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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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
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
Foundation Plate without Reinforcement,
poured under water
Second Foundation Plate with Reinforcement.
Both Plates are fixed by Micropiles TITAN 103/51
The job is at sea level; approx. 30 miles from coast. Structure of soil is typical for Western Part of the Netherlands.
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.
Dutch standard CUR 2001-4 gives for estimation of ultimate skin friction
qs ~ qc
qs = 150 kN/m²
This value is confirmed by Eurocode (EC 7), which gives for sand same figure.
Soil Investigation by CPT
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")
254 mm Ø
254 mm Ø
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
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.
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
FKV,0 = Pile Force in
Monitoring the distribution of the load transfer to the ground by extensometers, installed inside the hollow TITAN pile.
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
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.
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.
Mini excavator with
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).
Prepared material for micropile TITAN 103/51
Quality control sheet of Micropiles TITAN
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
Hinged Coupling Nut
Standpipe 219 mm Ø with collector for return flushing
Steps of installation for Micropiles TITAN 103/78
20 m below water table, to prevent heaving of concrete slab
Collector for used
cleaning the casing
Sheet pile wall