Digging & earthworks: giving the installations a firm, lasting foundation

Digging & earthworks: giving the installations a firm, lasting foundation

Digging occurs in many types of works that require a firm foundation and that could suffer from compaction and/or landslip due to their weight or the stresses they bear. For underground networks, digging is necessary to receive pipe or line, sleeves and other installations.
Digging works vary considerably from one project to another, according to the worksite’s configuration, the type of installation and the nature of the terrain.
Sheeting is often essential during digging operations. Appropriate sheeting for the excavations is one of the key elements in SADE’s active safety policy.

SADE is able to implement many digging and sheeting techniques for its projects, while ensuring compliance with its ‘Clean Worksite’ charter.

Mechanised digging

By using machines, mechanised digging brings significant efficiency and greatly improves working conditions.

SADE has an enormous fleet of digging machines suitable for all environments, urban or non urban. All operators are trained and qualified to use them.

For digging operations, SADE innovates ‘responsibly’ by proposing suction digging or with trench excavator.

Suction digging

Using ’gentle’ technology and thanks to a fleet of suction excavators of various capacities, SADE operates quickly, discreetly and efficiently with optimum safety in the vicinity of existing networks.

This process applies to a wide variety of terrain and is suitable for many different types of intervention: network sounding, registration, cartography and inspection; digging trenches; cuts and rubble removal; cleaning and draining of outlets, manholes, pipes, pits, sand boxes; cleaning industrial sites; removing demolition rubble; tree root exposure, pollution control.

Suction digging
helps to find a positive ecological balance.

Manual digging

When mechanised digging is not technically or statutorily possible (proximity of utility networks, for example), manual labour takes over. Manual digging is the ‘conventional’ method in this industry.
SADE personnel are well-trained in the requirements of this technique.


Dewatering is intended, either temporarily or permanently, to lower the level of a water table in order to allow civil engineering operations. Lowering the table maintains a safe, dry site and ensures good cohesiveness of the ground.
SADE provides a range of solutions suitable for these complex geotechnical operations and has the appropriate expertise in the three main drawdown technologies : 

  • Using wellpoints
    This technique consists of carrying out mini-drilling in a ring very close to the dewatering area to install wellpoint tubes of approx. 100mm to be linked in groups of 25 to 50 units to a low pressure network. Dewatering using wellpoints is suitable for soils with low permeability (10-7 to 10-4 m/s) and depths not exceeding 6 metres, the limit for suction pumping. Depending on the nature of the soil, the choice of wellpoints and their method of installation are crucial to their effectiveness.

  • Using soakaways
    This technique consists of drilling tube wells from 30mm to 1,000mm around the excavation and installing at the bottom of each one a filter and a submerged discharge pump. Dewatering with soakaways allows the treatment of large flow rates and great depths in porous soils (10-4 to 10-2 m/s).

  • Using drainage ditches
    This technique consists of installing drains connected to a pumping system in trenches filled with filtering materials. It is suitable for soils with low permeability (10-7 to 10-4 m/s) and depths not exceeding 5 metres.

Whichever solution is employed, a tracking system monitors its effectiveness over time.

Vertical kirving

Vertical kirving consists of constructing a ground installation then digging it out inside so that it is gradually lowered. This technique is particularly suited to unstable ground with water present and has the advantage of reducing the amount of excavated material produced and saving on backfill.

SADE has all the necessary expertise to carry out works using the Vertical kirving technique.


The practice of sheeting is one of the elements that are essential to safety in all our interventions. With regular training, SADE personnel have long experience and practical know-how in this subject.
An excavation of over 1.30 metres in depth must be systematically sheeted. The type of sheeting used depends on its depth: urban or extra deep (over 4 metres).
SADE has expertise in all appropriate techniques:

  • aluminium sheeting (4’38) ,
  • wooden sheeting,
  • steel sheet piling,
  • interlocking sheet piling,
  • caisson sheeting (braced centrally or at the ends),
  • sliding sheeting.

Materials recycling

Materials recycling is an eco-responsible development that both meets landfill regulations and helps contribute to the demand for aggregates for worksites estimated in France to be nearly 400 million tons annually.

As an innovative international contractor that is fully committed to sustainable development, SADE offers a whole range of fixed or mobile solutions for recycling excavated material.

A fixed recycling centre in the Lille region

At Wambrechies (Nord department), SADE has a 20,000m2 recycling centre that treats more than 200,000 tons of excavated material per year. It supplies construction and civil engineering companies in the region with end products of various granularities (0/6, 6/20, 20/40, etc.)
Registered with the local Prefecture, this lime treatment plant is additionally certified to ISO 9001, ISO 14001 and OHSAS 18001. It also uses monitoring logistics to ensure traceability of the end products.

Mobile solutions on a case by case basis

SADE also has screening buckets for a simple and quick treatment of excavated materials. These solutions are very flexible, easy to use and suitable for any type of project. This activity is certified ISO 9001.

RECYCLOR: an innovative on-site recycling solution for excavated material

A SADE technological innovation, RECYCLOR is a mobile excavated material treatment unit that provides effective on-site back-filling with self-compacting material. The RECYCLOR unit’s compact format is ideally suited to urban environments: both small and larger versions are available.
By reducing the rotations of trucks transporting the excavated and backfill materials, RECYCLOR is one of SADE’s technological developments that help to reduce significantly its worksites’ carbon footprint.

On-site recycling of road coatings

SADE operates equipment that enables it to recycle its worksite road coatings: this means technological rationalisation, improved working conditions and reduced greenhouse gas emissions.
On urban sites, this technique allows SADE to quickly carry out minor ground surface repair work, even during periods when road coating supply centres are closed: pavements, roads, car parks.


Compaction checking

After back-filling, compaction checking is a stage prior to the final acceptance certificate. It provides reassurance that the ground around the pipes is in accordance with its correct mechanical hold and that it will not cause any surface slippage especially under road ways.

When necessary, SADE will carry out these checks with a dynamic penetrometer. This device drives a rod into the back-fill at various points and measures at each one the relationship between rod penetration depth and energy applied. The diagram resulting from the series of tests is then compared with the expected theoretical results.

SADE’s teams have at their disposal a fleet of modern, multi-purpose compaction checking devices.

SADE - 23-25 av. du Docteur Lannelongue - CS 51450 - 75685 Paris Cedex 14