lateral earth pressure between concrete wall and sheet pile wall
lateral earth pressure between concrete wall and sheet pile wall
(OP)
I am presently working on a bridge replacement project where the existing abutment will remain. However, in order to increase its stability under the new loading, a sheet pile wall is proposed to be driven behind this existing wall to reduce lateral earth pressures.
The sheeting will need to be driven beyond the toe of the existing wall; therefore, a reduced lateral loading will still be felt by the existing wall. How should I be approaching the development of the reduced lateral load since the triangular shape of the pressure envelope is no longer triangular? Any suggestions would be appreciated.
The sheeting will need to be driven beyond the toe of the existing wall; therefore, a reduced lateral loading will still be felt by the existing wall. How should I be approaching the development of the reduced lateral load since the triangular shape of the pressure envelope is no longer triangular? Any suggestions would be appreciated.





RE: lateral earth pressure between concrete wall and sheet pile wall
What needs to be improved? Sliding resistance? Overturning resistance? Tension steel in the stem? Can you install tieback anchors through the stem or footing? Can you install tie rods and deadmen? Can you increase the weight on the heel of the abutment footing?
RE: lateral earth pressure between concrete wall and sheet pile wall
Engineering is the art of not constructing...of doing that well with one dollar what any bungler can do well with two after a fashion.
RE: lateral earth pressure between concrete wall and sheet pile wall
RE: lateral earth pressure between concrete wall and sheet pile wall
RE: lateral earth pressure between concrete wall and sheet pile wall
If you have pressure on both sides of the sheet pile where do you get a substantial net pressure? Thus I do not see how you can reduce earth pressure on the abutment even with tiebacks.
Another item is that pressures and distributions for flexible verse rigid retaining systems are different.
Regards
VOD
RE: lateral earth pressure between concrete wall and sheet pile wall
RE: lateral earth pressure between concrete wall and sheet pile wall
I agree that at time = 0, the full pressure will be felt at the existing wall; however, since the sheeting is estimated to deflect up to 1.25 inches, the existing abutment would need to deflect that much before reduced loading kicks in. With the existing abutment approximately 19 feet high from the bottom of footing to the top, 1.25 inches of deflection is not considered significant.
The bridge will remain open during a phased construction process with the two abutments and two piers rehabilitated to support the new superstructure.
PEinc - Based on a stability analysis performed for the proposed rehabilitated abutments, factors of safety against overturning and sliding do not satisfy the minimum requirements and the maximum calculated bearing pressures under both existing abutments are greater than the allowable bearing capacities with the vertical force resultant outside the middle third of the footing.
We've looked at installing tieback anchors directly through the stem; however, the required anchor force will overstress the stem. One other feasilble option was to use Controlled Low Strength Material (CLSM) behind the abutments. The cost to temporarily support the roadway to install the CLSM cause this alternative to not be one of the top ranked alternatives.
RE: lateral earth pressure between concrete wall and sheet pile wall
Please see FAQ731-376 for great suggestions on how to make the best use of Eng-Tips Fora. See FAQ158-922 for recommendations regarding the question, "How Do You Evaluate Fill Settlement Beneath Structures?"
RE: lateral earth pressure between concrete wall and sheet pile wall
RE: lateral earth pressure between concrete wall and sheet pile wall
Although tis solution I feelis technically feasible, my concren would be long term corrosion of an important system that you would not be able to inspect. Also achiving sufficent compaction along the wall and especially at the wale will be difficult.
the previosly noted bored pile wall is certianly one option. Retriculated minipiles are another option.
Good Luck!
RE: lateral earth pressure between concrete wall and sheet pile wall
RE: lateral earth pressure between concrete wall and sheet pile wall
The top 6 feet of abutment was proposed to be demolished and rebuilt to support the new superstructure and reinforced enough to act as an internal waler for the tiebacks. The existing plans for the abutments indicate a deficiency in steel reinforcement to carry the bending moments when the tiebacks were tensioned up. Drilling and grouting additional rebars below the location of the tiebacks will be an option to look into (thank you PEinc).
RE: lateral earth pressure between concrete wall and sheet pile wall
For example, I recently designed temporary tieback anchors for the stem of an existing, 18' high, concrete retaining wall. I designed the tiebacks for the full earth and surcharge pressures. The work was completed a few months ago with no problems. The wall needed to be tied back so that the contractor could make a deep (17' to 27'), soil nailed excavation immediately in front of and below the wall's footing toe. I may be wrong but couldn't your problem be similar to, if not less critical than, mine?
RE: lateral earth pressure between concrete wall and sheet pile wall
That soil nail supported cut below the existing abutment footing is quite impressive! What was the purpose of such an excavation?
RE: lateral earth pressure between concrete wall and sheet pile wall