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What is the purpose of building foundations?

Down, Not Out Building foundations don't always have to spread the load out to a larger area. Sometimes the load only needs to be transferred to a stronger (harder) layer. This layer may be deep in ...
hazzey's user avatar
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9 votes
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For train track, why does the ballast need "good drainage"?

There are a number of good reasons why the ballast layer needs to be free draining. The main objective of the ballast layer being free draining is somewhat tautologically to keep the water out of the ...
Big Luke's user avatar
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9 votes
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PE exam: situations in which two question choices are close to my final answer: how to pick one?

You are worrying about the numbers and forgetting what the numbers mean. This is for the PE exam, so this is a very important topic to make clear in your mind. You solved the problem. You came up with ...
hazzey's user avatar
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8 votes

What is the purpose of building foundations?

Building foundations perform many tasks. They provide a strong base to take the weight of the building, penetrate through incompetent layers of soil to reach a layer strong enough, they resist the ...
kamran's user avatar
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7 votes
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What does "crs" mean in structural engineering / construction?

"CRS" is an abreviation for "Centers". So, for example the statement "Deck Joist @ 400mm crs" means "at 400mm centers", i.e. that the centreline of the joists ...
Jonathan R Swift's user avatar
6 votes
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why are foundations designed at SLS

No. In fact, SLS frequently leads to a higher factor of safety than ULS. This is because ULS deals with whether or not the structure will collapse. It does not care whether the structure will stand ...
Wasabi's user avatar
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6 votes

What is the purpose of building foundations?

Those stones have larger stones underneath them in the ground so that they will not sink - as the load is spread. The purpose is to prevent rats getting into the storage - this was a technique used ...
Solar Mike's user avatar
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4 votes
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Building Uplift due to water pressure

There are a few possible solutions. You can use pile foundations, where the piles dig deep into the soil and resist the uplift. They'll work entirely in tension, instead of the usual compressive load,...
Wasabi's user avatar
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4 votes
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Why is this construction site pouring gravel over a wire mesh, and then covering it with dirt?

You are correct, this is the subbase that the foundations will be built on top of. The gravel can be used as you say for water run off but it also allows for a level base on which to lay the ...
loogle1's user avatar
  • 170
4 votes

For train track, why does the ballast need "good drainage"?

For both kinds of track, the answer is the same: to prevent the track from shifting as a result of freeze-thaw cycles. The idea with ballasted track is that water is not allowed to accumulate in the ...
Dave Tweed's user avatar
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4 votes
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How do extra building levels affect the foundation design apart for the extra load?

Foundation's task is not just to support gravity loads, it should resist lateral loads, wind and earthquake, as well. Wind loads are dependent on the geometry of the building and seismic loads are ...
kamran's user avatar
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3 votes

What does "crs" mean in structural engineering / construction?

Does not apply to this example, but just for completeness: I've also seen CRS as an abbreviation for cold-rolled steel in a material callout in machine drawings, e.g. "1018 CRS".
Pete W's user avatar
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3 votes
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Foundation Excavation: How much larger than the RCC footing?

I don't know of any code which defines this, but a one meter "working perimeter" around the footing is probably more than enough. Regarding the slope of the excavation walls, that's trickier to ...
Wasabi's user avatar
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2 votes

Why dig out and then fill in before building a large structure?

In addition to the other answers, some soils (e.g. clay) expand and contract as their moisture content changes, and wet soil expands as it freezes. This movement is rarely even across site, and ...
Robin Bennett's user avatar
2 votes

Bored Pile construction Procedures When having Water in the ground

Water accumulating in the bottom of the bore is not a concern, as long as concrete is delivered at the bottom of the bore via a hose. Concrete with the slump of less than 4inches with some ...
kamran's user avatar
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2 votes

Building Uplift due to water pressure

In such a case following multiple solutions are suggested. Tension piles are the best solution. Raft often creates uplift pressure if the water table is high or may vary season to season. Now the ...
Abid Qazi's user avatar
2 votes

Why is the wet/dry boundary of ground not dangerous for foundations?

That water you have described where the ground is wet but the lower ground at the foundation levels were dry, is generally not going to cause significant problems because the weight of the water will ...
Isa's user avatar
  • 298
2 votes

Why is the wet/dry boundary of ground not dangerous for foundations?

Depending on the type of soil at your site, moisture content under the foundation can change depending on the change in surrounding soil. The typical footing depth in the majority of cases will be ...
kamran's user avatar
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2 votes

Concept design for an extension to a blanket raft slab

Foundation design starts from soil and geology and ends to the structure, live and dead loads. First one needs to investigate the soil, its competency, stratification, any subterrainian water level, ...
kamran's user avatar
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2 votes
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Capacity of plain concrete foundation on grade [Civil UK]

In order to determine the capacity, you will need to know a couple of things. Dimensions of the pad and container Bearing capacity of the soil under the slab. You would normally receive this from a ...
Forward Ed's user avatar
  • 1,221
2 votes

At what level is the Grade Beam most effective at pile cap level or at Slab-on-grade level?

The grade beam typically must be supported by competent soil. In some cases they are designed as per recommendation of soils report for specific tasks such as integrating soldier piles or supporting ...
kamran's user avatar
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2 votes

Low pile capacity during pile driving

Since you said that the piles are not reaching the desired capacity, I am assuming that these are friction piles instead of bearing piles. There are two ways in which the capacity of friction piles ...
hazzey's user avatar
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2 votes
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3 x 1 stone under footing and sump crock

If the excavation has a slope of roughly 3 vertical to 1 horizontal, that's about 70 degrees with horizontal. An unloaded slope in stones, gravel or sand will not be stable at an angle of more than ...
ingenørd's user avatar
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1 vote

Small building basement foundation moisture: permeable vs impermeable

You are missing seepage with humidity. Seepage is the infiltration of water into the living space (basement) and makes the space wet or moist. It does cause concern about humidity, but seepage alone ...
r13's user avatar
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1 vote

Distance of raft foundation outwards

Raft foundation doesn't necessarily have to extend byond the exterior column. On occasion a column may start at 2nd or 3rd floor even outside of the footprint of the raft, having the floors above ...
kamran's user avatar
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1 vote

Low pile capacity during pile driving

I worked for a main contractor as project engineer. Taking my experience from one of my project. To be more specific, when we are driving piles into the soil, say we are using hydraulic hammer pile ...
Disrudog's user avatar
1 vote

Low pile capacity during pile driving

It is assumed we are still in fill layer. Usually we keep going down till we hit the competent strata. Then we log the depth and keep going. In some jobs variation of the fill depth is normal. Unless ...
kamran's user avatar
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1 vote

Difference between Allowable Bearing capacity Service and Ultimate?

Let me raise an example: By Ultimate Capacity, my slab thickness required is 80mm for a particular span X meter. Which my slab would not fail to carry the load into the beam and column. By ...
Disrudog's user avatar
1 vote
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Concept design for an extension to a blanket raft slab

We don't see the magnitude and layout of the load. That will determine how the slab needs to work. Your layout seems fine to me, but someone may disagree. Also at the top left corner, too narrow of a ...
upstream's user avatar
  • 462
1 vote

18' header beam installation for single story room addition

You need to go to your city building department and pull a permit. They usually have a code engineer who tells you what you need to do in detail. If your soil is ok and you are not in a hillside, it ...
kamran's user avatar
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