| Summary: | The dolomitic limestones on study area are small scale mining activity which
operates with simple equipments. These dolomitic limestone mining study areas are located
on Kecamatan Semanding, Kabupaten Tuban, Propinsi Jawa Timur which geographically are
located on 111° 59� � 112° 7� E longitude dan 6° 58�� 7° 2� S latitude. All of the 77 dolomitic
limestone mining areas are distributed just on 3 villages, Desa Bektiharjo, Desa Prunggahan
Kulon and Desa Jadi.
The dolomitic limestones on study area are operates with simple surface mining
methods results vertical steep slopes, or by underground mining methods results caves.
According with that, needs an evaluation and recomendation to determined the condition of
dolomitic limestone mining based on Geomechanical Classification (RMR/Rock Mass Rating)
and Geological Strength Index (GSI), and also for define the correlations between both
rockmass classifications in the study areas.
From field observation data, laboratory analyzed, evaluation criteria and so many
rock mass classification parameter calculation, even with qualitative or quantitative methods
that found in 77 dolomitic limestone mines location at Kecamatan Semanding, results GSI�s
grades for rock mass that contain discontinuities are range between 61 � 79 (GSI = 100, for
intact rockmass) with cohesion (c�) variations between 0,03 � 0,52 Mpa and friction angle (�')
42,69 � 55,90°. This results shows that the study areas contains soft to hard rock masses with
no major structural disturbing.
According to kinematic analysis from surface mining of the dolomitic limestone that
contain discontinuities, there are 3 locations which have potential instability (plane failures),
OC-17, OC-32 and OC 73. After analyzed with slope stability analysis, we find those slopes
are completely stable.
RMR89�s grades (corrected RMR) for underground mining rock mass that contain
discontinuities are range between 51 � 69 (RMR�s class III � II). On RMR class II, can be set
wire mesh occasionally and complete support 20 m from face. For the next excavation
process, preferably to make narrower span, around 2 � 4 meter for no support tunnel require.
On RMR class III, can be set wire mesh in specify locations and complete support 10 m from
face. For the next excavation process, preferable to make narrower span, around 2 � 3 meter
for no support tunnel required with Top-Heading and Bench excavations method.
SMR�s grades for surface mining rock mass that contain discontinuities are range
between 15,80 � 76,03 (SMR�s class V � II). On SMR class II and III, can be apply slopebench
mining method to decrease steepness angle into the safe slope. On SMR class IV and V,
suggest to re-excavate from another slope face side
From GSI and RMR89 (adjustment to dry basic RMR) grades, we can find relation
between GSI and RMR for dolomitic limestone mining on semanding area is GSI = 0,52 RMR
+ 34,30 , with range of RMR89 (adjustment to dry basic RMR) = 63 � 79 and GSI = 66 � 79.
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