0 - ta3111-1 batuan & mekanika batuan
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Batuan & Mekanika BatuanTRANSCRIPT
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an BATUAN DAN BATUAN DAN
MEKANIKA BATUAN MEKANIKA BATUAN -- 11
Suseno Kramadibrata
Made Astawa Rai
Ridho K Wattimena
Laboratorium Geomeknika
FIKTM - ITB
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PendahuluanPendahuluan
� Over the last decade there has been an unprecedented increase in the development of civil and mining works, both for surface and underground in Indonesia. The civil work that concerns to the geomechanics engineers have been mostly associated with tunnelling development. Most of the open pit mining development has been related to the exploitation of low to medium grade gold, coal deposits, and to some extents to the expansion of a nickel mine and limestone quarries for cement factories. On the other hand, underground mining development apparently has been attributed to the expansion of the existing underground coal mines and development of two underground gold mines.
� It is clear that the geomechanics engineers, who are responsible of designing and implementing the proposed mining method should take account economic considerations as well as safety awareness. Moreover, design of large rock excavations must rely on many geomechanics parameters, which are often determined on laboratory as well as insitu tests. Obviously, the data obtained from laboratory tests are frequently based on relatively small size samples. The insitu tests to determine the direction and magnitude of insitu stress are very rare to be carried out, as they are very expensive.
� Although insitu underground monitoring has been practiced at a number of mines, roof collapse, wall and floor deformation and support failure still take place. This may relate to inability of the geomechanics engineers to fully understand the behaviour of the real rock mass condition. And this is due a limited information could be obtained, either from laboratory tests, insitu tests or field observation.
� Problems identified in the open pit mines have apparently been linked to, slope stability of working bench and outside dump, low bearing capacity and rock breaking efficiency. On the other hand, problems encountered in the underground mines may be as follows; determination of input parameters for analysis of an underground opening stability, insitu stress determination, and selection of rock excavation method.
� This paper therefore describes the parameters controlling the stability of open pit and underground mines. These may be elaborated as follows; the overall geology of Indonesia, tropical weather, the typical slope and underground opening failures, behaviour of geological materials, laboratory test procedures and case studies associated with the geomechanics problems in Indonesian mining are given.
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Magmatic Belts in IndonesiaMagmatic Belts in Indonesia
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Distribution of Metallic, NonDistribution of Metallic, Non--metallic metallic
Minerals and Coal in IndonesiaMinerals and Coal in Indonesia
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KeunikanKeunikan GeologiGeologi UmumUmum IndonesiaIndonesia
� There are three interesting geology phenomena of Indonesia. First, about 80 - 90% of Indonesian land is covered by quarter sediment namely, alluvial, clastic, and pyroclastic sediments resulted from volcano activities, as well as trass alluvial, and soils resulted from rock weathering. Second, the rock formation in Indonesia is very young, and third there are many tectonic activities taking place in Indonesia.
� The young rock formation apparently should have not been well compacted, and this particular rock formation has a very wide range rock types. This rock type is seemingly not quite dense, and as a results the porosity is relatively higher than that of old rock formation.
� About 13% - 17% of the active volcanoes in the world are located in the Indonesian archipelago and there are 3 volcanoes magmatic belts, stretching from Sumatra to Irian Jaya. As far as the rock type is concerned, sedimentary rock and rock formation formed from volcanic activities are dominant in Indonesia.
� Regarding the tectonic activities, it should be borne in mind that there are three tectonic plates i.e., Eurasia - Australia - Indian Pacific Ocean, intersect each other in Indonesia. Thus, it is not unusual if strong and many tectonic activities take place in Indonesia. As a matter of fact, about one tenth of earth - quakes in the world happens in Indonesia. The earth - quakes normally cause tension zones that ultimately create unstable zones.
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General Geology Of IndonesiaGeneral Geology Of Indonesia
� ± 80 - 90% Indonesian land is covered by quarter sediment & the rock
formation is very young
� There are many tectonic activities occurring in Indonesia
� The young rock formation have not been well compacted, & has a very wide
range rock types; not quite dense, high porosity
� ± 13% - 17% of the active volcanoes in the world are located in Indonesian archipelago
� 3 volcano magmatic belts: stretching from Sumatra to West Papua & mineral belts also relatively occupying the same magmatic belts
� High rainfall 3000 - 4000 mm & mostly in Sumatra, Kalimantan & Java
� A combination of high rainfall, ambient temperature & intensity of ultraviolet
rays over a year period causes chemical weathering occur frequently, & this turns hard rock formation into so-called soft rock
� Rapid mining development coupled with soft rock behaviour lead to Geomechanical or rock engineering problems
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IklimIklim & & CuacaCuaca
� Indonesian archipelago is located within the Equator and between Asia and Australia continents and surrounded by Pacific and Indian oceans. As a result of this unique condition Indonesia has a very high rainfall rate. This happens mostly in the areas of Sumatra, Kalimantan, west Java, and the average annual rainfall rate being 3000 - 4000 mm.
� Beside the high rainfall rate, it can be noted as well that the ambient temperature and intensity of ultraviolet ray over a year period are relatively high. These facts of course cause a great contribution toward the weathering process, particularly the chemical weathering. Hence, it is not surprising when rock changing takes place frequently.
� This weathering process would therefore turn hard rock formation into so called soft rock formation. Laterite and monmorilonite clay is the typical materials resulted from weathering process. And, monmoriloniteclay is the most interesting one, because once it gets wet it will expand very quickly and consequently influence the deformation behaviour.
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Definisi BatuanMenurut Geologiwan
1. Batuan adalah susunan mineral dan bahan organisyang bersatu membentuk kulit bumi.
2. Batuan adalah semua material yang membentuk kulitbumi yang dibagi atas :
� Batuan yang terkonsolidasi (consolidated rock).
� Batuan yang tidak terkonsolidasi (unconsolidated
rock).
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Klasifikasi Geologi Batuan
� Batuan Beku (igneous rocks)
� Batuan Sedimen (sedimentary rocks)
� Batuan Malihan atau metamorf (metamorphic rocks)
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ProsesProses PembentukanPembentukan BerbagaiBerbagai JenisJenis
BatuanBatuan
Proses pembentukanbatuan metamorphic
Proses pembentukanbatuan beku
Proses pembentukanbatuan sediment
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BerbagaiBerbagai JenisJenis BatuanBatuan PentingPenting DalamDalam
RekayasaRekayasa BatuanBatuan
Basalt
Gneiss
Gneiss
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PengaruhPengaruh GeologiGeologi BatuanBatuan TerhadapTerhadap
RekayasaRekayasa BatuanBatuan--11
� Out of the three generic categories of rocks, metamorphic rocks exhibit
highest degree of anisotropy [1].
� Segregation of constituent minerals, in response to high pressure and
temperature gradients, is associated with tectonic evolution and development
of layers of contrasting mineralogical assemblages.
� Rocks flow and recrystallize under new tectonic stresses to form weak
foliation planes. Such planes of weakness (i.e. schistosity) affect the strength
and deformational behaviors of rocks with orientation to the applied stresses.
Irrespective of the size of the engineering projects, either dealing with
inherent intact rock anisotropy from an exploratory borehole or induced rock
anisotropy due to in situ fracturing [1], where stability of large rock mass is
concerned, evaluation of intact rock anisotropy in terms of strength and
modulus is inevitable.
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PengaruhPengaruh GeologiGeologi BatuanBatuan TerhadapTerhadap
RekayasaRekayasa BatuanBatuan--22
� Prediction of the anisotropic responses of strength and deformation of rocks
involves study of specimens at different orientation angles, β (the angle between the major principal stress direction and the foliation plane).
� Anisotropy, which is characteristic of metamorphic rocks such as schists, is
due to a process of metamorphic differentiation.
� Preferred orientation of minerals like mica and chlorite in response to
tectonic stresses makes schistose rocks foliated.
� As a result their engineering properties vary with the direction of loading.
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JenisJenis StrukturStruktur BatuanBatuan
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Definisi BatuanMenurut Teknik Sipil - Geoteknik
1. Istilah batuan hanya untuk formasi yang keras dan
padat dari kulit bumi.
2. Batuan adalah suatu bahan yang keras dan
koheren atau yang telah terkonsolidasi dan tidak
dapat digali dengan cara biasa, misalnya dengan
cangkul dan belincong.
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Definisi BatuanMenurut Talobre
Menurut Talobre, orang yang pertama kali
memperkenalkan Mekanika Batuan di Perancis
pada tahun 1948, batuan adalah material yang
membentuk kulit bumi termasuk fluida yang
berada didalamnya (seperti air, minyak dan
lain-lain).
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Definisi BatuanMenurut ASTM
Batuan adalah suatu bahan yang terdiri dari
mineral padat (solid) berupa massa yang
berukuran besar ataupun berupa fragmen-
fragmen.
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Definisi BatuanMenurut Umum
� Batuan adalah campuran dari satu atau lebih mineral yang berbeda,
tidak mempunyai komposisi kimia tetap.
� Batuan tidak sama dengan tanah. Tanah dikenal sebagai material
yang “mobile”, rapuh dan letaknya dekat dengan permukaan bumi
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Komposisi Batuan
2,02H2O
2,69Fe2O33,7MgO
2,98K2O4,9CaO
3,25Na2O14,9AI2O
3,39Fe59,8SiO2
%Mineral%Mineral
Batuan terdiri dari batuan padat baik berupa kristal maupun yang tidak
mempunyai bentuk tertentu dan bagian kosong seperti pori-pori, fissure,
crack, joint, dll.
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DefinisiDefinisi Soft RockSoft Rock
� There are many terms used to describe materials being considered as soft rock (Johnston, 1991,
Fairhurst, 1993 and Vutukuri & Katsuyama, 1994). However, the following term “rocks which are
susceptible to physical and chemical weathering resulting in such effects as deterioration in strength,
slaking, squeezing and swelling” may be appropriate.
� Unlike the hard rock properties, which are mainly controlled by discontinuities, a considerably close
relationship is observed between the properties, determined for rock and those determined for rock
masses. Accordingly, the behaviour of the ground composed of such soft rock and weak rock largely
depends upon the physical and mechanical properties of rock elements. Hence, it is not unusual that
rock-engineering problems involving soft rocks have traditionally been solved by extrapolating from the
historically separate technologies of either soil mechanics or rock mechanics. For example, when soft
rock have been encountered in an open pit or an underground mines, it has usually been a specialist of
rock mechanics who has sought a solution. Consequently, the technology applied has usually involved
the empirical hard rock approached. This approach has been much concerned with the defects within
the rock mass rather than the rock material it self.
� As mentioned earlier, the descriptor soft would appear to be far more appropriate as it applies to the
intact rock material. The intact rock material is supposedly independent of any discontinuities that may
or may not influence its engineering behaviour. The most well known intact rock classification scheme
frequently used by geomechanics engineers is the one from the ISRM (Brown, 1981).
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DefinisiDefinisi Soft RockSoft Rock
� Considering the intact rock classification, it is therefore of importance to set up a guideline to define the
range of soft rock in term of strength. The Rock Mass Classifications proposed by Bieniawski (1973)
and Barton et al (1974) implied that intact rock that is considered as very weak corresponds to the
unconfined compressive strength (UCS = sc) of less than 25 MPa and the RQD is less than 25%
respectively. Furthermore, Francis (1994) claims that weak rock is associated with the UCS (sc),
Young’s Modulus (E) and Poisson’s Ratio (n) of < 5 MPa, < 1.5 GPa and > 0.25 respectively. According
to Johnston (1991) and Vutukuri and Katsuyama (1994) the UCS of soft rocks is in the range of 0.25 –
25 MPa and less than 20 MPa respectively. Thus, it can be said if any intact rock processing the UCS
of less than 25 MPa can be regarded as soft rocks.
� The behaviour of Ombilin claystone and Tennessee marble (Kramadibrata, 1999 and Wawersik &
Fairhurst, 1970) during triaxial tests is illustrated in Figure 6. The results of claystone, for low confining
pressure, demonstrate a typical of overconsolidated behaviour with relatively brittle stress strain curves
and well defined failure planes as well as degree of dilatancy. As the confining pressure is increased, it
turns to normally consolidate and ductility becomes apparent, ultimately failure is characterised by
bulging.
� There is ample evidence in the rock mechanics literatures to show that the same characteristic is
repeated with hard rocks as shown in Figure 6 for Tennessee marble. This indicates that a transition
from brittle to ductile behaviour becomes apparent, as confining is increased. Again, the strength
characteristics of, soft rocks and hard rocks are similar, yet the different is the order of the stress level,
within which the brittle ductile transition takes place.
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Soft RocksSoft Rocks
� Soft rocks are rocks that have failed under their in situ stresses.
� Soft rocks are what they are because of where they are.
� Soft rocks are what they are relative to where they are.
� Generally, soft rocks may be described as geomaterials with properties between soils and rocks.
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Physical characteristics of Soft RocksPhysical characteristics of Soft RocksS.D. Glaser, D.M. Doolin / International Journal of Rock Mechanics and Mining Sciences 37 (2000) 683±698
Change in effective stresses by swelling or slaking
Volume changes
Squeezing may occurCreep sensitive
Sliding on weak interfaceNaturally occurring fractures
Failure through intact portionLow ratios of strength to applied stress
Associated problemsPhysical characteristic
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Categories of Soft RocksCategories of Soft RocksS.D. Glaser, D.M. Doolin / International Journal of Rock Mechanics and Mining Sciences 37 (2000) 683±698
� Melange
� Clays and gouge
� Marls, saprolite
� Tectonics
� Fault zones
� Weathering/chemical
reaction
Chemically or
mechanically altered
� Shale, mudstone,
sandstone, diatomite,
marl, chalk
� NaCl KCl, gypsum
� Coal, lignite
� Structurally weak
� Evaporites
� Organics
Naturally Weak
Example rocksCauseNature of weakness
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KurvaKurva TeganganTegangan ReganganRegangan
OmbilinOmbilin claystoneclaystone & Tennessee marble& Tennessee marble(Kramadibrata, 1999; Wawersik & Fairhurst, 1970).
0
100
200
300
0 0.2 0.4 0.6
Axial strain (%)
Ax
ial s
tre
ss
(M
Pa
)
6.9 MPa
48.3 MPa
27.6 MPa
13.8 MPa
0
Claystone - PTBA Ombilin
0
10
20
30
40
50
0.0 0.5 1.0 1.5 2.0 2.5
Axial strain (%)
De
via
tori
c S
tre
ss
(M
Pa
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5 MPa
10 MPa
15 MPa
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EfekEfek SkalaSkala UCS Hard Rocks & Soft RocksUCS Hard Rocks & Soft Rocks(Kramadibrata and Jones, 1993; Marsland, 1971).
LONDON CLAY
0
1
2
3
4
5
0 1 2 3 4 5Diameter of specimens
Spacing of f issures
Str
en
gth
mea
su
red
in la
bo
rato
ry
Str
en
gth
es
tima
ted
fro
m in
situ
te
sts
LONDON CLAY
0
1
2
3
4
5
0 1 2 3 4 5Diameter of specimens
Spacing of f issures
Str
en
gth
me
as
ure
d in
lab
ora
tory
Str
en
gth
es
tima
ted
fro
m in
situ
te
sts
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Development Of Engineering Development Of Engineering
Geomechanics In IndonesiaGeomechanics In Indonesia
� Up to date: ± 20 Mining Schools & > 50 School of Civil Engineering
� Of 20 Mining Schools ±15 undergraduate levels & the rest is three year
mining degree & < 5 mining departments teach well rock mechanics
� The DME Institut Teknologi Bandung ITB has been the benchmark of the mining education in Indonesia ever since.
� The rock mechanics has been taught at the DME since mid 60s
� The development of rock mechanics had not been noteworthy until large U/G power houses & tunnelling in the Hydro Electric Projects were built in
Indonesia (1982 in Saguling, West Java)
� Since then the U/G constructions & development of U/G coal & gold mine as well as the expansion & new development of open pit coal mine, gold mine,
copper mine & nickel mine have significant contributions to the
geomechanics development in Indonesia
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Field Surveys & Studies in Open Pit Field Surveys & Studies in Open Pit
& U/G Mines& U/G Mines
� U/G monitoring: convergence & magnesonic probe extensometer at hydro electric power projects, U/G Ombilin coal mine & U/G Pongkor gold mine
� Insitu deformability: pressure meter & plate loading tests at civil projects
� Rock mass & geological structure mapping: quarries, open pit copper & coal mines & U/G gold & coal mines
� Slope stability monitoring: prisms, counter weight balance, magnesonicprobe extensometer at Muara Tiga Besar open pit coal mine
� Rock blasting performance: fragmentation (Kuz Ram method), ground vibration monitoring based on scaled distance at a number of civil projects, surface mines & quarries
� Cuttability, diggability & excavatability: tunnel boring machine for tunnelling at hydro electric project in Singkarak, raise boring ventilation shaft in U/G Pongkor gold mine, road header for driving at U/G Ombilin coal mine, & Bucket Wheel Excavator, ripping and shovel at a number of open pit coal mines
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Research Development at The Research Development at The Geomechanics Laboratory DME ITBGeomechanics Laboratory DME ITB
� DME ITB possesses the most well equipped geomechanics laboratory
& teaching resources in Indonesia
� The geomechanics research is mostly associated with final year
students, Doctoral research projects & commercial
� Main areas of research: rock mechanics related, rock blasting, rock
cutting and safety related to the instability of open pit & U/G excavations
� Interesting phenomena to be studied: soft rock engineering, time
dependent behaviour and the role of scale effect on the extrapolation of
laboratory test result into rock mass condition
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Blok Diagram Model Blok Diagram Model MekanikaMekanika BatuanBatuan & &
RekayasaRekayasa BatuanBatuanX.-T. Feng, J.A. Hudson / International Journal of Rock Mechanics & Mining Sciences 41 (2004) 255–273
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Definisi Mekanika BatuanMenurut Talobre
1. Mekanika batuan - teknik & juga sains yg tujuannya mempelajari behaviour
batuan di tempat asalnya agar dapat mengendalikan pekerjaan yang dibuat
pada batuan tsb seperti penggalian dibawah tanah dan lain-lainnya.
2. Mekanika Batuan merupakan gabungan dari:
� Teori + pengalaman + pekerjaan/pengujian di laboratorium + pengujian in-
situ.
3. Mekanika batuan tidak sama dengan ilmu geologi yg didefinisikan oleh
Talobre sebagai sains deskriptif yg mengidentifikasi batuan & mempelajari
sejarah batuan.
4. Mekanika batuan tidak sama dengan ilmu geologi terapan - banyak
mengemukakan problem yg paling sering dihadapi oleh para geologiawan
di proyek bendungan, terowongan. Dengan mencari analogi-analogi,
terutama dari proyek-proyek yang sudah dikerjakan dapat menyelesaikan
kesulitan-kesulitan yang dihadapi pada proyek yang sedang dikerjakan.
Meskipun penyelesaian ini masih secara empiris dan kualitatif.
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Definisi Mekanika BatuanMenurut Coates (Canada)
1. Mekanika adalah ilmu yang mempelajari efek dari gaya atau tekanan pada
sebuah benda - percepatan, kecepatan, perpindahan.
2. Mekanika batuan adalah ilmu yang mempelajari efek dari gaya terhadap batuan
� Efek utama Geologiwan - perubahan bentuk.
� Efek utama Geofisika aspek dinamis dari perubahan volume & bentuk -
gelombang seismik.
3. Bagi para insinyur, mekanika batuan adalah :
� Analisis dari beban atau gaya yang dikenakan pada batuan.
� Analisis dari dampak dalam yang dinyatakan dalam tegangan (stress),
regangan (strain) atau enersi yang disimpan,
� Analisis akibat dari dampak dalam tersebut, yaitu rekahan (fracture), aliran
atau deformasi dari batuan.
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Definisi Mekanika BatuanUS National Committee On Rock Mechanics (1984)
Mekanika batuan adalah ilmu pengetahuan yang mempelajari perilaku (behaviour) batuan baik secara
teoritis maupun terapan, merupakan cabang dari ilmumekanika yang berkenaan dengan sikap batuan terhadap
medan-medan gaya pada lingkungannya.
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Definisi Mekanika BatuanMenurut Budavari
� Mekanika batuan adalah ilmu yang mempelajari mekanika perpindahanpadatan untuk menentukan distribusi gaya-gaya dalam dan deformasiakibat gaya luar pada suatu benda padat.
� Hampir semua mekanika perpindahan benda padat didasarkan atasteori kontinum. Konsep kontinum adalah fiksi matematik yang tergantung pada struktur molekul material yang digantikan oleh suatubidang kontinum yang perilaku matematiknya identik denga media aslinya.
� Material ekivalennya dianggap homogen, mempunyai sifat-sifat mekanikyang sama pada semua titik. Penyederhanaannya adalah bahwasemua sifat mekaniknya sama ke semua arah pada suatu titik di dalamsuatu batuan
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Definisi Mekanika BatuanMenurut Hudson & Harrison
� Mekanika batuan adalah ilmu yang mempelajari reaksi batuan yang
apabila padanya dikenai suatu gangguan. Dalam hal material alam, ilmu
ini berlaku untuk masalah deformasi suatu struktur geologi, seperti
bagaimana lipatan, patahan, dan rekahan berkembang begitu tegangan
terjadi pada batuan selama proses geologi.
� Beberapa tipe rekayasa yang melibatkan mekanika batuan adalah
pekerjaan sipil, tambang dan perminyakan.
� Topik utama mekanika batuan adalah batuan utuh, struktur batuan,
tegangan, aliran air, dan rekayasa, yang ditulis secara diagonal dari kiri
atas ke kanan bawah pada Gambar berikut Garis ini sering disebut
sebagai diagonal utama. Semua kotak lainnya menunjukkan interaksi
antara satu dengan lainnya.
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atu
an
–B
atu
an
& M
ekanik
aB
atu
an Matriks
interaksimekanika
batuan &
rekayasabatuan yang
menunjukkansubyek-
subyek utama
& interaksinya(Hudson dan
Harrison, 1990).
TA
3111 M
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aB
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an
–B
atu
an
& M
ekanik
aB
atu
an
Sifat Batuan
1. Heterogen
� Jenis mineral pembentuk batuan yang berbeda.
� Ukuran dan bentuk partikel/butir berbeda di dalam batuan.
� Ukuran, bentuk dan penyebaran void berbeda di dalam batuan.
2. Diskontinu
� Massa batuan di alam tidak kontinu (diskontinu) karena adanyabidang-bidang lemah (crack, joint, fault, fissure) dimana kekerapan, perluasan dan orientasi dari bidang-bidang lemah tersebut tidakkontinu.
3. Anisotrop
� Karena sifat batuan heterogen, diskontinu, anisotrope maka untukdapat menghitung secara matematis misalnya sebuah lubangbukaan yang disekitarnya terdiri dari batuan B1, B2, B3, diasumsikan batuan ekivalen B’ sebagai pengganti batuan B1, B2, B3, yang mempunyai sifat homogen, kontinu dan isotrope
TA
3111 M
ekanik
aB
atu
an
–B
atu
an
& M
ekanik
aB
atu
an
Asumsi batuan ekivalen untuk mempermudah
perhitungan di dalam mekanika batuan
B1 B2 B3 B1 Ekivalen
TA
3111 M
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aB
atu
an
–B
atu
an
& M
ekanik
aB
atu
an
Homogeneous Rock
� fine-grained homogeneous rock - basalt
containing minerals undetectable by the
naked eye.
� claystone - fine-grained rock consisting of ...
TA
3111 M
ekanik
aB
atu
an
–B
atu
an
& M
ekanik
aB
atu
an
Beberapa Ciri Dari Mekanika Batuan
� Dalam ukuran besar, solid & massa batuan yang kuat/keras, maka batuan dapat
dianggap kontinu.
� Karena keadaan alamiah & lingkungan geologi, batuan diskontinu karena adanya
kekar, fissure, schistosity, crack, cavities dan diskontinuitas lainnya. Untuk kondisi
tertentu, dapat dikatakan bahwa mekanika batuan adalah mekanika diskontinu atau
mekanika dari struktur batuan.
� Secara mekanika, batuan adalah sistem “multiple body “
� Analisis mekanika tanah dilakukan pada bidang, sedang analisis mekanika batuan
dilakukan pada bidang dan ruang.
� Mekanika batuan dikembangkan secara terpisah dari meknaika tanah, tetapi ada
beberapa yang tumpang tindih.
� Mekanika batuan banyak menggunakan:
� teori elastisitas
� plastisitas
� dan mempelajari batuan, sistem struktur batuan secara eksperimen
TA
3111 M
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aB
atu
an
–B
atu
an
& M
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aB
atu
an
Multiple –body rock system
a) single-body sound rock system Mono-system rock
b) Fissured, multiple-body rock system
c) Very fissured poly-body rock system
d) Articulate rock system
TA
3111 M
ekanik
aB
atu
an
–B
atu
an
& M
ekanik
aB
atu
an
Lubang bukaan besar
Kuari
Bendungan
Tunnel
Tambang Dalam
Tambang Dangkal
TA
3111 M
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aB
atu
an
–B
atu
an
& M
ekanik
aB
atu
an
PermasalahanPermasalahan RekayasaRekayasa BatuanBatuan--11
� Theoretical questions on fractured media, possibly reflecting that engineers do not feel comfortable with the level of theoretical understanding, even though engineers design in fractured materials as a matter of course.
Questions posed included:� Are data collected for theories that intact actual rock mass behavior, or
is sampling biased by theory?
� Can the discontinuity system of a rock mass be detected, mapped, and parsimoniously represented?
� Can scale-dependent properties of a rock mass be measured and incorporate into models?
� Can behavior of fractured media be predicted at an acceptable level?
� What is the best way to represent rock mass for fluid flow and transport modeling (uncoupled or coupled)?
� Is the present understanding of coupled phenomena adequate?
TA
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aB
atu
an
–B
atu
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& M
ekanik
aB
atu
an
PermasalahanPermasalahan RekayasaRekayasa BatuanBatuan--22
� Rock engineering problems in the open pit and underground mines are not much different. However, the open pit mines are more concerned with slope stability, whereas deformation behaviour of back, wall and floor of underground openings is one of the important geomechanical properties to be understood.
� In general, the instability or failure that occur both in open pit and underground mines obviously involves two major mechanisms, including failures controlled by geological structures and failures independent of geological structure
� The following rock engineering or geomechanical problems and resolutions occurring in the open pit and underground mines are explained. These are gathered from a number of mine sites that would have been relevant to be exposed.
� According to one of the regulations from the Department of Mines of Indonesia, a study of slope stability analysis must be conducted prior to the bench development with height is greater than 15 m, and these regulations are enforced with the intention of reaching a high safety standard. The regulations have been employed since 1995.
� A key factor in the successful development of the open pits should have been the overall wall slope angles that would hitherto have been considered at best optimistic and worst rarely achievable.
TA
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aB
atu
an
–B
atu
an
& M
ekanik
aB
atu
an
PermasalahanPermasalahan RekayasaRekayasa BatuanBatuan--33
1. Bagaimana reaksi dari batuan ketika diambil untuk dipergunakan ?
2. Berapa dan bagaimana besarnya daya dukung (bearing capacity) dari batuan
dipermukaan dan pada berbagai kedalaman untuk menerima berbagai
beban ?
3. Bagaimana kekuatan geser batuan ?
4. Bagaimana sikap batuan di bawah beban dinamis ?
5. Bagaimana pengaruh gempa pada sistem fondasi di dalam batuan?
6. Bagaimana nilai modulus elastisitas dan Poisson’s ratio dari batuan ?
7. Bagaimana pengaruh dari bidang-bidang lemah (kekar, bidang perlapisan,
schistosity, retakan, rongga dan diskontinuitas lainnya) pada batuan terhadap
kekuatannya ?
8. Metode pengujian laboratorium apa saja yang paling mendekati kenyataan
untuk mengetahui kekutan fondasi atau sifat batuan dalam mendukung massa
batuan ?
9. Bagaimana memperhitungkan kekar dan sesar dalam perencanaan pekerjaan
di dalam batuan ?
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ekanik
aB
atu
an
–B
atu
an
& M
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aB
atu
an
PermasalahanPermasalahan RekayasaRekayasa BatuanBatuan--44
1. Bagaimana menanggulangi deformasi yang diakibatkan oleh perbedaan yang bersifat
perlahan-lahan (creep) pada batuan.
2. Hukum apa saja yang menyangkut aliran plastik (plastik flow) dari batuan ?
3. Bagaimana pengaruh “anisotrope” terhadap distribusi tegangan dalam batuan ?
4. Bagaimana korelasi dari hasil-hasil pengujian kekuatan batuan yang telah dilakukan
di lapangan dan di laboratorium dalam menyiapkan percontoh batuan ?
5. Bagaimana metode pengujian yang akan dilaksanakan yang sesuai dengan kondisi
lapangan terhadap sifat-sifat batuannya.
6. Bagaimana mekanisme keruntuhan/kehancuran dari batuan (failure of rock)?
7. Dapatkah keadaan tegangan di dalam massa batuan dihitung secara tepat, atau
bahkan dapat diukur ?
8. Faktor-faktor apa saja yang menyangkut perencanaan kemiringan lereng dari suatu
massa batuan ?
9. Apakah roof bolting pada atap sebuah lubang bukaan di bawah tanah sudah aman
sehingga lubang tersebut dapat digunakan sebagai instalasi yang permanen ?
TA
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aB
atu
an
–B
atu
an
& M
ekanik
aB
atu
an
RuangRuang LingkupLingkup MekanikaMekanika BatuanBatuan
1. Menyelenggarakan penyelidikan yang bersifat teknik pada batuan.
2. Mengembangkan cara pengambilan percontoh batuan secara rasionil dan metode
identifikasi serta klasifikasi batuan.
3. Mengembangkan peralatan uji batuan yang baik dan metode standar pengujian untuk kuat
tekan serta kuat geser batuan.
4. Mengumpulkan dan mengklasifikasikan informasi batuan dan sifat-sifat fisiknya dalam
dasar ilmu mekanika batuan, teknik fondasi dan teknik bangunan air.
5. Berdasarkan hasil-hasil pengujian yang dilakukan pada batuan, dapat dipelajari sifat fisik,
sifat mekanik (statik dan dinamik), elastisitas, plastisitas, perilaku batuan, dan bentuk
kerusakan (failure) di bawah beban statik dan dinamik dari batuan tersebut.
6. Mempelajari sifat batuan di bawah kondisi thermal dan sistem keairan (water regimen).
7. Menyangkut struktur statik dan dinamik dari batuan.
8. Mengembangkan metode pengukuran di lapangan (in-situ) dari sifat deformasi statik dan
dinamik batuan serta tegangan sisa di dalam batuan di bawah kondisi lingkungan yang
bermacam-macam seperti pelapukan, “leaching”, seismik dan tektonik.
9. Menyelenggarakan penelitian terhadap mekanisme kerusakan/kehancuran batuan.
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aB
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aB
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an
RuangRuang LingkupLingkup MekanikaMekanika BatuanBatuan
1. Mengorganisir penelitian tentang perkuatan batuan dan pengukuran tegangan in-situ.
2. Mengganti dengan metode ilmiah dari perencanaan teknik pada batuan yang banyakmenggunakan media empiris sebelumnya, sehingga turut memberikan konstribusiterhadap kemajuan disiplin ilmu mekanika batuan.
3. Merangsang dan menyebarkan ilmu pengetahuan tentang batuan dan mekanika batuan.
4. Mempergunakan mekanika batuan untuk memecahkan persolan-persoalan teknik secara praktis.
5. Mempelajari sikap massa batuan asli dibawah kondisi beban dan kondisi lingkungannya
6. Menyangkut struktur statik batuan dan kestabilan batuan sangat penting ditinjau dari sudut keamanan (safety) dan ekonomi.
7. Mempelajari stabilitas struktur rekayasa yang material utamanya adalah batuan.
8. Mempelajari proses pengurangan ukuran batuan dengan menggunakan gaya-gaya luar seperti pemboran, peledakan, pemotongan dan pengasahan.
9. Mempelajari pengaruh gaya-gaya pada batuan dan yang utama adalah berkaitan dengan fenomena yang mempengaruhi pendugaan rekahan dan deformasi.
10. Mempelajari beban atau gaya yang bekerja pada batuan, analisis dari efek dalam, maksudnya tegangan dan regangan, energi dalam, dan akhirnya analisis dari gaya-gaya dalam seperti rekahan, aliran, atau deformasi batuan.
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ekanik
aB
atu
an
–B
atu
an
& M
ekanik
aB
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an