Geotech Imp Questions!!

[geobuddy]

I have following questions. If someone can clarify, it will be a big help

1) When analysing retaining walls, how do we know which method to use (if not mentioned) Rankine or Coloumb??

2) For inclined backfills and vertical retaining wall, there are two diff formuls: As per Lindeburg Ka (active earth presuure coefficient) can be calculated by formuala (Equation 37.6) which is different then curves/graph used by NAVFAC manual (7.2-64). I am getting different values of ka. Which one should I use??

3) Lindeburg has last probelm in which to calculte Ka nd Kp he mentioned either to use the formula (Eqn 37.6) or to use graphical solution (Kah and Kav) valus from Appendix 37.1 which one should we use?? I am getting different values of horizontal and vertical forces/ length of wall

4) When it is said that conditions are 'drained' we use total density, when it is said undrained (even though soil may not be fully saturated) we use submerged density. Why??

5) If problem is for excavation in sand/clay, and it is not mentioned that execavtion is barced/unbraced should we use bracing lateral pressure formuals by default or we should use Rankines lateral earth pressure formaula.

 

[Civ_Guy]

I have following questions. If someone can clarify, it will be a big help
1) When analysing retaining walls, how do we know which method to use (if not mentioned) Rankine or Coloumb??

2) For inclined backfills and vertical retaining wall, there are two diff formuls: As per Lindeburg Ka (active earth presuure coefficient) can be calculated by formuala (Equation 37.6) which is different then curves/graph used by NAVFAC manual (7.2-64). I am getting different values of ka. Which one should I use??

3) Lindeburg has last probelm in which to calculte Ka nd Kp he mentioned either to use the formula (Eqn 37.6) or to use graphical solution (Kah and Kav) valus from Appendix 37.1 which one should we use?? I am getting different values of horizontal and vertical forces/ length of wall

4) When it is said that conditions are 'drained' we use total density, when it is said undrained (even though soil may not be fully saturated) we use submerged density. Why??

5) If problem is for excavation in sand/clay, and it is not mentioned that execavtion is barced/unbraced should we use bracing lateral pressure formuals by default or we should use Rankines lateral earth pressure formaula.

Are you asking in reference to the exam as opposed to in work practice?

I would state in general (means my opinion) the type of approach will have to be specified in the exam question. There is more than one way to answer the questions but given the approach of the exam, on approach may be more conservative than another.

For question 4, are you referring to Lateral Earth Pressures specifically? I believe you may have answered your own question. If it is drained, there is no pore pressure to be concerned about. I hope this is what you have describing?