I am aiming to simulate a deep excavation near an existing tower with 4 levels of below grade parking (shaded in grey). The approximate loading of the building is 10 ksf. Therefore I have simulated the material (shaded in grey) as a non-porous Mohr Coloumb material with stiffness and strength parameters equivalent to concrete. The density is0.187 kips/ft3 in order to achieve the 10 ksf vertical pressure at the base of the building. I have also added a negative interface on the outside of the building with Rinter of 0.6. The soil layers are simulated with the Hardening Soil model. I was wondering if this approach makes sense and if not, what is the best way to simulate a nearby burried structure.
Hi Boris, your model seems correct. It is your expectations that you should reconsider. "Higher deformations at top" is never a case for laterally supported excavations - if you see higher deformations at top for laterally supported excavations, you should reconsider your design. You can only see that on cantilever excavations.
Also, now you have much less load at the back of your retaining wall. You do not have any lateral load from building (was that the case when you model with linear elastic soil), so, it is very easy to carry all the load at upper levels which even shows that you don't need all those soil nails.
Thanks Berk. How do you typically initialize your stresses when it comes to the building loading? I Tried both the K0 procedure and the Gravity loading. Gravity loading seems to be working better, however I still see quite a lot of lateral movement in the model after I start the excavation. I understand that I am unloading quite a bit of load on the right side so that is likely the cause - see plots from the third excavation stage. I have set up the model with the following steps currently:
1) Phase 1 - Gravity loading step - activating the building surcharge and the lane surcharge.
2) Phase 2 - Set displacements to 0. Install Soldier pile plate element for the excavation
3) Phase 3 and onwards - Excavation stages.
Boris, everything seems OK. This is becoming consulting rather than software help, but as I said, it looks OK.