The surface friction of the soil is taken into account when sizing the pile. There are basically two types of friction on the skin. Both negative and positive friction are taken into account when sizing the pile.
Positive skin friction is calculated based on soil conditions.
Depending on the soil parameters, surface friction is calculated.
Generally, geotechnical parameters are specified in the soil investigation report (geotechnical investigation report). Depending on the parameters specified in the report, we can calculate the positive skin friction.
Some geotechnical investigation reports provide values for skin friction. There are different layer thicknesses for different soil types. This must be taken into account when calculating friction.
If the unit surface friction is given depending on the type of soil, the surface friction can be calculated by multiplying the surface friction per unit area by the surface area of the pile in contact with the soil.
Compared to the evaluation method with geotechnical parameters, this is a very simple method.
There are many methods that can be used to calculate the surface friction of soils. Depending on the geotechnical parameters and available methods, surface friction can be calculated.
If the soil is weak and can settle due to overburden pressure, negative surface friction would act on the piles.
For example, with peat, negative skin friction can occur on the cuttings.
In particular, if the standard penetration value (SPT) is less than five, this is referred to as negative skin friction on the pile.
Negative skin friction affects the geotechnical capacity of the piles and exerts additional axial force on the piles.
If there are different types of layers that can produce positive and negative skin friction on piles, the skin friction is calculated by subtracting the negative skin friction from the positive skin friction.
If the pile is driven into very soft soil, in addition to geotechnical resistance tests, structural resistance tests of the pile must also be carried out.
In weak soil, the stakes deform freely compared to good soil. Therefore, the buckling effect must be taken into account during construction planning. Furthermore, the final state of the piles must be taken into account when calculating the effective lengths.
The article Design of individual piles could be used to apply the theoretical aspects discussed in this article.
