Sjotroll
Geotechnical
- Jan 2, 2018
- 30
Hello, I'm curious to know what approach you would use in the following situation.
Consider you have to design a pile group (vertically loaded) and calculate the bearing capacity and settlement. I know that there are many methods of estimating the group bearing capacity and settlement factors, but I'll focus on the recommendations given by EAP (2013) Recommendations on Piling. They provide diagrams to estimate these factors, which all require the embedment depth in the load-bearing strata as input. Each factor can be estimated for three types of soil: Cohesive (I), Cohesive (II), and Non-cohesive. It is easy enough to use with one soil layer, but when there are multiple layers it is not so clear as to what to do.
First, as I understood it, they define the load-bearing strata as any kind of material (cohesive or non-cohesive) which have the tip cone resistance (from CPT) or the undrained strength over a certain value. This means that if all we install the pile through one or more fine grained soils and end up in a coarse grained soil, but all have the corresponding parameters' values over the thresholds, then all of them are considered load-bearing and the embedment depth is equal to the whole pile length. Then, if the resistances are equally divided between the base and the shaft, how would you apply the diagrams?
I'm thinking my approach would be to analyse separately the base and shaft resistances. Then I'd determine the factor for the base resistance using only the one diagram for the soil in which the base is. For the shaft, I'd use all the necessary diagrams to get the factors, and interpolate them based on the length of the pile in each layer. This would require determining a lot of factors and a lot of interpolations.
I'm interested to hear how would you approach this situation, given your different experiences.
Consider you have to design a pile group (vertically loaded) and calculate the bearing capacity and settlement. I know that there are many methods of estimating the group bearing capacity and settlement factors, but I'll focus on the recommendations given by EAP (2013) Recommendations on Piling. They provide diagrams to estimate these factors, which all require the embedment depth in the load-bearing strata as input. Each factor can be estimated for three types of soil: Cohesive (I), Cohesive (II), and Non-cohesive. It is easy enough to use with one soil layer, but when there are multiple layers it is not so clear as to what to do.
First, as I understood it, they define the load-bearing strata as any kind of material (cohesive or non-cohesive) which have the tip cone resistance (from CPT) or the undrained strength over a certain value. This means that if all we install the pile through one or more fine grained soils and end up in a coarse grained soil, but all have the corresponding parameters' values over the thresholds, then all of them are considered load-bearing and the embedment depth is equal to the whole pile length. Then, if the resistances are equally divided between the base and the shaft, how would you apply the diagrams?
I'm thinking my approach would be to analyse separately the base and shaft resistances. Then I'd determine the factor for the base resistance using only the one diagram for the soil in which the base is. For the shaft, I'd use all the necessary diagrams to get the factors, and interpolate them based on the length of the pile in each layer. This would require determining a lot of factors and a lot of interpolations.
I'm interested to hear how would you approach this situation, given your different experiences.
