About Jeanette A Expertise Willing to answer all civil engineering-related questions through the undergraduate level. I will explain unclear concepts and suggest approaches to solving problems, but would prefer not to completely solve homework problems for you. If you are completely stumped on homework/assignment I will do my best to try and guide you in the right direction. Also willing to give advice on issues not related to study although related to civil engineering.
Experience I have been studying for 5 years in Civil Engineering and have a sound knowledge of various civil engineering subjects. I have also worked as a consultant in the Roads and Highways Department for Sinclair Knight Merz (SKM).
Education/Credentials Undergraduate
Bachelor of Civil Engineering and Diploma in Engineering Practice, University of Technology Sydney, NSW
Question hi, can you please assist me with the following.
1.) fully describe the construction of a pad foundations for a building.
2.) what is meant by the term underpinning
Answer Hello Tim,
A pad footing is mainly used for isolated loads and the process which is adopted for pad footings is very similar to the process used for strip footings.
The basic outline for the construction is as follows:
- A trench is excavated with a backhoe
- A reinforcing cage is placed in the trench
- Concrete is then poured into the trench
- Depending on the building code of the country, the trench can be left to stand without any formwork (eg clayey soil. The only place formwork will be required is for the part of the foundation that is above ground level
- For sandy soils, the trench will need to be excavated and completely formed before the concrete can be poured to prevent the sand from collapsing
- For areas subject to wind and erosion, footings should be constructed at least 300mm below the surface the prevent undermining
- For cold areas, footings should be constructed below the depth frost penetration so the footing is not affected by frost heave
- Backfill should be provided against sides with non-frost susceptible soil
The term underpinning refers to:
Material or masonry used to support a structure, such as a wall.
Here is some information from the internet:
In construction, underpinning is the process of strengthening and stabilising the foundation of an existing building or other structure. Underpinning may be necessary for a variety of reasons:
- The original foundation is simply not strong or stable enough.
- The usage of the structure has changed.
- The properties of the soil supporting the foundation may have changed (possibly through subsidence) or were mischaracterized during planning.
- The construction of nearby structures necessitates the excavation of soil supporting existing foundations.
- It is more economical, due to land price or otherwise, to work on the present structure's foundation than to build a new one.
Underpinning is accomplished by extending the foundation in depth or in breadth so it either rests on more supportive soil stratum or distributes its load across a greater area. Use of micropiles and jet grouting are common methods in underpinning. An alternative to underpinning is the weakening of the soil by the introduction of a grout. All of these processes are generally expensive and elaborate.
Underpinning may be necessary where P class (problem) soils in certain areas of the site are encountered.
