岩芯卸荷扰动的声学反应与卸荷敏感岩体

声波测试是工程岩体质量评价的最主要手段之一。将岩体与岩块的纵波波速比的平方定义为岩体的完整性系数。不仅为国内外学者广泛认同。而且是现行规范的定义。这是源于如下认识：原位岩体的纵波波速小于其中岩块的波速；岩体越破碎。小得越多。然而。通过润扬大桥声波测试发现。用通常手段得到的大部分岩体的测井波速反而大于岩样波速。对该桥基岩40余个钻孔数百个岩样进行了多种手段的对比研究和综合分析。探讨了测试结果的可靠性及产生原因。进而提出了岩芯卸荷扰动和卸荷敏感岩体的概念和相应的工程对策。

ACOUSTIC RESPONSES TO ROCK CORE UNLOADING-DISTURBANCE AND UNLOADING-SENSITIVE ROCK MASS

Ultrasonic testing is one of the most frequently used measurements in geotechnical rock mass evaluation. The square of the ratio of longitudinal wave (P-wave) velocity of rock mass to that of rock block is defined as intactness index of rock mass. As we know,the P-wave velocity of in-situ rock mass is believed to be lower than that of relevant rock block. The more broken the rock mass is,the lower its P-wave velocity is than that of rock block. However,according to the result of ultrasonic testing carried out at Runyang Highway Bridge,it is surprised to find that most P-wave velocities of rock mass are higher than that of rock block. Many different measurements are applied in the comparative research,which is based on hundreds of rock cores collected from over 40 boreholes in the bed rock of the Bridge site,and the reliability and causes of the results are analyzed. The concepts of rock core unloading disturbance and unloading-sensitive rock mass are then put forward,with relevant engineering countermeasures.