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Folie 1. Main dimensions of trough: width is 15 m (45 ft) for double track length is 1200 m (1400 yards) depth is 14 m (46 ft) to pass the river. Finished Trough "West" without Tracks. Folie 2. Trough during installation of Micropiles TITAN and Foundation Plate.

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Presentation Transcript
Folie 1
Folie 1

Main dimensions of trough:

width is 15 m (45 ft) for double track

length is 1200 m (1400 yards)

depth is 14 m (46 ft) to pass the river

Finished Trough "West" without Tracks


Folie 2
Folie 2

Trough during installation of Micropiles TITAN and Foundation Plate.

2 Drill Rigs operate from a Bridge, which runs on

rails on top of sheet pile wall

In Front

Foundation Plate without Reinforcement,

poured under water

Behind

Second Foundation Plate with Reinforcement.

Both Plates are fixed by Micropiles TITAN 103/51

Soil Investigation

The job is at sea level; approx. 30 miles from coast. Structure of soil is typical for Western Part of the Netherlands.

Backfilled sand

Organic Veen with layers of soft clay

Medium dense sand, Dutch cone resistance qc = 15 MPa

from - 16 m (52 ft) to -34 m (112 ft)

Micropiles transfer the load to the layer of medium dense sand.


Folie 3
Folie 3

Dutch standard CUR 2001-4 gives for estimation of ultimate skin friction

qs ~ qc

100

qs = 150 kN/m²

This value is confirmed by Eurocode (EC 7), which gives for sand same figure.

Soil Investigation by CPT

10 MPa

15 MPa

- 14


Folie 5
Folie 5

Exhumed Micropiles TITAN 103/51

The grouted body was flushed clear and lifted out of the ground.

The holes were backfilled with bentonite. Average diameter of grouted body was measured with 254 mm (10").

Exhumed Micropiles TITAN 103/51

average diameter 254 mm (10")


Folie 6
Folie 6

254 mm Ø

10“

254 mm Ø

10“

 Neat grout = Portland cement, qualtity B25,

unconfined compressive strength > 25 N/mm²

 Filtercake = concentration of cement, arch effect, diaphragm

 Interlocking shear bond by jet grouting effect

 TITAN 103/51 centered in the micropile, equal cement stone

cover, best shear bond

Exhumed Micropile TITAN 103/51

Structure of Grout body in medium dense sand below water table


Folie 7
Folie 7

Measuring Crack Width of Exhumed Micropiles TITAN 103/51

The excavated micropiles were tested concerning micro cracks at the University of Munich. Up to a load of 1200 kN (540 KIPS) all measured cracks were below 0,01 mm. No cracks in longitudinal direction were observed.

Result: Simple corrosion protection by cement cover of min. 50 mm (2") is sufficient for permanent micropiles TITAN 103/51 on tension.

TECHNISCHE UNIVERSITÄT MÜNCHEN

INSTITUT FÜR BAUSTOFFE UND KONSTRUKTION

LEHRSTUHL FÜR MASSIVBAU

Prof. Schießl-Prof. Zilch

Testing Exhumed Micropiles TITAN 103/51 with respect to micro cracks

cumulative frequency (%)

crack width ( mm)

Furthermore the area of the couplings was investigated in the tension test. The play for alternating loads on tension and compression was measured below the 0,01 mm acc. to DIN 1045 for connections of reinforced steel bars.


Folie 8
Folie 8

Investigation of Load Transfer and Load Distribution in Micropiles TITAN

Tell tales (extensometers) were installed in the test micropiles TITAN 103/51 to monitor load transfer from micropile to sand.

Result: Up to gravity point of bonded length approx. 2/3 of the load is already transferred to the ground.

Load Transfer and Load Distribution in Micropiles TITAN 30/11

FDR,0 = Pile Force

in Tendon

FKV,0 = Pile Force in

Grout Body

Monitoring the distribution of the load transfer to the ground by extensometers, installed inside the hollow TITAN pile.


Folie 9
Folie 9

On pile head a min. length e.g. 408 mm for TITAN 30/11 is necessary to activate the full bearing capacity of the grout body. The load transfer from steel tendon to grout body stops, when strain rate in interface is the same.

The load transfer by shear bond from steel tendon to grout body causes circular tension forces in cement grout body.

To avoid very dangerous axial cracks in grout body, caused by circular tension forces, a minimum cement cover and a smooth HD-PE tube is recommended for pile head.

Calculation Model for Circular Forces R

caused by Shear Bond e.g. TITAN 30/11

Necessary protected length


Folie 10
Folie 10

Installation sequence

14 TITAN 103/51 micro piles are installed per day, each 20 m long. This is achieved by 2 teams each 3 men and 2 hydraulic drill rigs. The rigs are positioned on a bridge, 5 m above the water level. This bridge moves on rails, being supported by the sheet pile walls.

This rigid support enables precise drilling operations in comparison to a floating pontoon.

This bridge is also used for tension testing, the sheet piles are used as reaction piles.


Folie 11
Folie 11

A small excavator, equipped with a hydraulic manipulator, handles the 3 m long bars with 130 kg (290 lbs.) weight, and positions it onto the rig.

Important is a standpipe 219 mm diam. (9”), 21 m long (22 yards) with a flushing collector welded to it’s top.

This standpipe is pressed 2 m (2yards) into the soft ground. The TITAN micro pile is inserted and drilled through that standpipe. The return flow of flushing is being pumped from the top collector and enables excellent control over the drilling process. Return flushing is going into a de-sanding unit and the remains are collected in container, cladded with a PVC foil.


Folie 12
Folie 12

Mini excavator with

hydraulic manipulator

lift the TITAN piles,

each 130 kg weight

hinged coupling nut for seperation of

the TITAN piles.

The standard coupling nuts are fixed

with Hilti Hit C 100 glue.

standpipe 219 mm diam., 21 m long long with

grout collector vibrated 2 m deep into the soil

This standpipe prevents an uncontrolled underwater spill and pollution of the water with the cement flushing. It also acts as directionally stabilizing guide for the free drill length, in water and air of 20 m (22 yards).


Folie 13
Folie 13

Prepared material for micropile TITAN 103/51

Quality control sheet of Micropiles TITAN


Folie 14
Folie 14

Handling Advantages with Micropiles TITAN in this applicaton:

- Positioning pile head to the desired precise level

- Nearly no spill of grout close to pile head, which reduces static effective

thickness of slab.

Screwing the Drill Bit

Inserting the

Micropile in

Standpipe


Folie 15
Folie 15

Hinged Coupling Nut

Standpipe 219 mm Ø with collector for return flushing


Folie 16
Folie 16

Steps of installation for Micropiles TITAN 103/78

20 m below water table, to prevent heaving of concrete slab

Collector for used

cement flushing

cleaning the casing

before pulling

casing

Rope

Diver

Sheet pile wall


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