A shoring system is used to describe a system that helps retain earth, water and all adjacent structures present during the period an excavation is required. This process used in supporting buildings, structure, vessel or trench with shores or props while alterations or repairs takes place or when there are signs of danger of collapse. Shoring systems usually come from timber or metal props. A
Shoring system could be vertical, horizontal or angled. Designing a shore could be very complicated. Here the designer has to face the challenges of so many unknowns and other circumstances that will affect the excavation shoring system. There are two major trenching methods that must be used during excavation: Earth Retention Shoring System which supports the wall of the earth during excavation and to support trench safety equipment which is the internal and external bracing that helps protect the earth retention system.
The process of taking up detailed calculation for both Shoring Systems is always very tedious and time consuming especially when the parameters used have to be changed. Also many new software programs which is being used does not include an integrated platform of structural and geo-technical analyses required for the design of Shoring System excavations. Due to this, the designer will have no other alternative than to use several other software programs to analyze the excavation and structural systems separately. Without including finite elements analysis, there are only few only few theoretical solutions that can be used in calculating lateral soil pressures from complex surface profiles. The designer will also have to save the different stages of the same excavation process with different file names. As a result of this, the whole excavation process becomes more complicated and time consuming. A professional will address all these issues and solve the problems using integrated structural and geo-technical platform for deep excavations. A shoring system is usually designed using both non-linear and traditional method of analyses. While it is known that traditional method of analyses have several limitations in accurately getting the real behavior, they are very useful in framing the problem and providing back-check for more rigorous finite element methods.
Various Types of Shoring System
Shoring system could also be done by the assembly of vertically oriented steel wide flanges covered in a cylinder of concrete arranged every 6-8 feet on in a straight line referred to as piles. Wood boards which are referred to as lagging are also arranged horizontally from one wide flange to the next and letting the whole assembly hold back earth on one side which will lead to a vertical cut on the other side. The main purpose of the shoring wall is to be the retaining wall even though the physics and construction methods are different. On a residential project, the height of shoring ranges from 6-12 feet while commercial projects uses shoring techniques that goes way beyond that range to a much deeper level using tie-backs. These shoring walls could be either temporary or permanent. A temporary application is usually supplemented with concrete walls when the earth has been properly retained. Shoring system is known to be very effective when two criteria are present on a site. It is necessary for a flat ground to be built on and also for the proximity of the building footprint to an existing structure. Cutting back and retaining the earth is needed for a flat and build-able ground. There are several ways this could be done. But a concrete retaining wall requires a large amount of space for it to be done. While building a framework for concrete footing and walls, the surrounding earth is required to be temporarily removed (usually about 45 degree angle) on both sides of the wall in other to make the space accessible. If this structure is located very close to an existing structure, the required space for excavation is then prohibitive. A shoring wall requires just a few inches while the concrete retaining wall needs few feet’s.
Despite the growth in the construction shoring techniques, engineers and Shoring System contractors still do face a lot of challenges builders faced in the past. The design and building of these shores could be more complicated due to the soil structure, depth of the cut and also the ground water, seismic loads, vibrations, weather condition, superimposed loads and adjacent construction. Properly designed and constructed excavation system is needed when excavation is being done in wet soil, sandy soil or areas that have been previously back-filled due to instability. Hard rock can also be hazardous to excavate. A Shoring System engineer will have to guard against an unstable excavation bottom especially when this is below water level. Some known permanent and temporary shoring system are steel sheet piling, soldier piles and lagging, jet or chemical grouting, secant or tangent piles and soil walls. To provide lateral support of sheeting and shoring system, anchors and bracing is used. A circular shoring system is designed as a compression ring to access shafts for tunneling and trench-less construction to resist loading. It is required that during construction Shoring System for excavations, an open extended period of time is needed for protections from weather conditions.