The Boussinesq method is one way to transfer a finite surcharge load to a retaining wall. There has been plenty of threads on here about it. I even think someone provided an example calc. Do a search on the topic.
You could just apply the load for the full width of the active wedge behind the wall. Based on 25KN/track equals a bearing pressure of 67kPa. Thats a high surcharge, typically we adopt 10-20KPa for construction traffic, but if you can make that work without it being uneconomical then why not. Its more conservative and the calcs are easier.
On the topic of the applied bearing pressure, i wouldnt go working out the applied bearing pressure yourself (even though its relatively easy). Anytime we design working platforms for drill rigs etc we were always supplied that info from the contractor. Just covers your ass more tbh.
What type of wall is it? How high and whats the soil type? More info = better responses.
