Deep excavations for new structures require earth retention systems, particularly
in urban areas.

Layne has developed advanced ground retention systems over the years to suit a variety of site and ground conditions. Permanent earth retention structures are designed and constructed to provide long-term support and enduring performance. Layne has extensive experience and advanced capabilities to offer the latest technologies and to provide the best and most cost effective solutions for all types of deep excavation retention systems.

  • Slurry / Diaphragm Walls
  • Secant Walls
  • Retaining Walls
  • Earth Support Systems
  • Tunnel Access Shafts
  • Ground/Rock Anchors
  • Soil Nailing
  • Soil Mixing
  • miniJET® Technology
  • Top Down Construction
  • Underwater Anchors
  • Marine Foundation Construction
  • Composite Foundation Systems
  • Advanced Jet Grouting Technologies
  • Ground Freezing
  • Real Time Monitoring
  • Environmental Cutoff Walls
  • Specialized Foundation Equipment Design
    and Manufacturing

Slurry / Diaphragm Walls

The term “Slurry Wall” is used to refer to the construction of a wall beneath the ground surface using a slurry fluid
to stabilize the sidewalls of the trench from collapsing during the excavation before being filled with concrete.

Diaphragm Walls refers more specifically to a slurry wall built for some type of structural support. Since most Diaphragm Walls are usually thick (>2.5ft) and built of reinforced concrete, they are very rigid walls offering significant resistance to bending from lateral loads as well as being very water resistant. Diaphragm Walls are ideal for lateral earth support for deep excavations and are often incorporated as the permanent building basement walls. This creates additional savings for the project by eliminating the need for temporary earth support and extensive dewatering.

Secant Walls

Secant walls are created by drilling a series of vertical bored piles that overlap each other creating a continuous wall. The so called primary piles are installed along an alignment and spaced far enough apart so that when the secondary piles are drilled they overcut 20% to 30% into the sides of the existing primary piles. Secant Walls can use a variety of drilled pile sizes depending on the depth of the wall. Typical sizes are 18” to 60” diameters although larger diameter piles have been used on some deeper walls or heavily loaded cantilever type walls. Secant walls can be effective earth retaining walls to depths up to 60ft or more depending on pile diameter and loading configuration. Secant walls can also be relatively water resistant.

Retaining Walls

Retaining walls are used to retain earth when there is a differing grade elevation on either side of the wall. Retaining walls must have the structural capacity to hold back the lateral earth pressures and maintain long term stability from bending, sliding and overturning. Retaining walls can be temporary structures or permanent. There are many different types of retaining wall systems available out on the markets. Retaining walls are constructed from a variety of materials. Rigid structural walls that are free standing rely on gravity and are usually made of concrete or rocks for the weight. Reinforced concrete is the most common type of rigid structural wall. Horizontal anchors may also be used to provide additional lateral support. Steel sheetpiling is also placed in the ground for retaining walls.

Another type of retaining wall system that has been around for a number of years relies on Mechanically Stabilized Earth (MSE) to self-support the lateral earth pressures that exist. These types of walls use some type of facing panels to provide an attractive protective cover for the wall (usually made of precast concrete) and are very commonly used in highways and bridge construction.

Earth Support Systems

Any type of deep excavation requires that the earth be laid back on a slope for safety and stability. If there is no room for laying back then some type of earth support system will be required. There are different types of earth support systems that are used but the most common utilizes steel beams and wood lagging also known as “sheeting.” The function of sheeting is to laterally support the earth in place around an excavation for a period of time while a new structure is being constructed below existing grade. Depending on the depth of excavation multiple levels of anchors or bracing may be required. Sheeting systems are usually for temporary support so they are not designed and built to last more than several months. After the structure has been completed up to existing grade, backfill may be placed between the structure and the temporary sheeting system is buried in place. Some municipalities require that some of the sheeting elements such as anchors and tops of steel beams be removed.

In order to allow for deeper excavations in congested areas, an increased need for economical earth support systems have been developed and installed by Layne. Soldier beams with wood lagging using tiebacks or bracing, soil nailing, and cast-in-place bored piles are typical retaining wall techniques that are offered. The company's activity in these fields extends to the installation of diaphragm wall systems supported by the use of bracing and/or tiebacks, drilling and grouting, and jet grouting for underpinning.

Tunnel Access Shafts

Modern Tunnel construction projects often use Tunnel Boring Machines (TBM) to excavate the tunnel. These large machines either drill directly into a vertical face such as the side of a mountain or portal. If the tunnel starts below the ground surface however, the TBM needs to be lowered into the ground through a vertical access shaft. This vertical shaft is usually round for stability and needs to be of a diameter large enough to allow for the TBM to be lowered down to the design tunnel elevation. At the other end where the tunnel ends, a similar shaft needs to be constructed to allow for the TBM to be extracted and raised back up to the ground surface for reuse on another tunnel project. These shafts can vary in depth and diameter depending on the project. For shallow shafts less than 60ft steel beams with wood lagging or secant shaft walls are an effective means to provide earth support.

For deep tunnel access shafts where the bedrock is also far below the ground surface and groundwater inflow is significant, the use of slurry diaphragm walls is the most cost effective means of earth support. The superior strength, rigidity, vertical accuracy and water resistant performance of diaphragm walls cannot be replaced by other foundation systems. The equipment used to excavate diaphragm walls such as hydromills, have the capability to excavate deep panels through nearly any material and maintain very accurate verticality (<.3%) which is essential for proper closure at depths of hundreds of feet.

Bencor (a Layne company) has been a world leader installing diaphragm walls since 1969 and has the largest and most modern fleet of state of the art hydromills in North America, capable of excavating down to depths of 490ft (150meters) complete with all of the supporting service equipment and experienced personnel.

Ground/Rock Anchors

Anchors are designed to counteract lateral forces and overturning on dams and other critical structures; they also provide lateral excavation support. Anchors consist of post-tensioned grouted steel bars or multi-strand steel wires.

Applications include:

  • Earth Retention Systems
  • Post Tensioning Dams
  • Seismic Stabilization

Anchors provide a cost effective bracing system for all soil conditions. Additional advantages include:

  • Final strength of the stabilized soil can be predetermined.
  • Attainable large loads.
  • Installation in limited access areas and complex drilling conditions.

Ground anchors are also frequently utilized for lateral support of slurry diaphragm. Since the ground anchors provide intermediate points of support at one or more levels, they reduce bending moments and consequently reduce the need for thicker walls, reinforcement, and depth-of-toe requirements. Anchors eliminate the need for internal steel bracing and strutting within the excavation and leave it free of obstructions which reduce excavation costs and speeds up construction. This aspect can be particularly valuable in congested urban locations with limited surrounding space for equipment and materials. Anchors are may be used in soils or in rock and may be either permanent or temporary.

Soil Nailing

Soil Nailing is a type of earth support system which consists of driving, screwing or drilling and grouting a series of steel bars or nails behind the excavation surface and then covering the face with shotcrete which may or may not be reinforced.

The placement of near horizontal steel bars or nails behind an excavation in a fairly close pattern increases the shear resistance of the soil against rotational sliding as well as resistance against lateral stresses within the soil mass. Soil nails are normally located in a square or rectangular grid pattern and are placed horizontally or inclined 20 degrees or less from horizontal. After a row of nails are installed the excavation surface is covered with layers of shotcrete, which is generally reinforced with a steel wire mesh and may depend on site conditions. After the shotcrete has gained sufficient strength, steel bearing plates connect the nails to the finished face. When a row of nails is completed, the installation operation progresses down to the next row, repeating the procedures until the excavation is complete. Soil nail walls are usually designed for temporary earth support but can also be designed to be permanent under the right conditions.

Soil Mixing

Soil Mixing refers to a technique where a mechanical device consisting of drills, augers, paddles or mixing wheels break up the soil matrix while a cement grout is injected in. The resulting soil will have improved engineering properties such as higher strength, homogeneity and impermeability. Soil Mixing is used for ground stabilization and improvement, cutoff walls, earth support systems and seismic retrofitting.

miniJET® Technology

This technology was developed and is patented by Tecniwell (a Layne Company) based out of Italy. It incorporates the use of jet grouting through hollow, high strength drill rods that are left in place in the ground and become the structural element. They are available in different sizes to handle load requirements. It has developed into several versatile applications, including a new type of micropile system, and also a robotic Under Water Anchor system that provides a cost-effective rehabilitation option for existing marine wharf structures.

Top Down Construction

This term refers to a type of construction which involves, as the name implies, going down with the building basement excavation while at the same time starting the erection of the building superstructure. This technique has been successfully used on projects that have a relatively deep basements as well as high rise construction. This process can save significant time on the overall construction schedule, cost and deliver the finished building to the owner sooner.

Diaphragm Walls are used to install the perimeter walls which can also be designed to provide load bearing support for exterior columns of the building. The interior column loads are supported by either drilled shafts or barrette piles using the same slurry wall techniques. Since these column supporting elements must be installed at the same time as the perimeter diaphragm walls so that superstructure erection can begin it is often advantageous to use barrette piles rather than have a separate drilled shaft contractor trying to occupy the same tight construction site. It is much more effective for all parties involved to have one contractor install both the diaphragm walls as well as the barrette piles for the columns.

After the diaphragm walls and the barrette piles are completed the excavation of the basement can begin as well as the erection of the superstructure. Building structures made of structural steel as well as reinforced concrete have both been successfully built around the world using top down techniques.

Underwater Anchors

Underwater Anchor System (U.W.A.) is an innovative and unique solution to wharf deepening using the miniJET® technology developed by Tecniwell, a Layne company. Conventional techniques typically require installing new seawalls in front of existing ones in order to deepen the wharfs.This results in very costly and time consuming work with significant impact to shipping operations. The U.W.A. eliminates the need for a new seawall by installing additional horizontal anchors at the proper level to allow safe dredging to the new depth required. Jet grouting can also support and safely deepen the existing seawall if required.

After the Under Water Anchors are installed and the jet grouting has cured to gain sufficient strength, a galvanized anchor head assembly is lowered into place through the anchor rod. A diving crew using a crane and calibrated hydraulic ram set will post tension each anchor to the required loading.

Marine Foundation Construction

Layne offers a variety of pile systems used for structural support on the water for marine foundations and earth support. In addition to driven piles which are traditionally made from steel pipe, H-Pile sections, precast concrete, wood and recycled materials, Layne has the expertise and equipment to install bored piles as well as reverse circulation piles. Additional specialized services for marine and river works are offered through Costa Fortuna,
a Layne company, which provides bored piles with sacrificial steel casing, and installation of precast concreted bored piles utilizing reverse circulation drilling techniques.

Layne also offers the Underwater Anchor System (U.W.A.). It is an innovative and unique solution to wharf deepening using the miniJET® technology developed by Tecniwell. Conventional techniques typically require installing new seawalls in front of existing ones in order to deepen the wharfs.This results in very costly and time consuming work with significant impact to shipping operations. The U.W.A. eliminates the need for a new seawall
by installing additional horizontal anchors at the proper level to allow safe dredging to the new depth required.Jet grouting can also support and safely deepen the existing seawall if required.

After the Under Water Anchors are installed and the jet grouting has cured to gain sufficient strength, a galvanized anchor head assembly is lowered into place through the anchor rod. A diving crew using a crane and calibrated hydraulic ram set will post tension each anchor to the required loading.

Composite Foundation Systems

This refers to a method of construction that incorporates the most effective use of different foundation techniques to produce a more cost effective design. For example:

  • The use of slurry diaphragm walls to form the permanent basement walls eliminates the need for traditional sheeting, shoring, and underpinning.
  • Barrette piles, installed using the same diaphragm wall equipment, provide for structural column support and eliminate the need to bring on a different contractor to install piling.
  • A jet grouted base seal installed in advance from the ground surface eliminates the need for massive dewatering if next to a large body of water in permeable soils.

All of these systems when combined can produce significant savings to the overall project construction.

Advanced Jet Grouting Technologies

Jet grouting is a specialized process that produces in-situ mixing of soil and cement grout. After drilling to the required depth, the jet grout drill rods are rotated and raised to the ground surface at controlled rates, while injecting cement grout at a high pressure, forming a soil-cement column. When placed in engineered configurations, the columns can be constructed to provide effective treatment of large masses of soils.

Advantages to the jet grouting method include: higher compressive soil strengths in comparison with other soil improvement methods; more uniform soil treatment; capability to improve isolated soil areas; and definitive quantity and scheduling.

Key principals of Geo have been engaged in jet grouting production and technology since its origins in Italy. Many jet grouting techniques and specialized equipment improvements that have become industry standards were conceived and advanced by these individuals – several during their associations with predecessor companies of Layne Christensen.

Ground Freezing

Ground freezing is a process involving the circulation of a refrigerated coolant through a series of subsurface pipes to convert soil water to ice, creating a strong watertight material. It is the primary method of groundwater control and soil support for deep shaft construction. The frozen barrier is created by drilling and installing freeze pipes around the perimeter of the project. Pipes are then connected to an enclosed coolant system that delivers refrigerated brine to each individual pipe.

Applications include:

  • Groundwater Control
  • Excavation Support

Advantages of this ground improvement system are many:

  • Environmentally compatible
  • Proven Technology (has been in existence for over 100 years)
  • Significantly less impact on surrounding water table than conventional dewatering techniques

Real Time Monitoring

Layne Geo remains an industry leader in the development of computerized systems for real-time monitoring of critical drilling and grouting parameters. Long-range wireless communication with remote field equipment can provide engineers with ground improvement telemetry from multiple production rigs and locations.

Drilling and grouting data are collected through a network of sensors and are recorded by dedicated on-board computers. Engineers can monitor real-time telemetry simultaneously through a long-range wireless link.

Applications include:

  • Jet grouting with single- or multi-axis drill rigs and connected high-pressure injection pumps
  • High-mobility grouting and associated water testing
  • Low-mobility grouting and ancillary ground response

Advantages include:

  • Provides real-time, continuous quality control to verify compliance with design parameters
  • Allows real-time analysis of water test data
  • Allows monitoring of pressure-displacement and ground response during compaction grouting

Environmental Cutoff Walls

These types of walls are not used for typical earth retention but rather to retain contaminated soils from moving
or flowing past the wall. Layne offers several construction techniques to address the containment of subsurface contaminants. Depending on jobsite requirements, our environmental cutoff wall remediation methods can be applied for the following:

  • Soil Encapsulation
  • Soil Treatment
  • In-Situ Stabilization
  • Cut Off Walls

Using single or multi-axis jet grout drilling equipment, Layne can encapsulate radioactive waste in-situ with a special hot wax injected at high pressure or other liquid stabilizing agents. Using our bioJET® technology, we have also completed in-situ treatment of organic waste by injecting Synergistic Biochemical System at high pressure into the contaminated area below the ground.

Resonant Sonic Drilling

Resonant sonic drilling is a useful and versatile drilling technique that has applications within the geotechnical construction industry. The sampler barrel is vibrated vertically at high frequencies between 50 and 180 Hz as it is rotated so that the sampler barrel advances by slicing through the soil, even very hard formations allowing the extraction of undisturbed samples.

Specialized Foundation Equipment Design and Manufacturing

Tecniwell S.r.L. of Podenzano, Italy, was established in 1987 with the goal of designing, developing, and fabricating state of the art ground improvement equipment, specifically machines used for advanced jet grouting.

Tecniwell (a Layne company since 1996) gives Layne the unique capacity to design, customize, manufacture and test grouting and drilling equipment under a multitude of varying field conditions.

Tecniwell’s factory manufactures equipment used for jet grouting, grouting, miniJET® applications, vibroflotation (vibratory ground improvement and stone columns), and the drilling and oil field industries. In addition Tecniwell produces a complete range of hydraulic crawler multipurpose drill rigs for piling (large and small diameter), anchoring, jet grouting, CFA, reverse circulation drilling, and hydromining.

All products are manufactured according to the UNI EN ISO 9001/2008 standards and the fabrication process complies to the most rigid environmental rules. For product orders,catalogues, and descriptions please visit www.tecniwell.com

Dam / Levee Rehabilitation

Layne provides a variety of specialized, geologic-specific drilling andgrouting technologies, along with sophisticated deep cutoff walls and anchors to address seepage and stability issues at dams and levees.

Techniques include:

  • Diaphragm / Slurry walls
  • High Mobility Grouting
  • Low Mobility Grouting
  • Jet Grouting
  • High capacity post-tensioned Anchors

Layne also provides exploratory sonic and diamond core drilling services over the course of a dam / levee rehabilitation project, along with a full suite of borehole logging capabilities.