Successful Pilot Hole Breakthrough of Two Ore Pass at Pulang Project
Time£º2019/9/29 8:39:00 424 Browse
Good news was received recently from Pulang Project. The pilot holes for ore pass S4 and ore pass S5 have been successfully cut through by JCHX raise boring team through the application of new technology and continuous efforts within two months, despite of various obstacles.
Ore pass S4-1 is between 3720mL and 3660mL, designed with a depth of 48m and a diameter of 1.4m. JCHX raise boring team was challenged by high risks of hole collapse due to poor rock conditions and water ingress from strata. Hence the work was proceeded much slower than expected. Several times of grouting were carried out for water sealing and sludge pumps were used in later stage for drainage. After 63 days of painstaking works, the pilot holes were cut through on 18 July 2019.
Ore pass S5 is designed with the same parameters as S4. The geological conditions of two ore pass are basically the same considering S5 is less than 50m away from S4. Therefore, the team on site summed up experiences and lessons learnt from S4 and decided to think out of the box, after which the construction method was improved as follows.
i. Replace ¦µ250mm drill bit with ¦µ216mm ones, and diameter of stabilizer was changed to 214mm~215mm so as to reduce muck and thus increase mucking efficiency.
ii. Replace production water with high pressure air for cleaning, the air shall be supplied through air pipe installed between drill rods. This way, the rock was not soaked and less likely to collapse. Also, the efficiency of pilot hole drilling was much improved.
iii. Blow-over with high-pressure air may lead to heavy dust, thus dust prevention and control were prioritized. The crew collected dust using dust collectors and steam separators. They also covered the air outlet with cotton quilt and sprayed water for dust suppression. Those methods were proved to be practical.
New method was tried out for ore pass S5 starting from Aug 6, and the pilot hole was cut through on Aug 7, which only took two days. All the design requirements were satisfied with deviation well under control. JCHX team demonstrated that their think-out-of-the-box solution is more efficient, more cost-effective and much safer.