Laboratory investigation on relationship between degree of saturation, B-value and P-wave velocity

Abstract

Laboratory tests were performed on Toyoura sand specimens to investigate the relationship between degree of saturation S_r, B-value and P-wave velocity V_p. Different types of pore water (de-aired water or tap water) and pore gas (air or CO₂) as well as different magnitudes of back pressure were used to achieve different S_r (or B-value). The measured relationship between B-value and V_p was not consistent with the theoretical prediction. The measurement shows that the V_p value in the specimen flushed with de-aired water is independent of B-value (or S_r) and is always around the one in fully saturated condition. However, the V_p value in the specimen flushed with tap water increases with B-value, but the shape of the relationship between V_p and B-value is quite different from the theoretical prediction. The possible explanation for the discrepancy between laboratory measurement and theoretical prediction lies in that the air exists in the water as air bubbles and therefore the pore fluid (air-water mixture) is heterogeneous instead of homogenous assumed in the theoretical prediction.

Keywords

degree of saturation / B-value / P-wave velocity / bender element

References

[1] IshiharaK, TsuchiyaH, HuangY, KamadaK. Recent studies on liquefaction resistance of sand-effect of saturation [C]. Proceedings of Fourth International Conference on Recent Advances in Geotechnical Earthquake Engineering and Soil Dynamics, 2001San Diego, CaliforniaCD-ROM1-7

[2] TsukamotoY, IshiharaK, NakazawaH, HuangY. Resistance of partly saturated sand to liquefaction with reference to longitudinal and shear wave velocities [J]. Soils and Foundations, 2002, 42(6): 93-104

[3] YangJ. Liquefaction resistance of sand in relation to P-wave velocity [J]. Géotechnique, 2002, 52(4): 295-298

[4] SkemptonA W. The pore-pressure coefficients A and B [J]. Géotechnique, 1954, 4(4): 143-147

[5] YangJ. Pore pressure coefficient for soil and rock and its relation to compressional wave velocity [J]. Géotechnique, 2005, 55(3): 251-256

[6] LeeS H, ChooY W, YounJ U, KimD S. Determination of P, S-wave velocities and pore water pressure buildup with B-value for nearly saturated sands [J]. Journal of the Korean Geotechnical Society, 2007, 23(2): 71-84

[7] NaesgaardE, BryneP M, WijewickremeD. Is P-wave velocity an indicator of saturation in sand with viscous pore fluid? [J]. International Journal of Geomechanics, 2007, 7(6): 437-443

[8] TamuraS, TokimatsuK, AbeA, SatoM. Effect of air bubble on B-value and P-wave velocity of a partially saturated sand [J]. Soils and Foundations, 2002, 42(1): 121-129

[9] NakazawaH, IshiharaK, TsukamotoY, ToshiyukiK. Investigation of in-site elastic wave velocity for assessment of liquefaction [J]. Symposium C of JGS, 2007, 62(2): 346-359

[10] HakanataM, MasudaT. Experimental study on the relationship between degree of saturation and P-wave velocity in sandy soils [C]. Geotechnical Engineering for Disaster Mitigation and Rehabilitation, Part 4, 2008BeijingScience Press346-351

[11] LeeJ S, SantamarinaJ C. Bender element, performance and signal interpretation [J]. Journal of Geotechnical and Geoenvironmental Engineering, 2005, 131(9): 1063-1070

[12] LingsM L, GreeningP D. A novel bender/extender element for soil testing [J]. Géotechnique, 2001, 51(8): 713-717

[13] ViggianiG, AtkinsonJ H. Interpretation of bender element tests [J]. Géotechnique, 1995, 45(1): 149-154

[14] WangY H, LoK F, YanW M, DongX B. Measurement biases in the bender element test [J]. Journal of Geotechnical and Geoenvironmental Engineering, 2007, 133(5): 564-574

[15] BiotM A. Theory of propagation of elastic waves in a fluid-saturated porous solid. I. Low frequency range. II. Higher frequency range [J]. Journal of the Acoustic Society of America, 1956, 28(2): 168-191

[16] NakagawaK, SogaK, MitchellJ K. Observation of Biot compressional wave of the second kind in granular soils [J]. Géotechnique, 1997, 47(1): 133-147

[17] GuX-qiangDynamic properties of granular materials at the macro and micro scales [D], 2012Hong KongThe University of Hong Kong