theCorkster
Geotechnical
- Sep 2, 2005
- 146
I'm working on a project involving temporary excavations to provide working benches for installation of permanent shoring walls. The boring lots indicate the material is fill comprised of Ml, GM, SM, GP materials. Stability analysis of existing topography indicates the slope is not stable as is without minimal cohesion (100 psf) in the ML, GM and SM materials. Since this material is fill and was at one time compacted, the presence of some cohesion due to dilation during shearing would be expected. Review of NAVFAC and USBR Table 8 for compacted soils does provide some guidance on the soil cohesion issue.
Currently, I'm not aware of any standard or process to provide specific data other than performing SPT tests,in place soil density tests or geophysical methods to provide guidance on the soil consistency (loose, medium dense, dense or very dense). And of course, all of this data would then have to be correlated to known empirical data.
SPT data could be used at comparable elevations to the boring logs SPT test elevations to give some guidance as to whether the soil classification and consistency is similar or not. While this provides guidance on friction angle it does not give any quantifiable indication of cohesion.
Measuring in place moisture/density with NDT gauge would require laboratory vibratory table or impact compaction tests to assess relative compaction; this information, in conjunction with classification would provide guidance on friction angle but no cohesion.
Finally, surface shear wave velocities could be measured with the slope gradient, and the wave velocity correlated to ranges of SPT.
Regardless, each of these approaches involves considerable costs and time, which may be unavoidable.
I'd appreciate any experiences or alternate approaches you may be familiar with.
Currently, I'm not aware of any standard or process to provide specific data other than performing SPT tests,in place soil density tests or geophysical methods to provide guidance on the soil consistency (loose, medium dense, dense or very dense). And of course, all of this data would then have to be correlated to known empirical data.
SPT data could be used at comparable elevations to the boring logs SPT test elevations to give some guidance as to whether the soil classification and consistency is similar or not. While this provides guidance on friction angle it does not give any quantifiable indication of cohesion.
Measuring in place moisture/density with NDT gauge would require laboratory vibratory table or impact compaction tests to assess relative compaction; this information, in conjunction with classification would provide guidance on friction angle but no cohesion.
Finally, surface shear wave velocities could be measured with the slope gradient, and the wave velocity correlated to ranges of SPT.
Regardless, each of these approaches involves considerable costs and time, which may be unavoidable.
I'd appreciate any experiences or alternate approaches you may be familiar with.