Braced sheet pile shoring wall in sensitive clay

This case history describes the design and performance of a temporary braced sheet pile shoring wall constructed within the median between heavily-trafficked lanes of the Trans Canada Highway in Langley near Vancouver, British Columbia, Canada. The excavation extended to 9.7 m depth below the existing road grade into soft, high plasticity, sensitive glaciomarine clay. Glaciomarine clay is locally notorious for excavation and embankment stability and foundation settlement problems. The shored excavation was required to provide an access pit to allow the installation of a 3 m diameter steel pipe culvert by Horizontal Pile Driving (HPD).

The braced sheet pile wall was designed using the Terzaghi Apparent Earth Pressure distribution and conventional limit equilibrium analysis methods. The excavation was undertaken in stages as the bracing was installed and ground deformation was monitored using slope inclinometers and by survey of surface targets. The case history describes the performance of the excavation and compares predicted to monitored displacements. A particular issue related to face stability due to clay squeezing and running sand during bulkhead sheet pile removal required to commence HPD for culvert installation. The bulkhead face was stabilized by grouting with a water reactive polyurethane grout prior to sheet pile removal.

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Box Sheet Piling – Steel Structures

Hot-rolled steel sheet piling is more extensively used nowadays in permanent as well as temporary retaining walls. Applications are not only above-ground earth-retaining structures but also composite basement wall construction, urban railway and road cuttings, bridge abutments, river bridge pier caissons, as well as the traditional river and coastal protection works. Economic design is enabled by better knowledge of soil–structure interaction and highly developed design and analysis programmes.

Box piles are particularly suitable for marine structures, such  as jetties and dolphins, where part of the pile shaft is exposed above seabed level and the pile functions as a free-standing column or is connected at the head in clusters of columns.

Box piles are formed by welding two or more sheet pile sections together. Both Larssen and Frodingham steel sheet piles (see section 29.2.3) can be used.They can be introduced into a line of sheet piling at any point where local heavy loads are to be applied, for instance beneath bridge beams, or used separately.They are clutched together with adjacent sheet piles and can be positioned in a sheet pile abutment so that its appearance is unaffected.

Larssen box piles are formed by welding together two sheet pile sections with continuous welds, and Frodingham plated box piles are formed by  continuously welding a plate to a pair of interlocked and intermittently welded sheet piles (see Fig. 29.2).

Special box piles can be formed using other combinations of sheet piles.

20170927Fig. 29.2 Box piles

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Pile Driving

The pile driving technique is powered by pneumatic or diesel pile drivers of which the dynamic weight is driven by hydraulics. By pulsating load on top of the sheet pile, the critical frequency is being passed and the sheet pile is driven into the soil. This technique is mainly used for the driving of piles and solid caissons, especially in cohesive soils and fine-grained soils including silts and clays. What pile driver to use, is depending on the soil conditon, working depth and strength of the sheet pile wall. For plastic and composed sheet pile walls, there are special pile drivers on the market with less impact pressure in order not to damage the elements. Pile driving can also be done by a conventional drop hammer, with or without steel framework.

(This article comes from PVE Piling & Vibro Equipment editor released)

Single sheet pile cofferdam

These are generally used to enclose small foundation sites in water for bridges at a relatively shallow depth. In this type of coffer dams, there is a single row of cantilever sheet piles. The piles are sometimes heavily braced. Joints in the steet piles are properly sealed. This type of coffer dams are suitable for moderate-flow velocities of water and for depth upto 4 m. The depth of penetration below ground surface is about 0.25h for coarse sand and gravels, 0.5h for dine sand and 0.85h for silts, where h is the depth of water. Sometimes single-sheet coffer dams are provided with earth fills on one or both sides to increase the lateral stability. The figure of single sheet pile cofferdam is shown in follow.


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Steel sheet piling

VolkerGround Engineering can design and install a variety of sheet pile retaining walls depending upon the individual project requirements and ground conditions. A sheet pile wall can be used in either a permanent or temporary works application in either a land or marine environment.

This application has been used on a number of flood alleviation schemes around the country, providing both existing embankment stabilisation and flood prevention barriers.

In permanent works a high quality finish can be achieved to such an extent that the steel face can be merely painted rather than providing a concrete facing wall in front of the sheet piles. This has been widely used in the construction of underground car parks within basement structures, which has proved to be extremely cost effective.

Retaining wall design is one of the key services provided by VolkerGround Engineering, whether at the initial costing of project works or the final construction scheme. Our experienced designers are able to advise and provide clients with the most cost effective structural solution for either temporary or permanent schemes.

Once designed and priced, VolkerGround Engineering are able to select the most suitable plant from their own fleet, for the construction of the sheet pile retaining wall.

Steel piles can provide a cost effective solution to a wide range of foundation applications. Manufactured in continental Europe, steel piling is especially suitable for building structures in a sustainable and cost effective manner. Major manufacturers form steel sheet piling in electric arc furnaces, utilising a blend of scrap products from a variety of sources. The chemical content of steel piles is strictly controlled in order to produce material of acceptable section modulus, to satisfy all current construction and design codes, particularly with regard to the relevant Euro Codes, and CE certifications.

HZM/AZ steel piles can provide an economical combination wall using steel sheet piling and sections combined to form a permanent wall that is capable of supporting both vertical and lateral building loads. The high section modulus of the steel piles can ensure that minimal surface deflections are recorded. This makes the system useful for deeper excavations, where only concrete diaphragm walls had previously been considered.

Steel piling, in the form of interlinked tubular piles and sheets, has been widely used in this country in the formation of marine quay walls. VolkerGround Engineering has completed such a structure, in partnership with VolkerStevin, on the refurbishment of Berths 201 – 202, for the Port of Southampton. The berths were dredged and extended to take the new generation of pan panamex container vessels with increased berth depth requirements.

(This article comes from VolkerGround Engineering editor released)

U type sheet pile and its size calculation

U type pile is a new type of application support structure which has just started in recent years. Because U type cross-section of the structural design, not only can save material, but also to ensure its adequate bending performance and shear strength. However, due to the cross-sectional thickness of the pile structure is small, there is no connection between the pile and other issues, if you need to enter the pile will take a long construction time. At the same time, in the process of calculating the geometrical size of U type piles, it is necessary to select and design the pile type reasonably, and combine the actual situation of water dike project according to the size of supporting pile. Not only to meet the support requirements, but also give full play to its sealing effect, to achieve the sheet pile as a block pile type design effect, and maximize the U type piles used in water conservancy projects in the advantages. At the same time, the connection between the U type sheet pile and the pile needs to be sealed. In addition, if the mechanical calculation method according to the structure and bearing capacity, the bearing capacity calculation process is complex, the equivalent method required by the cross-sectional form rule. As the U type support pile is mainly subjected to the horizontal earth pressure and the opposite direction of the ring beam transfer, the U type pile will be subjected to bidirectional bending and shearing. From the analysis of the principle, the equivalent cross section of the U type plate pile should choose reasonable symmetrical cross section, and then ensure the application effect of U type plate pile in water dike.

How to Choose Piling Equipment for Steel Sheet Pile Construction

The smooth progress of the construction of the sheet pile is largely determined by the choice of construction machinery. When deciding which machinery to use, consider the following conditions:

Project size: the number of steel sheet pile, size, shape, in particular, to consider the weight and length of steel sheet pile, often these two factors are the main.

Soil conditions: to be combined with the soil conditions, in order to facilitate the steel pile hit or pull out.

Operational capability: to meet the requirements of the progress of the project.

Operating environment: the choice of machinery to meet the noise, vibration and other pollution control requirements, combined with on-site conditions such as traffic conditions terrain, scaffold and so on. Taking into account the above conditions, so that the selected machinery is economical, safe and can ensure the construction efficiency.

What are the mechanical properties of the support plate pile?

Cantilever plate pile: insert the soil part as a fixed end, the upper part of the free end; that is, as a cantilever structure.

Shallow buried single anchor pile: insert the soil part as a fixed hinge, the upper anchor point for the activities of the hinge; that is, as a simple beam structure.

Deeply buried single anchor pile: insert the soil part as a fixed end, the upper part of the anchor point for the activities of the hinge; that is, as a static structure of the beam.

Multi-layer anchor sheet pile: insert the soil part as a fixed end, the upper part of the anchor point of action for the activities of the hinge; that is, as a continuous beam structure.

What are the types of sheet pile support?

Sheet pile support According to the presence or absence of an anvil structure, there are two types of anchor plate and an anchor plate pile.

No anchor plate pile is cantilevered plate makeup. This pile is very sensitive to the nature of the soil, the size of the load is very sensitive, because it only rely on the soil part of the soil to maintain the stability of the board makeup. So its height is generally not greater than 4m, otherwise it is not economical, it is only applicable to the shallow foundation pit soil support.

Anchorage sheet pile is fixed in the upper part of the plate with a pull anchor device to improve the support of the board makeup. Single anchor sheet pile is commonly used as an anchor form of anchor plate pile. It is composed of sheet pile, beam, tie rod, anchor pile and nut, etc., steel sheet pile through the beam (steel), steel rod, nut fixed on the anchor pile.

In the construction of steel sheet pile, how to deal with the adjacent sheet pile

This phenomenon often occurs in the soft soil plate pile, when faced with unknown obstacles, rock or pull pile tilt, etc., the sheet pile resistance increases, will bring the adjacent sheet into the pile. Can be handled as follows:

  1. Not once the plate pile hit the elevation, leaving part of the ground, until all the pile pile soil, with the screen to the rest of the people hit the soil.
  2. The adjacent sheet pile welding in the rub on the rub.
  3. Several pieces of sheet pile are joined together by steel.
  4. In the connection lock mouth coated with butter and other grease, reduce resistance.
  5. The use of special plugs to prevent the sand into the connection lock.

After the sheet pile is brought into the soil, the same type of sheet pile should be welded at the top to supplement the insufficient length.