Tunneling(4)

V] TUNNELING THROUGH THE FRACTURES ZONES:-

1) Fracture is defined as passive consequencies of tectonic forces that were acting in the Deccan trap without any movement. But it is fear of only leakage due to which rock decomposed on both sides of fractures.

2) fractures are not shear zones but are merely vertical and nearly vertical fractures along which no movement has been takes place.

3) Fractures is seen to be cutting a no. of lava flows without movement. It is only possible channel of leakage.

4) If tunnel is across the fractures the site is completely suitable without any trouble.

     i) Malshaj ghat tunnel- tunnel left unlined 3 fractures are crossing.

    ii) Borg hat tunnel.

  

5) If tunnel is along the fractures then it creates trouble of roof falls and leakage of water lining is required.

   i) Katraj ghat tunnel – Poona- Banglore road NH-4.

 GROUND WATER PROBLEM:-

                 The impervious rock formation should be selected for tunneling. The water bearing formation should be completely avoided. The ground water is most trouble some single factor in tunneling because not only does it create difficulties of it own also aggravates other difficulties. Therefore detailed ground water studies must be essential part of geological investigation for all tunnels. Those which are in low-lying area or area of heavy precipitation, or those passing below rivers.

Eg:- 1) Bassein creck tunnel.

        2) Koyna 3^rd stage tail race tunnel.

       3) Sanjacinto tunnel in California.

TUNNELING THROUGH SOFT ROCKS:-

1) Tunneling in soft material ( unconsolidated ) will be easier than in hard consolidated rock.

2) Faster process in soft material but it will not stand by them selves when support is removed. Therefore the tunnel will need permanent lining.

3) Example:- i) Ramganga dam project in Himalayas diversion tunnel- roof fall rock saturated with water.

                   ii) Umian Barapani tunnel in Meghalaya in loosely compacted sandstone band saturated with water roof collapse take place.

I] REQUIREMENT:-

1) There should not be overbreak.

2) There should not be roof collapse.

3) There should not be ground water problem.

II] TYPES:-

           There are various types of tunnels depends on purpose.

1) Road tunnel. 2) Railway tunnel. 3) Water carrying tunnel. 4) Ventilation tunnel. 5) Power tunnel.- i) Head race tunnel .

                             ii) Tail race tunnel.

                            iii) Pressure fault.

III] ENGG. GEOLOGY :-1) Economy.

                                              2) Safety.

                                              3) Speed.

                                                                                                                                IV] TUNNELING  in D. T. rock / sedimentary rock / fault zone/ folded area / limestone /fracture zone / jointed rock.

EXAMPLES:-

I)Tunnel along strike – Lochobar tunnel in Scotland 40% along 60% across the strike rock was mica schist.

II) Tunnel along jointed compact basalt- 1) Koyna 3^rd stage tail race tunnel. 2) Bassein creek tunnel carry water from Vaitarana river to Bombey city.

III) Tunnel along Amygdaloidal Basalt- 1) Koyna 3^rd stage head race tunnel. 2) Thal ghat ( Bombey – Delhi line) 3) Bhar ghat on ( Bombey – Pune line).

IV) Tunnel along fault- 1) Koyna 3^rd stage tail race tunnel fault zone 13m collapsed. (Rank JCB). 2) Beas- Sutlag link project (Jointed Quartzite).

V) Tunnel along fracture- Tansa tunnel, Bhivpuri tunnel.

        1) Katraj ghat tunnel – ( Pune- Banglore NH4).

VI) Tunnel across fracture- 1) Malshaj ghat tunnel. 2) Bhor ghat tunnel. 3) Khandald tunnel. 4) Bhatsa TRT tunnel.

VII) Ground water problem- 1) Bassein creek tunnel. 2) Koyna 3^rd stage tail race tunnel. 3) San Jacinto tunnel in California.

VIII) Tunnel in unconsolidated sediments- 1) Ramganga dam project diversion tunnel. 2) Umian Barapani tunnel in Meghalaya.

IX) Tunnel in compact basalt ( RTB) &V.B.-

  1) Arphal tunnel for Arphal dam project.

  2) Man & Kanhar tunnel for Urmodi dam project.

 3) Khambati ghat tunnel on ( NH4- Pune – Banglore).

 4) Kamshet tunnel.