本文件规定了一种确定土工布或土工布相关产品平面内恒定水头流量的方法。本文件描述了平面内水流指数测试，仅适用于工厂组装的产品。平面内水流性能试验见ISO 12958-2。

This document specifies a method for determining the constant-head water flow capacity within the plane of a geotextile or geotextile-related product. This document describes the in-plane water flow index test, only applicable to factory-assembled products. For the in-plane water flow performance test, see ISO 12958-2.