Cavity Lock Systems Limited -Test Data Reports

Laing Technology Group Limited
Page Street London NW7 2ER
Telephone 01-9593636 Telex 8958471
Facsimile 01-9065297
Direct Line 01-906
Our ref:
RN/Sj
Date         :    20 June 1994
Your ref    :
Contract   :    94160
Code        :    RT22030


Client        :    WT Specialist Contracts 
Unit 4 & 8, Arundel Mews, Brighton 
BN2IGD

Project Proof load tests on anchors for signal gantry supports - Fenchurch Street Line.

Date of test     : 8th,10th, 15th & 17th June 1994

Object of test    : To proof load grout fixed anchors , as follows:

1. 2no. anchors, installed at an angle of 30°, to a load of 130kN (1.5 x working load) in compression. At location UR 120.
   
2. 2no. anchors, installed at an angle of 20°, to a load of 140kN (1.5 x working load) in tension. At locations UR 112,117and 120.
   
3. 2no. anchors, installed normal to the wall, to a of 25kN (1.5 x working load) in shear. At location 112, 117 and 120.
   
4. 2no. anchors, installed at an angle of 20°, to a of 48kN (1 1/2 x working load) in tension at location UR 516.
   
5. 3no. anchors, installed normal to the wall at lower level, to a load of 75kN (1 1/2 x working load) at location URS 516.
   
6. 1no. anchor, installed normal to the wall at the upper level, to a load of 120kN (1 1/2 x working load) in shear at location UR 516.

Method of Test

1. Compression tests
Load was applied in increments of 10kN by means of a 300kN capacity hydraulic ram acting through a 1250mm long, 89mm O.D. tubular strut to the face of the anchor located 900mm into the viaduct wall. A reaction base for the ram was provided by a rolled steel column section inclined at 60° to the horizontal and restrained at its nominal mid span by tie bars to the tension anchors installed in the wall and a timber baulk and packing between its lower end and the wall, as shown in plates 1 & 2.

The applied load was monitored by a precision pressure gauge calibrated with the hydraulic ram against a proving ring (lab no. 2349) traceable to, national standards.

Displacement was measured by two dial indicators mounted diametrically opposite each other on the tubular strut to measure axial movement of the strut relative to the viaduct wall. See plate 2.

Each increment of load was held for a brief period prior to reading the displacement gauges and the maximum proof load was maintained for 1 hour prior to unloading in five increments. The residual displacement was then recorded.

2. Tensile tests

Load was applied in increments of 10kN by means of 300kN capacity hollow hydraulic ram reacting on a bridge supported at 600mm centres and adapted to enable the force to be applied axially to the anchor bars installed at 20° to the viaduct wall. See plate 3.

The applied load was monitored by a precision pressure gauge calibrated with the ram against a proving ring (lab no.2349) traceable to national standards.

Displacement was measured by a dial indicator mounted from the wall and arranged to measure the axial displacement of the anchor bar. Each increment of load was held until stable prior to reading the displacement and the maximum proof load was maintained for 1 hour prior to unloading.

3.

3.1 Shears tests (locations UR 120, 117 & 112)

The two shear anchors were tested simultaneously each providing a reaction base for the other. Shear plates 38mm thick were located on each anchor and fixed by screwing a nut on the anchor bar and lightly tightened using a normal spanner. See plate 4.

Load was applied in 5kN increment by means of a 120kN hydraulic ram positioned between the shear plates parallel to the viaduct wall. The load was measured using a precision pressure guage calibrated with the ram inst a proving ring (lab no. 2348) traceable to national standards. 

Displacement was measured by dial indicator mounted on the wall, one for each anchor assembly and arranged to measure movement of the shear plate in the direction of the applied force. Each increment of load held until stable prior to reading the displacement the maximum proof load was maintained for 1 hour r to unloading.

3.2 Shear tests (locations UR 516)

The 3 no. lower shear fixings were loaded using method described in 3.1, but in increments of 10kN. The upper shear fixing was loaded using a frame consisting of a shear plate on the fixing, as previously described, with a beam over and tie bars loaded by a 300kN hydraulic ram reacting on the two outer shear fixings at lower level. See plates 5 & 6. Load was applied in increments of 10kN. Load and displacement were measured as described in 3.1.

Results

The results are presented in tabular form -

Compression anchor No. 1 (first loading)         Table 1
Compression anchor No. 1 (second loading)   Table 2
Compression anchor No. 2                       Table 3

Tension anchor No. 1 & 2 UR120                 Table 4
Tension anchor No. 1 & 2 UR117                 Table 5
Tension anchor No. 1 & 2 UR112                 Table 6
Tension anchor No. 1 & 2 UR516                 Table 7

Shear anchor No. 1 & 2 UR120                   Table 8
Shear anchor No. 1 & 2 UR117                   Table 9
Shear anchor No. 1 & 2 UR112                   Table 10
Shear anchor No. 1 & 2 UR516                   Table 11
Shear anchor No. 2 & 3 UR516                   Table 12
Shear anchor Upper UR516                       Table 13

Results

Location UR 120 Anchor No. I Compression load test - 1st test loading

Date of test: 8th June 1994

Recovery = 68%

Results                                        Table 1

Location UR 120 Anchor No. 1 Compression load test - 2nd test loading

Date of test: 8th June 1994

Total Recovery

Table 2

Results

Location UR 120 Anchor No. 2 Compression load test

Date of test: 8th June 1994

Recovery = 95%

Table 3

Commentary of Compression Tests

During the loading sequence, the tubular strut tended to re-align its axis relative to the set angle. In  order to restrain this movement, timber packing was inserted in the hole around the tube. See plate 2. However, vertical movement in the order of 7mm was recorded at the jack end of the tube and there was some lateral movement. This represents a very small angular change in the direction of loading, in the order 0.3° and would have no significant effect on the magnitude and direction of the applied load. It would however affect the recorded values of displacement since the movement gauges were attached to the tubular strut, parallel to its axis - see plate 2. ie at 30° to the viaduct wall relative to which movement was measured. Consequently the vertical movement referred to the above would result in the gauges travelling up a 30° ramp and recording movement additional to the actual displacement of the anchor occurred.  anchor. It is the writers considered opinion that movements recorded were due largely to the above effect plus compressive strain the 1250mm long tubular strut and therefore no significant displacement of the anchor occurred.

Results

Location UR 120
Tensile load tests
Date of test: 10th June 1994

Recorded movement represents elastic strain in the projecting anchor rod. No movement of the anchor or signs of damage to surrounding brickwork.

Table 4

Results

Location UR 117
Tensile load tests
Date of test: 15th June 1994

Recorded movement represents elastic strain projecting anchor rod. No slip or creep or signs of damage to surrounding brickwork.

Table 5

Location UR 117
Tensile load tests
Date of test: 15th June 1994

Recorded movement represents elastic strain in projecting anchor rod. No movement of the anchor or signs of damage to surrounding brickwork.

Results

Location UR 117
Tensile load tests
Date of test: 15th June 1994

Table 6

Results

Location UR 516
Tensile load tests
Date of test: 17th June 1994

Table 7

Results

Location UR 120
Shear load tests
Date of test: 8th June 1994

Table 8  see comment p. 15

Results

Location UR 117
Shear load tests
Date of test: 15th June 1994

Table 9

Results

Location UR 112
Shear load tests
Date of test: 10th June 1994

Table 10  see comment p. 15

Location of UR 516
Shear load tests - lower anchors no. 1 & 2
Date of test: 17th June 1994

                            Table 11  see comment p. 15

Results
Location UR 516
Shear tests - lower anchors no. 2 & 3
date of tests: 17th June 1994

Table 12   see comment p. 15

Results
Location UR 516
Shear tests - upper anchor
Date of test: 17th June 1994

Table 13  see comment p.15

Comments on the shear tests

1. Locations UR120, UR117, & UR112

These anchors sustained the 25kN proof load with no visible signs of distress to the surrounding masonry. There was no measurable increase in displacement ie  'creep', after the load had been applied for about 10 minutes. The results show some permanent displacement due to 'bedding' of the test shear plate on the anchor bar and of the anchor to the surrounding masonry.

2. Location UR 516 - lower anchors. 

These anchors were tested in pairs, anchors no. 1 & 2 together and 2 & 3 together. Anchor 1 & 2 were loaded in 10kN, increments up to the proof load of 75kN.This was maintained for 1 hour. There was no measurable creep after about 10 minutes and no visible signs of distress to the anchors or surrounding masonry. However, displacement recovery for anchor no. 1 was less than 50% due we believe to ‘bedding’ of the anchor in the masonry. In the light this, it was decided to reload the anchor in two increments and record displacements. Recovery of displacement in this load cycle was 100%.

In view of the experience testing anchor 1 & 2, the loading procedure for test anchor 2 & 3 was changed. The proof load was applied in two increments and then removed in order to ’bed’ in the anchors.          The anchors were then loaded in 10kM increments to 75kN which was maintained for 1 hour. Recovery over this load cycle was better than 97% and there was no visible signs of distress to the anchor or masonary.

3. Location URS 16 - upper shear anchor.

This anchor was loaded in 10kM increments to the proof load of 120kM which was maintained for 1 hour. There was no measurable creep after about 5 minutes of achieving the proof load and no visible signs of distress to the anchor or masonary. However, displacement recovery was less than 50%, the anchor was therefore reloaded in two increments to the proof load. Recovery over this load cycle was 100%.

Tested by: D Winter, Senior Technician
Approved by: R. Newby CEng MIMechE Associate Engineer

Plate 1
Arrangement of compression test reaction frame.

Plate 2
Arrangement of hydraulic ram, tubular loading and displacement gauges.

P GRIFFIN ,WITCHTHORN, PATCHETTS LANE,
BEWDLEY, WORCESTERSHIRE DYI2 2DA,
TEL (0299) 400860 FAX: (0299) 405204
Report No :0l:AI:
21st June 1994

WESTMINSTER TUNNLEL, LIVERPOOL
TRACK LOWERING
GROUND ANCHORS TO RESTRAIN TUNNEL
BRICK LINING WALLS
TEST OF PROPOSED GROUND ANCHOR FOR
BRITISH RAIL INFRASTRUCTURE SERVICES
CINTEC HARKE GROUND ANCHOR
Supplied, manufactured, and installed by Cavity Lock
Systems Limited.

TEST REPORT :Testing of a ground anchor in the side wall of Westminster tunnel on 19th June 1994.

INTRODUCTION :The anchor had been installed on 12th June 1994, and was in accordance with the parameters set out in the soils report issued by Infrastructure Services for tender purposes. The materials, and installation process were in accordance with the manufacturers requirements.

Minor deviations were noted. The 3m fixed inner Iennth of the anchor, was, due to the thickness of the wall approximately 800mm behind the brickwork, I m specified.

The diameter of the anchor was increased to 150mm from the 125mm specified, for practical reasons.

The anchor bar used, macalloy 500 Re-bar, 4Omnn nominal diameter, having a failure load of 691kN, and a yield load of 628kN. The area of the bar, 1256mm, with a modulus of elasticity of 205^kN/mm^2.

The Presstec Grout used to inflate the inner sock of the fixed anchor length, has an ultimate crushing strength of 40ⁿmm².

The hydraulic ram used for the test had a capacity of 600kN , related to a hydraulic pressure of 10,000 p.s.i. The 5OkN increments were based on this pressure\load relationship.

TEST ARRANGEMENT:

The test equipment was set up as shown in diagrammatic sketch above. At this stage a small load was applied to the anchor to stabilise the equipment. The dial gauge was fixed position via a bracket attached to the wall, to measure movement off a square bar welded to the final locknut.

Dial gauge re-set.

Note: The dial gauge readings following re-set show very little variation. Measurement of the ram extension shows 2.0mm. This indicates that dial gauge was for some reason not functioning correctly. The free length of bar from the front of the fixed 3m anchor sock is 2m approximately.

The theoretical extensions on this length are:

For full test load of 450kN = 450x 1000x2000/256x205x1000 = 3.50mm
For increment of 50kN               =0.39mm
Total ram extension measured  =7.00rnm
Ram extension at 150kN            =4.50mm
Ram extension over 300kN       =2.50mm
Theoretical extension 300kN     =2.33mm
Dial Gauge readings over 150kN to 200kN. 1.650 - 1.350 =0.30mm

CONCLUSIONS :The anchor sustained the full 450kN test load satisfactorily with a loss of load over 30mins of 10kN approximately. The anchor sustained each load increment satisfactorily with a loss of load over 10mins of 5kN approximately, reducing as the loading increased. It appeared that the dial gauge was not functioning correctly, However, the check extensions taken measuring the projection of the ram confirm that the anchor performed satisfactorily. The test demonstrates clearly that up to and including the test load of 450kN, the anchor and the sandstone in which it is embedded performed very satisfactorily.