Design and construction of the Neelum-Jhelum Hydro Power Project has incorporated extensive
analytical studies both prior to and during the period of construction. Nevertheless, it is not until
the completed structures are put into service that the results of the efforts of WAPDA, the
Engineer, and the Contractor can be truly confirmed. For the headrace tunnel (HRT) all
appurtenant structures, this confirmation occurs when the tunnel is filled and live pressure loads
are applied to tunnel linings and all appurtenant structures.
The purpose of this First Filling Plan is to set forth the designers criteria and rates under which
tunnel filling is to proceed, to provide reference data to adjust, modify, and manage the first
filling process.
The first filling of the HRT of the Neelum-Jhelum Power System is a governing load case for
proper function of the tunnel and an event of first importance. Proper Planning and execution of
the first filling is relevant in order to:
- Slowly saturate and load the rock strata surrounding the HRT;
- Identify leakages at each of the tunnel plugs (Plugs at Adits A4, A4a, A5, and the Bypass
tunnel being the critical locations); - Measure overall tunnel leakage rates;
- Monitor and identify any leakages into the Power House cavern from both the manifold and
the tailrace tunnels; - Monitor rock seams and faults for local ground stability in localized areas identified during
construction along the HRT alignment.
2 PHYSICAL CONDITIONS
2.1 HYDRO-GEOLOGICAL CONDITIONS
HRT layout depicts a total length of 28,587 m between intake and powerhouse. An additional
length of 14,610 m involves two twin tunnel stretchesof 11,205 m and 3,405 m length.