Drilled Pier installation near a MSE wall

[evenbetter]

Drilled piers will be installed near a new MSE wall. I know how to analyze the additional horizantal stress on the wall caused by the weight of the installation equipment. But how to analyze the influence (installation process, vibration) of the piers on the wall? What's the typical spacing required between the pier and the wall?

 

[BigH]

Can you give a better description of what you are doing? I surmise you are going to install drilled piers just behind the MSE wall - outside the zone of reinforcement or will you be installing within the zone of reinforcement - else why do you have horizontal forces on the "wall" - the weight of equipment will probably be small to the weight of the soil if you are in the "retained" area. Or are you going to install the drilled piers at the base of the wall - outside the wall? How large will the drilled piers be?

 

[evenbetter]

After discussing with the structural engineer, I finally figured out what he needs. Basically, they want to build a MSE wall first, then install drilled piers near the toe of the MSE. The center line of drilled piers is 4.5 feet away from the face of the MSE wall. The diameter of the drilled piers is 36 inches.

 

[cdh61]

evenbetter,

The 4.5 ft away from the toe of the MSE wall should not be a problem, but you will need to assess soil conditions to ensure there will be no problems during drilling or during the pouring of the concrete. A fast set concrete may be required depending on site conditions, such as the height of the MSE wall and the potential for a local slide or soil creep into the bore hole.

regards

 

[BigH]

As intimated by cdh61 - you would have to consider sloughing into your drilled pier. If you have firm to stiff clays, this wouldn't be a problem. Even in softer clays, you would not likely encounter a problem because of the flexible nature of the MSE walls - still, you should be careful and determine the various factors - then use your judgment.

 

[BigH]

Sorry for this second post - but I was thinking as to why you want to build the wall first, then the piers. The wall will introduce restrictions on your pier installations. If you are thinking of reducing negative skin friction (dragdown forces), then you could cover this in design of the piers. In a practical sense, you might find the resrictions to installation - while not great - still a headache.

 

[evenbetter]

Thanks for the reply. I am not sure why the design team want to build the wall first.

In the reality, geotechnical is not included in the design team 90% of the time. Just my 2 cents.