Mat Foundation

What is mat foundation?

Mat foundation is a type of shallow spread footing. The word ‘mat’ means that the soil is placed and compacted in layers to provide a stable, level, and resisting base for construction works.

The term mainly refers to construction where the footings bear on soil with an insufficient bearing capacity or might be subject to excessive settlement. In such cases, low-density fill material (e.g. sand) supported by geotextiles and laterally reinforced by steel beams called matting, is placed over the ground surface prior to construction work commencing. After the finished building has been constructed on top of this mat, as time goes by, as long as it hasn’t been made from too dense materials which can result in a high settlement, the mat will be compacted by the weight of the building and the even distribution of load over an increased surface area.

The basic advantages of mat foundation are that it provides excellent bearing, low settlement characteristics combined with quick installation speed; also easy to construct on soft ground (e.g. sandy soil). However, it is suitable only for certain geotechnical conditions and some limitations may apply to its usage.

For instance, if the property is not strong enough or firm enough to support a certain structure, you can build on top using mat foundations without problems. But mat foundation design must take into consideration whether local environmental factors like saltwater could damage your structure due to caused by high concentrations of chloride found in saltwater.

Mat foundation design and construction are of utmost importance to the strength and integrity of your building or structure. If you had consulted a structural engineer who specializes in mat foundation design, they would have had more knowledge on what type of materials to use and how much weight it can take for maximum effectiveness.

You should choose your contractor carefully, as there are some contractors out there that might cut corners which could be dangerous! Be wary about hiring someone with no references; word-of-mouth recommendations from friends and family members can go a long way too.

Furthermore, mats will eventually settle over time as the weight of the building gradually decreases due to factors such as erosion, and damage by equipment degradation due to weathering conditions.

Mat Foundation Design

Mat foundation is one of the most efficient and cost-effective structural foundations in construction. It is a mat used for supporting a factory, storehouse, or similar building on the ground which is generally very soft.

Mat foundation design consists of a series of steel angles encased in concrete, these mats are laid across the ground to distribute the load over a wider area. The mat itself has many holes drilled through it from end to end so that when it comes time to pour concrete into these holes, they become continuous passages filled with concrete from end to end of the mat. This gives added strength and also helps prevent water from seeping into softer soils under areas covered by the foundation. This is also used for landing or takeoff areas on airfields, they can also be laid very quickly by placing the mat at an angle across adjacent piles of lumber.

Types of mat foundations

There are three types of mat foundation which include the following:

Continuous strip foundations

 A continuous strip mat foundation is a mat foundation that is continuous over the length of the structure. It is not broken up into smaller sections. In comparison to other types, continuous strip mat foundations are very flexible and can handle movements in the ground much better than other types of mat foundations. They are suitable for large structures such as bridges, dams, and even dams. These are the most frequently used type of continuous foundations in civil engineering across the globe due to their lower cost and ease of installation. These continuous strip foundations require less space than other continuous mats, making them ideal choices for buildings where there is minimal disturbance allowed such as historical sites or residential areas. When designing continuous strip mat foundations, engineers need to take into account many factors including soil condition and load-bearing capacity.

Continuous strip mat foundations are extremely useful in numerous applications due to their ability to be placed on uneven surfaces and to flex with movement. Their continuous nature makes them ideal for long-term use in design projects, while their flexibility helps bring stability to designs while mitigating the risk of failure or displacement. In designing continuous strip mat foundations, there are a number of factors that need to be taken into consideration such as the soil type and the load it will need to bear. Construction engineers and designers use different kinds of continuous mat foundations depending on their requirements and specifications.

The continuous mat foundation was first used in the 1960s and has since been extensively used for buildings where deep basements or underground spaces were required. These continuous strip foundations also provide additional benefits such as:

•  Energy efficiency – having a continuous mat foundation means that less heating is lost through conduction as compared to other types of piling techniques.
• Reduction in settlement – unlike other methods which involve large impacts to the ground during installation, continuous mats cause minimum disturbance to the surface as they are continuous.
• Installation flexibility – continuous mat foundation can be installed at any time throughout the year, effectively reducing the risk of delays due to unfavorable weather conditions.

Types of continuous strip foundations

The main types of continuous mat foundations include continuous strip mat, mat-pad and edge-supported mat. They vary in design as well as the materials used for installation which depends on soil type, loading conditions and space availability etcetera.

1. Continuous strip foundations are suitable for load-bearing capacity up to 100 MN/m2.
2. Mat-pad continuous foundation works best on soft soils or where there is minimal disturbance to the surface
3. Edge supported continuous mat foundation is ideal for use under high buildings where large concentrated loads will be present.

Advantages of continuous strip foundation

A continuous mat foundation has many advantages over other types of continuous strip foundation.

• They require less space and the installation process is faster and more efficient than other continuous mat foundations, especially in conditions where little soil disturbance is allowed such as in historical or residential areas.
• The continuous mat foundation can be designed to support both vertical and lateral loads.

Disadvantages of continuous strip foundation

However continuous mat foundations also have their disadvantages much like any other kind of continuous strip foundation technique:

• Requires extra compaction effort which increases overall costs
• Can only be used for shallow installations
• Prone to differential settlement due to lack of stiffening at the center point
• Less suitable for large concentrated loads and deep basements

Moment frame Foundation

Moment frame mat foundation moment frame is a moment-resisting system used in the construction of moment-resisting frames, the resisting systems are usually employed with masonry infill walls or reinforced concrete or prestressed concrete infill walls.

Moment frame mat foundation systems are also used for high towers, where lateral stability needs to be provided quickly.  For this application, moment frames are normally used as inner frames within the structure of the building.

Materials needed for moment-frame construction are diverse.  A typical conventional moment-resisting steel system requires that each column be designed to carry both axial force and bending moment due to gravity load effects acting alone on the stories above the level under consideration. They can be used in a variety of moment-frame constructions.  These include sloped moment frames to accommodate large moment deflections, moment-resisting braced frames for special applications, and moment-resisting braced core frames to provide adequate lateral resistance in tall buildings.

Moment frame mat foundation construction is done with the use of different types of building materials. however, the moment frame is mainly constructed using either reinforced concrete or steel with wood blocks making up the infill between vertical members.  For most modern buildings, a fully framed moment frame is popularly used; but there is still certain classic flat slab construction that uses masonry infill walls simply because moment frame mat foundation moment-resisting systems are generally more expensive to construct as moment frame mat foundation is a moment-resisting system that allows designers to obtain greater stiffness and strength than infill walls permit.

These were first designed for use with reinforced-concrete walls, although moment frames can be used with any light wall, such as brick or metal studs, the system was designed using the standard size and weight of concrete blocks.  It reinforces masonry walls so they can carry moment loads that would otherwise cause them to collapse.

Moment frame mat foundation steel structures have been used since the early 1920s in Europe and since about 1945 in North America etc, this type of moment-resisting system has been popularly used in various moment-resisting designs.

Moment frame construction does not allow large deflections, but it allows structural systems to function more efficiently while reducing vibration and increasing lateral stiffness, this type of system is most costly when compared with other types of structural systems because it requires a rigid core or infill wall. Uses for moment-frame systems are only limited by the imagination of the engineer, who can find countless opportunities where some form of moment resistance is appropriate, these include: high towers, moment-resisting braced frames for special applications, moment-resisting braced core frames to provide moment resistance in tall buildings. They are usually employed with masonry infill walls or reinforced concrete or prestressed concrete infill walls etc.

Hollow-core slab mat foundation

Hollow-core slab mat foundation is an engineered floor, made of hollow steel or concrete hollow core slabs, which are sandwiched between two layers of different strength reinforced concrete beams. Hollow-core slab mat foundation is acknowledged for its high strength and durability under seismic loading. It provides all the advantages of prestressed hollow cores (lightweight, high resistance to deformation) with steel or concrete materials (high compression). When used in buildings, it is complementary to traditional foundations; hollow-core slab mat foundations can be used instead of piling in buildings on soft soils where conventional piling cannot be installed due to environmental restrictions or because digging into the soil is complicated by existing structures (buildings, etc.). Although more expensive than conventional foundations when compared per square meter, hollow-core slabs are often more economical than conventional foundations due to the high reduction of the foundation depth.

A hollow-core mat can be used as a hollow core slab mat foundation. There are many types of hollow-core mats that are mainly made of steel hollow core slabs or concrete hollow core slabs with different thicknesses. The hollow core slab is sandwiched between two concrete beams whose strengths are different so that it could satisfy the compression load and tensile load bearing of the hollow-core mat during the construction progress.  Hollow-core mats’ ideal application circumstances include a soft soil layer under a structure base that cannot afford additional excavation cost, environmental restrictions on any conventional piling work, etc. However, many people may doubt their advantages over conventional piling due to their prices, However, in the long run, a hollow-core slab foundation can save lots of expenses.

A hollow-core mat normally has a thickness of around 200mm and a width ranging from 1m to 3m. When installing a hollow-core mat foundation, the first step is to take out the topsoil layer where the hollow-core mat will be installed on, dig down several meters deep with a certain slope if necessary for preventing groundwater from pooling hollow-core mats directly. Then install a waterproof membrane on the soil surface and reinforce concrete beams bond beam steel rods onto them using the precast technique under the guidance of SGS/TUV certification company’s workers or inspectors’ instructions. After that, place the second improvement hollow-core mat on the first hollow-core mat and reinforce concrete beams bond beam steel rods onto them using the precast technique.

In conclusion, hollow-core slabs are made of hollow steel or concrete hollow core slabs which are sandwiched between two layers of different strength reinforced concrete beams. It provides all the advantages of prestressed hollow cores (lightweight, high resistance to deformation) with steel or concrete materials (high compression). This type of mat foundation is equivalent to conventional piling in some circumstances due to its economical benefits over conventional piling.