Introduction

Van Elle is an award-winning, multi-discipline specialist ground engineering contractor

working in all sectors to deliver ground-breaking geotechnical solutions using the

world’s most reliable, efficient and innovative plant.

Our rotary capability, experience and range of rigs is extensive, enabling us to install

piles of all depths and diameters. We regularly design temporary cased rotary secant

piled and contiguous piled retaining walls allowing for tighter vertical tolerances

compared to that of traditional or cased CFA solutions.

Rotary bored piles are formed by

drilling through a temporary

casing to the designed depth

using an auger or other tools

attached to a telescopic or

sectional Kelly bar. Other tools

such as drilling buckets or core

barrels can be used to cope with a

variety of ground conditions. The

casing gives support to the pile

through unstable ground and

once the required depth is

reached, the auger is removed,

the reinforcement is added and

the concrete is poured. When the

concrete reaches the required

level, the casing is removed,

allowing it to be reused in future.

In cases where the ground is still unstable at depth, support fluids such as bentonite

or polymers can be added.

The casing is as long as it is required to be to support the bore.

Rotary Bored Piling

Advantages

Can deal with a wide range of

ground conditions.

Tools can be added to give

much greater capability for

obstruction penetration than

other techniques.

Penetrates ground which is too

hard for the CFA technique.

Reinforcement cage can be

installed to much greater depths

(limited only by pile depth) than

in CFA piles.

More stringent installation

tolerances than a CFA solution

giving greater flexibility in

retaining wall detailing and

design.

Pile diameters of up to 2400mm

allows much greater loads to be

carried than other techniques.

The sequencing process

Technique Options

Oscillator

Where either, extreme accuracy or

minimum disturbance is essential

owing to the proximity of existing

structures, an oscillator can be used to

install the steel casing to greater

depth with precision. It is more

commonly used to extract the casing

in difficult ground conditions.

Plunge Columns

Commonly used in top-down construction and

enabling the simultaneous development of both

superstructure and substructure, the use of

plunge columns can significantly reduce the

overall construction programme.

Plunge columns usually consist of H-section

beams inserted into the concreted pile.

Drilling Fluids

Where unstable ground is below a depth impractical to case to, support fluids such as

vinyl polymers or bentonite can be used to support the bore during excavation. When

the concrete is tremmied to form the pile, the fluid is displaced, pumped out, filtered

and cleaned so that it may be used again.

Cage Safety Latch Systems

There is nothing more important to Van Elle than

the safety of its employees and fellow contractors

on site.

As part of this philosophy, the company has worked

with Total Construction Supplies to fit its new RCL

Super-Latch splicing system to prefabricated pile

cages.

When installing a two-part cage, it

negates the need for any site personnel

to place their hands inside the cage. Not

only safe but the cage sections simply

align and lock together without having to

line up bands and tighten up bolts.

Key Contact

Danny Quinton

Major Projects Manager

T: 07712 389325

E: danny.quinton@van-elle.co.uk

Over 25 years’ experience of

complex rotary bored piling

projects across the UK.

He specialises in the safe delivery

of major projects on time and

within budget. His hands-on

approach experience on site is key

to his success and his ability to

maintain programme regardless of

challenges encountered.

Contiguous Piled Retaining Walls

Contiguous piled retaining walls, also referred to as contig. walls, are formed by

installing a row/s of CFA or rotary bored piles leaving a relatively small space between

them. They are typically installed prior to one side of the wall being excavated and

they are designed specifically to retain earth and often to take a load applied by a

structure above too.

Unlike ‘secant piled retaining walls’, they do not prevent the ingress of water and can

be installed as a single wall or a 2/3 sided structure rather than having to be an

enclosed 360° construction. Contig. walls can be designed to be free standing, usually

when the retained height is relatively shallow, or with temporary or permanent

propping using anchors, props or hydraulic struts.

Secant Piled Retaining Walls

With the experience and equipment to competently design and install secant piled

retaining walls for all applications and in all locations, Van Elle have become

synonymous with complex and demanding projects of this nature.

Secant Walls, formed by installing overlapping CFA or Rotary bored concrete piles, or

a combination of the two, are used to retain earth as well as prevent the ingress of

water. In hard/soft secant walls, only the hard, also referred to as male or secondary,

piles are normally reinforced. In the case of less common hard/hard secant walls,

every pile forming the 360° beneath ground structure is reinforced to spread both the

horizontal and vertical loads. The primary piles are installed on the first pass with

secondary piles constructed in between the primary piles, once the latter have gained

sufficient strength. Pile overlap is determined by a number of factors but primarily by

the retained height, the diameter of the piles and the reinforcement used. In a wall

constructed of 600mm diameter piles, there would typically be 150-200mm overlap.

Secant walls offer a significant lateral strength advantage compared to that of sheet

piles and are also often designed to take a load applied by the structure above.

Rotary piles offer a significant degree of

accuracy to the overlap and help maintain

the verticality of the wall when augering,

preventing the piles from kicking off and

gaps forming between the piles.

Guide Walls

In order to form the piles in the correct position and helping

to maintain verticality, for both secant and some contig walls,

a circa 1m deep concrete guide wall is formed.

Rotary Bored Piling

Capabilities

Diameters from 450mm to

2400mm.

Depths up to 50m.

Can bore cohesive and granular

overburdens.

Can bore rock.

Suitable for:

Bearing piles.

Contiguous wall piles.

Secant wall piles.

Anchor/tension piles.

Lorry mounted rigs add the

ability to work in multiple work

location environments such as

highways gantry bases, etc. (low

mobilisation cost).

Oscillator available for longer

casing extraction.

Contiguous piled wall

Plant

As well as having one of the UK’s most extensive and varied fleets of CFA and driven

rigs, Van Elle also boasts a significant rotary capability using many state-of-the-art rigs

and ground-breaking support equipment. Our fleet consists of restricted access rigs

right up to the brand new 90 tonne Soilmec SR95 capable of installing large diameter,

deep rotary bored piles able to support extremely high loads.

Locations & Personnel

Van Elle has multiple offices, workshops and plant yards across the UK ensuring that

equipment and support is at hand regardless of where your project is.

Our extremely experienced designers, contracts managers

and site teams work together to ensure our clients receive

the very best service from initial design to site completion.

With 100% of our workforce being full-time employees of

Van Elle, you can be assured that every employee has

regular, industry leading training and our site audit

scheme makes sure that every project benefits

from the knowledge of our most experienced

engineers & management team.

For more information on any of our rotary capabilities, experience, personnel,

plant or to discuss a specific project, please contact Danny

Quinton at danny.quinton@van-elle.co.uk or on 07712 389325.

Training Requirements

All personnel required to be

trained to CSCS/CPCS level.

Site specific induction and job role

training.

Equipment Needed

Rotary Rig.

Temporary Casing.

Crane for Lifting Cage & Casing.

PPE as per method statement.

Oscillator as Required.

Safety Barriers & Signage.

Attendant Plant.

Consumables

Concrete to Design Spec.

Cage as per Design.

Reinforcement Caps.

Support Fluids if Required.

Soilmec SR95

Weight: 90t

Torque: 351 kNm

Max Diameter: 3000mm

Max Depth: 106.5m

Large Diameter/Deep

Soilmec R625

Weight: 70t

Torque: 240 kNm

Max Diameter: 2500mm

Max Depth: 77m

Medium Diameter Piles

Soilmec R312

Weight: 35t

Torque: 130 kNm

Max Diameter: 1500mm

Max Depth: 38.5m

Smaller Diameter Piles

Soilmec STM20

Weight: 19.3t

Torque: 185 kNm

Max Diameter: 1800mm

Max Depth: 24.5m

Highways & Similar