wblackke
Geotechnical
- May 1, 2021
- 2
Good afternoon,
I am performing a pavement design. My local DOT has recently changed from requiring an AASHTO 1993 design supported by CBR data to an AASHTO 1993 design supported by site specific Resilient Modulus data. This is a new process for us, we typically use CBR's. So we've completed our borings and have our Resilient Modulus testing back for the subgrade. The MR function is MR=25590*B^(-0.335), where B is the bulk stress. I'm now attempting to calculate my bulk stress.
Total Horizontal Stress = STRESS[sub]pavement section[/sub] + STRESS[sub]traffic loading[/sub]
I'm not good with HTML code, so please forgive my lack of Greek letters. I realize there are more steps to arriving at the bulk stress, but I'm hung up on this step. I have the STRESS[sub]pavement section[/sub] as calculated using the at-rest earth pressure. How do I calculate the stress caused by the traffic loading? The reference I'm using says to use Layered Elastic Analysis software, which I don't have. Is there another way this can be calculated without software?
I understand that multiplying the traffic loading by the Ko is not appropriate. This would give me an answer of about 40 psi and I'm looking for a stress of about 0.25 psi. Conceptually I would think that the stress at the subgrade level caused by the traffic loading would be much reduced since the pavement will distribute the tire load.
I am performing a pavement design. My local DOT has recently changed from requiring an AASHTO 1993 design supported by CBR data to an AASHTO 1993 design supported by site specific Resilient Modulus data. This is a new process for us, we typically use CBR's. So we've completed our borings and have our Resilient Modulus testing back for the subgrade. The MR function is MR=25590*B^(-0.335), where B is the bulk stress. I'm now attempting to calculate my bulk stress.
Total Horizontal Stress = STRESS[sub]pavement section[/sub] + STRESS[sub]traffic loading[/sub]
I'm not good with HTML code, so please forgive my lack of Greek letters. I realize there are more steps to arriving at the bulk stress, but I'm hung up on this step. I have the STRESS[sub]pavement section[/sub] as calculated using the at-rest earth pressure. How do I calculate the stress caused by the traffic loading? The reference I'm using says to use Layered Elastic Analysis software, which I don't have. Is there another way this can be calculated without software?
I understand that multiplying the traffic loading by the Ko is not appropriate. This would give me an answer of about 40 psi and I'm looking for a stress of about 0.25 psi. Conceptually I would think that the stress at the subgrade level caused by the traffic loading would be much reduced since the pavement will distribute the tire load.