Geotechnical Site Investigations for Underground Projects Volume 1 (1984) / Chapter Skim
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7. Interpretation of Case Histories
7. Interpretation of Case Histories
Pages 91-112
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From page 91... ...
For example, qualitative data included statements regarding problems related to ground conditions encountered during construction, comments on the effectiveness of the site investigation program, and opinions concerning disputes. The quantitative data covered a wide range of items, such as project costs and schedule, tunnel specifications, geologic criteria, types and number of exploration techniques, and construction methods and progress.
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From page 92... ...
Boreholes, spacing overburden, max and min Boreholes, $/lin ft water head, max and min overall advance per day Water inflow, max and min Advance per 8-hr shift Boreholes, number Labor, total man hours Boreholes, lin ft Labor, man hours/day Borehole depth, max and min Excavation, man hours/cu yd Boreholes, distance from centerline Excavation, cu yd/hr Compressive strength tests, number Claims made, $/cu yd Compressive strength, max and min Claims settled, $/cu yd Construction equipment/method Claims, $ settled as t made Primary support Advance per day, max and average Days worked Shifts worked Crew size Problems, construction Liquidated damages in specifications Claims made, $ Claims settled, $ The information summarized in the data matrix served for initial review of comprehensive results, following which the content of the matrix was expanded by additional basic calculations. This revised data summary 92
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From page 93... ...
A specialized computer program was written by personnel of Tudor Engineering Company to select and plot TBM, drill-and-blast, soft-ground and compressed-air tunnels built for rapid transit, railroads or water conveyance, or underground . subway stations or hydroelectirc powerhouses.
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From page 94... ...
est. 36 Exploration, as t cost Claims paid, as ' All total cost 37 Boreholes, LP/RF Claims paid, as t All total cost 38 Boreholes/1,000 RF Claims paid, as t All total cost 39 Boreholes, number Claims paid, as t All total cost 40 Exploration, as t cost Claims made, as t coat All 41 Boreholes, LP/RF Claims made, as ' coat All 42 Boreholes/1,000 RF Claims made, as \ cost All 43 Boreholes, number Claims made, as ' coat All 44 Length, LP Cost, 1982 $/cu yd TBM 45 Boreholes, LF/RF Cost, 1982 $/cu yd TBM (water)
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From page 95... ...
However, the plots generated to examine all projects were also subject to some reduction in sample size arising from availability of data for parameters. The effects were most apparent for parameters based on water inflow and on excavation and advance rates combined with work force units (number of length of shifts and crew size)
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From page 96... ...
TABLE 7.3 Problems and Claims* Reported for Mined Tunnels Blocky/slabby rock, overbreak, cave-ins ,, Problems of tunnelsl 38 ,, 16 ClaiiiS of tunnelsl Running ground 27 9 Flowing ground 5 4 Squeezing ground 19 8 Spalling, rock bursts 6 4 Groundwater inflow 33 6 Noxious fluids 6 4 Methane gas 7 2 Existing utilities 1 0 Soft bottom in rock 2 2 Soft zones in rock 4 2 Hard, abrasive rock (TBMs)
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From page 97... ...
The subcommittee believes that water plays a large and varied role in tunnel construction difficulties; yet it may not always appear in the simplified listing of problems encountered in a project because it is a secondary contributor to the primary problem. For example, face instability would in many cases not have been a problem without the presence of water to reduce friction along joint surfaces or create seepage pressure, although the water might exist in quantities too small to deserve mention under groundwater inflow.
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From page 98... ...
The cost impact is not limited to construction dollars alone, but extends to project reliability and longevity. Although certain aspects remain ill defined, the plots and tabulations of numerical data yielded several interesting trends and quantitative values that help delineate the extent of the interaction of geology with construction and the effect of the geotechnical site investigation.
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From page 99... ...
In addition, the task of apportioning costs for investigation programs overlapping several projects was complex. As a result, the figures for exploration costs are considered less reliable than others reported herein.
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From page 100... ...
OVerall, these results indicate that present practice is to devote a relatively small portion of project costs to a site investigation program. In some instances, low expenditures may be warranted because a sufficient body of information may be available from explorations conducted for overlapping projects, or nearby projects, or from other sources such as aerial surveys and regional geologic reports.
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From page 102... ...
0 0 0 w 80 • • , • 0 • • • • • • • 1 w ..J D 60 • :::E 0 0 ~ 40 • 20 .34 Median, Overall .42 Median, Common 0~~ -- ~ -- ~~U-~ -- -L -- ~ -- ~~ -- -L -- ~ -- ~_..J~~ -- -L -- ~ -- L-~ -- -L -- ~ 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 BOREHOLES, IN LINEAR FT PER ROUTE FT OF TUNNEL ALIGNMENT FIGURE 7.2
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From page 103... ...
< ~ •• • • 0 u 0 • 0 w 1 • • w ~ Q • ~ 0 u ,;, < .75 Median, Overall 0~-L~~ -- ~~ -- ~ -- ~~ -- -L -- ~ -- ~-L -- ~ -- ~~ -- ~ -- ~~L -- L -- ~~ 0 2 3 4 5 6 7 8 9 10 EXPLORATION COST, AS% OF BASIC CONSTRUCTION COST (EXCLUDES CHANGES AWARDED I FIGURE 7.3
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From page 104... ...
3, 4, 7. 8 Projct O.ta Not Shown: X Axis Y Axis 015.3 156.1 024.4 148.1 w ....
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From page 105... ...
, the convergence of the contractor's bid with as-completed costs is excellent, in terms both of degree and consistent pattern. The benefits resulting from the geotechnical site investigation are obvious.
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From page 106... ...
• 0 ci • • • • I (I) • • • • ~ a: ~ 0 c( a: 601 -- ' 0 1 z 0 •• 0 .34 Medien, Owrell 0~~ -- -L -- ~~~~~-L -- ~ -- ~ -- L-~ -- -L -- ~ -- L-~~-L -- ~ -- ~~~~ -- ~ 0 0.2 0.4 0.6 0.8 1.0 12 1.4 1.6 1.8 2.0 BOREHOLES, IN LINEAR FT PER ROUTE FT OF TUNNEL ALIGNMENT FIGURE 7.5
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From page 107... ...
4( ci • 0 iii Cl) • 0 iE: 0 0 • 1 u 4( a: 1 z 8 .34 Medilln, Ownlll .42 Median, Common 0~ -- ~~-' -- -~ -- -L -- -L -- ~ -- ~~ -- L -- -~ -- -' -- -- L -- -L -- ~ -- ~ -- -- ~ -- ' 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 BOREHOLES, IN LINEAR FT PER ROUTE FT OF TUNNEL ALIGNMENT FIGURE 7.6
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From page 109... ...
: total claims of $253.7 million, claims paid of $161.8 million, basic construction costs of $1,364.8 million, and as-completed costs of $1,526.6 million. Examination of the data for the 32 tunnels reveals that 11 of the claims (8 major and 3 minor)
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From page 110... ...
* Costs excluding claims paid.
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From page 111... ...
•• •pp a~ • 8 • • 0 0 3 8 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 BOREHOLES, IN LINEAR FT PER ROUTE FT OF TUNNEL ALIGNMENT FIGURE 7.8 111
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From page 112... ...
Improving site characterization by increasing exploration reduces the incidence of claims and attendant effects; when unnecessary claims are avoided, construction is more economical. • A significant portion of project costs stems from claims settlements rather than from investigation of the site for design and construction purposes.
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