“It is now such a sad state of affairs that codes” and building dept. There are also plenty of conditions which will alter this magic frost depth number, and a good foundation designer had better pay attention to them too. And, it seems that these qualities are becoming less and less common in our profession or in the agencies which watch over us and our work. But, this takes some engineering experience and judgement to determine with any confidence. The are plenty of instances where the footings or slabs don’t have to be below the frost line, and you still won’t have frost heaving problems. It seems to me that BigH is right on the money on several accounts. RE: Frost line depth pdzeng (Geotechnical) 19 Nov 13 11:56 Yes correct but it will also prevent the tempeartures going below 0`C under the raft wich will ensure me not to worry aboth slab heaving forces IF founded in "frost suspicious" ground. The "solution" was to dig out the "frost suspicious" ground and fill it up with well graded sand and gravel (fractions from 0.6mm to 60mm) wich have to be compacted and after compaction we usualy run plate test fi30cm wich determines the constrained copressibility modulus ( I dont know how you call this in USA but it ranges from 20 MN/m2 to 60MN/m2 for well compacted granular fills).Īttached your sketch implies is the use of rigid insulation to limit the lateral transfer of energy from the inside to the outside and vice-versa" We talked aboth "what if" you dont go by the book but still want to design foundations at shallower depths. So maybe better to bring those foundation to 0.70m depth and also benifit from aditional ground surcharge but at the cost of more concrete and reinforcement beeing instaled.
We agreed that this forcast is somewhat exaggerated but you never know what might happen and if it does youll be to blame to not designing by regulations.
In 40 years there has never been an temperature drop under -5`C in my region. In my region the minimum temperature forcast are -15`C wich we found unbelivable! The depth is defined due to minimum temperatures that could accur in 50 years period for a given region. I talked to a friend who works at the Civil Engineering University and the minimum foundation depth due to frost danger has change for my region from 80cm to 70cm. RE: Frost line depth GeoPaveTraffic (Geotechnical) 14 Nov 13 13:54 So, you dont follow your local regulation codes! So this would mean that you woudl also have to inslulte your foundation perimetar since your foundation solution is of an "raft action" and not just a strip perimetar I commonly use 18" as a minimum, but greater where required by the local jurisdiction"
Generaly at 50cm in the coldest months, temperatures were never below 4˙C and at 100cm there where never below 6˙C!Īnother problem that I can think of if going "by the book" is, even if I use edge perimetar beam for the raft, wich will ensure my foundation depth below the frost line, this still doesnt means that tempertures under the slab wont be below zero!Īs oldestguys pointed, concrete is a good thermal conducter, wich will also cold the groound beeneth the slab very fast unless there is an thermal material attached to the perimeter beam as seen from the sketch attached. I found few of these for my local town and one town up in the north thats colder in the winter. Maybe regulations on these minimum foundation depth are taken as very conservative.ĭoes anyone here maybe has any ground temperature data at define depths that were monitored during winter days/months for your local town and can you draw an comparison for regulations requirements? Very interesting and totaly contradicts the regulation requirements. " in the colder climate of northern USA states, with deeper "frost peroration", many non-heated buildings are on a slab on grade, yet heaving of the slabs seems to be a minimal problem, at least in my experience"
0 kommentar(er)
