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Development of Precise, Continuous Monitoring System of Sound Velocity In Situ

开发精确、连续的声速原位监测系统

基本信息

批准号：
08555258
负责人：
SANO Osamu
金额：
$ 0.9万
依托单位：
Yamaguchi University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
1996
资助国家：
日本
起止时间：
1996 至 1998
项目状态：
已结题

项目摘要

A precise, continuous monitoring of sound velocity is one of the useful tool for estimating stability and shielding effect of the rock surrounding the underground structure. When radio-active species and other environment-pollutants are kept in such an under ground structure, we have to monitor surrounding rocks with ex- tremely careful attentions. The main aim of this study is to establish a system for measuring sound velocity of the rocks in situ with a resolution of ppm. When the measurement path has to be longer than the size of the structure, we have to measure the sound velocity along the path more than a hundred meters. We have to be also careful to select transmitter, because we have to contrnue to measure very long time. The transmitting wave have to be free from damaging the rocks. As the amplitude of the wave, particularly with high frequency decreases exponen- tially with propagation, we have to measure very Low signals. In order to eliminate noises an averaging method was employed. This method requires very high reproducibility of the transmitting wave. A laminated piezo-electric transducers was used for transmitter in this study, because of low power and of high reprodu- cibility. In an underground drift of the Kamaishi Mine the sound velocity is measured continuously with half hour intervals now. The maximum measurement path was 126 m. The best resolution of the sound velocity was estimated as about ppm. A periodical change of the sound velocity with an interval of about 12.4 hours was found due to the Earth tide. The maximum variation of the sound velocity during 12.4 hours was a couple of ppms. Laboratory measurement of the pressure sensitivity of the rock suggests that such a small change of a couple of ppms corresponds to the small stress change of about 3 hectopascals, which agrees well with the order of the Earth tide.

精确、连续的声速监测是估计地下结构周围岩石稳定性和屏蔽效应的有效工具之一。当放射性物质和其他环境污染物保存在这样的地下结构中时，我们必须非常仔细地监测围岩。本研究的主要目的是建立一个分辨率为ppm的原位岩石声速测量系统。当测量路径必须长于结构的尺寸时，我们必须沿着一百米以上的路径测量声速。我们还必须仔细选择发射机，因为我们必须持续测量很长时间。发射波必须不破坏岩石。由于波的振幅，特别是高频波的振幅随着传播呈指数递减，我们必须测量极低信号。为了消除噪声，采用了平均方法。这种方法对发射波的再现性要求很高。本研究采用层压式压电换能器作为变送器，具有低功耗和高重现性的优点。在釜石矿地下巷道中，每隔半小时连续测量一次声速。最大测量路径为126 m。声速的最佳分辨率估计为ppm左右。由于地球潮汐的影响，声速的周期变化约为12.4小时。在12.4 h内声速的最大变化为几ppms。对岩石压力敏感性的实验室测量表明，这种几ppms的小变化对应于大约3百帕斯卡的小应力变化，这与地球潮汐的顺序非常吻合。