Shoring Shoring is the process of temporarily supporting a building, vessel, structure, or trench with shores (props) when in danger of collapse or during repairs or alterations. Shoring comes from shore, timber, or metal prop, it may be vertical, angled, or horizontal. Shoring follows a double-funnel principle signifies that an edge collects a load, channels it and safely redistributes it to a different surface or structure that may assist it. Here we are going to learn about shoring, types of shoring & much more. Introduction to shoring: Shoring is the availability of a support system for sludge, underground utilities, roadways and trench faces used to prevent foundation movement. Shoring or shielding is used when the cut place or depth makes the back slope the utmost allowable slope impractical. When shoring is preferred: When a structure has become or likely to become unsafe due to differential settlement, bad workmanship, negligence of maintenance. When an adjacent structure is to be dismantled. Supports may be given externally or internally or both. In which condition shoring is required in a construction? Shoring is required when the buildings slender members shows sign of buckling or its should be defective. Shoring is required when the wall of the building shows signs of bulging due to bad workmanship. Shoring is required to repair cracks of the wall due to unequal settlement of the foundation. Shoring is required to support defective walls, roofs, compound walls, floors, etc. Shoring is required when the foundation is to be inserted into the deep ground. Shoring is required to make a large opening in the wall. Types of shoring: 1.Raking shoring or inclined shoring: Raking shoring consists of bent wooden members called rakers. One end of which rests against a faulty wall through the wall plate and the other end against the sole plate which is embedded in the ground in a tilt to distribute the load evenly. The wall plate, approximately 20 to 25 cm wide and 5 to 7.5 cm thick, stands along the wall face and it is secured through 10 cm x 7.5 cm section needles. These needles penetrate the wall by about 10 cm, a wallplate is provided to distribute the load. The rakers are joined together by braces and tied at the bottom by hoop iron. The following points should be kept in mind while erecting the raking shoring: 1. Rakers must be tilted to the ground at 45 ° to make them more effective, however in practice the angle can vary from 45 ° to 75 °, the top raker should not be tilted more than 75 °. 2. To maintain balance, the three forces must meet at a point and form a triangle of forces. 3. Rakers should be braced properly at intervals. 4. Rakers should not be fixed by providing wedges, likely to damage the building. 5. The size of the rakers should be decided based on the thrust anticipated from the wall. 6. There is more uncertainty about the magnitude of destabilizing forces, so a higher factor of safety must be provided. 7. If support, spacing is required based on requirements for long lengths of wall. 2.Flying shoring or horizontal shoring: Horizontal shoring are termed as flying shoring, which are ideal edges to resist the horizontal component of unsteady force. Such shores are used to offer horizontal support to two adjoining, parallel party walls which have to become unsafe as a result of removing or collapse of the intermediate building. The following points should be kept in mind while erecting the flying shoring: 1. The centerline of horizontal shore and wall should meet at floor level. 2. Wedges are driven in between straining piece and strut. 3. The angle of the inclination of the strut should be between 45 to 60°. 4. Single shores must be used solely up to 9 m distance between two walls. 5. Flying shores are inserted when the outdated building is being removed and needs to be kept in position until the new unit is constructed. 3.Vertical shoring or dead shoring: This vertical shorings are provided when: It is necessary to strengthen or replace the existing unprotected foundation. For rebuilding the faulty lower part of the wall. To make large doors, windows, or openings in existing walls. Dead shores have vertical members known as dead shores and horizontal members are known as needles. The following points should be kept in mind while erecting the vertical shoring: 1. Doors, windows, open floors, and other parts of the structure, which are likely to be affected by the removal of a defective wall or demolition of the wall are properly straightened or supported. 2. The section of needles and dead shores should be sufficient to move the load, which can be estimated with reasonable accuracy. 3. Needles should be suitably braced. 4. The approximate end of the beam is supported by a heavy vertical strut called a dead shore. 5. Dead shores are supported on sole plates, the folding wedges are between them. 6. The floor must be suitably supported from the inside. 7. All the struts provided in all openings have been properly tested, then the faulty part is gradually removed. To prevent a structure from collapse, there has to be some kind of support, shoring usually provides this support. The most common shoring technique that we encountered during the early stage of construction is an excavation. Shoring is important in preventing a project mishap due to the retained soil overturning in an excavation. It is often the go-to option when 1.20 meters or more excavation support is needed. Although it depends on the soil type. However, shoring is not only about retaining excavation soil. In fact, it is completely different from an excavation retaining wall. The sole purpose of a retaining wall is to retain soil during excavation. Whereas, for a structural engineer, it is way more than that. For a structural engineer, it is important that you decide on what type of is necessary for a construction project, as early as the beginning of the design stage. This article features 5 common types of shoring and their uses. But before we dive right in, let’s discuss what shoring means. What is Shoring? Shoring refers to constructing a temporary structure that would serve as lateral support to an unstable structure. Here are some situations for the use of shoring: Fixing bulged out walls When walls crack due to unequal settlement of the foundation and repairs are to be carried out to the cracked wall Pulling down an adjacent structure Making openings in a wall or enlarging one. 1). H or I-Beam Shoring The first on this list of common shoring types is the H or I-Beam Shoring. Another name for this shoring type is soldier pile walls. Depending on the soil type, you can either drive prefabricated steel I or H sections into the ground by first drilling the soil or vibrate directly into the ground without having to drill the soil first. To construct the complete shoring wall, concrete panels are pre-cast and installed between the steel beams already in the soil. Uses The use of this type of shoring ranges from supporting excavation with a depth between 1.2 meters to that of a depth of 5 meters. However, it can exceed 5 meters, as long as it’s design accounts for the surcharge load along its perimeter. 2). Secant Pile Shoring The next type of shoring on this list is the Secant Pile Shoring. Its construction involves the intersection of two piles combination, a “reinforced” or “secondary” and an “unreinforced” or “primary” pile. Forming a continuous wall by interlocking each other. Uses For cases where there are no rooms for open excavation, secant pile shoring is the best option. Additionally, the absence of space maybe because of the proximity of an existing structure. The secant pile shoring type is usually used for this case. However, the design must take into consideration the surcharge load due to the structure of close proximity. 3). Contiguous Pile Shoring The Contiguous Pile shoring, also known as Tangent Pile shoring is a very useful shoring type. It consists of piles, tightly spaced, and the name tangent pile shoring comes from the fact that the piles lie tangent to each other. Contiguous or Tangent Pile Shoring is composed of closely spaced piles wherein the faces of the piles are almost touching or tangent with each other. This is used in areas where water is not significant or the water pressure is very minimal. Construction of contiguous pile is very similar to that of the secant piles as prior to the installation, a guide beam should be constructed to serve as a guide for the contiguous wall to install in place. Uses For clay soils or areas where water is not so important or areas of very minimal water pressure, Contiguous Pile shoring is usually recommended. As it can help retain dry granular material. However, in water-bearing granular soil, this type of shoring will allow water seepage through the gap in the piles. Grouting the gaps in the pile, forming a watertight wall, can prevent the water seepage. Additionally, Contiguous Pile shoring is not suited for a high groundwater table, especially without dewatering works. 4). Sheet Piles The next shoring type on this list is the Sheet Piles. Its construction is similar to that of soldier piles. A Vibro hammer is used to drive a prefabricated steel section (Z or U) into the ground. The complete wall results from the connection of the sheet piles. Uses In addition to retaining soil to soil excavation, this shoring type serves as a good option when there is a need for excavation isolation from a water body (creek. Pond or seaside). It is a common fit in the construction of ports and harbors. Sheet pile walls are commonly used for earth retention and excavation support. However, their feasibility in rock layers depends on several factors. Let’s explore this further: 1. Sheet Pile Wall Types: Cantilever Wall: A sheet pile wall that acts as a cantilever beam, relying solely on its self-weight and passive resistance from the soil behind it. Anchored Wall: A sheet pile wall that combines interaction with the surrounding soil and mechanical devices (anchors) to inhibit motion at specific points. 2. Installation in Rock: Challenges: Sheet piles are typically challenging to install in rock due to the hardness and resistance of the material. Feasibility: 1. Highly Weathered or Decomposed Rock: In some cases, sheet piles may be driven into highly weathered or decomposed rock for short distances. 2. Avoid Overdriving: However, overdriving can damage the sheets, so caution is necessary. 3. Shallow Rock: For seawalls, vinyl sheet piles can be installed to the depth of shallow rock, with anchor pins securing the wall into the rock layer. 4. Boulders or Cobbles: Installation becomes difficult when encountering boulders or cobbles, preventing the desired wall depth from being reached. 3. Design Considerations: Structural Design: When designing sheet pile walls in rock, consider: 1. Bending Moment: Select an appropriate sheet pile section based on the maximum bending moment. 2. Passive Resistance: Add a safety margin or divide the passive resistance force by a factor of safety. In summary, while sheet pile walls can be used in rock layers, practical challenges exist. It’s essential to assess the specific rock conditions, consider design factors, and choose an appropriate wall type. Always consult with a geotechnical engineer or a qualified professional for site-specific recommendations 5). Diaphragm Walls Diaphragm walls come into play when the above mentioned shoring types do not fit for the excavation depth. Its construction is reinforced concrete. Diaphragm walls are flexible as its design takes into consideration the load that needs to be resisted. Basically, for deep excavations like basements and tunnels, this is a good option. Although there are other shoring wall types, the above are most common in construction.
