30

This is to make sure they know what the foundation is made of. For all they knew there may have been an old tunnel underneath that would have collapsed when the new building is put on top. London is built on top of an old marsh, this type of soil is very prone to sinking and uneven settling, digging down and reinforcing the foundation alleviates that. It ...


21

There are a few reasons why the footprint of large buildings are excavated and replaced. All of the old building must be removed - Typically, older buildings will have been built with weaker materials or less stringent building standards than are currently used. Depending on the age of the existing structure, complete plans may not even exist. This means ...


18

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 the earth and have a softer layer on top of it. Layers Say you want to build a building in an area that has a lot of soft clay at the surface. This clay will ...


9

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 track structure. Why is this necessary? Well, there are are two main underlying reasons why you don't want water in your track structure: It tends to lead to ...


9

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 heaving forces of expansive clay soils, they anchor the building down against toppling in earthquakes and getting blown by the wind or washed away by the floods. ...


9

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 an answer for what is required. You now have two options: Choose a small footing that your own solution just proved is too small for the requirements. Choose ...


6

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 in many countries for barns etc This was also done to stop snow sitting against the lower part of the wall in many cases as well.


6

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 by generating absurd deformations, massive cracking (in the case of reinforced concrete structures), or if it will vibrate like a guitar string whenever you take ...


6

What is the down stand beam called at an edge of a surface bed or raft foundation? It is not exactly a grade beam or stem wall. It is more like a toe. This is probably a regional nomenclature thing, since I'm seeing quite a few ways for naming this. If you call it a grade beam, I don't think anyone will take it amiss. Examples below of different ways of ...


6

"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 should be 400mm apart. If you were to measure the gap between the joists, it would be less than 400mm, due to the thickness of the joist itself.


5

If one side of foundation has soil packed more loosely than the other side, the foundation may cause the ground to sink, and building may crumble. Even if it has a steel-reinforced concrete foundation, the building may tip sideways, causing uneven floors, or wood to shift and split, even if concrete remains in same shape. In my area we have a lot of caves, ...


4

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, so point bearing capacity is non-existent, only consider lateral capacity. Depending on the soil type (and remembering it is saturated), this may or may not ...


4

What you need is the modulus of subgrade reaction (MSR) of the soil. This is a measure of soil deflection under a given pressure, so the unit is in (for example) kPa/m, or equivalently, as I'm more accustomed to see it, kN/m3. MSR is obtained via plate-bearing tests, but there are also quite a few different tables that give some "typical values" for ...


4

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 ballast if it has good drainage. The idea with unballasted track is that the concrete redirects the water so that the ground immediately below it stays dry, ...


3

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 define with a blanket statement. The problem is that the slope is necessary to give the soil stability. Unfortunately, the soil's stability is highly dependent on ...


3

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 concrete. In areas where the ground becomes highly saturated it can protect the concrete foundation from erosion. The wire mesh is usually used for load-bearing ...


3

Before jumping into elastic support conditions, you have to realise that it's not a ground beam. For three reasons: With a minor axis width to depth ratio of 6ish, it's not far away from a square. If you stick a wide support somewhere near the ends of the section, the load will simply arch over the supports in pure compression. You'd almost be able to ...


3

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 dependent on the mass distribution throughout the buliding. For example of you will show access to the roof of your third floor container for its use as a deck, ...


3

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".


2

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 differential movement causes a building to crack. Foundations are dug down to below an expansive soil and below the frost line to avoid movement. They are then built ...


2

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 plasticizers to minimize cement washing and floating to the surface of concrete will be used and because of its density; it will push the water up and not mix with it. ...


2

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 cheapest one: Place pipes at various and multiple positions in the raft vertically to release the pressure. These pipes shall be interconnected above the raft in ...


2

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 geotechnical report. The strength of the concrete. This can be determined either through core testing or something called a "schmidt hammer". The schmidt ...


2

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 suspended structures such as utility rooms not getting support from their own foundation, or hillside structures overhanging over the slope. Then they are ...


2

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 slab left 80 cm (2000 - 600 - 600 mm = 80 cm)in between, you might as well do that section thick all the way, for ease of construction - just an idea. Whether ...


2

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 cause the water to migrate further down the ground, until such that it is held up by capillary action. Given such, the addition weight of the water coming from ...


2

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 enough to create some acceptable equilibrium below the level of the earth icing to handle moisture content changes in non expansive soils. But for many ...


2

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 approximately 40 degrees with horizontal, so it is not possible to make the excavation without disturbing the soil. That angle is called the angle of internal ...


2

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 can be increased: Increase the length Wait The first option is fairly obvious. To some degree, every additional unit length of pile will increase the total ...


1

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 soils engineer orders to stop the job and possibly take a sample for the lab.


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