Home | About Us | Instrumentation |Post Tensioning| Marble Mining |Ground Anchoring | Consulting | Drilling & Grouting| Contact Us | Publications

More information about Karun III project;

  

Karun III Hydroelectric Power Plant  

 

Client:  Ab-Niroo

Engineer:  Mahab-Ghods

Contractor:  Sabir

 

 

                                               

Karun III project is located on Karun river and is one of the biggest dams to produce power in Iran.  It consists of a powerhouse cavern , an inlet valve gallery and a transformer cavern.    The inlet valve gallery and the powerhouse cavern are located adjacent to one another.  The distance between them is about 20 meters although in many places due to the back break from blasting operations, the actual distance (or the thickness of the pillar formed in between these two caverns) is less than 20 meters.

The aim of the extra instrumentation that was put in this pillar was to study the stability of this narrow and tall pillar (20*40meters) in more details.  since the layers of the rock mass are high angled there and vertical stresses are believed to be the dominant stress at this site, the stability of this pills after completion of benchings were under investigation.

Two 20 meters long extensometers with 14 anchor points were designed by the company and put in place so that the last anchor point be close to the wall of the inlet valve gallery and the head of the extensometer be at the wall of the powerhouse cavern.  The design enables measurement of the whole displacement of the pillar as a result of bench blastings.  The anchor points were distributed along the length of the instrument to exactly pin point the displacement distribution and enables determination of the neutral access of deformation which believed to be laying somewhere in between the pillar.  The installation of this extensometer was very special and the assembling of the instrument was done at site due to the limitation of exporting it from Tehran.

The obtained results was very satisfactory as can be seen from the graph bellow and a back calculation was performed to determine the possible weak points in the pillar.  The perfect pick up of the displacements corresponding to the bench blasting is clear from the graph bellow.

 

 

As a complementary instrument, some pressure cells were also put in the rock of the caverns in different places to check the stress change while benching but unfortunately most of them were buried under the shotcrete by carelessness of the operators.

 
The displacement profile along the wall between the two caverns are depicted in this graph as a function of time.  It shows smoothly how the displacements are increasing with advances in the benching operations.

 

 

 

A close up of the head assembly before being grouted.
 

This experience is one of the most unique ones in its kind since usually the end of extensometers are far from the excavations and can be considered fixed but in this case one end of the instrument was sited by the powerhouse cavern and the other was at the valve gallery so both ends were moving.  By studying the displacement profile along this long pillar you can recognize the neutral point at which the rock movement in either direction is zero.

 

Home | About Us | Instrumentation |Post Tensioning| Marble Mining |Ground Anchoring | Consulting | Drilling & Grouting| Contact Us | Publications