Geotechnical Site Investigations for Underground Projects Volume 1 (1984) / Chapter Skim
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8. Conclusions and Recommendations
8. Conclusions and Recommendations
Pages 113-122
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From page 113... ...
In addition, although the subcommittee's study was confined primarily to mined tunnels at relatively shallow depth, the findings can be applied to most underground construction projects because the principles of subsurface investigation and contracting are so similar.
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From page 114... ...
before construction would permit timely recognition of a contract change and provision for cost adjustment during construction, i f the conditions encountered vary materially. This should assist in reducing or eliminating contingencies for possible delays and disputes, and lead to more realistic cost estimates and more competitive bidding.
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From page 115... ...
Site investigations have to proceed through, but should not always end with, co.pletion of the feasibility/alignment setting/final design prograJIS. Owners must recognize that the preconstruction site investigation should be an iterative process.
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From page 116... ...
Laboratory testing of the subsurface aaterials generally needs to be increased. Experience has shown, for example; that in rock tunnels at least 50 to 60 unconfined compression tests for each significant lithologic unit are necessary to adequately characterize the range and means of strength values.
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From page 117... ...
'l'he low level of expenditure typical of current practice does not correlate well with estimated and actual costs or with construction problems and claims. overall, increasing exploration can be expected to decrease the incidence and severity of construction difficulties and eliminate a significant portion of the extra costs associated with unanticipated geologic conditions, including project delays, claims, and litigation.
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From page 118... ...
Moreover, the cost of the overall exploration program includes expenses for report writing and other miscellaneous items which do not rise in direct proportion to borehole footage. The owner should make all his geotechnical information available to bidders, while at the sue tbae eliainating diaclabaera regarding tbe accuracy of the data or the interpretations.
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From page 119... ...
Such reports should result in much better informed bidders, improved construction procedures, and probably lowered costs associated with a reduction in bidding contingencies and changed condition claims. The WMATA Geotechnical Design Reports (Appendix D)
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From page 120... ...
Geologic information from preconstruction explorations and as-built tunnel mapping and construction procedures should be compiled in a report detailing project completion. It is rare to find wrap-up reports that describe the mapped tunnel geology and construction procedures, even among owners who build tunnel after tunnel.
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From page 121... ...
Illproved horizontal drilliDCJ techniques should be developed that can recover rock core and penetrate lODCJ distances without wanderiDCJ from line and grade. The need is especially severe for tunnels beneath mountains where, except for portal areas, difficult access and/or great depth generally make the necessary number of vertical boreholes prohibitively expensive.
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From page 122... ...
It should be noted that some federally financed research on deep remote sensing methods is being conducted; the methods are showing promise but still require extensive testing to prove dependability.
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