## Lateral earth pressure - short term and long term analysis

## Lateral earth pressure - short term and long term analysis

(OP)

I want to make sure I have a good understanding of the term effective stress, and how it impacts short and long term analysis (lets say a sliding analysis).

If you are calculating lateral earth pressures, your vertical stresses will be the same for long term or short term analysis, correct? The only item that changes is the c and phi values that impact your lateral earth pressures when you apply your Ko, Ka, or Kp factor. In other words, the vertical stress below the water table will be the effective unit weight *H, regardless of if you are doing a short term or long term analysis. It only impacts the K value.

Is that correct?

If you are calculating lateral earth pressures, your vertical stresses will be the same for long term or short term analysis, correct? The only item that changes is the c and phi values that impact your lateral earth pressures when you apply your Ko, Ka, or Kp factor. In other words, the vertical stress below the water table will be the effective unit weight *H, regardless of if you are doing a short term or long term analysis. It only impacts the K value.

Is that correct?

## RE: Lateral earth pressure - short term and long term analysis

## RE: Lateral earth pressure - short term and long term analysis

## RE: Lateral earth pressure - short term and long term analysis

The analysis can be a little more complicated than your example. It is rare that an analysis is for a completely static water table for all time. Water tables can vary and pore pressures in soil can take a long time to equalize, and so on. Long term strength properties can be difficult to define in many soils and they can change when the moisture content changes. Generally, it is best to be safe when water is involved and make conservative design assumptions regardless of soil test results in my opinion.

## RE: Lateral earth pressure - short term and long term analysis

the K coefficient is dependent on strength parameters and geometry. The Ko value can be affected, too, by overconsolidation pressures - such as induced high lateral stresses due to compaction.

## RE: Lateral earth pressure - short term and long term analysis

However, it is not always as simple as taking some test results, calculating a K, then applying that to the weight of the soil and height of wall. The math is that simple but the conditions have to be evaluated properly for water effects, tension cracks, etc. which is a little more complicated.

## RE: Lateral earth pressure - short term and long term analysis

## RE: Lateral earth pressure - short term and long term analysis

## RE: Lateral earth pressure - short term and long term analysis

f-d

ípapß gordo ainÆt no madre flaca!

## RE: Lateral earth pressure - short term and long term analysis

f-d - I agree also. Cohesion is not normal force dependent thus not weight dependent. However, the K part of the equation would be normal force dependent as the calculation is not normally based on c. The original question was about effective stress analysis so we will get back to how to use cohesion in an earth pressure analysis and so on...