Kelly-drilled bored piles: a comparison of construction practices between Europe and North America

Figures & data

Table 1 Select statistics about Europe and North America

		North America
	Europe	U.S.	Canada	Total
Composition	51 countries	50 states 5 territories	10 provinces 3 territories	60 states/provinces 8 territories
Languages	±35 official	1 official	2 official	3 official
Population	742 million	319 million	35 million	354 million
Area (mile^2) (km^2)	3.94 million (10.2 million)	3.81 million (9.86 million)	3.85 million (9.99 million)	7.66 million (19.85 million)
Population Density	188.3 ppl mi^–2 72.75 ppl km^−2	83.7 ppl mi^−2 32.4 ppl km^–2	9.1 ppl mi^–2 3.5 ppl km^–2	46.2 ppl mi^–2 17.8 ppl km^–2

(Sources: European Commission 2015; Government of Canada 2015; United States Census Bureau 2015; United States Government 2015).

1 Truncated map of North America. The regions used for the initial survey are delineated (modified from Cartographic Research Lab, University of Alabama 2015)

2 Map of Europe highlighting the countries from where responses to the initial survey were received (modified from Cartographic Research Lab, University of Alabama 2015)

3 Photograph of bored piles being constructed in a confined and congested work site (photo courtesy of Soilmec S.p.A.)

Table 2 Reported historical usage of different contracting mechanisms on projects incorporating Kelly-drilled bored piles – public and commercial projects (data source: initial survey)

	No. of responders	Design-Bid-Build	Design-Build	Private–public partnerships	Quality-Based Evaluation
Europe
Germany	5	4	4	2	2
France	1	1	1	…	…
Hungary	1	1	1	…	1
Italy	1	1	1	1	1
Netherlands	3	3	3	2	1
Switzerland	1	1	1	…	…
United Kingdom	6	4	5	4	2
North America
Canada	1	1	1	…	…
United States	81	76	60	26	21

Table 3 Reported usage of four different contracting mechanisms by owners on projects incorporating Kelly-drilled bored piles – public and commercial projects (data source: supplemental survey)

	No. of responders	Design-Bid-Build	Design-Build	Private–public-partnerships	Quality-Based Evaluation
Public projects
Europe	8	50–60%	50–60%	20–25%	20–25%
North America	8	90–95%	20–25%	10–15%	5–10%
Commercial projects
Europe	8	35–40%	70–80%	15–20%	20–25%
North America	8	90–95%	25–30%	<5%	15–20%

Table 4 Reported amount of Kelly-drilled bored pile work performed by contractors on public and commercial projects (data source: initial and supplemental surveys)

	No. of responders	0%	1–25%	26–50%	51–75%	76–99%	100%
Public projects
Europe	13	0	3	4	2	4	0
	Average = 60–65%
North America	67	0	17	16	15	12	7
	Average = 65–70%
Commercial projects
Europe	13	0	6	1	5	1	0
	Average = 50–55%
North America	67	6	12	18	14	16	1
	Average = 60–65%

Table 5 Reported influences or drivers for deciding equipment acquisition and construction method used on projects incorporating Kelly-drilled bored piles – public and commercial projects (data source: initial survey)

	Specifications drive equipment acquisition	Equipment dictates construction methods	Site conditions dictate the construction method
Public and commercial projects
Europe	0%	20–25%	75–80%
North America	0%	20–25%	75–80%

Table 6 Reported usage of different diameters of Kelly-drilled bored piles on public and commercial projects (data source: supplemental survey)

		Diameter
	No. of responders	24–48 in (0.61–1.21 m)	48–72 in (1.21–1.83 m)	72–96 in (1.83–2.44 m)	96–120 in (2.44–3.05 m)	>120 in (>3.05 m)
Public projects
Europe	8	70–75%	30–35%	20–25%	5–10%	0%
North America	8	55–60%	35–40%	35–40%	30–35%	15–20%
Commercial projects
Europe	8	70–75%	30–35%	20–25%	10–15%	0%
North America	8	55–60%	40–45%	30–35%	20–25%	10–15%

Table 7 Reported usage of different lengths of Kelly-drilled bored piles on public and commercial projects (data source: supplemental survey)

		Length
	No. of responders	10–25 ft (3–7.6 m)	25–50 ft (7.6–15.2 m)	50–100 ft (15.2–30.5 m)	100–150 ft (30.5–45.7 m)	150–200 ft (45.7–61 m)	>200 ft (61 m)
Public projects
Europe	8	15–20%	30–35%	50–55%	35–40%	25–30%	15–20%
North America	8	35–40%	55–60%	40–45%	15–20%	15–20%	<5%
Commercial projects
Europe	8	15–20%	40–45%	45–50%	25–30%	25–30%	15–20%
North America	8	40–45%	50–55%	40–45%	10–15%	<5%	0%

4 Photographs of different styles of drilling equipment: a European-style, hydraulic drill rig and b European-style crane attachment drill rig (photographs courtesy of Soilmec S.p.A.)

5 Photographs of different styles of drilling equipment: a truck-mounted, b excavator mounted and c North American-style crane attachment (photographs courtesy of A.C. Kraut at Watson Inc.)

Table 8 Reported average usage (ownership and rental) of different track-mounted rotary drilling equipment used to construct Kelly-drilled bored piles on public and commercial projects (data source: supplemental survey)

		Tracked Kelly bar drill rig
	No. of responders	<20 tons (18 tonne)	20–40 tons (18–36 tonne)	40–55 tons (36–50 tonne)	55–70 tons (50–64 tonne)	>70 tons (64 tonne)
Public and commercial projects
Europe	8	0%	10–15%	30–35%	35–40%	50–55%
North America	8	10–15%	20–25%	40–45%	30–35%	25–30%

Table 9 Reported average usage of different construction methods used to advance and/or stabilise a borehole for Kelly-drilled bored piles on public and commercial projects (data source: initial survey)

		Open hole		Cased hole
	No. of responders	Open hole – no slurry	Open hole – with slurry	Placed in oversized hole	Using drilling equipment/oscillator	Casing vibrated in
Public and commercial projects
Europe	10	5–10%	25–30%	5–10%	20–25%	20–25%
North America	68	40–45%	35–40%	40–45%	15–20%	20–25%

Table 10 Reported average usage of different open hole, temporary cased hole and permanently cased hole approaches used to advance and/or stabilise a borehole for Kelly-drilled bored piles on public and commercial projects (data source: supplemental survey and conversations)

		Open hole			Temporary cased hole
	No. of responders	No slurry	With polymer slurry	With mineral slurry	In oversized hole	Using drilling equipment/oscillator	Casing vibrated in
Public projects
Europe	8	10–15%	20–25%	35–40%	25–30%	50–55%	10–15%
North America	8	25–30%	25–30%	10–15%	50–55%	20–25%	35–40%
Commercial projects
Europe	8	10–15%	20–25%	35–40%	25–30%	45–50%	10–15%
North America	8	25–30%	30–35%	15–20%	40–45%	20–25%	45–50%
		Permanent cased hole
	No. of responders	Using drilling equipment/oscillator	Casing vibrated in
Public projects
Europe	8	10–15%	10–15%
North America	8	15–20%	30–35%
Commercial projects
Europe	8	10–15%	5–10%
North America	8	10–15%	25–30%

Table 11 Reported use of permanent casing (excluding for top/surface casing) with Kelly-drilled bored piles on public and commercial projects (data source: supplemental survey)

	No. of responders	In karst formations	For scour protection	Incr. structural strength	For impact resistance	Quality concerns
Public and commercial projects
Europe	8	15–20%	15–20%	15–20%	<5%	15–20%
North America	8	10–15%	30–35%	10–15%	15–20%	10–15%
	No. of responders	Casing through abandoned mines	Super-structure formwork	Casing through water (e.g. bridge piers)	Incr. lateral resistance (seismic loading)
Public and commercial projects
Europe	8	10–15%	5–10%	25–30%	<5%
North America	8	5–10%	20–25%	25–30%	30–35%

Table 12 Reported responsibility to provide the minimum 28-day design compressive strength and the design mix for the concrete used in Kelly-drilled bored piles on public and commercial projects (data source: supplemental survey)

		Owner		Contractor
	Total no. of responders	Provides strength only	Provides strength and mix	In-house engineer provides strength only	Engineer hired to provide strength and mix
Public projects
Europe	8	40–45%	15–20%	55–60%	5–10%
North America	8	35–40%	75–80%	5–10%	10–15%
Commercial projects
Europe	8	35–40%	15–20%	65–70%	5–10%
North America	8	45–50%	40–45%	10–15%	15–20%

Table 13 Reported usage of different minimum 28-day design compressive strengths for the concrete used in Kelly-drilled bored piles on public and commercial projects (data source: supplemental survey)

		Minimum 28-day compressive strength of the concrete mix
	No. of responders	3000 psi (20.7 MPa)	4000 psi (27.6 MPa)	5000 psi (34.5 MPa)	6000 psi (41.4 MPa)	≥7000 psi (48.3 MPa)
Public projects
Europe	8	10–15%	40–45%	55–60%	25–30%	5–10%
North America	8	20–25%	75–80%	40–45%	10–15%	5–10%
Commercial projects
Europe	8	10–15%	40–45%	60–65%	25–30%	5–10%
North America	8	20–25%	85–90%	30–35%	15–20%	5–10%

Table 14 Reported responsibility for on-site quality control and quality assurance of the work pertaining to Kelly-drilled bored piles on public and commercial projects (data sources: original and supplemental surveys)

	No. of responders	All QA/QC resp. of owner	QC resp. of owner; QA resp. of contractor	All QA/QC resp. of contractor
Public projects
Europe	18	25–30%	10–15%	55–60%
North America	70	30–35%	60–65%	<5%
Commercial projects
Europe	18	20–25%	10–15%	60–65%
North America	70	40–45%	35–40%	25–30%

Table 15 Reported use by contractors of different repair methods for Kelly-drilled bored piles on public and commercial projects (data sources: original and supplemental surveys)

	No. of responders	Full replacement	Drill-and-grout	Add'l steel reinforcement	Dental concrete	Pile-in-pile
Public and commercial projects
Europe	18	70–75%	65–70%	30–35%	20–25%	<5%
North America	78	75–80%	60–65%	15–20%	5–10%	5–10%

Table 16 Reported effect of safety regulations on cost, technique selection and/or installation of Kelly-drilled bored piles on public and commercial projects (data sources: original and supplemental surveys)

	No. of responders	Hoisting	Hours of work	Downhole inspection	Downhole cleaning	Ground vibrations	Silica exposure	Hazardous materials
Public and commercial projects
Europe	8	15–20%	20–25%	5–10%	10–15%	10–15%	5–10%	5–10%
North America	8	15–20%	15–20%	10–15%	10–15%	5–10%	5–10%	5–10%

Table 17 Select environmental restrictions on the Cityringen project in Copenhagen, Denmark (source: M. Chiarabelli, Soilmec S.p.A.)

Item	Restriction
Noise	Full jobsite containment wall 4 m tall made of recycled and green materials and with sound absorption construction. Sound level limits (8-h) were 80 dB for workers, and highest level allowed in neighbourhood was 70 dB in daytime and 40 dB at night
Dust	Wheel washers were installed at all jobsites to minimise the presence of dust on the roads. Watering units were used inside the job site to reduce dust
Subsidence	Vulnerability of some structures required full time laser and video monitoring of subsidence. Twenty-four hour monitoring system was used to detect and immediately react at any settlement of more than 0.1 mm (0.004 in.)

Table 18 Reported influence and effect of select environmental restrictions on construction techniques used with Kelly-drilled bored piles on public and commercial projects (data sources: initial and supplemental surveys)

	No. of responders	Noise/dust	Emissions	Drill spoil/slurry disposal	Water runoff	Ground vibrations	Concrete/slurry pH
Public and commercial projects
Europe	18	85–90%	10–15%	60–65%	10–15%	70–75%	15–20%
North America	76	50–55%	10–15%	55–60%	5–10%	50–55%	25–30%

European Commission 2015. Eurostat. <http://ec.europa.eu/eurostat>.

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Government of Canada 2015. Statistics Canada. <http://www.statcan.gc.ca/start-debut-eng.html>.

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United States Census Bureau 2015. <http://www.census.gov/>.

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United States Government 2015. Data and Statistics about the U.S. www.usa.gov/statistics.

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University of Alabama 2015. Cartographic Research Lab, Department of Geography.

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