Underground space is increasingly regarded as an economic resource and a developmental opportunity, rather than a technology of last resort to be used when aboveground solutions fail. Geotechnical investigations are needed in early stages of industrial and urban planning to define opportunities and avoid difficulties and conflicts in the use of underground space. The need to manage conventional energy resources and capture wasted or renewable energy resources is creating new uses for underground space. The energy-related functions of underground space are fuel storage and management, energy capture and storage, energy conservation, and nuclear waste isolation. Fuel storage is a developed industry. Energy storage is rapidly developing. Geotechnical classifications of mined space and porous rock storage systems and functional classifications of fuel and energy storage systems are presented.
The Rockstore conferences of 1977 and 1980 establish an historical precedent which should not go unnoticed. In these conferences, for perhaps the first time, the use of underground space is systematically treated as an opportunity driven by economic advantage, rather than a necessity forced by other considerations.
Historically underground space has often been constructed in difficult t and extraordinary geologic conditions. Ore deposits commonly occur in zones of sheared and shattered, badly altered rock. Coal mines must cope with weak rocks and gas. Most major cities have been situated on rivers, estuaries and bays, giving access to water, but often placing them on water-saturated deposits of mud, silt and sand. Truly, geotechnology has been developed and tested in the crucible of adversity. It has won renown for heroically surmounting obstacles when ordinary, aboveground solutions fail, but in doing so, it has acquired the image of a technology of last resort -- a dragon slayer to be called on for heroic measures only when conventional champions have left the field.
It is fitting now that this young Beowulf* of technology should come of age in Scandinavia. Here a number of cities and major industrial sites are located on strong, massive rock. This, coupled with a long tradition of hard-rock mining, certain strategic needs and a high value placed on preservation of environmental amenities, has led to the happy discovery that in appropriate settings underground construction can be quite simply the most economical solution to large space needs, not an adventure to be undertaken as a last resort. Our geotechnical Beowulf need no longer be dedicated to slaying dragons. He can, so to speak, beat his sword into a plowshare and cultivate a garden. However, cultivating gardens requires a certain sensitivity to natural conditions that is not demanded by dragon slaying. If we are to avoid Grendel's fearsome caverns, we need to know the ground before we start to dig, and the ground must be adapted to the use we plan to make of it.
In other words, underground space is an economic resource if careful geotechnical investigation has shown that the geology is right. As with other earth resources, it must be explored and mapped. It is a resource that is not available everywhere in like degree. Moreover, underground space is not a single resource or commodity. There are a number of different uses to be made of the storage capacity of the ground, each having somewhat different, or even radically different, geologic and geotechnical requirements. If underground space is to be developed as a resource, its availability must be carefully investigated and considered just as other resources are considered.