Architecture and management of a geological repository - Andra

7 – The shafts and the driftsFigure 7.3.4Section of the construction shaft7.3.4 The advantages of a rampA ramp is an inclined drift, normally at a slope less than 15 %, allowing access to the undergroundinstallations. This type of structure has been in widespread use in the mining industry since the secondhalf of the last century, together with the development of diesel mining machines and vehicles andconveyor belts. The comparison between shafts and ramps has become a permanent debate within themining industry. A large number of mines are equipped with both types of structures.The ramp is more flexible to work with than a shaft because it can be used without causing loadinterruptions by a wide variety of vehicles. It does not depend like a shaft on a single piece ofequipment, which even though highly reliable does require heavy-duty maintenance. However, theflows possible on a ramp are more limited than in a shaft and experience has shown that the risks ofincidents are higher.It should be noted among the factors which would lead by analogy to the mining industry favouring anaccess by ramp that :- The overlaying grounds are hardly aquiferous and have normally good mechanical characteristics ;- The package flows are limited in terms of the number of movements and consist of bulky andheavy loads ;- The material flows generated by construction remain small as long as construction is restricted tozones receiving B and C0 waste packages.On the contrary, the depth of 500 m is rather high for a ramp, but not without precedence. The layer’sgeometry and topography are simple, which would tend to favour the shaft solution.Aside from the air exhaust function, where the ramp has no interest here, the above list of factors doesnot allow a very sharp comparison between the two types of accesses. A ramp can be used for thelowering of packages, on the one hand, and for construction functions, on the other hand. At this stagein the studies, the use of ramps is only considered as a variant.The paragraphs below show two examples of possible ramps. The first example is an example of a“construction oriented” ramp designed to facilitate the flow of vehicles. It is very similar to a miningramp. The second example is an example of a “package transfer oriented″ ramp designed to limit theimpact velocity in case a vehicle transporting packages goes out of control.DOSSIER 2005 ARGILE -ARCHITECTURE AND MANAGEMENT OF A GEOLOGICAL DISPOSAL SYSTEM297/495