Liquefaction Potential Analysis and Possible Remedial Measure for Existing Structure in Kathmandu Valley

Narayan Marasini, Mitsu Okamura

Abstract


Evaluation of liquefaction potential of soils using empirical relations based on field in-situ test data is a common practice in liquefaction study. In this study, Standard Penetration Test (SPT) data were used to examine the liquefaction potential of the Kathmandu Valley. In total 66 SPT data among the collected 102 from 33 locations were used for the analysis. The factor of safety against liquefaction (FL) was calculated and found less than unity (FL<1) in 48 locations, which indicates the high probability of occurrence of liquefaction during the predicted scenario earthquake of magnitude 8 with peak ground acceleration 300gal.

Similarly, mineralogical composition and physical index of field soil were compared to the commercially available sand and found more comparable with Toyoura sand. Two Centrifuge models in which one is saturated foundation soil model (Case1) and the other is desaturated foundation soil model by air injection (Case2) using the Toyoura sand were prepared in the laboratory. Both the model consisted of a metal plate at the top (representing the existing building structure in Kathmandu Valley) which is imparting the average contact pressure of 35kPa.  The prepared model was then set on centrifuge. The air was injected in case2 through the injector at centrifuge acceleration 50g. The estimated residual degree of saturation at desaturated area was 85% in case2. Both the models were tested in the centrifuge at 50g acceleration with imparting a simulated sinusoidal wave of frequency 40Hz and typical acceleration amplitude of 190gal. The test results showed that excess pore pressure was significantly reduced from 65kPa in case1 to 7.5kPa in case2 at the same location of the model. Similarly, vertical settlement is reduced approximately 50% in the case2 as compared with the case1. Test results of this study show the desaturation by air injection technique can be a better solution to control the foundation soil liquefaction and save the millions of structure standing over it in Kathmandu valley.

Keywords


Liquefaction potential, Liquefaction countermeasure, Centrifuge test, Building

Full Text:

Remote PDF

References


Bilham R., (2004) Earthquakes in India and the Himalaya: tectonics, geodesy and history, Annals of GEOPHYSICS, vol. 47, N. 2/3, April/June.

Chandra U. (1992); Seism tectonics of Himalaya. Current Science, 62; pp 40-71.

Dixit AM, Dwelley-Samant LR, Nakarmi M, Pradhanang SB, Tucker BE (2000); The Kathmandu Valley Eartquake Risk Management Project: An Evaluation Paper no. 0788; 12th WCEE.

Dixit AM, Yatabe R, Dahal RK, Bhandary NP (2013); Initiatives for earthquake disaster risk management in the Kathmandu Valley, Natural Hazards DOI 10.1007/s 11069-013-0732-9.

Japan International Cooperation Agency (JICA),(2002), The study on Earthquake Disaster Mititgation in the Kathmandu Valley Kingdom of Nepal. Final Report, Vol-I,II,III and IV.

Liao S., and Whitman, RV. (1986a); Overburden correction factors for SPT in sand, Journal Geotechnical Engineering, ASCE, 112 (3), 373-377.

Ling HI, Mohri Y, Kawabata T, Liu H, Burke C, Sun L (2003); Centrifugal Modeling of Seismic Behavior of Large-Diameter Pipe in Liquefiable Soil , Journal of Geotechnical and Geoenvironmental Engineering , ASCE, Vol. 129, No. 12, pp. 1092-1101.

Molnar P. (1984); Structure and Tectonics of the Himalaya; constraints and implications of Geophysical Data. Ann. Rev. Earth planet Sci. 12: 489-518.

Ogata H and Okamura M (2006); Experimental study on air behaviour in saturated soil under air injection, Proc. Symp. On Natural Disaster Prevention, JSCE, Tokushima, Japan, 89-90 (in Japanese)

Okamura M and Inoue T (2010). “Preparation of fully saturated model ground”. Proc. Int. Conf. Physical Modeling in Geotechnics, Vol. 1, PP. 147-152.

Okamura M., Takebayashi, M., Nishida, K., Fujii, N., Jinguji, M., Imasato, T., Yasuhara, H. and Nakagawa, E. (2011); In-Situ Desaturation Test by Air Injection and Its Evaluation through Field Monitoring and Multiphase Flow Simulation, Journal of Geotechnical and Geoenvironmental Engineering, ASCE, Vol. 137, No. 7, pp. 643-652.

Okamura M., Tomida Y., Okamoto T., Yasuhara H. (2012); Remedial Measure for Highway Embankments on Liquefaction Prone Foundation, Second International Conference on Performance-Based Design in Earthquake Geotechnical Engineering, paper No. 6.15.

Okamura, M. and Soga, Y. (2006); Effects of Pore Fluid Compressibility on Liquefaction Resistance of Partially Saturated Sand, Soils and Foundations, Vol. 46, No. 5, PP. 695-700.

Okamura, M., Ishihara, M. and Tamura, K. (2006); Degree of Saturation and Liquefaction Resistance of Sand Improved with Sand Compaction Pile, Journal of Geotechnical and Geoenvironmental Engineering, ASCE, Vol. 132, No. 2, pp. 258-264.

Piya B.K (2004); Generation of a geological database for the liquefaction hazard assessment in Kathmandu Valley, Nepal; Journal of Nepal Geological Society, vol.30, PP141-152.

Rana BJB.(1935); Nepal ko MahaBhukampa (Great Earthquake of Neptal); Jorganesh Press, Kathmandu.

Rauch, A. F. (1998). Personal Communication. (As cited in Youd, et. al. (2001)).

Robertson PK, and Wide CE (1998); Evaluating cyclic liquefaction potential using the cone penetration test, Canadian Geotechnical Journal, Ottawa, 35(3), 442-459.

Seeber L. and Armbruster J.G. (1981); Great detachment earthquakes along the Himalayan arc and long-term forecasting;in:Earthquake Prediction –an international Review (eds). Simpson D W and Richards PG, Maurice Ewing Series, Am. Geophys. U. 4 259-277.

Seed H. B., Idriss, I.M. (1971); Simplified Procedure for Evaluating Soil Liquefaction Potential, Journal of the Soil Mechanics and Foundation Division, ASCE, Vol. 107, PP, 1249-1274.

Seed H.B., and De Alba, P. (1986). Use of SPT and CPT tests for evaluation of the liquefaction resistance of soils, Use of In-Situ Tests in Geotechnical Engineering, ASCE GSP 6, pp. 281-302.

Seed HB (1983); Earthquake resistant design of earth dams, Proc. Symp. Seismic Design of Earth Dams and Caverns, ASCE, New York, 41-64.

Shrestha S.R.; Karkee, M.B.; Cuadra, C.H.; Tokeshi, J.C.; Miller, S.N. (2004); Preliminary Study for Evaluation of Earthquake Risk to the Historical Structures in Kathmandu Valley, Nepal; Paper no. 172, 13th WCEE.

UNDP/HMG/UNCHS (Habitat)(1994); Seismic Hazard Mapping and Risk Assessment for Nepal.

Youd T.L., et al. (2001); Liquefaction Resistance of Soils: Summary Report from the 1996 NCEER and 1998 NSEER/NSF workshops on Evaluation of Liquefaction Resistance of Soils, Journal of Geotechnical and Geoenvironmental Eng. Vol. 127, No. 10, PP. 817-833

Youd, T.L., and Idriss, I.M., eds (1997). Proc., NCEER Workshop on Evaluation of Liquefaction Resistance of Soils, Nat. Ctr. for Earthquake Engrg. Res., Stat Univ. of New York at Buffalo.


Refbacks

  • There are currently no refbacks.