When should you call un a soils engineer ?
Many builders and architects are reluctant to hire engineers perform subsurface investigations, and that’s easy to understand : The cost of a house can go up few thousand dollars . Despite the cost, there are circumstances which consulting soil engineer is a wise investment.
If you wondering how earth you are supposed to build a house on a lot with a steep slope, then you need an engineer to determine the soil properties and to evaluate the stability of the incline.
A local history of the presence of the clay soils that are susceptible to shrinking and swelling with changes in moisture content also requires careful investigation and usually , specialized deign services and the use of an out of the ordinary foundation.
Consult your experience . If you are crossing your fingers and hoping the soil conditions would not cause a problem ,you are probably , right to be uneasy . Call in the specialist
Just like concrete in you basement slab. Failure to compact is what leads to cracking sidewalk uneven slabs.
It is particular important that fill be placed in thin layers so that the densification effect of the compaction equipment is it felt the all the way to the bottom each layer. The maximum thickness for each layer depends on soil type : Ordinarily about 12 inches for sandNS 6 inch to 8 inch for clay. The required degree denisification usually set forth by the local building code and specified as some percentage of maximum dry density as determined by one of several standard methods.
The moisture content of the fill material must also be controlled . If the moisture is too low , it is difficult for individual soil grains to realign themselves into the densest configuration ; adding moisture lubricates the grins and make realignment easier . But if there is too much moisture , the soil becomes unstable under the influence of compaction effort will be the water between the soil grins and result in a water bed like rolling the soil . Granular soils such as sand are most desirable for use as fill because their moisture content can be easily tweaked.
TO prevent settlement problems, soil that is stable and compacted must extend at least half the distance from the base of the footing to the influence depth ( the farthest distance beneath the footing that its weight is felt by soil particles.) Strip foundations ( such as the wall in the drawing below right ) as the pedestal the drawing and thus have greater influence depths.
Stable compacted fill extends half the influence depth. Only soil grains inside this stress bulb feel the weight of the foundation. The formula applied when the length of the foundation is 10 or more times greater than its width.
Stable compacted fill extends half the influence depth , Influence depth is (ID)=4xB