micro piles

MICRO PILE REINFORCEMENT SYSTEMSand CORROSION PROTECTION.

Horst Aschenbroich, Dipl. Ing. President and CEO

CON-TECH SYSTEMS LTD, Delta BC, Canada

Introduction:Since mankind started to design and build structures for different usages and environ-ments, foundation systems to support such structures had to be developed in order tomatch the architectural and structural needs. With the ever-increasing urban expansions,it is not always possible to find good supporting ground at or close to surface level.Therefore, foundations other than spread footings were designed to transfer compressionloads down to a suitable load-bearing stratum.

Higher and slender structures subjected to wind and seismic loads need foundationscapable to support compression as well as uplift and lateral forces. Instead of large, massconcrete foundations, which require large areas and mass excavations, smaller and deep-er drilled shaft or pile foundations became a more economical alternative, in which steelreinforcing systems embedded in concrete and cement grout are the major component.

Micro Piles belong in this category of foundation elements. They are very simple butunique in design and construction and are becoming more and more popular.

The evolution of Micro Piles

Since its original conception in the 1950’s by Dr. Fernando Lizzi, a number of micro pile sys-tems using steel-bar reinforcement / cement grout combinations with or without steel pipecasing, have been developed.

Lizzi’s idea was, to produce a foundation system consisting of small pile groups, which forma reinforced soil mass like the root system of a tree. He called these PALI RADICE or“ROOT PILES” (see Figure 1).

Further developments using different installation methods and reinforcing systems made itnecessary to capture them all under a general heading, first “MINI-PILES”, which was laterchanged to “MICRO PILES”.

With the creation of the International Workshop for Micro piles (IWM), first in North Americaand later internationally, MICRO-PILE became a household name in the Geotechnical andfoundation industry. They are mainly used as Friction Piles to take tension and / or com-pression loads.

1

What is a Micro Pile?

A generally up to 300mm diameter, drilled and grouted pile with a centrically placed steelreinforcing member consisting of single or multiple bars.

Why are Micro Piles such a unique foundation system?

They can be placed with relatively small drilling equipment, single or in groups, under lim-ited access and low headroom conditions. They can be installed, for instance as the TitanIBO system, using rotation boring only. This reduces or eliminates the risk of structuraldamages caused due to vibrations, by otherwise used heavy percussion and pile drivingmethods, especially inside or in close vicinities of buildings.

ADSC Micro-Pile Seminar, Charlotte NC, November 13, 20012

Figure 1: Pali Radice or Root Pile foundation examples (after FHWM-SA-97-070, 2000)

Figure 2: Typical micro pile sections, left with solid bar reinforcing, right with hollow barreinforcing or casing (after FHWM-SA-97-070, 2000).

The reinforcing materials are simply single solid or hollow bars with continuous outsidethreads, which can easily be spliced and coupled to any required length.

The intent of this presentation is to introduce, to designers and specialized foundation-engineering contractors, the different types of reinforcing systems and corrosion protec-tion methods available for drilled and grouted Micro Piles.

Pile Types and Reinforcing SystemsDuring the evolution process of developing Micro-Piles over the past 40 years, besidesdifferent drilling equipment, a variety of continuously threaded reinforcing bars and grout-ing systems have been successfully introduced.

The “GEWI PILE” System

When I first introduced the Dywidag Threadbar System in North America (in 1967), I had theopportunity to propose this bar as a post-tensioned single bar reinforcement in Tension Pilesfor the Bonnybrook Sewage treatment plant extension in Calgary Alberta, Canada.

Approximately 1500 piles were required to support large sewage aeration tanks againstuplift. This became the first application (worldwide) for Dywidag bars in Piles and in the geo-support industry. A drill-through Diesel Hammer was used driving casing through the over-burden, cleaning out the casing with an inner drill steel and advance-drilling the same intothe underlying bedrock. In the free stressing length, the bars were corrosion protected by ashop applied heat-shrink sleeve with inner asphalt coating (Yellow Jacket). As an addition-al bond breaker, a metal sheath was placed over the coated bar. The drill hole and casingwas tremie-grouted with cement grout. Each pile was stressed to a test load and locked offat a design load equivalent to the uplift force.

Soon after, in the early 1970’s,, Dywidag started to market the grade 60 and grade 75 rein-forcing steel thread-bar system, called GEWI Bars, which lead to the development of the

Micro-Pile Reinforcement Systems and Corrosion Protection, Horst Aschenbroich, Con-Tech Systems Ltd. 3

Figure 3: Threadbars, All-Thread Bars and hollow bars (left to right).


“GEWI PILE” by Dr. Thomas Herbst, who was at that time chief of the geotechnical devel-opment department. GEWI originates from the German word GEWINDE or THREAD.These piles are installed using open or cased hole drilling methods. The GEWI BAR formsthe concentric reinforcing element. The drill hole is filled with cement grout. In order toincrease the grout to soil bond capacity of the pile, especially in cohesive soils, post-grouttubes are installed at the outer perimeter of the grout body. Post-grouting can be repeatedseveral times until the required pressure or skin-friction is achieved.

GEWI® Bar Steel Properties ASTM A615 (Grade 75) CAN/CSA(G3018-M1982)

THREADBAR®

Designation

Yield Stress

Cross Sectional

Area

Yield Strength

NominalWeight

Maximum

THREADBAR®

Diameter

CouplerLength

C

Coupler Diameter

D

Hex Nut Length

A

Hex NutWidth2

E

in-lb mm MPa mm² kN kg/m mm mm mm mm mm

#10 32 517 819 423 6.41 36.3 144.8 51.2 65.0 48.8

#11 36 517 1006 520 7.91 40.9 161.8 57.0 73.0 54.4

#14 43 517 1452 751 11.39 47.2 198.6 64.8 90.2 64.0

#18 57 517 2581 1335 20.24 63.5 237.5 88.9 107.4 84.8

Grade 75

63mm 552 3168 1747 24.86 69.1 245.7 98.0 114.3 93.2

All couplers and hex nuts develop 100% of the ultimate strength of the bar 1) 63 mm bars and hardware available in grade 80 material only 2) Measured across flats

Imperial Sizes

GEWI® Bar Steel Properties ASTM A615 (Grade 75) CAN/CSA(G3018-M1982)

THREADBAR®

Designation

Yield Stress

Cross Sectional

Area

Yield Strength

NominalWeight

Maximum

THREADBAR®

Diameter

CouplerLength

C

Coupler Diameter

D

Hex Nut Length

A

Hex NutWidth2

E

in-lb mm ksi in² Kips lbs/lf in in in in in

#10 32 75 1.27 95.3 4.30 1.43 5.70 2.02 2.56 1.92

#11 36 75 1.56 117.0 5.31 1.61 6.37 2.25 2.88 2.14

#14 43 75 2.25 168.8 7.65 1.86 7.82 2.55 3.55 2.52

#18 57 75 4.00 300.0 13.60 2.50 9.35 3.50 4.23 3.34

Grade 75

63mm 80 4.91 392.8 16.70 2.72 9.68 3.86 4.50 3.67

All couplers and hex nuts develop 100% of the ultimate strength of the bar 1) 63 mm bars and hardware available in grade 80 material only 2) Measured across flats

Table 1: GEWI pile bar steel properties (courtesy DSI).


Figure 5: Typical post-grouting system (after FHWA-SA-97-070, 2000)

Figure 4: GEWI Pile (typical) with standard and double corrosion protected reinforcing bar(after FHWA-SA-97-070, 2000)

The “PIN PILE”System

The PIN PILE is a development in the 1970’s by the Nicholson Construction Company USA.This method uses an outer pipe casing to stabilize the drill hole and an inner drill rod forcleaning out the casing or drilling further into harder ground. After placing the centric rein-forcing element, single or multiple bars (see figures 6 and 7) and filling the casing withcement grout, the casing is slowly pulled under constant pressure grouting and partly left inthe ground as additional reinforcement to increase bending moment and / or lateral loadcapacities and to prevent grout loss in grounds with large voids. Post-grout systems can beused with these piles as well.

The Threadbar or All-Thread Bar systems (tables 2 - to 5) are supplied by the ADSCAssociate Members

CON-TECH SYSTEMS, (CTS)

DYWIDAG SYSTEMS INTERNATIONAL, (DSI)

WILLIAMS Form Engineering


Figure 6: Pin Pile installation sequence (FHWA-SA-97-070, 2000).


Figure 7: Single (left) and multiple bar (right) micro pile reinforcing.

All-Thread Bar Steel Properties Cold-Rolled Grade 75 (yield), ASTM-A615

Load Capacity No

Nominal Diameter

Steel Area Ultimate Yield Load

Major Thread

Diameter D

Weight

#9 1 1/8 in 1.00 in2 100 K 75.0 K 1 1/4 in 3.40 lbs/lf

28 mm 645 mm2 445 kN 333.6 kN 31.8 mm 5.06 kg/m

#10 1 1/4 in 1.27 in2 127 K 95.3 K 1 3/8 in 4.30 lbs/lf

30 mm 700 mm2 565 kN 423.9 kN 34.9 mm 6.40 kg/m

#11 1 3/8 in 1.56 in2 156 K 117.0 K 1 1/2 in 5.30 lbs/lf

35 mm 1000 mm2 694 kN 520.5 kN 38.1 mm 7.89 kg/m

#14 1 3/4 in 2.25 in2 225 K 168.7 K 1 7/8 in 7.65 lbs/lf

45 mm 1500 mm2 1001 kN 750.4 kN 47.6 mm 11.38 kg/m

#18 2 1/4 in 4.00 in2 400 K 300.0 K 2 7/16 in 13.60 lbs/lf

55 mm 2500 mm2 1779 kN 1334.5 kN 61.9 mm 20.24 kg/m

#20 2 1/2 in 4.91 in2 491 K 368.0 K 2 3/4 in 16.69 lbs/lf

64 mm 3168 mm2 2184 kN 1637.0 kN 69.9 mm 24.84 kg/m

Table 2: Properties of cold-rolled grade 75 (yield) All-Thread bars.


All-Thread Bar Steel Properties Cold-Rolled Grade 150 (ultimate), ASTM-A722

Load Capacity Nominal Diameter

Steel Area Ultimate 0.8 ULT 0.6 ULT

Major Thread

Diameter D

Weight

1 in 0.85 in2 127.5 K 102.0 K 76.5 K 1 1/8 in 3.09 lbs/lf

26 mm 549 mm2 567.2 kN 453.7 kN 340.3 kN 28.6 mm 4.60 kg/m

1 1/4 in 1.25 in2 187.5 K 150.0 K 112.5 K 1 7/16 in 4.51 lbs/lf


1 3/8 in 1.58 in2 237 K 189.6 K 142.2 K 1 9/16 in 5.71 lbs/lf


1 3/4 in 2.60 in2 400 K 320.0 K 240.0 K 2 in 9.06 lbs/lf


2 1/2 in 5.19 in2 778 K 622.4 K 466.8 K 2 3/4 in 18.2 lbs/lf


Table 3: Properties of cold-rolled grade 150 (ultimate) All-Thread bars.

All-Thread Bar Steel Properties Hot-Rolled Grade 75 (yield), ASTM-A615



Major Thread Diameter D

Weight

28 mm 616 mm2 405kN 319.0kN 32mm 4.83kg/m

1 1/8 in 0.95 in2 91.0K 71.7K 1.26 in 3.25 lbs/lf

32 mm 804 mm2 524kN 416.7kN 36mm 6.31kg/m

1 1/4 in 1.25 in2 117.7K 93.7K 1.42 in 4.24 lbs/lf

40 mm 1260 mm2 821kN 648.3kN 45mm 9.87kg/m

1 5/8 in 1.95 in2 184.6K 145.7K 1.77 in 6.63 lbs/lf

50 mm 1960 mm2 1285kN 1008.4kN 55mm 15.4kg/m

2 in 3.04 in2 288.9K 226.7K 2.17 in 10.35 lbs/lf

63.5 mm 3167 mm2 2215kN 1760.0kN 68mm 24.68kg/m

2 1/2 in 4.91 in2 497.9K 395.6K 2.68 in 16.58 lbs/lf

Table 4: Properties of hot-rolled grade 75 (yield) All-Thread bars.

The “TITAN / IBO - INJECTION-BORED MICRO PILE”

The successful construction of a Micro-Pile, involves a number of steps.

� Drilling,

� Placing of reinforcing steel.

� Grouting.

One of the latest developments is a system and method, which combines all in one singlestep installation.

This method uses hollow bars, sometimes in combination with inside solid bars or strand,which can also be post-tensioned (figure 10 and figure 14).

This Injection-Bored (IBO) pile is a joint development between the companies FriedrichIschebeck Gmbh, Germany and Con-Tech Systems LTD, Canada. The goal was to pro-duce a drilled, grouted and reinforced Micro Pile following the original Root Pile idea byLizzi. The pile totally integrates with the soil. It forms a foundation system of reinforcedsoil mass, in particular if placed in groups. The piles are drilled-grout-injected in one step,using the hollow bars as drill rods and grouting ducts with disposable special drill bits (fig-ure 12) and rotary drilling methods. The drill bits have jet openings allowing for pressuregrout penetration while drilling. During drill advancement and grout injection through thehollow bars, with the aid of a flushing head, the drill cuttings are continuously flushed or


Table 5: Properties of hot-rolled grade 96 (yield) All-Thread bars.

All-Thread Bar Steel Properties Hot-Rolled Grade 96 (yield), ASTM-A615



Major Thread Diameter D

Weight

28 mm 616 mm2 490kN 410kN 32mm 4.83kg/m

1 1/8 in 0.95 in2 110.2K 92.2K 1.26 in 3.25 lbs/lf

30 mm 720 mm2 575kN 480kN 34mm 5.65kg/m

1 1/4 in 1.12 in2 129.3K 107.9K 1.34 in 3.80 lbs/lf

35 mm 962 mm2 770kN 640kN 39mm 7.55kg/m

1 3/8 in 1.49 in2 173.1K 143.9K 1.54 in 5.07 lbs/lf

43 mm 1466 mm2 1170kN 980kN 47mm 11.51kg/m

1 5/8 in 2.27 in2 263.0K 220.3K 1.85 in 7.73 lbs/lf

57.5 mm 2597 mm2 2080kN 1740kN 62mm 20.38kg/m

2 1/4 in 4.03 in2 467.6K 391.2K 2.44 in 13.69 lbs/lf

63.5 mm 3167 mm2 2540kN 2120kN 68mm 24.38kg/m

2 1/2 in 4.91 in2 571.0K 476.6K 2.68 in 16.38 lbs/lf

tremied out by the cement grout. It is a clear advantage of this method that the drill hole isstabilized, and the ground cannot relax or cave, but to the contrary is grout penetratedand densified. Figures 8 and 13 show this on an exhumed pile.

The basic idea was, to produce a pile of very high capacity using small drilling equipment,which can operate in tight areas with limited overhead space inside buildings to underpinor seismic upgrade existing foundations (Figure 9).


Figure 8: Exhumed TITAN Pile

Figure 9: Limited overhead installation of TITAN micro piles.


Figure 10: Typical TITAN/IBO micro pile details


CTS-TITAN Hollow Bars Meets and Exceeds ASTM-A615 Specifications

Load Capacity Outside DiameterBar Size Ultimate Yield Test Design Design Effective Nominal

Weight

Dout/Din

Steel Area

G.U.T.S. 80% G.U.T.S. 70% G.U.T.S. 60% G.U.T.S.

mm in2 kips kips kips kips kips in in lbs./lf.

mm2 kN kN kN kN kN mm mm kg/m

30/16 0.59 49.5 40.5 39.6 34.6 29.7 1.02 1.18 2.02

382 220 180 176.0 154 132.0 26 30 3.00

32/20 0.69 58.5 47.2 46.8 40.9 35.1 1.10 1.26 2.30

445 260 210 208.0 182 156.0 28 32 3.42

30/11 0.69 76.0 63.0 60.8 53.2 45.6 1.03 1.18 2.35

446 338 280 270.4 236.6 202.8 26.2 30 3.50

40/20 1.00 114.7 96.7 91.7 80.3 68.8 1.42 1.57 3.60

644 510 430 408 357 306 36 40 5.35

40/16 1.36 148.4 123.2 118.7 103.9 89.0 1.42 1.57 4.64

879 660 548 528.0 462 396.0 36 40 6.90

52/26 2.07 208.9 164.2 160.1 146.2 125.3 1.92 2.05 7.06

1337 929 730 712.0 650.3 557.4 48.8 52 10.50

73/53 2.53 260.9 218.1 208.7 182.6 156.5 2.76 2.87 8.60

1631 1160 970 928.0 812 696.0 70 73 12.80

103/78 4.88 438.5 353.0 350.8 306.9 263.1 3.94 4.06 16.60

3146 1950 1570 1560.0 1365 1170.0 100 103 24.70

103/51 8.53 778.1 613.0 610.3 544.6 466.8 3.94 4.06 29.00

5501 3460 2726 2714.0 2422 2076.0 100 103 43.15

130/60 15.66 1585.5 1249.2 610.3 1109.9 951.3 4.96 5.12 53.09

10100 7051 5555 2714.0 4935.514 4230.4 126 130 79.00

MAI Hollow Bars Meets and Exceeds ASTM-A615 Specifications

Load Capacity Diameter Weight Rod Size

Ultimate Yield Test Design Design Inner Outer

Dout

Steel Area

G.U.T.S. 80% G.U.T.S. 70% G.U.T.S. 60% G.U.T.S.

mm in2 kips kips kips kips kips in in lbs./lf.

mm2 kN kN kN kN kN mm mm kg/m

R25N 0.51 45.0 33.7 36.0 31.5 27.0 0.47 0.98 1.75

330 200 150 160.0 140 120.0 12 25 2.60

R32N 0.69 63.0 51.7 50.4 44.1 37.8 0.71 1.26 2.35

444 280 230 224.0 196 168.0 18 32 3.50

R38N 1.18 112.4 96.7 89.9 78.7 67.5 0.75 1.50 4.03

761 500 430 400.0 350 300.0 19 38 6.00

R51N 1.89 179.9 141.7 143.9 125.9 107.9 1.34 2.01 6.45

1217 800 630 640.0 560 480.0 34 51 9.6

Table 6: Properties of CTS-TITAN hollow bars

Table 7: Properties of MAI hollow bars


Figure 11: CTS-TITAN hollow bars

Figure 12: CTS-TITAN special disposable drill bits for various grounds


Two types of hollow bars are available (see tables 6 and 7)

The CTS-TITAN Hollow Bars (table 6, figure 11), supplied by CON-TECH SYSTEMSLTD, in sizes up to 130 mm, 5 1/8” diameter with tension design load capacities in excessof 400 Tons. These bars are rolled with special continuous TITAN Threads for excellentbar to grout bond development. The bond development and crack width distribution ofTITAN bars in tension and embedded in cement grout, had been tested at the TechnicalUniversity of Munich in Germany. The results show, that at 125% of the maximum allow-able design load, the maximum crack width in the grout is less than 0.1mm. This is stillconsidered complete corrosion protection of the steel under the German Industry Norm(DIN). No additional corrosion protection is thus required.

For variable ground and load conditions, different drill bits (figure 12) are designed andavailable. For the TITAN IBO Micro Pile, venturi jet-grout holes in the drill bits allow the jetgrouting pressure to over-ream and pressurize the drill hole. Because of the continuoustremie-cement grouting operation, 100% grout cover can be guaranteed (figure 13).

The MAI Hollow Bars (table 7), supplied by DSI. These bars are rolled with a standardcontinuous Rope Thread (R-Thread).

All hollow bars are generally supplied in 10 foot lengths, (a standard length of a drill rodfor easier handling) spliced together with special couplers.

Figure 13: Section of exhumed TITAN / IBO micro pile

Densified Ground

Soil / Cement Mix

Neat Cement Grout

Hollow TITAN Bar


Another feature of the hollow bar is the possibility of adding an additional solid rebarinside the grout filled bar, or placing a strand tendon inside to apply an internal pre-stressforce to control elastic movement of the hollow bar (figure 14).

A special type of pile is used in California by Caltrans to upgrade existing viaduct founda-tions for seismic events. This pile consists of a steel pipe casing drilled through the over-burden. DCP, Double Corrosion Protected Strand tendons are placed through the pipeand anchored into the bedrock below. The pile is then vertically post-tensioned and castinto the foundation (figure 15).

Figure 15: Post-tensioned piles for seismic upgrading of bridge foundations (CalTrans).

Figure 14: Internal post-tensioningof TITAN micro pile.

CORROSION PROTECTIONIf, besides cement grout, additional corrosion protection is required, several methods areavailable:

1.) Hot Dip Galvanizing or Zinc-Metallizing

Steel bar components can be hot dip galvanized or metallized as per ASTM A-153(AASHTO M232). Zinc is a well known, common and relatively inexpensive coat-ing material for iron and steel. Zinc acts as a sacrificial anode, i.e. it corrodes in acorrosive environment and lets the steel play the role of the cathode. The high alka-linity of concrete and grout (pH > 12) dissolves the zinc to a certain extent, at pH <12 a very low corrosion rate of zinc occurs due to the development of a passivationfilm on the zinc surface. This film will stabilize if atmospheric CO2 reaches the sur-face of the zinc coating. This is the reason for the known durability of zinc coatingsunder open-air conditions.

Galvanizing requires tight control of coating thickness to assure threadability. In mostcases the thread inside the nuts or couplers has to be oversized, which could causea reduction in load capacity. We have found that by using the metallizing method,oversizing the threads is not necessary. Both methods, if properly applied to theASTM Standard, provide a good protective coating.

2.) Fusion bonded Epoxy Coating

Epoxy Coating shall conform to one of the following: ASTM A-934, ASTM A-775, orAASHTO No. M284. Applying this coating requires oversizing of the hardwarethreads. Care must also be taken not to damage the coating.

3.) DCP, Double Corrosion Protection System. (Not for hollow bars)

This method is mostly shop applied to solid Threadbars or All-Thread Bars. This Type


Figure 16: Corrosion protection: 1) Hot dip galvanizing, 2) Epoxy coating 3) DCP (left topto bottom) and DCP detail (right)

1)

2)

3)


of additional corrosion protection was part of the original Dywidag GEWI PILE andground anchor development and has found worldwide acceptance.

The bar is centered using spacers and is fully encapsulated inside a corrugated PVCor HDPE sheathing. The annular space between bar and sheathing must be a mini-mum of 5 mm (0.2 inch) thick and shop cement grouted.

The sheathing must have sufficient strength to prevent damage during constructionoperations, shall be watertight, chemically stable without embrittlement, softening,and nonreactive with concrete. The minimum sheathing wall thickness shall be 40mils. The material must conform to ASTM D-3350 polyethylene, Index No. 335520 C,Table 1, ASTM D-1248, and AASHTO No. M252 for HDPE or ASTM D-1784 Class13464-B for PVC.

The encapsulation shall be fabricated from material with the following properties:

� Capable of transferring stresses from the grout surrounding the tendon to thegrout in bond length

� Able to accommodate movements during testing and after lock-off;

� Resistant to chemical attack form aggressive environments;

� Resistant to aging by ultra-violet light;

� Non-detrimental to the tendon;

� Capable of withstanding abrasion, impact and bending during handling and instal-lation and

� Capable of resisting internal grouting pressures.

If steel bar couplers are used, they will be field installed with a double or multiple cor-rosion protection (DCP or MCP) system as per manufacturer instructions.

The cement grout inside the annular space between steel and corrugated sheathingis the most efficient element of corrosion protection. It must provide a proper alkalin-ity, low permeability, high resistivity, minimum to no shrinkage in both plastic andhardened states, proper fluidity, little or no segregation and no bleeding.

4.) Sacrificial Steel design method (see table 8 next page)

Is used primarily for oversizing pipe casing but can also be used for the pile rein-forcing bars. The ISCHEBECK Hollow TITAN Bars are tested in various non-aggres-sive, mild-aggressive and aggressive soils for loss of steel area over a 60 to 120 yeardesign life (see table 8). This method is extensively used in Europe and presentlystarted to be accepted in North America.


Corrosion Of Buried Metal

Taken from: TRL Report 380/1993Applied to: Ischebeck TITAN hollow groutable anchors

Sacrificial Steel MethodThe data and information can be used to determine the sacrificial steel thickness, if noadditional corrosion protection (metallizing, galvanizing, stainless steel) is used onCTS/TITAN IBO Bar anchors.

Bar Size CrossSectionmm2

GroundAggression

DiameterLossmm

ReducedAreamm2

% Loss DiameterLossmm

ReducedAreamm2

% Loss

30/16

30/11

40/16

52/26

73/53

103/53

382

446

879

1337

1631

3146

NoneMild

Aggressive

NoneMild

Aggressive

NoneMild

Aggressive

NoneMild

Aggressive

NoneMild

Aggressive

NoneMild

Aggressive

0.91.52.9

0.91.52.9

0.91.52.9

0.91.52.9

0.91.52.9

0.91.52.9

342318263

408384331

828794718

127112261124

153314691320

299829042688

10.517.031.0

8.514.026.0

5.89.7

18.3

5.08.3

16.0

6.010.019.0

4.77.7

14.6

1.52.54.9

1.52.54.9

1.52.54.9

1.52.54.9

1.52.54.9

1.52.54.9

318278190

384346261

794739613

12261153983

146914151112

290427502385

17.027.050.0

14.022.541.5

9.716.030.3

8.314.026.5

10.013.032.0

7.712.624.2

60 Years 120 Years

Table 8: Sacrificial steel method

ReferencesMicro Pile Design and Construction Guidelines: Implementation Manual, US Department ofTransportation - Federal Highway Administration, FHWA-SA-97-070, 2000.

Grouted Piles, DIN 4128 9.2, Deutsche Industrie Norm (German Industry Norm)

Crack Width Distribution in TITAN Anchors, Technical University Munich, Institute of CivilEngineering, Prof. Dr. Ing. K. Zilch and H.H. Mueller.

Corrosion of Buried Metal, TRL Report 380/1983, Great Britain, 1983.


micro piles

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