stemac
Geotechnical
- Jun 19, 2024
- 1
Hi Everyone,
I am working on a 2-story parking garage excavation project located next to a ~60' slope. As you can see in my crude drawing, the slope has been covered with wire mesh and an ~4" layer of shotcrete. The toe of this slope is set back 3' from the excavation.
The Structural engineer has proposed the construction of a cantilevered MSE wall that extends from the bottom of the excavation to 12' above the toe of the slope. They have requested us to provide calculations of the expected earth pressures on the wall and expected deflections. The proposed plan is to leave the shotcrete in place and place granular fill with geogrid reinforcement on top of it.
I am currently thinking that I can use the Rankine lateral earth pressures to calculate the force on the wall, but I am unsure of using this method with geogrid soil reinforcement. Additionally, I am unsure if it is safe to assume no lateral pressure will come from the (currently freestanding) shotcrete slope. A conservative approach would be to assume that there is no shotcrete on the slope, as the slope is only designed as a temporary soil retaining structure and the long term behavior has not been considered, but this may be overly conservative. I think it is also important to consider the friction angle between the MSE wall granular fill and the shotcrete as this will not be a soil-soil interface. I am also curious if anybody has experience with MSE walls that have variable length reinforcement layers like those in my drawing. I have read that it can be useful to extend the upper layers of reinforcement, however it is also my understanding that the bottom layers will have to withstand the most force and therefore it may not be ideal to truncate them.
I am working on a 2-story parking garage excavation project located next to a ~60' slope. As you can see in my crude drawing, the slope has been covered with wire mesh and an ~4" layer of shotcrete. The toe of this slope is set back 3' from the excavation.
The Structural engineer has proposed the construction of a cantilevered MSE wall that extends from the bottom of the excavation to 12' above the toe of the slope. They have requested us to provide calculations of the expected earth pressures on the wall and expected deflections. The proposed plan is to leave the shotcrete in place and place granular fill with geogrid reinforcement on top of it.
I am currently thinking that I can use the Rankine lateral earth pressures to calculate the force on the wall, but I am unsure of using this method with geogrid soil reinforcement. Additionally, I am unsure if it is safe to assume no lateral pressure will come from the (currently freestanding) shotcrete slope. A conservative approach would be to assume that there is no shotcrete on the slope, as the slope is only designed as a temporary soil retaining structure and the long term behavior has not been considered, but this may be overly conservative. I think it is also important to consider the friction angle between the MSE wall granular fill and the shotcrete as this will not be a soil-soil interface. I am also curious if anybody has experience with MSE walls that have variable length reinforcement layers like those in my drawing. I have read that it can be useful to extend the upper layers of reinforcement, however it is also my understanding that the bottom layers will have to withstand the most force and therefore it may not be ideal to truncate them.
