DEALING WITH GEOLOGICAL HAZARDS
or exceeding one (1.0) are most likely to be affected. But it should be noted that
DRL = 1 is not an upper limit. Indeed, the Weibull distribution model indicates that 72% of the model population should
occur at DRL ≤ 1 but that 28% should occur at DRL > 1 (Figure 2). (Although the Weibull distribution is not neces-
sarily the best statistical fit to the data, it is the model that is most frequently referenced in failure-rate analyses.)
Among the 39 counties studied, the
lowest index value was 0.02 (El Paso County, in far west Texas) and the high- est value was 1.40 (McLennan County, in central Texas). The Weibull distribu- tion model of all values peaks near an index value of 0.70 although a total of 18 counties cluster within the index range of 0.80-1.20 (Figure 2).
meant to be a predictor of actual damage costs from expansive-soil movements. The index formulation was based upon one particular type of hazard outcome ― road damage ― and for the purpose of evaluating relative likeli- hood rather than absolute financial consequence. Instead,
Applications and Limitations of the Index The DRL index presented here is not
DRL is suggested as an easily calculable index that can assist geohazard analysts in quickly ranking Texas locations accord- ing to their relative likelihoods to experience expansive-soil effects.
whether more work-intensive field and laboratory studies are needed for a particular location. Because the index is heavily weighted on PI, and the National Resources Conservation Service (NRCS) Web Soil Survey provides insights into PI values differentiated within parts a county, the index could be made useful at scales smaller than the county-wide scale used in the current study. With reasonable modifications and appropriate compilation of input data, the index might also be useful in some locations outside Texas. Indeed, the availabil- ity of county-wide PI, CNP and NRE data for all U.S. states should make the DRL index approach easy to test in any state.
As a reconnaissance tool, a DRL value might serve to inform References
Hudak, P.F., 1998, Geologic controls on foundation damage in north-central Texas, GeoJournal, 45(3), 159-164.
NDMC, 2019, “Drought in Texas from 2000-2019. National Drought Mitigation Center, Online report at https://www.
drought.gov/drought/states/texas 2019)
(Accessed February 20,
Nowamooz H. and Masrouri, F., 2008, Swelling Soils Behaviour in Cyclic Suction-Controlled Drying and Wetting. Paper No. 7.42a, Sixth International Conference on Case Histories in Geotechnical Engineering, August 11-16, 2008, 7 p.
NCEI County Time Series. Climate at a Glance: County Time Series. National Centers for Environmental Information, National Oceanic and Atmospheric Administration. https://
www.ncdc.noaa.gov/cag/county/time-series (Accessed February 20, 2019)
NRCS Web Soil Survey. National Resources Conservation Service, U.S. Department of Agriculture. https://web-
Figure 2. Relative Likelihood Index Values for Expansive-Soil Damage in Texas Counties.
soilsurvey.sc.egov.usda.gov/App/WebSoilSurvey.aspx (Accessed February 20, 2019)
Thomas P. J., Baker J. C. and Zelazny L. W., 2000, An Expansive Soil Index for Predicting Shrink–Swell Potential. Soil Sci. Soc. Am. J., 64, 268-274
TXDOT, 2012, Pavement Repair Strategies for Selected Distresses in FM Roadways. Report Number HWA/TX-11/0- 6589-1, Texas Department of Transportation, June 2012, 114 p.
TXDOT, 2013, District and County Statistics (DISCOS), Fiscal Year 2013, Texas Department of Transportation, December 2013, 12 p. plus Excel workbook data file.
Wang J. X., 2016, Expansive soils and practice in foundation engineering, Presented at 2016 Louisiana Transportation Conference, February 28-March 2, 2016, Baton Rouge, Louisiana, 71 p.
Wise J. R. and Hudson W. R., 1971, Study of Expansive Clays in Roadway Structural Systems, Research Project 3-8-68- 118, Center for Highway Research, The University of Texas at Austin, July 1971, 98 p.
Congratulations! AIPG Student Chapter of the Year!
Central Michigan University
AIPG Student Chapter Certificate of Excellence!
SRTMU, Nanded, India – Swami Ramanand Teerth Marathwada University &
Northern Arizona
www.aipg.org Jul.Aug.Sep 2019 • TPG 11
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