A great idea, but hard to do practically. I refer to the practice called Co-Disposal of tailings and waste rock. Mike Gowan, a principal of Golder Associates in Brisbane is probably the expert. Here is a link to one of his few publications on the topic. It is best to download and save the PowerPoint presentation, rather than try to open directly from the source.
As Mike defines it, Co-Disposal is the combining of tailings with waste rock. The idea is simple: waste rock may have lots of void. If you can fill these voids with fine-grained tailings, the result is a high-strength material. It is all kind of like making concrete: you mix coarse and fine materials and get them to set up and you have a strong material.
Co-Disposal has been tried and used at but few mines, in spite of its theoretical advantages. The problem is that it is hard to do. Just as mixing sand and cement is energy-consuming, so too is mixing of fine tailings and coarse waste rock.
Thus we have Co-Mingling, which is the placement of a layer or pile of rock and the placement of an adjacent pile of tailings. In the presentation at the link provided above, Mike illustrates how this may be done. Or Co-Placement or Co-Location. All are variants of the idea of producing a large pile of tailings and waste rock by placing gobs of waste rock and gobs of tailings to produce, on average, a mass of some strength—-preferably enough to stand without further ado or perimeter dike or embankment.
The big issue in co-xx, is the tailings. Theoretically you can place a pile of waste rock and then hydraulically deposit fluid tailings onto the pile. The fluid tailings may then flow or move into the voids of the pile of waste rock. If this really happens at your site, you are lucky. You have just the right gradation of waste rock and the right gradation and viscosity of fluid tailings.
Alternatively, if your tailings are viscous, you may have to physically mix them in simulation of a cement mixer with the waste rock. This will cost a lot.
If your tailings are partially dewatered, but still soft and weak, you could co-locate them with waste overburden. The idea is to dump a series of piles of water rock to form cells, pod, or paddocks. Then into these cells (or whatever you choose to call them) you dump you semifluid tailings. If you get the right spacing of waste piles to tailings infill pods, the overall mass may be strong, stable, and of low consolidation potential.
Perfection of this approach awaits a genius of practical bent. Maybe it could work on the oil sands to meet Directive 74, although I hate to think how the ERCB is going to agonize over this.