how do we apply a pressure line(surcharge load). 4

[maisir666]

I have a model where a 3 storey building sits on top of a slope. the pressure applied by the building is 30kN/m2. i am informed that we have to use a pressure line to modal this pressure. my question is, how long does the pressure line has to be,how long does the distance between the pressure line and the ground line have to be and what value should be used for the unit weight. i have read the manual and all it says is that the area between the pressure line and the ground line indicates the pressure applied on the ground.(we are using slope/W software package). can you tell me how i can apply the pressure line please. thanks.

 

[PEinc]

Hire a geotechnical engineer? Knowing that information is his or her job. You're in over your head.

 

[BigH]

Totally agree with PEinc. Do the work that you are qualified to do.

But given that - and for guidance to others - I would use a separate soil layer for the building, say 1 m high and width equivalent to the building's footprint in that direction and use a unit weight that will give you the building's weight. Use zero strength for this layer; piezo layer at the bottom of the 'building' layer. So, basically, you place a heavy pile where your building is located. Others might do it differently, but this has been okay in my experience to date.

 

[emmgjld]

maisir666

Your description of the problem leaves me with the impression that the building is to be supported on a matte foundation, as the building is described as "30kN/m2" and therefore, BigH's recommendation for modeling would be appropriate.

Your stated requirement that "i am informed that we have to use a pressure line to model this pressure" would imply that:
either the building can be truly modeled using a line load, actually a line load for each and all of the building load lines
or the stated requirement is given by one who understands the scale of the project, slope height vs. building size and loading and the line load magnitue is to be computed from the building footprint/building width and applied using the Slope/W instructions
or the stated requirement is given by one who is not competent to be stating requirements.

I agree that you need a geotechnical engineer. To continue the discussion, when dealing with the scale of the project, here is another point where a geotechnical engineer would add a great deal to the analysis.

The scale of the project would determine the method of applying the building load, assuming the foundation system is a footing and stemwall, not a matte. (It should be obvious that the building loads must be accurately determined for the appropriate foundation elements.)

A small slope height, fairly close to the foundation, may be directly affected by the concentrated foundation line load. The application of the line load should be at the base of the footing. (This may be important in a discussion involving the Building Code H/3 dimensioning)

A large slope height, under consideration for Global Stability, may actually be relatively unaffected by the building surcharge. However, the small part of the slope immediately adjacent to the building load may be affected.