| Author | Cimafranca, Abner Rosello |
| Call Number | AIT Thesis no.GT- 79-22 |
| Subject(s) | Slopes (Physical geography)
Philippines--Cebu
|
| Note | A thesis submitted in partial fulfillment of the requirement for the degree of Master of Engineering, School of Engineering and Technology |
| Publisher | Asian Institute of Technology |
| Abstract | Biga open pit mine of Atlas Consolidated Mining and Development Corporation (ACMDC) in Central Cebu, Philippines has been besetted by
slope stability problems since 1965. ·The Atlas porphyry copper district is located within two parallel steeply dipping E-NE trending ·major faults,
the North Barot Fault and the Cantabaco Fault .in the south. The block bounded by these two faults is about 3 to 4 kilometers wide and all copper deposits of economic significance have been found within this block. The rocks in the district were divided into four major groups, namely
(from the oldest to the youngest) the late Cretaceous metasediments, the late Cretaceous metavolcanics, the early Tertiary or Paleocene quartz diorite and dacite porphyries; and the Tertiary Oligo-Miocene sedimentary
series. Biga pit is located within the fault bounded block. The North Barot Fault .cuts the northern tip of Biga orebody. Another major fault trending NNE and dipping vertically slices longitudinally through the
center of the pit arid of the orebody. The rocks within the block and in Biga pit are deeply weathered, highly jointed, fractured and brecciated.
Slope. instabilities in Biga pit are mostly confined within the S-SW
and ·NE-E-SE cutslopes where the rocks arechiefly moderately to completedly weathered metavolcanics. The overall S-SW cut-slopes generally
trends N 70°w and dips 24°NE while the overall NE-E-SE cutslopes ·trends
0
0
0
0
0
0
N 52 E and dips 24 NW. A prominant and persistant N 80 -83 ·E, 22 -36
NW fault cuts across theNE-E-SE cutslopes and extends to the S-SW cut
slopes. Another persistent fault striking N 4° E and dipping 20° NW · cuts through the S-SW cutslopes. Numerous joints trending NW, NE and due
E and dipping at varying angles exist in the study area. 'The .general orientations of these three joint sets are N65° W, 40° NE; N60°E, 45° NW; and E-W 60° N, ·respectively. · The present pit bottom is an elevation 240
meters while highest point along pit perimeter is 660 meters. The
length of Biga open pit is generally trending due ,north. Both cutslopes have been involved in post slides involving hundreds of thousands to several million toµs of slide ·materials. The present S-SW and NE-E-SE cutslopes are still moving at varying rates ranging from 0:01 to 8.o ·cms of horizontal and vertical movement per day, depending on the existing piezometric levels and to the intensity and .level of blasting. Seepages, ponded waters and tension cracks are a plenty in both cutslopes.
During heavy rainfall surface erosion due to surface water runoff is
rampant and ·sometimes vicious where bench ramps are washed away and
deep wide gullies formed. Most of the intersections between joints
and faults in both cutslopes results into potential wedge failure planes.
In the NE-E-SE cutslopes most of the potential wedges analyzed have factors of safety less than unity. Wedges whose line of intersection is trending at a "high obligue angle with respect to the .dip direction of the overall slope face are generally stable with factors of safety ranging from 1.073 .to 2.943 depending on the water saturation condition.
In the · s-sw cutslopes the factors of ·safety of wedges for a 100% water saturation condition are mostly less than unity and increases to more than 1.0 as saturation goes down to 20%. Only the soaked 6 and c values of the metavolcanic rock was used in the stability analysis. |
| Year | 1980 |
| Type | Thesis |
| School | School of Engineering and Technology |
| Department | Department of Civil and Infrastucture Engineering (DCIE) |
| Academic Program/FoS | Geotechnical and Transportation Engineering (GT) |
| Chairperson(s) | Prinya Nutalaya; |
| Examination Committee(s) | Brenner, R.P.
; Jerasak Premchitt |
| Scholarship Donor(s) | Government of the United States of America. ; |
| Degree | Thesis (M. Eng.) - Asian Institute of Technology, 1980 |