Geotechnical Engineering Reliability: How Well Do We Know What We Are Doing?
This article has been corrected.
VIEW CORRECTIONPublication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 130, Issue 10
Abstract
Uncertainty and risk are central features of geotechnical and geological engineering. Engineers can deal with uncertainty by ignoring it, by being conservative, by using the observational method, or by quantifying it. In recent years, reliability analysis and probabilistic methods have found wide application in geotechnical engineering and related fields. The tools are well known, including methods of reliability analysis and decision trees. Analytical models for deterministic geotechnical applications are also widely available, even if their underlying reliability is sometimes suspect. The major issues involve input and output. In order to develop appropriate input, the engineer must understand the nature of uncertainty and probability. Most geotechnical uncertainty reflects lack of knowledge, and probability based on the engineer’s degree of belief comes closest to the profession’s practical approach. Bayesian approaches are especially powerful because they provide probabilities on the state of nature rather than on the observations. The first point in developing a model from geotechnical data is that the distinction between the trend or systematic error and the spatial error is a modeling choice, not a property of nature. Second, properties estimated from small samples may be seriously in error, whether they are used probabilistically or deterministically. Third, experts generally estimate mean trends well but tend to underestimate uncertainty and to be overconfident in their estimates. In this context, engineering judgment should be based on a demonstrable chain of reasoning and not on speculation. One difficulty in interpreting results is that most people, including engineers, have difficulty establishing an allowable probability of failure or dealing with low values of probability. The plot is one useful vehicle for comparing calculated probabilities with observed frequencies of failure of comparable facilities. In any comparison it must be noted that a calculated probability is a lower bound because it must fail to incorporate the factors that are ignored in the analysis. It is useful to compare probabilities of failure for alternative designs, and the reliability methods reveal the contributions of different components to the uncertainty in the probability of failure. Probability is not a property of the world but a state of mind; geotechnical uncertainty is primarily epistemic, Bayesian, and belief based. The current challenges to the profession are to make use of probabilistic methods in practice and to sharpen our investigations and analyses so that each additional data point provides maximal information.
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Endnotes
1.
It might be argued that, if we knew enough about the linear and angular velocities of the dice, their inertia, the rebounding characteristics of the dice and the table, and so on, we would be able to predict the outcome of any throw. However, this is so impractical that the expressions “throw of the dice” and “crap shoot” have entered the language as synonyms for totally random events.
2.
It should be noted that it is possible to apply Bayesian methods when probability is defined by relative frequency or classical methods to degree-of-belief probability. However, to avoid excessive and extraneous complication, the presentation follows the line that frequentist definitions of probability tend toward classical statistics while degree-of-belief approaches are more congenial with Bayesian approaches. This is also the historical distinction.
3.
This database has been superceded by many more observations since the analyses were first carried out, but the point about the meaning of the curves remains valid.
4.
This is one instance of Stigler’s Law of Eponymy, which states in its simplest form, “No scientific discovery is named after its original discoverer” (Stigler 1999).
5.
A similar analysis applies to many other exploration problems; the liquefiable zone problem is chosen for convenience.
6.
This story was told to the author by the National Research Council evaluator.
7.
Many engineers have learned to their sorrow that relying simply on “engineering judgment” in an adversarial proceeding can lead to embarrassing cross examination.
8.
The plot has both cost and lives lost axes because some of the original references wrote about costs and others about lives lost. In a particular application one should use one or the other, but not both.
72.
Aitchison, J., and Brown, J.A. C. (1969). The lognormal distribution: With special reference to its uses in economics, Cambridge University Press, Cambridge, U.K.
73.
Australian, New Zealand Committee on Large Dams (ANCOLD). (1994). “Guidelines on Risk Assessment 1994.” Brisbane, Australia.
74.
Baecher, G. B. (1982). “Statistical methods in site characterization.” Updating subsurface samplings of soils and rocks and their in-situ testing, Engineering Foundation, Santa Barbara, Calif., 463–492.
75.
Baecher, G. B., and Christian, J. T. (2003a). “Discussion of ‘Evaluating site investigation quality using GIS and geostatistics’ by R. L. Parsons and J. D. Frost.” J. Geotech. Geoenviron. Eng., 129(9), 867–868.
76.
Baecher, G. B., and Christian, J. T. (2003b). Reliability and statistics in geotechnical engineering, Wiley, Chichester, U.K.
77.
Bea, R. G. (1999). “Characteristics of a platform in the Mississippi River Delta.” J. Geotech. Geoenviron. Eng., 124(8), 729–738.
78.
Bernoulli, J. (1713). Ars Conjectandi, quoted by Luigi Luca Cavalli-Sforza, Genes, People, and Languages, North Point Press, New York, 2000.
79.
Bjerrum, L. (1972). “Embankments on soft ground: State-of-the-art report.” Specialty Conf. on Performance of Earth and Earth-Supported Structures, ASCE, New York, 1–54.
9.
Budnitz, R. H., Apostolakis, G., Boore, D. M., Cluff, L. S., Coppersmith, K. J., Cornell, C. A., and Morris, P. A. (1997). “Recommendations for probabilistic seismic hazard analysis: Guidance on uncertainty and use of experts, NUREG/CR-6372.” U.S. Nuclear Regulatory Commission, Washington, D.C.
10.
Budnitz, R. H., Apostolakis, G., Boore, D. M., Culff, L. S., Coppersmith, K. J., Cornell, C. A., and Morris, P. A. (1998). “Use of technical expert panels: Applications to probabilistic seismic hazard analysis.” Risk Anal, 18(4), 463–469.
11.
Calderon, A., Catalan, A., and Karzulovic, A. (2003). “Modelo de riesgo geotecnico y bases geotecnicas, Plan Minero CBV-2003, Mina Chiquicamata.” CODELCO, Chile.
12.
Carnap, R. (1936). “Testability and meaning.” Philos. Sci., 3, 420.
13.
Casagrande, A. (1965). “The role of the ‘calculated risk’ in earthwork and foundation engineering.” J. Soil Mech. Found. Div., 91(4), 1–40.
14.
Chow, V.T., Maidment, D.R., and Mays, L.W. (1988). Applied hydrology, McGraw-Hill, New York.
15.
Christian, J. T., and Baecher, G. B. (1999). “Point-estimate method as numerical quadrature.” J. Geotech. Geoenviron. Eng., 125(9), 779–786.
16.
Christian, J. T., Ladd, C. C., and Baecher, G. B. (1994). “Reliability applied to slope stability analysis.” J. Geotech. Eng., 120(12), 2180–2207.
17.
Christian, J. T., and Swiger, W. F. (1975). “Statistics of liquefaction and SPT results.” J. Geotech. Eng. Div., Am. Soc. Civ. Eng., 101(11), 1135–1150.
18.
Christian, J. T., and Swiger, W. F. (1976). “Closure to statistics of liquefaction and SPT results.” J. Geotech. Eng. Div., Am. Soc. Civ. Eng., 102(12), 1279–1281.
19.
Christian, J.T., and Urzua, A. (1996). Productivity tools for geotechnical engineers, Magellan Press, Newton, Mass.
20.
Cornell, C. A. (1968). “Engineering seismic risk assessment.” Bull. Seismol. Soc. Am., 58, 1583–1606.
21.
Cornell, C. A. (1969). “Structural safety specifications based on second-moment reliability analysis.” Dept. of Civil Engineering, Massachusetts Institute of Technology, Cambridge, Mass.
22.
De Finetti, B. (1972). Probability, induction and statistics: The art of guessing, Wiley, New York.
23.
De Groot, D. J., and Baecher, G. B. (1993). “Estimating autocovariances of in situ soil properties.” J. Geotech. Eng., 119(1), 147–166.
24.
Duncan, J. M., Navin, M., and Wolff, T. F. (2003). “Discussion of ‘Probabilistic slope stability analysis for practice’ by El-Ramly, Morgenstern, and Cruden.” Can. Geotech. J., 40(4), 848–850.
25.
El-Ramly, H., Morgenstern, N. R., and Cruden, D. M. (2002). “Probabilistic slope stability analysis for practice.” Can. Geotech. J., 39(3), 665–683.
26.
El-Ramly, H., Morgenstern, N. R., and Cruden, D. M. (2003a). “Closure to discussion by Duncan, Navin, and Wolff of ‘Probabilistic slope stability analysis for practice’.” Can. Geotech. J., 40(4), 851–855.
27.
El-Ramly, H., Morgenstern, N. R., and Cruden, D. M. (2003b). “Probabilistic stability analysis of a tailings dyke on presheared clay-shale.” Can. Geotech. J., 40(1), 192–208.
28.
Fischhoff, B., Slovic, P., and Lichtenstein, S. (1997). “Knowing with certainty: The appropriateness of extreme confidence.” J. Exp. Psychol., 3(4), 552–564.
29.
Fishman, G.S. (1995). Monte Carlo: Concepts, algorithms, and applications, Springer, New York.
30.
Gelman, A., Carlin, J.B., Stern, H.B., and Rubin, D.B. (1995). Bayesian data analysis, Chapman & Hall/CRC, Boca Raton, Fla.
31.
Gigerenzer, G. (2002). Calculated risks, Simon & Schuster, New York.
32.
Gigerenzer, G., Swijtink, Z., Porter, T., Daston, L., Beatty, J., and Kruger, L. (1989). The empire of chance: How probability changed science and everyday life, Cambridge University Press, New York.
33.
Hacking, I. (1975). The emergence of probability, Cambridge University Press, Cambridge, U.K.
34.
Hartford, D.N. D. (2000). “Judged values and value judgements in dam risk assessment: A personal perspective.” ANCOLD Bull., 114, 78–86.
35.
Hasofer, A. M., and Lind, N. (1974). “Exact and Invariant Second-Moment Code Format.” J. Eng. Mech., 100(1), 111–121.
36.
Hoek, E. (1998). Rock engineering: The application of modern techniques to underground design. Brazilian Rock Mechanics Committee (CBMR), Brazilian Tunneling Committee (CBT), Brazilian Society for Soil Mechanics and Geotechnical Engineering (ABMS), Sao Paulo, Brazil.
37.
Hong Kong Government Planning Department. ( 1994). “Potentially hazardous installations.” Hong Kong planning standards and guidelines, Chap. 11, Hong Kong.
38.
Hynes, M., and Vanmarke, E. (1976). “Reliability of embankment performance predictions.” Proc., Engineering Mechanics Division Specialty Conf., University of Waterloo Press, Waterloo, Ont., Canada.
39.
Jensen, J. L. (1997). Statistics for petroleum engineers and geoscientists, Prentice Hall, Upper Saddle River, N.J.
40.
Kondziolka, R. E., and Kandaris, P. M. (1996). “Capacity predictors for full scale transmission line test foundations.” Uncertainty in the geologic environment: From theory to practice, ASCE, Reston, Va. 695–709.
41.
Lacasse, S., and Nadim, F. (1996). “Uncertainties in characteristic soil properties.” Uncertainty in the geological environment: From theory to practice, ASCE, Reston, Va. 49–75.
42.
Leps, T. M. (1987). “Comments on lessons learned.” Eng. Geol. (Amsterdam), 24(1–4) 94–94.
43.
McCann M. (1999). “National performance of dams program.” 〈http://npdp.stanford.edu/〉.
44.
Meyerhof, G.G. (1953). “The bearing capacity of foundations under eccentric and inclined loads.” Proc., 3rd Int. Conf. on Soil Mechanics and Foundation Engineering, Zurich, Switzerland, 440–445.
45.
Meyerhof, G. G. (1963). “Some recent research on the bearing capacity of foundations.” Can. Geotech. J., 1(1), 16–26.
46.
Morgan M.G., and Henrion, M. (1990). Uncertainty: A guide to dealing with uncertainty in quantitative risk and policy analysis, Cambridge University Press, New York.
47.
National Research Council (NRC). (1995). Flood risk management and the American River basin: An evaluation, National Academies Press, Washington, D.C.
48.
National Research Council. (2000). Risk analysis and uncertainty in flood damage reduction studies, National Academy Press, Washington, D.C.
49.
Parr, N.M., and Cullen, N. (1988). “Risk management and reservoir maintenance.” J. Inst. Water Environ. Manage., 2.
50.
Peck, R. B. (1969). “Ninth Rankine lecture: Advantages and limitations of the observational method in applied soil mechanics.” Geotechnique, 19(2), 171–187.
51.
Riela, J., Urzua, A., Christian, J.T., Karzulovic, A., and Flores, G. (1999). “Sliding rock wedge reliability analysis of chuquicamata mine slopes.” Proc., 11th Pan-American Conf. on Soil Mechanics and Geotechnical Engineering, Foz do Iguacu, Brazil.
52.
Rosenblueth, E. (1975). “Point estimates for probability moments.” Proc. Natl. Acad. Sci. U.S.A., 72(10), 3812–3814.
53.
Rosenblueth, E. (1981). “Two-point estimates in probabilities.” Appl. Math. Model., 5(2), 329–335.
54.
Sivia, D.S. (1996). Data analysis: A Bayesian tutorial, Oxford University Press, Oxford, U.K.
55.
Stedinger, J.R., Heath, D.C., and Thompson, K. (1996). “Risk assessment for dam safety evaluation: Hydrologic risk.” USACE Institute for Water Resources, Washington, D.C.
56.
Stigler, S.M. (1999). Statistics on the table: The history of statistical concepts and methods, Harvard University Press, Cambridge, Mass.
57.
T. W. Lambe & Associates. (1982). “Earthquake risk to patio 4 and site 400.” Longboat Key, Fla.
58.
T. W. Lambe & Associates. (1989). “Earthquake risk analysis for KSS tank area.” Longboat Key, Fla.
59.
Terzaghi, K. (1929). “Effect of minor geological details on the stability of dams.” Technical Publication No. 215, American Institute of Mining and Metallurgical Engineers, New York, 31–44.
60.
Terzaghi, K., Peck, R.B., and Mesri, G. (1996). Soil mechanics in engineering practice, Wiley, New York.
61.
Tversky, A., and Kahneman, D. (1971). “Belief in the ’law of small numbers’.” Psychol. Bull., 76, 105–110.
62.
U.S. Nuclear Regulatory Commission. ( 1975). “Reactor safety study: An assessment of accident risks in U.S. commercial nuclear power plants.” Washington, D.C.
63.
Van Zyl, D., Miller, I., Milligan, V., and Tilson, W.J. (1996). “Probabilistic risk assessment for tailings impoundment founded on Paleokarst.” Uncertainty in the geologic environment: From theory to practice, ASCE, Reston, Va.
64.
Veneziano, D. (1995). “Uncertainty and expert opinion in geologic hazards.” Massachusetts Institute of Technology, The Earth, Engineers, and Education: A Symposium in Honor of Robert V. Whitman, Cambridge, Mass., 102–124.
65.
Versteeg, M. (1987). “External safety policy in the Netherlands: An approach to risk management.” J. Hazard. Mater., 17, 215–221.
66.
Vesic, A. S. (1973). “Analysis of ultimate loads of shallow foundations.” J. Soil Mech. Found. Div., 99(1), 45–73.
67.
Vesic, A.S. (1975). “Bearing capacity of shallow foundations.” Foundation engineering handbook, H. F. Winterkorn and H.-Y. Fang, eds., Van Nostrand–Reinhold, New York, 121–147.
68.
Vick, S.G. (2002). Degrees of belief: Subjective probability and engineering judgment, ASCE, Reston, Va.
69.
Vick, S.G., and Stewart, R.A. (1996). “Risk analysis in dam safety practice.” Uncertainty in the geologic environment: From theory to practice, ASCE, Reston, Va., 586–603.
70.
Von Thun, J.L. (1996). “Risk assessment of Nambe Falls Dam.” Uncertainty in the geologic environment: From theory to practice, GSP 58, ASCE, Reston, Va., 604–635.
71.
Whitman, R. V. (1984). “Evaluating calculated risk in geotechnical engineering.” J. Geotech. Eng., 110(2), 143–188.
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Published In
Journal of Geotechnical and Geoenvironmental Engineering
Volume 130 • Issue 10 • October 2004
Pages: 985 - 1003
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Copyright © 2004 ASCE.
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Published online: Oct 1, 2004
Published in print: Oct 2004
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