33
votes
Accepted
Why does the Channel Tunnel enter the ground around 10 km from the coast?
The picture, below, of the exaggerated long section of the Channel Tunnel was taken from Wikipedia.
Full-sized image here.
Some of the limiting factors for the Channel Tunnel are:
Railways don't ...
- 9,642
7
votes
Accepted
Why are home geothermal systems usable anywhere in the U.S. but industrial geothermal plants limited in geographical use?
Because they're two completely different systems that have, in some circles, accidentally been given the same names.
The things that are sometimes (particularly in the USA) called home geothermal ...
- 3,751
6
votes
How does excess water makes soil compaction more difficult?
Beyond a certain level of saturation, the bulk modulus of water starts playing an important role. Since water is nearly incompressible at moderate pressures, the pore pressure increases rapidly and ...
- 1,443
6
votes
Difference between 'plastic yielding' , 'plastic yield strength', plastic strength' and 'plastic stress'?
All these terms refer to the effect of loading on the deformation of materials. Let us assume that we start with zero load and zero deformation.
Elastic deformation
If you increase the load you ...
- 1,443
6
votes
Accepted
How to determine the lateral earth pressure in a double-walled cofferdam?
From what I read, you are looking at the pressure the sand between the sheet piling exerts on them. In this case, I see two possibilities: (1) log-spiral analysis or (2) elastic analysis of ...
- 652
5
votes
Why dig out and then fill in before building a large structure?
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,...
- 181
4
votes
Accepted
What is the difference between "Crushed Stone" and "Crushed Gravel" aggregate?
It's of importance to note that historically, "stone", "gravel", and many other related terms have great regional variability. It is always advised to make certain what is meant by such terms when ...
- 1,156
4
votes
Accepted
Are pumps used in geothermal systems
They are both correct. There are actually a number of different types of geothermal power plant with the most common being, dry steam, flash steam, and binary cycle.
Dry steam plants require pumps ...
- 170
4
votes
Accepted
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 ...
- 170
3
votes
Accepted
To Which distance Punching Shear Reinforcement is placed in Mat Foundation?
For a more complete discussion see: ACI 421.1R-08 - Guide to Shear Reinforcement for Slabs.
But in principle you need to continue to provide punching shear reinforcement until the shear capacity of ...
- 2,631
3
votes
Is there a torsion test in rocks?
I am unaware of a torsion test for rock. Shear, compression & tensile strength tests yes, but not torsion.
All the civil engineers, mining engineers and geotechnical engineers I have worked with ...
- 9,642
3
votes
How do you convert "kps" to Pounds per Square Foot (psf)?
I've done some searching, according to this converter kps or KPS stands for Kilo Pascal, but don't use that abbreviation.
The actual abbreviation for Pascal is Pa, and for kilo a small k, combined kPa....
- 1,166
3
votes
Accepted
What is the meaning of these two inverted triangle water table symbols in a borehole record?
The water table in some locations may vary during the day or over time. For this reason, the borehole drilling process includes waiting periods to see if there are any changes to the water table.
The ...
- 13.1k
3
votes
how much force is required to drive a fence post 2ft into soil or sand using a hydraulic press?
What you are proposing is similar to the cone penetration test (CPT) used by geotechnical engineers to characterize the soil layers of a site before construction.
The measured resistance to a ...
- 154
3
votes
Accepted
what kind of expert can analyze drought effect on rock fall risk?
You need to consult a geomechanical engineer. Sometimes they can also be referred to as geotechnical engineers.
A geologist can tell you overall geology of the region of interest, but to determine ...
- 9,642
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 ...
- 171
2
votes
Active vs passive earth pressure
If a retaining wall is immobile, it incurs lateral soil pressure from both sides, and that is the so called resting pressure.
When the retaining wall, due to load from the retained soil massive, ...
2
votes
How does excess water makes soil compaction more difficult?
For a given compaction energy, this is a volumetric problem. Keep in mind that we are working with a given volume (say 1 cubic metre) of dry particles (solids), water and air, thus:
...
- 652
2
votes
What is a safe soil load to avoid settlement?
The PRESUMPTIVE LOAD-BEARING VALUES table in the IBC is meant to be used with ASD loads (see section 1806.1). As such there are already factors of safety "built in" to those values. The only thing I ...
- 1,156
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 ...
- 22.1k
2
votes
Accepted
Base or foundation?
The part of the building that is in contact with the soil is the foundation:
the lowest division of a building, wall, or the like, usually of masonry and partly or wholly below the surface of ...
- 3,135
2
votes
Accepted
Dynamic Cone Penetrometer (DCP) results and correlation
Standard
The official description of the test can be found in one of the following depending on your location of interest:
BS 1377 Part 4
ASTM D 6951 or ASTM D 3441
These should have all of the ...
- 10.7k
2
votes
Accepted
Postion of overturning moment for retaining wall
I have designed plenty of (probably several dozen) retaining walls with long toes in situations with low allowable bearing capacities. Usually designed with RetainPro (which is not FEA), but also ...
- 1,156
2
votes
Base or foundation?
As was said in the other answers, the part in contact with the soil is the "foundation", or perhaps "footing" (a specific type of foundation, but there are also piles, drilled shafts, rafts - all of ...
- 1,156
2
votes
Load conversion for geotech problem
In the comments you seem to already understand that kN/m/m means "kN per meter along your screen, per meter into your screen". This can be simplified as kN/m2: kN per meter in each direction.
The ...
- 13.1k
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 ...
- 22.1k
2
votes
Drained and undrained shear strength of clay correlated?
They are certainly correlated but there is no simple relationship. A commonly used rule of thumb, where I live, is $c'=0.1c_u$ for overconsolidated clays and zero otherwise, but reality is much more ...
- 1,288
2
votes
The best foundation type?
It is the right foundation type that is the best. Not necessarily pylons or any one size fits all solution.
Design of foundation is a process tightly tied to the type of soil, geology of the site, ...
- 22.1k
2
votes
Accepted
Missing items in geotechnical reports
A structural engineer should never conduct their own soil testing unless being supervised by a competent person. This is not your area of expertise, let the geotechnical engineer do their job.
...
- 266
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 ...
- 10.7k
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