クラック状空隙に含まれる水分が岩石の弾性波速度に及ぼす影響
1976 年 92 巻 1056 号 p. 73-78
詳細
1976 年 92 巻 1056 号 p. 73-78
Variation of longitudinal wave velocity with respect to water content was measured for quartz diorites by using ultrasonic pulse method, and the result is illustrated in Fig. 1. The difference between the dry and saturated longitudinal wave velocities increases with increasing porosity. In this paper, we examine quantitatively the effects of saturation on longitudinal wave velocity of quartz diorites.
Walsh's equations for bulk and shear moduli are adopted to evaluate the longitudinal wave velocities of dry and saturated rocks, and applied to the explanation of velocity increase in saturation condition.
The examples of comparison between the observed velocities and the computed results are given in Tables 1-3. It is clearly seen from these tables that the water content in cracks increases greatly the longitudinal wave velocity. Therefore the increase in longitudinal wave velocity due to saturation of pores occurs when the pores are in the form of cracks, and the increase amount of velocity in saturation condition can be explained by crack model based on Walsh's expression.
The velocity variation due to saturation is also calculated by assuming equations (11) and (12), and the comparison of computed curves and observed values is shown in Fig. 5.
