Resolving serious seepage through karstified limestone at the Mujib Dam, Jordan

摘要

The 67 m high Mujib Dam (Jordan) was built between 1999 and 2003 in Cretaceous limestone with intercalated marls in the middle of the section. Initial investigations indicated only moderate permeability, hence prior to impoundment a normal grouting program was undertaken extending to 50 m in depth. Initially, little seepage was observed when the lower section of the reservoir was filled. After a dry summer, heavy rainfall filled the reservoir overnight to its maximum water level (194 m a.s.l.). A sudden seepage began downstream of the right abutment, which reached 140 1/s by morning, increasing to up to 240 1/s during the following 2 weeks. Although a second grouting program reduced the seepage to some 3 1/s of highly mineralized water, there were concerns as to the adequacy of the Phase 1 grouting. A detailed analysis of the testing and grouting results indicated that the hydraulic pressures created by the sudden increase of water in the reservoir had washed out the natural infill which had previously sealed karstic voids.