松动圈是地下洞室支护成败的关键，松动圈与开挖深度、围岩岩性、时间等因素有关，它实际是一个动态变化过程。首先阐述了声波法在松动圈动态分析中的适用性，并采用声波法对某大型地下厂房上游边墙松动圈进行了测试分析，绘制了开挖深度、岩体波速、时间、空间位置与松动圈的相互关系曲线，通过对上述关系曲线的分析，获得了松动圈的变化分布规律，提出了相应的工程措施。其分析方法为类似工程提供了借鉴及指导意义。

The loose zone is of essential importance to the supporting of underground caverns. It changes dynamically with the change of time, excavation depth, and lithology of the surrounding rock. To provide reference and guidance for alike projects, the applicability of sonic wave method in dynamically analyzing loose zone is expounded, and the loose zone at upstream sidewall of an underground powerhouse is measured and tested by the method. Curves of the loose zone versus the depth of excavation, the wave velocity of rock mass as well as the time and space are given. By analyzing the curves, the variation and distribution of loose zone are obtained, and corresponding engineering measures for the project construction are put forward.