determination of the existence of rock cavities method based on

International Journal of Applied Engineering Research ISSN 0973-4562 Volume 11, Number 4 (2016) pp 2932-2937

© Research India Publications. http://www.ripublication.com

2932

Determination of the Existence of Rock Cavities Method Based on

Geoelectric Method (2D) in the Karangputih Hill Indarung

West Sumatra Indonesia.

Agus Santoso

Ph.D. Student, Physics Department, Gadjah Mada University, Geophysical Engineering, UPN "Veteran" University, Yogyakarta, Indonesia.

Sismanto

Physics Department, FMIPA Gadjah Mada University, Yogyakarta, Indonesia.

Ary Setiawan

Physics Department, FMIPA Gadjah Mada University, Yogyakarta, Indonesia.

Subagyo Pramumijoyo

Geological Engineering, Gadjah Mada University, Yogyakarta, Indonesia.

Indriati Retno Palupi

Geophysical Engineering, UPN "Veteran" University, Yogyakarta, Indonesia.

Abstract

Geoelectric dipole dipole method (2D) is used to determine

the formations that are conducive in the earth, the purpose of

this study is to describe (configuration) geology below the

surface resistivity that is high in areas of potential is estimated

there are cavities in rocks.

In the method of dipole dipole resistivity electrical current

injected into the earth through the current electrode, then the

potential difference arising measured via two electrode

potential. From these measurements for different electrode

spacing can then be lowered resistivity variations in the price

of each of the layers below the measuring point.

Interpretation is done by software RES2DINV, the end result

that best represent each region will each be analyzed

geologically (qualitative) and quantitatively, the end result is:

the cavity below the surface can be determined based on the

amount of value resisitivitas rock> 6000 ohm meter, the

greater the resistivity then the greater the hollow cavity in the

rock. While the resistivity value Cracks have 4000-6000 ohm-

meter.

Keywords-Dipole dipole, cavity, geoelectric,, RES2DINV

program, resistivity

Introduction Geolistrik is a geophysical method that review the electricity

flow in the subsurface and how to detect it in the surface. In

this regard include the potential measurements, currents and

electromagnetic fields occur, either naturally or as a result of

current injection into the subsurface. There are many kinds of

geoelectric method, they are self potential method, teluric

current, magneto teluric, electro-magnetic, induced

polarization and resistivity (resistivity).

This method is done by sending a current into subsurface and

measure the voltage or potential that is legible on the surface,

in order to obtain resistivity between the layers of rock below

in the subsurface, and also the thickness of each layer of the

rock. The resistivity value than used as a base of rock

lithologic interpretation contained in the layer.

The final results showed hollow cavities in the subsurface as it

appears on the map of the 12 line are programmed. The

hollow cavities found in limestone of faulting result from the

collision of Indian plate and Australian plate [1].

Basic Theory The basic principle of geoelectric resistivity method is Ohm's Law. Resistivity value is obtained by measuring the potential

difference and the current that is passed in a medium.

I

VR

(1)

where R is the resistivity in ohms, V is potential difference in

Volt and I is the current in Ampere. Because the medium in

the subsurface is not homogenous (similar), then there is a

concept of resistivity Which depend on current and electrode

that depending on the installation of the potential and current

electrode configuration factor (k), in addition to the voltage

reading (V) and current that is sent (I).

I

Vk

(2)

mailto:[email protected]



2933

Implementation of the resistivity method is sending the

current then measuring the potential with varied current and

potential electrode spacing. Thus the resistiviti’s value for

each range of current and potential electrode spacing is

obtained.

By plotting the resistiviti’s value versus the current electrode

spacing, then relationship between the current electrode

spacing (space) and resistivity is obtained.

Installation of Dipole-dipole electrodes Dipole-dipole electrode configuration. The current and

potential electrode separated by a distance na, where a is the

spacing or distance of each electrode [2].

V I

P1 C1O C2P2

anaa

Figure 1: Configuration of Dipole-dipole

To obtain configuration factor of dipole-dipole is like this

bellow:

C 1 P 1 = a + na = a (n + 1) ; C 1 P 2 = na

C 2 P 1 = a + na + a = a (n + 2) ;

C 2 P 2 = na + a = a (n + 1)

In the following equation is obtained as follows: 1

d)1n(a

1

na

1

)2n(a

1

)1n(a

12k

1

dna

1

)2n(a

1

)1n(a

22k

1

d)2n)(1n)(n(a

)2n)(1n()1n)(n()2n)(n(22k

1

222

)2)(1)((

23422

nnnannnnnnkd

1

)2)(1)((

22

nnnakd

)2n)(1n)(n(akd (3)

Geoelectricity Equipment The equipment used is :

1. Syscal R1 resistivity digital meters.

2. 4 rolls cable with more than 300 m length

3. Two electrode both for current and potential electrode

4. Accu 12 volt 60Ah

5. GPS (Global Positioning System)

6. Geological Hammer and compass

7. Meter measuring tool and topographic maps

The flowchart of Geoelectricity’s method can be seen in

Figure 2

Start

Design surveyGeology information

Calibration Instrumen

Filtering data

2D Profile

Interpretation

Finish

Res2Dinv Program

yes

no

.

.

Data Acquisition

Figure 2: Flowchart of Geolectricitiy method

The Data Acquisition Preliminary investigations were carried out is the collection of

secondary data such as geological data, the publication of

West Sumatra on the composition of rocks and minerals as

well as other supporting data. Prior to the acquisition of data,

then the equipment must be calibrated so that it meets the

standard operating procedures.

Difficulties and obstacles encountered in the field is the rainy

season and the hilly terrain that is too steep, making it difficult

mobilization of equipment in the field, so the track is designed

very difficult. The rainy season resulting watery or muddy

ground, so it is difficult for an electric current conduct into the

ground, so it is necessary to use CuSO4.

In this investigation the data were recorded and measured in

the field are [3] :

Note No location, azimuth and Geographic Location.

measured: The range of electrode currents, The range of

potential electrode, a current flows, as well as the apparent

resistivity (ohm-m). The tools used in this measurement is



2934

reading digitally, which could determine the course of the

current injected, so that it can be seen when disturbed flow is

happened.

General Geology The oldest rocks exposed in Indarung and around it is include

to Pre-Tertiary age (Yura) comprising groups of metamorphic

rocks that generally underlies the hills and ridge-the ridge of

this area[1]. The rock group composed of sandstones meta,

meta siltstone and mudstone associated with filit tufa which

mixed and crystalline limestones group is marmeran / solid

(crystalline).

Furthermore, above of group Pre-Tertiary rocks, the group of

Tertiary volcanic rocks is deposited by quaternary and

quaternary sediment [4], for quaternary Tertiary volcanic

deposits consist of lava flows interlude with andesite flows

and tuffs crystal that hard / solid and cemented well. For

quaternary sediment is from sediment alluvial fan, which is

the result of destruction of volcanic sediment[5] and it is the

youngest alluvial deposits composed of igneous rock

boulders, Krakal, and gravel loose sand.

Geological structure of the main encountered in the vicinity of

the probe is sliding down (normal) fault with east-west

direction and some almost North-South direction.

Data Processing Based on the results of the final analysis performed by

computer programs, and also supported local and regional

geological data area of research, then the final result is

obtained that the depth which correlated with the magnitude

of the actual resistivity ("True resistivity") of the rocks were

split into several rocks as follows:

1. Covers (Soil). Resistiviti’s value ranging from 50 to

more than 1000 Ohm meters, consisting of loose sand,

marl, silt, gravel and gravel.

2. Unit of clay / marl Resistiviti’s value less than 10 ohm-

m, consisting of marl. Generally permeable.

3. Unit of calcareous sand Resistiviti’s value range form 10

to 100 ohm-m, comprises calcareous sandstones are

generally a result of clastic limestone sediment volcanic

eruption.

4. Unit of Limestone with sand. Resistiviti’s value range

from 100 to 200 ohm-m, consist of limestone that has

the size like sand-a bit rough.

5. Unit of Limestone Resistiviti’s value range from 200 to

500 ohm-m, consist of limestone with fragments of

limestone boulders with size of 5-10 mm, matrix of sand

and carbonate cement.

6. Unit of compact Limestone Resistiviti’s value range

from 500 to 1500 ohm-meters. Consist of compact

fragments of limestone boulders with size range from 50

to 100 cm, matrix calcareous sand, cement carbonate.

7. Igneous rocks Resistiviti’s value range from 1500 to

4000 ohm-m, igneous basalt dominantly.

8. The cavity-the cavity in the limestone. Resistiviti’s value

> 60 00 ohm meter, the greater resistivity make greater

the cavities in the rock. While the cracks have

Resistiviti’s value of 4000-6000 ohm-m.

Interpretation Interpretation is based on Computer program, then take the

final result that take from best represent of each region and

will each be analyzed geologically (qualitative) and

quantitatively, the end result is as follows[6] :

Table 1: Coordinates of Line 1 to line 12

LINE AZIMUTH

X point 0 meter Y point 0 meter X point 500 meterY poijnt 500 meter

Line - 01 N 180 E 664057 9892332 664057 9891846

Line - 02 N 180 E 664107 9892332 664107 9891846

Line - 03 N 180 E 664157 9892332 664157 9891846

Line - 04 N 180 E 664207 9892332 664207 9891846

Line - 05 N 180 E 664257 9892332 664257 9891846

Line - 06 N 180 E 664307 9892332 664307 9891846

Line - 07 N 180 E 664357 9892332 664357 9891846

Line - 08 N 180 E 664407 9892332 664407 9891846

Line - 09 N 180 E 664457 9892332 664457 9891846

Line - 10 N 180 E 664507 9892332 664507 9891846

Line - 11 N 180 E 664557 9892332 664557 9891846

Line - 12 N 180 E 664607 9892332 664607 9891846

UTM coordinates

Line 1:

Rongga

Rongga

Retakan

Retakan

Batuan beku

Batuan beku

Batuan beku

Batugamping

Figure 3: Resistivity section of Line 1

Composed of igneous rocks, limestones and sandstones. Voids

and cracks found in space of 20 to 260 m with the depth> 80

m, the cavity also found in space of 450 to 480 m with the

depth> 80 m, at a shallow depth (3 m) is also found the cavity

in space of 405 to 415 m. There are existence of two normal

faults that form a graben

Line 2 :

Rongga

Rongga

Rongga

Batuan Beku

Batugamping

Batugamping


Cavities are found at the beginning and middle of the track in

space of 0 to 15 m, 140 to 280 m with the depths> 75 m and at

the end of the track in the space of 390 to 410 m, with the



2935

shallow depth of 3-10 m. Igneous rocks and limestone are

dominantly.

Line 3 :

Rongga

Rongga


Cavities found in space of 160-230 m with the depths> 80 m,

while at shallow depths (5 m) cavities found in space of 212

to 214 m, 235 to 237 and 292 to 296 m, voids at shallow

depths forming many cavities with the diameter of 5 cm.

Limestone and igneous rocks that are separated by the normal

faults.

Line 4 :

Rongga

RetakanRongga


Cavity contained in the initial trajectory of 0-5 m, with a

depth of 15-25 m, and at 330-360 m with a depth> 80 m,

while the cracks are in the 304-307 at a depth of 10-15 m, the

shape of the holes that fractured / cracks. Limestone and

igneous rocks that are separated by the normal faults.

Line 5 :

Batuan Beku

Batuan Beku

Batuan Beku

Batugamping

Batugamping


There are no cavities.

Line 6 :

Rongga

Rongga

Rongga


Cavities are found at the beginning of the track in space of 7

to 12 m with a depth of 5 m. At the mid of the track exactly

located in space of 260 to 265 m, with the depth depth> 60 m,

also in space of 320-340 m with the depth> 85 m, and in the

space of 410 to 420 m with a depth> 85 m, there are cavities

founded too. There are three normal Fault, whereas the normal

faults are thought to exist at the beginning of the track.

Line 7 :

Elevation Retakan

Batugamping

Batuan Beku

Batuan BekuBatupasir

Batugamping

BatugampingBatuan Beku


There are no cavities, but cracks are found at the near of

surface of the rocks contained in space of 234 to 238 m with a

depth of 5 m, also in space of 290 to 380 m with the depth of

5 m.

Line 8 :

Elevation

Batuan beku

Batuan beku

Batuan beku

Batugamping

Batugamping

Batupasir

Batugamping




2936

There are no cavity, but cracks are found in the space of 50 to

60 m with a depth of 20 m. Large cracks found in space of

380 to 425 m with the depth of 30 to 90 m.

Line 9 :

Elevation

Batugamping

Retakan

Retakan

Rongga

160

Batuan BekuBatuan Beku

Batugamping


Cavities are found in space of 285-290 m with teh depth of 5

m, in space of 295 to 305 with the depths of> 30 m and in

space of 405 to 417 with the depths> 30 m. Cracks found in

space of 0 to 10 m with the depth> 80 m and in space of 85 to

100 m with the depth of 10 m.

Line 10 :

DETEKSI RONGGA-RONGGA DALAM TANAH Line - 09. PT SEMEN PADANG (Karang putih)

Elevation

x=y=

x=y=

Retakan Rongga

160

Elevation

Batuan Beku

Batuan Beku

Batuan Beku

Batugamping

Batugamping

Batugamping


There are no cavities or cracks.

Line 11 :

160

ElevationRongga

Rongga

Batuan bekuGamping pasiranBatuan beku

Batugamping


The cavities are found in space of 220 to 230 m, with the

shallow depth of 5 m, and the cavity is also present in space of

300 to 330 m, with the depth> 85 m. Igneous rocks, limestone

and sandy limestone are dominantly

Line 12 :

Elevation

160

Retakan Retakan

Batupasir

Batugamping

Batuan beku

Ba

tu b

ek

u

Batuan beku


There are no cavities,but there are cracks in 5 places in the

space of 85 to 100 with the depth of 15 m, in space of 120 to

130 m with the depth of 5 m, in space of 150 to 160 m with

the depth depth of 10 m, in space of 245 to 255 with the depth

of 10 m and in space of 290 to 310 m with the depth> 50 m.

Figure 15: Cavity Survey Map in research location

Cavity large enough form caves (Figure 15 with red color) is

the limestone cave with the depth > 50 meters

Conclusion 1. The dominant composition of rocks consist of Limestone

with Oligocene-Miocene age, sandy limestone, marl and

massive limestone mixed with igneous basalt that result

from collision plate between Asia and the Australian.

There are cavities in the fractured of the cracks forming

the cavities with small diameter of 2 to 5 cm.

2. Interpretation Cavities [7] : Cavities are in line 1, 2, 3 and

4. Line-01: Cavities are at depths of > 50 m, the cavity is

formed cave associated with line 2, 3 and stopped at line 4.

At the beginning of the line the cave only at line 1 and 2.



2937

3. The existence of interconnected caves form a pattern of

underground rivers that flow from the NW-SE that are

characteristic of karts topography

References

[1] Kustowo and Gerhard 1973 "beginning Geological

Survey cement plant Indarung Padang, West Sumatra"

Not published.

[2] Keller, GV and Frischkenect, FC, 1970, "Electrical

Methods in Geophysical Prospecting", pp 17-166,

Pergamont Press, New York

[3] Dobrin, M, B & SAVIT, CH 1988, "Introduction to Geophysical Prospecting", Mc Graw Hill Co., Fourth

edition, New York, San Francisco

[4] Van Bemmelen, RW., 1949. The Geology of Indonesia, Vol IA. Government Printing Office, The Hague, 732 h.

[5] Cas, RAF, and Wright, JV, 1987. Volcanic Succession: Modern and Ancient, Allen & Unwin, London, 534 p.

[6] Telford, W, M, Geldart, LP, Sheriff, R, E & Keys, D, A,

1976, "Applied Geophysics" Canbridge University Press,

New York, London, Melbourne

[7] Grant, F, S. & West, G, F, 1965, "Interpretation Theory in Applied Geophysics", Mc Graw Hill Co., New York,

San Francisco, Toronto, London, Sydney.

determination of the existence of rock cavities method based on

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