Does a good quality backfill have a minimum unit weight, friction angle or any other standards? Which are the usually used backfill materials for retaining wall, embankment ?
Dear Ashana,
Normally backfill will be chosen based on local availability, and if the locally available soil is reactive clay, then need to mix with the inert materials such as sand / fly ash / quarry dust etc. Avoid if organic content is there. Ensure stability and shearing resistance.
In general properties of backfill material must be considered at design stage. In case of reinforced soil retaining wall if better backfil material is available then less reinforcement needs to be used. Typically non-cohesive materials are preferable. No special restriction on monimum unit wiegth as fly ashes are in use in some parts of the world. Friction angle higher is better. Cohesion - even if material is cohesive no more than 5kPa should be considered for calculation.
Dear Ashna K N
You may find some references in previous answers.
But the key problem is the availability of large amounts of suitable backfill material in required destination (see Hanumantharao Chappidi comment).
The second problem is uniformity of material and our ability to control its properties before and after its application. It is vital especially for crushed rocks, where some of their properties may be seriously affected in the process of compaction.
One can make a long list of other factors but I'd emphasize the important role of communication between the design office and the building site. It i crucial and make it possible active designing (fast reaction to any changes of parameters of materials delivered on building site).
Best regards
The choice of backfill materials in case of Retaining Wall, emabnkment are governed by several factors like Fines content, Availble angle of internal friction, local availability, and also permeability of the material when rained analysis will be considered.
It's common practice to say that Granular materials are good as the backfill materials but there are several practical aspects on it.
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