An Experimental Study Among P-wave Velocity of Sandstones, Pressures and Water Saturation in Hami, Xinjiang, China

We have developed a new modeling approach for the complex-valued P-wave modulus of a rock saturated with two-phase fluid accounting for the variation with frequency and water saturation. Our method is based on the dynamic-equivalent-medium approach theory, which predicts P-wave modulus dispersion due to mesoscopic-scale wave-induced fluid flow (WIFF). Although the application of the original theory was limited to small fluctuation media, we have extended it to also be applicable for high-fluctuation media such as partially saturated rock. Our modification and extension consists of two components. The first is introducing a scaling by the rigorous bounds for P-wave velocity dispersion by mesoscopic-scale WIFF. The second is to develop a model representing the effective patch size of stiffer fluid that controls the location of the dispersion curve. We have found that the spatial correlation length of heterogeneity of saturated rock used in the original theory does not appropriately capture the effective heterogeneity scale responsible for mesoscale pressure diffusion. Its variation with saturation can be properly accounted for by the proposed patch-sized variation model. The comparison of the theoretical prediction with the published laboratory velocity and attenuation measurements suggests that our approach predicts the wave properties for high-fluctuation media with reasonable accuracy. The effect of mesoscopic-scale pressure diffusion is significant and the amount of velocity dispersion and attenuation is large in high-fluctuation media; therefore, our extension will improve quantitative characterization of, for example, a [Formula: see text]-sequestrated reservoir either by P-wave velocity or attenuation.

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Effects of Saturation Levels on the Ultrasonic Pulse Velocities and Mechanical Properties of Concrete

Materials ◽

10.3390/ma14010152 ◽

2020 ◽

Vol 14 (1) ◽

pp. 152

Author(s):

Ma. Doreen Esplana Candelaria ◽

Seong-Hoon Kee ◽

Jurng-Jae Yee ◽

Jin-Wook Lee

Keyword(s):

Mechanical Properties ◽

Compressive Strength ◽

Wave Velocity ◽

Water Saturation ◽

P Wave ◽

Saturation Level ◽

Saturation Condition ◽

P Wave Velocity ◽

Compressive Strength Of Concrete ◽

The Relationship

The main objective of this research is to investigate the effect of water content in concrete on the velocities of ultrasonic waves (P- and S-waves) and mechanical properties (elastic modulus and compressive strength) of concrete. For this study, concrete specimens (100 mm × 200 mm cylinders) were fabricated with three different water-to-binder ratios (0.52, 0.35, and 0.26). These cylinders were then submerged in water to be saturated in different degrees from 25% to 100% with an interval of 25% saturation. Another set of cylinders was also oven-dried to represent the dry condition. The dynamic properties of concrete were then assessed using a measurement of elastic wave accordance with ASTM C597-16 and using resonance tests following ASTM C215-19, before and after immersion in water. The static properties of saturated concrete were also assessed by the uniaxial compressive testing according to ASTM C39/C39M-20 and ASTM C469/C469M-14. It was observed that the saturation level of concrete affected the two ultrasonic wave velocities and the two static mechanical properties of concrete in various ways. The relationship between P-wave velocity and compressive strength of concrete was highly sensitive to saturation condition of concrete. In contrast, S-wave velocity of concrete was closely correlated with compressive strength of concrete, which was much less sensitive to water saturation level compared to P-wave velocity of concrete. Finally, it was noticed that water saturation condition only little affects the relationship between the dynamic and elastic moduli of elasticity of concrete studies in this study.

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