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38 RAPID EXCAVATION The quality of present-day environmental-control technology in excavation is spotty and, in general, varies inversely with the novelty o f the excavating method. With conventional excavation, using drilling and blasting, an accept- able environment can be maintained. With mechanical excavators o f the bor- ing type, dust and electrical hazards are intensified, and control is rendered more difficult and perhaps inadequate. With other, yet untried continuous excavating processes (such as thermal and chemical), new and intensified hazards will exist, and present control practices are apt to become obsolete. Overall, i t appears that considerable effort must be devoted to (a) improv- ing the base of knowledge concerning the qualitative and quantitative nature of the hazards that exist with current excavating technology or might exist with evolving excavating technology, (b) developing better and less expensive methods for controlling dust, and (c) developing more efficient and less expensive air-transmission methods for use in long, rapidly advancing tunnels. R E S E A R C H PROGRAM Despite the rather long, segmented articulation o f the numerous underground- excavation problems and shortcomings just presented, it is quite clear that the performance of the over-all excavation process can, indeed, be measurably improved. Moreover, i t is clear that major improvements in time and cost o f underground rock excavation can be made i f (a) continuous mining and tun- neling techniques for hard rock are developed; (b) the downtime o f current mining and tunneling machines is reduced; (c) muck-removal systems with higher rates of advance and greater speed in loading and transporting mate- rials become available; (d) major improvements are made in the rationality of current lining design practice; and (e) the rates of installation practice and capabilities of ground-control measures are upgraded appreciably. I t is also apparent that the long-term growth o f underground-excavation technology requires a concomitant broadening o f both geological and rock-mechanics knowledge as well as environmental-control technology. The technological basis for achieving the foregoing goals is attainable within a reasonable and desired time period (10 years) and at a reasonable total cost (approximately $200 million, in constant 1964 dollars) through implementa- tion of a supplemental research program, i.e., a research program over and above current governmental and private research efforts. However, it is essen- tial that the research program address "first things first," that the objectives and efforts of govemment-industry-academic participants in the program are coordinated, and that suitable mechanisms for developing and testing complete excavation systems are devised.
NEEDS S» It is confidently expected that the establishment of this base of knowledge will set the stage for reducing over-all underground-excavation costs by 30 percent, and for raising the sustained rates o f advance 200 to 300 percent in soft-medium and hard rock by 1990. As shown in Table 8, only a few technological areas now merit high pri- ority research consideration. Although i t is beyond the s&ope o f this report to identify specific research projects or precise fields of research to be pursued, it is recommended that research projects be selected for inclusion in the pro- gram on the basis o f their potential contribution to the coordination of the several elements o f the imderground-excavation' process into a highly engi- neered system and to the improvement of the basic knowledge required to subsequently effect engineering advancements in the following critical areas, given in approximate order of priority: 1. Development o f processes and equipment for boring tunnels and shafts in hard abrasive rock and for reducing the downtime experienced with cur- rent mining and tuimeling machines in soft or medium rock masses 2. Improvement o f processes and equipment for removing muck and han- dling supplies and materials for compatibility with advanced mining and tunneling machines 3. Development of geological techniques for determining rock and ground- water conditions qualitatively prior to excavation operations, and for probing immediately ahead o f the working face during excavation operations to de- termine rode quality and groundwater conditions more precisely 4. Development o f rock-mechanics techniques for measuring mechanical, electrical, and thermal properties and behavior o f rocks in situ 5. Improvement of rock-mechanics techniques for measuring subsurface stress field in deep boreholes and for determining stress distribution in walls of underground excavations 6. Improvement of processes, materials, and equipment for temporarily and permanently supporting long tunnels and deep shafts in wet, broken rock 7. Improvement of processes, materials, and equipment for producing temporary support, in a wide range o f rock mass conditions, at speeds com- patible with advanced mining and tunneling machines 8. Development of rational methods for designing temporary and perma- nent support systems 9. Development of standards, processes, and equipment for attaining ade- quate environmental quality and safety in long, continuously excavated tunnels and shafts 10. Improvement o f drilling and blasting techniques
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NEEDS 41 Specifically in reference to 1 above, notice must be taken of the many novel rock-disintegration techniques now being studied. Only a few of these techniques show promise for application in the bulk of anticipated under- ground excavation or of economical application within the next two decades. Although the potential advantages of these techniques include the possibility of greater destructive energy at the working face and the creating of shapes other than circular, the formidable obstacles faced in the application of these techniques include excessive power needs, environmental contamination, and extreme variation of response of many different rock types. In light of the foregoing, it is recommended that research resource allocations in support of new rock-disintegration techniques be made in accordance with the priorities listed in Table 9. Satisfactory pursuit of the outlined research cannot be unilaterally achieved by government, industry, or university sectors. Parts of each of the research objectives can be attained only in the context of actual construction or mining operations; parts can be achieved only in the context of manufacturing opera- tions; parts can be achieved only in the context of large, interdisciplinary re- search laboratories; and some parts can best be achieved in the departmental laboratories of universities and goveriunent agencies. Considerable attention must be given to harnessing properly the required manpower-facility research resources. Moreover, in keeping with the objective of developing an integrated under- ground-excavation process, and bearing in mind that no one supplier of the heavy-construction industry can provide a complete, integrated excavating system, it is essential that consideration be given to establishing a field labora- tory at which such systems and their components can be tested and evaluated.
42 RAPID EXCAVATION TABLE 9 Priorities for Rock Disintegration Research Present Recommended Geneial Knowledge Research Technology Specific Technical Aiea or Activity* Priority* Drill and blast Drill design and materials 1 L Drill and blast Automation of drilling 2 H Drill and blast Drilling pattern 2 H Drill and blast Explosives studies 1 L Drill and blast Controlled cavity shape 2 M Drill and blast Loading automation 2 H Drill and blast Gas-exhaust improvement 2 M Rolling cutter Weak-rock cutter 1 L Rolling cutter Medium-rock cutter 1 L Rolling cutter Hard-rock cutter 2 H Rolling cutter New energy modes 3 H Rolling cutter New conflguratmn of cutter head 2 H Rolling cutter New cutter materials 1 H Mechanical Fluid erosion 2 HC Mechanical Spark 2 Mechanical Ultrasonic 2 M Mechanical Abrasion 2 L Mechanical Exptosive 2 M Mechanical Implosive 3 - L Mechanical PeUet 1 L Thermal High-velocity flame 2 hp Thermal Cryogenic 3 L Thermal Jet piercing 1 L Thermal Electron disintegration 2 L Thermal High-frequency electric 3 L Thermal Induction 3 L Chemical Softeners 2 M Chemical Dissolvers 0eaching) 2 M Fusion Plasma 2 HC Fusion Laser 3 M Fusion Atomic 3 L Fusion Fusion 2 L Fusion' Electric arc 2 L Fusion Electron beam 3 L «1 = high, 2 = medium. 3 = low. *H = high, M = medium, L = low. <'Small-scale projects.
