Ground anchors can be used for many applications in civil engineering and building projects in a wide variety of ground conditions. Cementation Skanska has extensive experience in the use of ground anchor systems and can provide a full in-house service, from design and installation to testing. Ground anchors generally range from 100kN to over 3,150kN, with lengths of up to 70m. Cementation Skanska has a comprehensive fleet of ground engineering drill rigs to install anchors using various drilling techniques.

1. Ground
Engineering
Datasheets
Anchors
Grouting
Minipiles
Soil Nails

2. Ground
Anchors
Technical Data
Applications
Typical examples of where ground
anchors may be used include:
Supports to bored pile walls
Stabilising marine structures
Cofferdams
Anti-flotation for deep structures
Tie backs to river and canal walls
Dam upgrading
Rock face stabilization
Strengthening of dock structures
Advantages
• Cost effective and
practical alternative to propping
• Provides open
excavation – removes obstacles
for bottom up construction
• Versatile form of earth retention
• High loads can be obtained
in relatively poor ground
Ground anchors can be used for many factory conditions. Various types of anchor are
• Can be used in a wide applications in civil engineering and available to suit a particular application.
variety of soil conditions
building projects in a wide variety of Permanent anchors incorporate full double
• Used to install ‘active’ ground conditions. corrosion protection via two concentric
forces into structures Cementation Skanska has extensive corrugated UPVC ducts. Depending on the
experience in the use of ground anchor design life, temporary anchors may
systems and can provide a full in-house incorporate a single duct, or no corrosion
service, from design and installation to protection at all. Removable anchors can be
testing. used where there are wayleave issues beneath
Anchor capacities generally range adjacent properties.
from 100kN to over 3,150kN, with Cementation Skanska have a
lengths of up to 70m. The capacity comprehensive fleet of ground engineering
achievable depends upon the quality of drill rigs ranging in weight from 1.5 to 12.0
the anchored ground and the number of tonnes. Anchor holes can be bored using a
tendons used. variety of drilling techniques including rotary,
A recent development has been the top-drive rotary percussive, down-the-hole
introduction of multistage anchors. These hammer, and augering. The type of drill rig
are used to improve efficiency and used will depend on the access, working room
achieve high loads in poor ground through and ground conditions.
the use of multiple discrete unit bond In difficult ground conditions simultaneous
lengths. drilling and casing systems can be employed
Tendons can be made of steel bar, wire to temporarily support the boreholes prior to
strand or GRP and are fabricated under installation of the anchors.
08/07/08
Rev 1

3. Ground
Anchors
Further information
Cementation Skanska
Maple Cross House
Denham Way
Maple Cross
Rickmansworth
Hertfordshire
WD3 9SW
United Kingdom
Tel: +44 (0)1923 423100
Fax: +44 (0)1923 423681
cementation@skanska.co.uk
www.skanska.co.uk
Offices
Head Office +44 (0)1923 423100
North +44 (0)1302 821100
South West, Midlands & Wales
+44 (0)1454 453200
Scotland +44 (0)1698 735899
Northern Ireland +44 (0)28 9024 2746
Republic of Ireland +353 (0)1296 0790
When the borehole is complete, the
anchor is either lowered into a pre-grouted
hole or post-grouted after installation
using an integral primary grout tube.
When the grout has achieved a
compressive strength of 30MPa the
anchor is stressed using a portable
hydraulic jack and locked off against a
head plate in accordance with BS8081.
Restressable head blocks with load
cells can also be provided for long term
monitoring and adjustment if required. †
08/07/08
Rev 1

4. Ground
anchors at
Rosyth Royal
Dockyard
Technical Data
Client
Ministry of Defence
Main contractor
Cementation Skanska
Skanska Construction
Engineer
Schal
Cementation Skanska together with However, due to the size and complexity of this
Skanska Construction were involved in project, Cementation, in ‘partnership’with
the design and installation of over 1,200 Dywidag Systems International (DSI), set up a
high capacity rock anchors to strengthen dedicated fabrication yard at Cementation’s
the entrance lock at the Royal Rosyth plant depot in Bentley Works, Doncaster.
Dockyard. Associated civils works were This gave greater control over the programming
carried out to replace the quayside subway and manufacture as well as significant cost
roofs and side walls. The aim of the savings for the client.
project was to bring the lock structure up All anchors incorporated full double corrosion
to the required seismic loading standards. protection in accordance with BS 8081.
Inclined anchors were installed at five Holes up to 30m deep were bored using six
different levels through the dock walls, Casagrande C6 rigs. The holes were
along with vertical anchors either side of constructed using down-the-hole hammer air
an existing subway at ground level. The flushed drilling techniques. Typical hole sizes
working load was generally 2,250kN (15 were 200mm nominal diameter for the 2,250kN
no. strands), with a smaller number anchors and 130mm nominal diameter for the
of450kN (3 no. strands anchors.) Ground 450kN anchors.
anchor tendons would normally be made
at an anchor manufacturer’s own facility A vital component of the construction process
and transported to site. were the temporary works platforms used to
access the holes along the dock walls. These
platforms consisted of portal towers supporting
Bailey Bridgedecks, allowing up to five
different levels to be utilised simultaneously.
11/07/08
Rev 2

5. Ground
anchors at
Rosyth Royal
Dockyard
Further information The platforms were moved by the use of a
wide range of mobile cranes. The
Cementation Skanska programming involved in moving these
Maple Cross House supports whilst maintaining a high level
Denham Way
Maple Cross
of production was key to the success of
Rickmansworth the project.
Hertfordshire
WD3 9SW The vertical anchors were drilled prior to
United Kingdom
Tel: +44 (0)1923 423100 removal of the subway roof. After
Fax: +44 (0)1923 423681 drilling, these were plugged to allow the
roof to be removed in advance of the
cementation@skanska.co.uk
www.skanska.co.uk anchor installation.
Offices The anchors were lifted into the boreholes
Head Office +44 (0)1923 423100
using mobile cranes. A neat O.P.C grout
North +44 (0)1302 821100
was batched on site using high shear The project was completed within the agreed
South West, Midlands & Wales
+44 (0)1454 453200
colloidal mixer/pump units. The grout was programme and budget, with successful
Scotland +44 (0)1698 735899
injected into the base of the bore using an installation and stressing of all of the anchors.
Northern Ireland +44 (0)28 9024 2746
integral primary grout tube within the This would not have been possible without the
Republic of Ireland +353 (0)1296 0790
anchor body. In accordance with BS8081, close co-operation of all parties on site.
the anchors were stressed after the grout
strength had reached 30MPa.
Access for stressing the dock wall anchors
was achieved using a purpose built
stressing platform suspended from a dock
running rail. Along with other operations
on this project extensive craneage was
used to move the jacking equipment into
position.
All stressing was carried out using DSI
jacks which incorporated an innovative
locking off stool within the jack itself.
This enabled test cycles and locking off to
be undertaken without jack removal thus
allowing a much quicker stressing
process.
Project logistics were complex and
required the interfacing of all operations
on site and liaison with other facets of the
dockyard activity. This continued
throughout the contract, including the
docking of a nuclear submarine during a
testing programme.
11/07/08
Rev 2

6. Grouting Grouting
Further information Awards Technical Data
Cementation Skanska’s proactive approach to
Cementation Skanska safety, quality and production has received Techniques
Maple Cross House recognition from within the industry in recent Bulk Infill Grouting
Denham Way years. Permeation Grouting
Maple Cross Compaction Grouting
Rickmansworth
Specifically, the Company has proven Compensation Grouting
Hertfordshire capability to design and carry out complex
WD3 9SW geotechnical projects and deliver them on time Applications
United Kingdom Bulk Infill
Tel: +44 (0)1923 423100
and within budget to their client’s satisfaction. † Old Coal Workings
Fax: +44 (0)1923 423681 Void Filling
cementation@skanska.co.uk Permeation Grouting
www.skanska.co.uk Shafts
Tunnels
Offices Excavations
Head Office +44 (0)1923 423100 Ground Stabilisation
North +44 (0)1302 821100
Compaction Grouting
South West, Midlands & Wales
Underpinning
+44 (0)1454 453200
Ground Stabilisation
Scotland +44 (0)1698 735899
Northern Ireland +44 (0)28 9024 2746 Compensation Grouting
Tunnelling
Republic of Ireland +353 (0)1296 0790
Settlement Prevention
Advantages
Bulk Infill
• Economic development of land
previously considered unsafe.
Permeation Grouting
• Ground improvement to ease
construction of basements.
• Eliminates unwanted
ground water.
Application of Grouting Techniques Bulk Infill/Ground Stabilisation
Cementation Skanska’s grouting Developers now seek to build new projects in
techniques can be used to provide a cost areas once deemed uneconomic due to their
effective solution to both temporary and poor ground conditions. In order to provide
permanent geotechnical problems. Voids, economic foundation solutions, ground
soft ground, settlement and water inflow stabilisation has become widely used for
are just a few obstacles encountered turning unsuitable soils into useful founding
where grouting solutions can be employed strata. The technique is often used in areas
to mitigate their effects during which have been heavily mined. Old workings
construction. Since the Company was are now in various states of distress and pose a
founded in 1920 Cementation Skanska has potential risk of collapse – with or without any
played a leading role in the development application of load from the surface.
of grouting solutions to stem water flow, Expensive mass blanket treatments may be
stabilise soils, improve ground bearing avoided by the effective use of detailed site
pressures and negate settlement. investigation and knowledge of the workings.
Effective grouting requires an Cementation Skanska can provide a value-
understanding of theoretical principles, engineered solution to enable further
accurate interpretation of ground development of the site.
characteristics, skilled application and
careful monitoring. Cementation Skanska Permeation Grouting
can draw on a wealth of experience and Basement construction, shaft sinking, dam cut-
resources to provide an effective grouting offs and tunnel excavations are all prime
solution tailored to the client’s needs. examples where the need for ground water
control is necessary.
08/07/08
08/07/08
Rev 1
Rev 1
4

7. Grouting Grouting
Permeation grouting relies upon the liquid most appropriate grout and delivery system.
Coefficient of permeability (m/s)
grout flowing through the soil, displacing Choice of grout
Compensation Grouting
-1 -2
water and gases by forcing them out as the 10 10 10-3 10-4 10-5 10-6 10-7
grout steadily advances. The grout must The excavation of tunnels produces settlement
Cement
be pumped steadily, taking care not to which can propagate to the surface and cause
disturb the soil structure. This is a critical structural damage to those structures which lie Grout with filler (PFA/sand)
operation and one which needs to be on or near their path. The philosophy of
Bentonite (or clay)/cement
controlled and monitored appropriately. compensation grouting is to reduce, or even
Cementation Skanska has custom prevent settlement by injecting relatively small Grout with improved penetrability
made computer-controlled grouting units quantities of grout between the source of the
to monitor and control flow and pressure Microfine cements
settlement, (the tunnel) and the foundations of
during specialist grouting operations. the structures that require protection. Silicate gel (high resistant gel)
Specific instructions can be set to control Typically, horizontal arrays of Tube a
each injection, and in turn each injection Manchettes are installed over the treatment Silicate gel (low resistant gel)
is recorded and downloaded immediately area which allow repeat injections at any one Resins
for the engineer to analyse. Grouting location. This allows multiple injections to be
demands full application of the made in areas where settlement is predicted or Ground conditions Coarse ground/scree/ Coarse pre-treated alluvial/fine
observational method, and electronic data has occurred. coarse alluvial/highly alluvial (sand & gravel, sands, silty
management of the grouting data fissured rock sands)/finely fissured rock
improves this iterative approach. Cost
effective grouting requires comprehensive
knowledge of the ground and ground
water conditions in order to select the An essential component of compensation
grouting is the monitoring of movements.
Precise levelling and electrolevel
monitoring of the ground and structures
overlying the tunnel provide key data to
designing the daily grouting instructions.
The data is collated and analysed using
our award winning software CemSMART
(formerly known as Surpoint +). Close
coordination and cooperation is essential
to the success of the works.
Plant and Resources
The Company’s plant depot and
workshops are centrally located in the UK
to provide first class support to sites and
projects throughout the UK. Bentley
Works is the traditional home of
Cementation Skanska and has grown into
the premier plant depot within the
industry. It houses and maintains the
largest fleet of specialist plant in the UK.
From the development of the
Cementation pump during the early
1920’s to the latest computerised grouting
units, Bentley Works.
08/07/08
08/07/08
Rev 1
Rev 1
2 3

8. Jet Grouting
Technical Data
Application
Structural
Ground improvement
Basement slabs
Excavation support
Underpinning
Tunnelling
Groundwater control
Dam cutoffs
Contaminated ground
Advantages
• Vibration free
• Applicable to a wide range
of ground conditions
• Slabs and supporting struts can
be formed below the
water table and before
bulk excavation
• Single process allows programme
advantages compared to
other techniques Jet grouting is a versatile and effective the ground and the placement and mixing of grout
• Predictability of in-situ strength technique which can be used across a wide in the soil. This method produces the most
and permeability range of ground conditions. It involves the in- homogeneous soil-cement element with the highest
situ mixing of soils with cement grout to form strength and the least amount of grout-spoil return,
a predetermined strength / permeability matrix. but can cause heave problems in certain ground
The inclusions formed by this process may be conditions.
used for structural support, or for the control of
groundwater. Double system - A two-phase internal system is
employed for the separate supply of grout and air
Process down to different, concentric nozzles. Grout is used
Cementation developed Jet Grouting in the for eroding and mixing with the soil. The air
1960's for ground water control applications in shrouds the grout jet and increases erosion
the Middle East and Africa. The process efficiency. The double system is more effective in
involves the insertion of a special drilling tool cohesive soils than the single system. However, the
to the required depth using a rotary drilling presence of the air reduces the strength of the
technique, followed by carefully controlled column as compared to the single system, and the
grout injection whilst rotating and air produces greater spoil returns.
withdrawing. The column is formed by the
action of the high pressure grout eroding the Triple system - Grout, air and water are pumped
in-situ ground perpendicular to the angle of through three different lines to the tool. High
insertion to a predetermined radius around the velocity coaxial air and water form the erosion
tool. The eroded material is mixed with the medium. Grout emerges at a lower velocity from
grout to form a soil-grout matrix. separate nozzles below the erosion jet. This
The strength and permeability of the somewhat separates the erosion process from the
columns can be controlled by the water / grouting process and yields a higher quality
cement ratio and the addition of admixtures to inclusion. The triple system is the most effective
the grout. The diameter of the columns is system for cohesive soils, and because the grout
controlled by the rotation and lift speed of the replaces a substantial portion of the eroded soil, it is
drill tool. less likely to cause heaving of the ground.
Jet grouting systems are traditionally
divided into three categories, depending on the Applications
number of injection nozzles and the medium Groundwater control - Often used for the control of
used to erode the soil: groundwater around dams or areas of contaminated
ground, the jet grouted columns are overlapped to
Single system - Grout is pumped down through form a continuous barrier of known thickness.
the drilling rods and exits horizontal nozzles in Ground permeabilites can be reduced to the order of
10-9 m/s.
08/07/08
the tool at high velocity. This causes erosion of
Rev 1

9. Jet Grouting
Further information Ground improvement - Columns are installed Tunnelling - Break out zones for tunnelling
on a regular grid to improved the global machines may be formed using overlapping
Cementation Skanska stiffness and bearing capacity of the soil mass. columns adjacent to launching chambers. This
Maple Cross House locally stabilises the ground, enabling the tunnelling
Denham Way Underpinning - The technique is extensively machine to complete the initial ring construction in
Maple Cross used for the improvement of existing shallow conditions of controlled water ingress and ground
Rickmansworth
Hertfordshire foundations. It is possible to drill through movement. The technique is also used to stabilise
WD3 9SW existing footings, forming a new jet grouted tunnel crowns during open face tunnelling methods.
United Kingdom column underneath. The small size of the plant
Tel: +44 (0)1923 423100 required means that it is ideally suited to Plant
Fax: +44 (0)1923 423681
congested city centre locations. Cementation Foundations Skanska's plant depot and
cementation@skanska.co.uk workshops are centrally located in the UK and
www.skanska.co.uk provide first class support to sites and projects
worldwide. Bentley Works is the traditional home
Offices
Head Office +44 (0)1923 423100 of the Company and has grown into the premier
North +44 (0)1302 821100
plant depot within the industry. It houses and
maintains the largest fleet of specialist plant in the
South West, Midlands & Wales
+44 (0)1454 453200 UK.
Scotland +44 (0)1698 735899 From the development of the Cementation pump
Northern Ireland +44 (0)28 9024 2746
during the early 1920's to the latest computerised
grouting units, Bentley Works ensures that contracts
Republic of Ireland +353 (0)1296 0790
are carried out with the best plant available.
Excavation support - Jet grouting can be used
to construct basement slabs and supporting
struts for deep excavations. Overlapping
columns can be formed below the water table
and before bulk excavation minimising access
constraints. Primary
A typical slab arrangement
Secondary
1 2 3 4 5
08/07/08
Rev 1

10. Teesport Tank
Af8b Stabilisation
Technical data
Client
Huntsman Petrochemicals Limited
Main Contractor
Cementation Foundations Skanska Limited
Engineer
ABB Eutech
Contract Value
£0.25m
Commencement Date
August 2001
Construction Period
10 weeks
Site Address
Huntsman Petrochemical
Teesport The tanks were constructed circa 1960 and risk the integrity of containment. However
Contact in July 2000 ground settlement was noticed of greater concern was that the settlement
Philip Ball in the concrete floor and drainage channel might develop to impair the stability of tank
of the containment bund, just to the west of Af8b. In view of the concerns expressed
tank Af8b. Precise-level monitoring carried Huntsman approached specialist contractors
out revealed that further settlement was including Cementation Foundations
continuing to occur reaching a maximum of Skanska to design and price ground
46mm by mid-February 2001. stabilisation schemes with the objective of
Investigations conducted by Huntsman achieving long term stability of tank Af8b
and their consultants ABB Eutech revealed and the containment bund by grouting voids
that the settlement appeared to be the result in the rubble fill. Included in the contract
of movements within brick and concrete would also be the repair/replacement of the
rubbble used to infill a large hole in the damaged concrete elements of the bund to
ground which existed some time prior to the achieve integrity of containment.
construction of the tanks. The hole was It was not considered necessary or
present within the approximately 6m thick economic to grout the rubble fill over the
layer of generally slag fill, derived from the whole of it’s plan area and the specialist
nearby steel works, which had been used to contractors were invited to propose means
reclaim the site in the early 20th century. of limiting the spread of grout within the
The hole itself was believed possibly to rubble fill while still attempting to
have been created by a bomb dropped on adequately fill the voids present within the
the area during the Second World War. The rubble. Further requirements were that the
hole was believed to have been back-filled spread of grout within the surrounding
with materials arising from the demolition general slag fill should also be limited and
of nearby buildings in 1948. that the cost of the project should be
The settlements experienced appeared to minimised.
be limited to the concrete bund but put at The successful design prepared by
08/70/08
Rev 1

11. Teesport Tank
Af8b Stabilisation
Further information Cementation Foundations Skanska (see assess the effectiveness of the grouting as
inset picture) was based on the construction work proceeded. Test holes were also
Cementation Foundations Skanska
PO Box 293 of a grout curtain around the treatment area, successfully drilled and grouted.
Bentley Works The grouting works were completed in
where it was practical to do so, in order to
Pipering Lane
Doncaster minimise the spread of grout beyond the November 2001 ahead of programme and
South Yorkshire
DN5 9RX
designated treatment areas, followed by within the budgets set. This permitted the
Tel: 01302 820888 bulk infill grouting to minimise the removal of the previously distressed areas
Fax: 01302 793203
subsequent grout takes during tube-a- of concrete slab and reconstruction, along
cementations@skanska.co.uk manchette (TaM) grouting conducted in with additional works instructed during the
www.skanska.co.uk
grout holes raked directly beneath the tank. course of the contract, to be completed
Offices The drilling of the grout injection holes within the 14 week tender programme.
Head Office +44 (0)1923 423100
and the installation of the TaMs were In August 2001 Cementation
North +44 (0)1302 821100
carried out using a Casagrande C6 drilling Foundations Skanska were awarded a
South West, Midlands & Wales
+44 (0)1454 453200 rig employing rotary and rotary percussive ground stabilisation contract by Huntsman
Scotland +44 (0)1698 735899 water flush open hole and cased drilling Petrochemicals Limited at their Teesport
Northern Ireland +44 (0)28 9024 2746 techniques. The grout curtain construction Storage Site. This Storage Site is situated
Republic of Ireland +353 (0)1296 0790 and bulk grouting works were completed within the extensive Teesport Docks
using one of Cementation’s modular bulk complex on the south bank of the River
grouting stations and the TaM grouting Tees near Middlesborough, Cleveland.
using one of the Company's containerised Within the site are two large hydrocarbon
TaM grouting units. Throughout the storage tanks used for storing cyclohexane.
grouting the injection pressures and Each tank is approximately 24.6m in
volumes were carefully controlled to diameter and 14.4m high with a storage
3
minimise unnecessary grout travel, grout capacity of approximately 6,00 m per tank.
wastage and possible damage to the tank, Each of the tanks is surrounded by, and
bund or other facilities structures. contained within, a reinforced concrete
Before, during and after the drilling and bund with the bund wall approximately
grouting works a network of precise level 1.5m high.
points and electrolevel beams installed in
conjunction with Cementation's Field Data
Acquisition Department (FDAD) were also
directly and remotely monitored to ensure
that distress was not caused to the
structures. Altogether over 1200 tonnes of
PFA, cement, sand and bentonite were
injected during a nine week site works
period in order to stabilise the designated
areas. As work proceeded the respective
grout takes of the primary, secondary and
tertiary holes and the phases of TaM
injections were monitored and compared to
08/70/08
Rev 1
2

12. Minipiles
Technical Data
Application
Can be used in most types of soil.
Ideal for underpinning or
strengthening of existing
structures, internally
and externally.
Used to construct retaining walls,
high capacity small diameter piles,
slope stabilization, high capacity
small diameter tension piles.
Advantages
• Can work within low headroom
in restricted working conditions
• Virtually vibration free
• Ability to bore through masonry
or concrete foundations
• Permanent liners can be
incorporated as steel
reinforcement or through
very soft strata
Cementation Skanska is one of the world
leaders in piling and ground engineering.
Since it was founded in 1920 the company
has continually pioneered the research,
development and implementation of
numerous geotechnical solutions.
One of these techniques is the grouted
minipile which has been used successfully
for over 25 years.
Cementation Skanska offers a full in-
house service, from advice through to
detailed design and construction of
complex foundation packages. Mini piling
can also be used in conjunction with many
of our other processes.
Process
A mini pile generally has a diameter of
between 100 and 450mm and can extend
to depths of over 50m. Either a
reinforcing cage, circular hollow section
or a centralised re-bar may be used. The
Company can offer high capacity mini
piles with SWLs of up to 1,200 kN.
Some typical situations where mini piles
may be used include:
02/07/08
Rev 2

13. Minipiles
Further information • Provision of high capacity small
diameter piles.
Cementation Skanska • Underpinning or strengthening of
Maple Cross House existing structures both externally
Denham Way
Maple Cross
and/or internally.
Rickmansworth • Slope stabilisation works.
Hertfordshire • Construction of propped or
WD3 9SW
United Kingdom unpropped retaining walls.
Tel: +44 (0)1923 423100 • To resist hydrostatic uplift pressures.
Fax: +44 (0)1923 423681
cementation@skanska.co.uk
www.skanska.co.uk
Offices
Head Office +44 (0)1923 423100
North +44 (0)1302 821100 • Construction within restricted working
South West, Midlands & Wales areas and/or low headroom.
+44 (0)1454 453200 • Working within existing premises with
Scotland +44 (0)1698 735899 minimal disruption to other operations.
Northern Ireland +44 (0)28 9024 2746 • Low vibration.
Republic of Ireland +353 (0)1296 0790 • Remote power packs can be used to
further reduce noise and fumes within
enclosed areas.
• Permanent liners can be incorporated
through very soft ground conditions. †
Equipment
Cementation Skanska has a fleet of mini
pile drill rigs ranging in size from 1.5 to
12 tonnes. This plant is extremely
versatile and the smaller rigs can travel
through internal doorways. Piles may be
vertical or raked and can also be pressure
grouted for increased capacity if required.
Drilling techniques include case and
auger, rotary duplex and top or bottom
driven rotary percussive.
Some advantages of the grouted mini pile
are:
• Ability to bore through variable and
difficult ground conditions.
02/07/08
Rev 2

14. Large
Diameter
Bored Piles
Technical Data
Application
Can be used in a wide
range of strata.
Where non-cohesive or water
bearing soils exist temporary
casings and/or bentonite or
polymer suspension can be used
to progress the bores.
Diameters range from 600mm
to 3000mm with pile depths
up to 70 metres and maximum
working loads of 20,000kN
for straight-shafted piles
or 30,000kN for
under-reamed piles.
Advantages
• High load capacity
• Can be used with CEMLOC® to
plunge structural steel columns
• In stiff clays under-reamed
bases can be formed
to increase pile capacity
• Depending on ground
conditions, pile concrete can
be terminated below piling
platform level.
Patents
UK Serial No. 2138033 Class 7, 37
UK Patent No. 2373801
US Patent No. 6739412
UK Patent No. 2362665
Trade Mark Cementation Skanska has a wide range of can impart a vertical load on to the kelly bar to
CEMLOC® piling rigs within the plant fleet, including improve production in difficult strata.
crane-based units, and all-hydraulic In addition to installing vertical piles, rigs
purpose-built mast machines. Both are can install raking piles, up to 1:4 rake, without
suitable for the construction of large modification.
diameter cast-in-situ piles.
Mast machines are self-erecting. Depths
Establishment time on site is shorter than Kelly bars can be of single or telescopic
for crane-mounts and for contracts with construction. Standard triple telescopic kelly
small sites and/or few piles, this can be an bars allow for depths of up to 55m.
advantage. The crane-mounts are more Exceptionally, when required, extended triple
suitable for the larger diameter and deeper telescopic kelly bars can reach to 70m below
pile range. ground.
All of the rigs are fitted with a rotary
boring unit which operates a kelly bar. Boring Tools
The boring tools are fitted to the kelly bar. Boring tools are available to cope with
This equipment has been used to construct different strata. The range includes general
large diameter piles in a wide range of purpose augers, rock augers, boring bucket and
strata, including very soft silty clays, non- coring barrels amongst others.
cohesive soils and weak rocks. The rigs
02/07/08
Rev 2

15. Large
Diameter
Bored Piles
Further information
Cementation Skanska
Maple Cross House
Denham Way
Maple Cross
Rickmansworth
Hertfordshire
WD3 9SW
United Kingdom
Tel: +44 (0)1923 423100
Fax: +44 (0)1923 423681
cementation@skanska.co.uk
www.skanska.co.uk
Offices
Head Office +44 (0)1923 423100
North +44 (0)1302 821100
South West, Midlands & Wales
+44 (0)1454 453200
Scotland +44 (0)1698 735899
Northern Ireland +44 (0)28 9024 2746
Republic of Ireland +353 (0)1296 0790 Standard sizes of boring tools range from In both situations it is often practical to
600mm to 1800mm in increments of terminate the concrete at a low level. This is
150mm, and thereafter in increments of typically used for top-down construction of
300mm up to 3000mm. deep basements. In this situation it is possible
In suitable strata it is possible to for a steel column to be plunged into the head
construct a dry bore; in water-bearing of the concrete. Our unique CEMLOC®
strata it is often necessary to progress the equipment can be used to position the columns
bore under flooded conditions, i.e water, to structural steel tolerances.
bentonite or polymer.
Pile Load Bearing Capacity
Concrete Depending on ground conditions pile loads of
Concrete grades up to 40N/mm2 are 20,000kN or greater can be safely carried on
common, and higher grades can be used straight-shafted piles.
where necessary. Special tools are available to form enlarged
Where the pile bore is dry, a hopper bases or "under-reamed" piles in suitable
with a short tube is used to direct the strata, typically stiff clays. Under-ream
concrete down the centre of the diameters are usually specified in increments
reinforcement. Under flooded conditions a of 150mm, and diameters of 5400mm or
full-length tremmie pipe is used. greater can be provided. Piles of 30,000kN
capacity have been formed in London clays
using under-reamers. †
02/07/08
Rev 2

16. Slope
Stabilisation
Technical Data
With a wide range of experience, Infrastructure Embankments and
expertise and foundation techniques at its Cuttings
disposal, Cementation Skanska is able to
offer a solution to nearly all slope The constantly increasing demands upon
stabilisation problems. railway and highway infrastructure are
necessitating renewal and remediation
The term "slope stabilisation" is relevant works to both cuttings and embankments.
to the stabilisation of both existing slopes Remediation processes implemented by
and new excavations, in either natural or Cementation Skanska have comprised
man-made ground conditions. both hard (or mechanical) stabilisation
solutions, such as bored and mini-pile
Examples of situations requiring walls and ground anchors, and soft
stabilisation include: solutions such as lime stabilisation,
gabions, drainage, mix-in-place grout
• infrastructure embankments and logs, reinforced soil and regrading of
cuttings slopes in combination with revegetation.
• excavations
• existing retaining walls
• tunnel portals
• natural slopes
• cliff faces.
The range of techniques that can be
applied is as necessarily diverse as the
range of problems and includes ground
anchors, soil nails, minipiles, bored piles,
lime stabilisation, drainage, earthworks
and vegetation.
08/07/08

17. Slope
Stabilisation
Further information Excavations In-situ retaining walls (e.g. reticulated
minipiles & contiguous bored piles), soil
Cementation Skanska Excavations for new developments often nails and ground anchors can be used to
Maple Cross House require support in the temporary stabilise slopes in this situation. Drainage
Denham Way condition, before a permanent retaining
Maple Cross
measures assist with the stabilisation
Rickmansworth
structure is constructed. Where process by reducing the disturbing forces.
Hertfordshire appropriate the temporary support can be
WD3 9SW incorporated within the permanent works
United Kingdom
Cliff Faces
Tel: +44 (0)1923 423100
leading to cost savings. Cementation
Fax: +44 (0)1923 423681 Skanska can offer a range of methods to There is a significant number of cliff faces
support excavations. These include soil in the UK that border on an unstable
cementation@skanska.co.uk
www.skanska.co.uk
nailing, anchoring, mini-piling and condition and their failure could be
guniting. Such methods often produce not detrimental or dangerous to adjacent
Offices only cost effective solutions but clear and properties. The stabilisation of cliff faces
Head Office +44 (0)1923 423100 open excavations. can be effected by a variety of methods;
North +44 (0)1302 821100
however, access is usually the prime
South West, Midlands & Wales
+44 (0)1454 453200 consideration in proposing the most
Existing Retaining Walls appropriate method.
Scotland +44 (0)1698 735899
Northern Ireland +44 (0)28 9024 2746
Existing retaining walls, which are in an Cementation Skanska
Republic of Ireland +353 (0)1296 0790
unstable condition can be stabilised by the
use of ground anchors or soil nails, where With an extensive range of foundation
ground conditions are appropriate. These techniques and technical support at its
methods of renovation are generally less disposal, Cementation Skanska is equally
disruptive than demolition and able to tackle minor stabilisation works, or
subsequently more cost effective. major design and construct packages, with
Cementation Foundations Skanska has the degree of quality, safety and reliability
carried out the remediation of several expected of the UK’s leading foundation
existing reatining walls ranging in height and ground engineering contractor.
from 3m to 6m.
Tunnel Portals
Access for tunnel headings often require
excavation into an existing slope. Where a
portal is being constructed in soil it is
usually necessary to stabilise the
surrounding soil either by soil nailing
and/or some form of retaining wall and
anchoring. Anchored or reticulated mini
pile walls have successfully been used in
this situation by Cementation Foundations
Skanska for retained heights of up to 15m.
Natural Slopes
Natural slopes can often creep due to
changes in ground water conditions, the
existence of residual shear surfaces, or a
combination of both.
08/07/08

18. Soil Nails
Technical Data
Applications
Slope stabilisation
Vertical or battered cuttings
Embankments
Support to existing
or new gravity walls
Can be used for
both permanent and
temporary applications
Advantages
• Cost effective
• Quicker than alternative
retention methods
• Small rigs can achieve access to
difficult and tight locations
• Working space requirements
are less than for normal piling rigs
• Excavation and construction of
wall progresses concurrently
• Provides open excavation
• Can be used in a variety
of soil conditions
Soil nailing forms part of the The nails are installed using a variety of
comprehensive range of ground processes, including driving or drilling and
engineering processes designed and grouting. Access requirements often dictate the
constructed by Cementation Skanska. method and plant used. The most frequently
Developed in the late 1960’s, nailing has used method is that of drilling and grouting, as
since been widely used throughout the it copes with a large variety of ground
world. It is a slope stabilisation process conditions. It also has the advantage of
that utilises arrays of fully bonded passive mobilising high bond stresses between the soil
ties installed in the ground. These are and nail, and facilitates the installation of
usually grouted bars, made from steel, corrosion protection measures.
stainless steel or glass fibre. For shallower slopes, vegetation is often
The technique can be cost effectively adequate to stabilise the face. As the angle
employed to create both temporary and becomes progressively steeper, the use of a
permanent cuttings. It can also be used to geogrid in combination with seeded mats or
support slopes or to repair slipping ultimately reinforced sprayed concrete is used.
embankments and gravity walls. The facing is held in place by plates bolted
Soil nails tend to work best when onto the threaded ends of nails.
installed in granular materials, but are also Drainage measures are also provided if
commonly employed in soft rocks and deemed necessary to maintain long term
stiff clays. stability and to reduce the potential for
sloughing of the surfaces.
08/07/08
Rev 1

19. Soil Nails
Further information The process is designed to improve the
strength and deformation characteristics
Cementation Skanska of the existing ground. It is similar to
Maple Cross House reinforced fill techniques in that the soil
Denham Way nails generate tensile forces in response to
Maple Cross
Rickmansworth slope deformation. This is in contrast to
Hertfordshire ground anchors that are intentionally
WD3 9SW stressed to minimise ground deformations.
United Kingdom
Tel: +44 (0)1923 423100 Soil nails are normally designed to
Fax: +44 (0)1923 423681 operate with working loads in the range
25kN to 100kN.
cementation@skanska.co.uk
www.skanska.co.uk Long term monitoring of full-scale
structures has increased Cementation
Offices Skanska’s fundamental understanding of
Head Office +44 (0)1923 423100
soil nail design. Load testing of soil nails
North +44 (0)1302 821100
is often a design requirement and the
South West, Midlands & Wales
+44 (0)1454 453200
Company has the capability to carry out
Scotland +44 (0)1698 735899
both manual and fully automated soil nail
Northern Ireland +44 (0)28 9024 2746
pullout tests. †
Republic of Ireland +353 (0)1296 0790
08/07/08
Rev 1

20. Soil Nails at
Ebbsfleet
Technical Data
Client
Union Rail
Main Contractor
Hochtief/Norwest Holst JV
Engineer
Rail Link Engineering
Further information
Cementation Skanska
Maple Cross House
Denham Way
Maple Cross
Rickmansworth
Hertfordshire
WD3 9SW
United Kingdom
Tel: +44 (0)1923 423100
Fax: +44 (0)1923 423681
cementation@skanska.co.uk
www.skanska.co.uk
Offices
Head Office +44 (0)1923 423100
North +44 (0)1302 821100
South West, Midlands & Wales Soil nailing was used at two locations on The second location where soil nails were used
+44 (0)1454 453200 the Ebbsfleet project. was at the Pepper Hill junction of the A2
Scotland +44 (0)1698 735899 The first application was to allow where improvement works were carried out for
Northern Ireland +44 (0)28 9024 2746 construction of a wing wall to bridge the Highways Agency. Permanent corrosion
Republic of Ireland +353 (0)1296 0790 3590. This involved installation of 11m protected nails of 3-6m in length were
long fully corrosion protected nails installed through embankment fill and chalk.
through rock fill, made ground and chalk The face of the cutting was at 50° to the
to form a near vertical triangular shaped vertical and was stabilised using a flexible
cut. Sprayed concrete was used to facing (comprising double twist galvanised
provide temporary face stability, followed wire mesh). For both sites comprehensive
later by permanent cast-in-situ concrete testing was carried out. †
wing wall to provide a compatible
architectural appearance to other wing
walls for the bridge.
08/07/08
Rev 1

21. Cementation Skanska
Maple Cross House
Denham Way
Maple Cross
Rickmansworth
Hertfordshire
WD3 9SW
Tel: 01923 423100
www.skanska.co.uk