=ar:i oressureexoerimen:s
s
onciaoaracmwa
by Dr. W. ROTT" and Prof. Dr. Ch. VEDER>
Introduction
obtained at the time, it was possible to
draw conclusions regarding earth pressure
and earth resistance and their distribution
for the important junctions of the underground route (subway), such as at Karl's
Square, Stephen's Square and Sweden
Square.
Measurement
gauges
nts. A modification of thes
was planned for use on the diaphragm
wall reinforcement
of the test cross-section at the Wiedner Guertel.
The vibrating frequency of the gauges
was measured from a c ntral control station. Special care is necessary in placreinforcement
cages into the
ing the
trench because of the mounted gauges
and cables, Some of the strain gauges on
the steel bars did not function, but it was
m
ORDER TO examine the amount and
the distribution of earth pressure on relawalls, a series
tively stiff cast-in-place
of experiments was carried out on the
tunnel walls of traffic routes in Vienna.
were suggested
These experiments
by
Professor Ch. Veder, and financed by th.
City Council of Vienna. Two test sites
were chosen on the basis of suitability for
the experiments as well as for soil conditio ns.
First a d scription is given of the site
instruments
the measuring
conditions,
procedure
used and the measurement
followed. Methods of evaluation are explained and the results grouped according
to the different soil characteristics.
On the basis of the test evaluations
IN
points and the subsoil
Two test sites were chosen at tunnels
which were either under construction or
in the preparatory
stage. The first was at
Lastenstrasse where the soil is primarily
non-cohesive. The second, at the Wiedner
Guertel, is in mainly cohesive soil. In both
cases the ground water level is below
the tunnel invert. Figs. 1 and 2 show a
schematic diagram of the measurement
points in cross-section and layout, inand
cluding the stages of construction
the respective soil profiles.
The physical and mechanical properties
of undisturbed soil samples were determined, including unit weight, liquid and
plasticity limits and grain size distribution. Additional tests were carried out in
the triaxial apparatus (fast and slow tests)
and in the direct shear apparatus
(also
fast and slow tests; slow tests partly
with repeated shearing; also tests with
e=constant). A comparison of the earth
pressures
calculated from the various
expsriments
indicates major differences.
An example is given in Fig. 3.
Qrs
Ill
o
~
i
I
I
I
assi
I
I
Loess, loamy
Tegel
Construction
stages in cross section
0 2 4 6 810m
)So
cs
struts
Measuring
f 5o
340
Fig. 1. Schematic diagram of the Lasten
Street test site
So
Gravel
Loam
~40
560
Cross section
cv
/
Tegel
ahullÃ
Ground water
+.s-50
0 -Fine sand/]
Tegel
co
0
Fine sand
—Teg el
4 6
2
8
TT""
1 0m
50
t
)j,j..... i,
Measuring struts
50
Layout
~375
Fig. 2. Schematic diagram of the Wiedner
Guertel test site
e,„u„,
1
—50
50
0
100
Triaxial test,
Ia =
'in
slow—
-t~
Direct shear test,
—
slow, once —
r
Direct shear test,
repeaterl shearing
8-
c)
150 ku
—--
——
',
rs
I
fs
s
14—
"Dipl. Ing. Dr. tech.
Sieveringerstr. 209
W
Rott,
A
1190 Wien,
Prof, Dipl, Ino. Dr, tech. Dr. Ing.
h.c. Ch. Veder, A-8010 Graz, Rechbauerstr. 12
This article is a translation from the German of
which
Schlitzwanden"
"Erddruckversuche
an
appeared in Bauingenieur 52 (1977) 473-475 and
is published here by permission of the publishers,
'I Deiitii, ni
tiEm. o, Univ.
Springer-Verlag.
screens with scratched concentric circles
were installed as sighting targets. These
markers were set before and during the
excavation. They need to be protected durprocedure because the
ing the installation
slightest damage renders them unusable.
Measurements
t
ci
4
directly
the earth pressure
acting on the diaphragm walls. This was therefore ascertained from measurements
of the strains
in the wall and the forces in the struts.
These forces were measured by means
of a vibrating wire system which is particularly suitable for long-term measure-
i
320I
to measure
It was not possible
.l
Gravel
2-
Measuring devices and their
application
720[
'1'i
0 ravel
Sand
not possible to determine the reason for
their malfunction because they were then
inacc ssible.
Wall deformation
was measured with
inclinometers which were lowered to the
bottom of the diaphragm panels in nearly
vertical tubes. Optical markers were also
fixed on the wall in the excavated area
to measure the deformation. Two steel
tubes were installed in the reinforcement
cage in each of the tunnel walls at the
Wiedner Guertel site. These were concreted and measured before and after the
change in loading (excavation). In addition, the tube's deviation with depth was
surveyed
optically. Illuminated
focusing
Fig. 3. Comparison calculation of earth
pressure, Wiedner Guertel. Active earth
pressure for wall friction equals soil
friction
Because the diaphragm
wall at the
Lasten Street was already finished at the
start of this investigation, only measuring
methods that did not require any preparatory measures on the wall itself could be
applied, i.e. the determination
of strut
forces and the optical measurement of
wall deformations
only. As can be seen
in Fig. 1 three stages of loading
were
observed: first, after installation
of the
upper struts and the first excavation
stage; then a further, deeper excavation;
and finally after installation of the lower
struts and removal of the upper onesthe cantilever stage.
The test results given for these three
stages are the mean values for both sides
of the tunnel and are shown in Fig. 4.
All measurements
were taken within two
months. During this period the temperature varied greatly but all data for this
Paper were determined when the temperature was between +3'C and +5'C.
The following measurements
were taken at the construction
site on Wiedner
Guertel:
strains in the struts
optical measurements of deformation
strains in the reinforcement bars
inclinometer measurements.
Fig. 2 shows the situation
with the
upper strut installed and excavation down
to tunnel formation. From these extensive
measurements it was possible to estimate
the earth pressure and to calculate the
strain of the wall and also to check the
bending moment and reaction forces from
the pressure measurements. Measurements
of deflection curve and stresses in the
reinforcement
bars of the test panel at
Wiedner Guertel are shown in Fig. 5.
—
—
—
—
Methods of evaluation
Differen methods were available for
evaluating the data, taking into consideration the rigidity of the wall. An inversion
of the deflection curve method is a suitable graphic method. In contrast, to deterApril, 1980
35
M
a~,290131
290
l
xl
Mean reaction force
40
~ Strut
kN. m
114 kNI s
150
force
114 kN/m
I,
-50 —100 I<N
Ql
tll
ring
U
O
ce
I'
60 40.20- 20 40 60I kN/m
cs
I
Earth pressure
Moment due to
measurements of
the reinforcement
I
100~200
I
I
159 kNmf
Stress of
I the reinforcement
Moment
I
aeax
I
Inc tin
I
Deformation
1mm
+ —4- 50
10
3mm
I
20
Exca
in
c
I
30
37 kNml
mm
-e —4—50cm
+ —4-50
zE
&5
Fig. 4. Deformations
Lasten Street
Fig. 6. Moments, shearing force and
loading. Mean values of both walls at the
Wiedner Guertel
and strut forces at
3
4mrn
-10
i
10 20 30
N/mm'
I
Fig. 5. Wall deformation
at Wiedner Guertel
bending moment and embedded
mining
depth on the basis of given loading, the
unknown
load is determined by measuring the deflection curve. It must, however,
be mentioned that the process of differentiation
gives this graphic method a
certain degree of inaccuracy and thus it is
suitable for determining
the total earth
pressure but not its distribution.
To simplify the evaluation, the stiffness
was taken as "State I", i.e. no tension
cracking in the concrete. This assumption
takes into account the value of the moment of resistance under that condition.
The load can be calculated from the ordin ates and the inclination
(inclino meter
measurements)
of the deflection curve.
deflection moments can be
In addition,
checked by using the strain measurements
in the reinforcement
—El
=
M
=
R
where:
R
C
= radius
= distance
—El
Ae
C
of deflection curve
of reinforcement
and the bearing forces determined
by
measuring the strut forces.
Because the deflection curve and its
inclination is determined from somewhat
unreliable data, it is necessary to suppress
the errors by adjustment
to a polynom
which can be differentiated unambiguousDr'
t if
I
i
I
ill
Oft
tl
I Ill iii
811
I
!
and steel stresses
ly. Fig. 6 shows the results obtained for
the internal
forces and loads at the
Wiedner Guertel.
—here
Viennese
pressure distribution
was almost parabolic to the base, with the maximum value In. the middle of the wall.
(iii) The earth pressure indicated a soil
friction for clay of fo —
little
cohesion.
(iv) The passive earth pressure was less
than that theoretically
possible. At first,
its distribution showed a straight line increase and then a decrease.
(v) The back-calculated earth pressure
parameters agree best with the results of
slow shear tests.
(vi) T'e deformation of the diaphragm
wall as well as the displacements
of the
struts and the base, and the stresses in the
reinforcement remained small.
The results of the evaluation can be
seen in Fig. 7 and Fig. 8. For loose subsoil the measured deformations, the bearing forces and the almost uniformly distributed earth pressures, as well as the
triangular active earth pressure and earth
pressure at rest, can be seen in Fig. 7.
For cohesive subsoil the deformations,
the measured strut forces and the calculated
earth
pressure
distribution
are
shown in Fig. 8. The active, passive and
earth pressure at rest are shown
for
comparison. The values were calculated
from plausible values for unit weight, angle
of friction and cohesion.
The results may be summarised
as
follows for earth pressure in loose subsoil on the 'basis of measurements
made
at several stages of construction of the
wall for the
diaphragm
singly strutted
Lasten Street underpass:
(a) The earth pressure corresponds in
magnitude
to the active earth pressure.
(b) The earth pressure probably changed
uniformly from the bottom of the excavation to the top of the wall.
(c) The soil parameters are calculated
for gravel, sand and fill with ~ = 18
kN/m'nd ft —35'. The wall friction is
assumed to be equal to the internal friction of the soil.
(d) The deformation of the diaphragm
wall, as well as the displacement of the
struts and the base, remain small. Larger
occurred only from overdeformations
loading.
The following conclusions were drawn
for earth pressure in cohesive subsoil
made at the
based on measurements
wall at the
diaphragm
singly strutted
Wiedner Guertel underpass:
(i) The magnitude of the earth pressure
was between the active earth pressure and
the earth pressure at rest (valid for only
0 10 20 30ii
soil
Tegel).
(ii) Earth
Results of evaluation
3 liiiii
cohesive
slightly
20'ith
in
I
I
4 h
I
131kN
I'.
/
m'0 kN/m'0
E,irtti Iires<iir
F, it'rir:<srrre
po
kN
io
20 10
20 10
I
ie„with 1 = 18 kN/m',fI
=
35, c = 0, S
Ground
Engineering
De'lni
20 10
10 20
111
iII
(i i i
3
<50 1<M m
kN/m
= frt
Fig. 7. Diagram of the test results at Lasten Street
36
50
tli;
Tnrtr.l
e
<xi
1 eral
r
witli
..
—
191 N m'
=
20
kN nr
=
<r
=
18, r.
18, r
=
10 l,t'<
ni
= Iri kN m
Fig. 8. Diagram of the test results at Wiedner Guertel
1
%3EODRILLING
Two
The first use of the new machine
was
to sink a borehole for the Yorkshire Water
Authority at Cowick, near Snaith. This was
cased to 1.07m diameter for the first 20m,
then at 860mm down to 48m. From this
depth down to the bottom at 120m the
bore contains a 610mm stainless-steel
wellscreen
packed with gravel outside
to prevent the entry of loose materials
from the Bunter sandstone. This well will
yield some 6500m'/day.
One of the advantages of the L-4 rig
is that it is mounted on a semi-trailer with
standard fifth-wheel coupling so that it
can be easily towed to the site by a
road tractor of the type used for articulated
vehicles. For transporting,
the mast of
this 24 ton rig folds down to give a height
of 3.95m, while the overall width is 2.5m
and the length 12.9m. On site the tubular
steel mast is rapidly erected to a height
of 14.75m.
At the rear of the chassis is the Deutz
F12L 413 air-cooled diesel engine, which
is rated at 230hp at 1 800rpm. This provides the power for all motions, and also
for two air compressors, each with an
output of 5.7ms/min. at 20 atm.
Mechanical drive is provided
to the
rotary table, which has an opening of
1.5m dia., provides a maximum torque of
8000kg.m and a speed range of 10 to
60 rpm.
Dimensions and weights:
position:
Drilling
14.75 m
2.50 m
Mast height
Max. width
Crown block
Transport position:
3.95 m
Height
Width
Length
2.50 m
12.90 m
Weight:
depending on
rig specification
24 tons
Travelling block
Swivel
Discharge hose
Two-winch drawworks
Kelly
Hydraulic powerpaek
Elevators
Engine
Two
draw-works
winches,
rated at
5.0tf respectively are driven
through
a three-speed
torque converter,
while the cat-head winch is mechanically
driven. The rig is equipped with a centrifugal pump with a capacity of 240m'/hr
against a head of 60m. In the working
position, the chassis is supported by hydraulic levelling jacks.
8.5tf and
Cath end
tllechanical
feeding device
Control panel
Gearbox
tlf
lot
Watery
':ble
41
fl
i!
1]
r
s
r
rwe
I
11
I
ai
I
I
as a
I'
I
r
4'
~+is
v
5
Top right: Side elevation of a typical L-4
rig. Right: In the foreground, the doubletube drill rods are stacked ready for use.
Above: Detail of the swivel mounting
38
Ground
Engineering
~
e