S
tage
Con
stru
ctio
n
Vert
Soil
on R
oof
Max
Lat
Soi
l (Ko
) on
Lt W
all
Max
Lat
Soi
l (Ko
) on
Rt W
all
Vert
Soil
on R
oof
Max
Lat
Soi
l (Ko
) on
Lt W
all
Max
Lat
Soi
l (Ko
) on
Rt W
all
Vert
Soil
on R
oof
Min
Lat
Soi
l (Ka
) on
Lt W
all
Min
Lat
Soi
l (Ka
) on
Rt W
all
Vert
Soil
on R
oof (
exc
avat
ion
top
1.5m
soi
l)
Max
Lat
Soi
l (Ko
) on
Lt W
all
Max
Lat
Soi
l (Ko
) on
Rt W
all
Min
Lat
Soi
l (Ka
) on
Lt W
all
Min
Lat
Soi
l (Ka
) on
Rt W
all
Vert
Soil
on R
oof (
varie
s) -1
.5m
/-4.5
m
Vert
Soil
on R
oof (
varie
s) -4
1.5m
/-1.5
m
Vert
Soil
on R
oof
Max
Lat
Soi
l (Ko
) on
Lt W
all
Max
Lat
Soi
l (Ko
) on
Rt W
all
Vert
Wat
er o
n R
oof
Upl
ift o
n Ba
se S
lab
Late
ral W
ater
on
Lt W
all
Late
ral W
ater
on
Rt W
all
Vert
Wat
er o
n R
oof
Upl
ift o
n Ba
se S
lab
Late
ral W
ater
on
Lt W
all
Late
ral W
ater
on
Rt W
all
Vert
Wat
er o
n R
oof
Upl
ift o
n Ba
se S
lab
Late
ral W
ater
on
Lt W
all
Late
ral W
ater
on
Rt W
all
Vert
Wat
er o
n R
oof (
exc
avat
ion
top
1.5m
soi
l)
Late
ral W
ater
on
Lt W
all
Late
ral W
ater
on
Rt W
all
Late
ral W
ater
on
Lt W
all
Late
ral W
ater
on
Rt W
all
Vert
Wat
er o
n R
oof (
varie
s) -1
.5m
/-4.5
m
Upl
it on
Bas
e Sl
ab (v
arie
s) -1
.5m
/-4.5
m
Vert
Wat
er o
n R
oof (
varie
s) -4
.5m
/-1.5
m
Upl
it on
Bas
e Sl
ab (v
arie
s) -4
.5m
/-1.5
m
Live
Loa
d on
Int S
lab
Live
Loa
d on
Bas
e Sl
ab
Trai
n lo
ad
Vert
Surc
harg
e on
Roo
f
Late
ral S
urch
arge
on
Lt W
all
Late
ral S
urch
arge
on
Rt W
all
Late
ral S
oil (
Ko -
Kpla
xis)
on
Lt W
all
Late
ral S
oil (
Ko -
Kpla
xis)
on
Rt W
all
Late
ral S
oil (
Ko -
Kpla
xis)
on
Lt W
all
Late
ral S
oil (
Ko -
Kpla
xis)
on
Rt W
all
LC No s/n 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 54 45 46 47 50 51 52 53 GWT=GLSurcharge on Roof and int LL 1 101 1.35 1.35 1.35 1.35 1.35 1.35 1.35 1.35 1.35 1.50 1.50 1.50 1.50
GWT=GLSurcharge on Roof and w/o int LL 2 102 1.35 1.35 1.35 1.35 1.35 1.35 1.35 1.35 1.35 1.50 1.50 1.50
GWT=+1.0m(No surcharge)With int LL
3 103 1.35 1.35 1.35 1.35 1.35 1.00 1.00 1.00 1.00 1.50
GWT=+1.0m(No surcharge)Without int LL
4 104 1.35 1.35 1.35 1.35 1.35 1.00 1.00 1.00 1.00
GWT=FEL(Not applicable to top down construction)Surcharge on Roof and int LL
5 105 1.35 1.35 1.35 1.35 1.35 1.50 1.50 1.50 1.50 1.50 1.50
GWT=FEL(Not applicable to top down construction)Surcharge on Roof and w/o int LL
6 106 1.35 1.35 1.35 1.35 1.35 1.50 1.50 1.50 1.50 1.50
GWT=-5.0mSurcharge on Roof and int LL 7 201 1.35 1.35 1.35 1.00 1.00 1.20 1.20 1.00 1.00 1.50 1.50
GWT=-5.0mSurcharge on Roof and w/o int LL 8 202 1.35 1.35 1.35 1.00 1.00 1.20 1.20 1.00 1.00 1.50
GWT=GL1.5m top excavation, no top surcharge with int LL
9 301 1.35 1.35 1.35 1.35 1.00 1.00 1.35 1.35 1.00 1.50 1.50 1.50 1.50 1.50
GWT=GL1.5m top excavation, no top surcharge w/o int LL
10 302 1.35 1.35 1.35 1.35 1.00 1.00 1.35 1.35 1.00 1.50 1.50 1.50 1.50
GWT=-1.5m/-4.5mSurcharge on top and int LL 11 401 1.35 1.35 1.35 1.35 1.35 1.20 1.20 1.20 1.20 1.50 1.50 1.50 1.50 1.50
GWT=-1.5m/-4.5mw/o surcharge on top and int LL 12 402 1.35 1.35 1.35 1.35 1.35 1.20 1.20 1.20 1.20 1.50
GWT=-4.5m/-1.5mSurcharge on top and int LL 13 403 1.35 1.35 1.35 1.35 1.35 1.20 1.20 1.20 1.20 1.50 1.50 1.50 1.50 1.50
GWT=-4.5m/-1.5mw/o surcharge on top and int LL 14 404 1.35 1.35 1.35 1.35 1.35 1.20 1.20 1.20 1.20 1.50
GWT=GLSurcharge on Roof and int LL 15 501 1.35 1.35 1.35 1.35 1.35 1.35 1.35 1.50 1.50 1.50 1.50 1.35 1.35
1) Int LL + SDL w/o LL @ Base slab
GWT=+1.0m(No surcharge on top)Surcharge on Roof and int LL
16 502 1.35 1.35 1.35 1.00 1.00 1.00 1.00 1.50 1.50 1.50 1.50 1.35 1.352) Full uplift water at Base Slab w/o LL @ Base skab
GWT=FEL(Not applicable to top down construction)Surcharge on Roof and int LL
17 503 1.35 1.35 1.35 1.50 1.50 1.50 1.50 1.50 1.50 1.35 1.35 1.35 1.353) Vertical and Horizontal Surcharge = 25 - 20 = 5kPa
GWT=FEL(Not applicable to top down construction)Surcharge on Roof and w/o int LL
18 504 1.35 1.35 1.35 1.50 1.50 1.50 1.50 1.50 1.35 1.35 1.35 1.354) WT @ FL = 10kPa (excess of WT @ GL) to Roof and DW
LOAD COMBINATION 6(Case 2)
Locked-in forceMin Vertical and Max
Horizontal
GWT=GL1.5m top excavation, no top surcharge with int LL
19 601 1.35 1.35 1.00 1.00 1.35 1.35 1.00 1.50 1.50 1.50 1.50 1.50 1.50 1.35 1.35
5) Vertical soil on roof = -1.5m soil removed. 6) Vertical water on roof = -15kPa (1.5m water removed)
For Locked-in Force CaseWT = GL
REMARKS
V) Live LoadIV) Water Pressure VI) Surcharge VII) Soil Pressure
WT = +1.0m WT = -5.0m WT = -1.5m WT = -4.5m WT = unbalanceWT = -1.5m WT = -4.5m WT = unbalance
LOAD COMBINATIONS Descriptions
LOAD COMBINATION 2
(Case 3)Max Vertical and Min
Horizontal
LOAD COMBINATION 3
(Case 3)
Min Vertical and Max Horizontal
LOAD COMBINATION 4
(Case 3)Unbalanced Case
WT = +1.0m WT = -5.0m
III) Soil Pressure
LOAD COMBINATION 5(Case 2)
Locked-in forceMax Vertical and Max
Horizontal
WT = BaseWT = GL
Load
Com
bina
tion
Nos
. In
the
Anal
ysis
BASIC LOADS
WT = GL & +1.0m WT = FEL
Ulti
mat
e Lo
ad C
ombi
natri
ons
LOAD COMBINATION 1
(Case 3)
Max Vertical and Max Horizontal