PROCEEDINGS

Jogja Earthquake in Reflection 2016

24–26 May 2016

Correlation of Geoelectric and the Test Pit to Determine Position of Sliding Surface in the

Prendengan Landslide , Banjarnegara Regency, Central Java Province

Indra Permanajati1, Zufialdi Zakaria2, Euis Tintin Yuningsih2, Herryal Zoelkarnain Anwar3, Eko Bayu

Purwasatriya4, Asmoro Widagdo4

1Doctoral Student at Geological Engineering, Padjadjaran University

1 & 4 Geological Department Jenderal Soedirman University Purwokerto 2 Department of Geology Padjadjaran University, Bandung

3Indonesian Institute of Sciences, Bandung

Abstract

This research aimed to determine the correlation between the

data of geoelectric with test pit to know the position of sliding

surface in Prendengan landslide. Prendengan area is an area that

goes in District Banjarmangu, Banjarnegara regency, Central

Java province. The area is close to the location of Mount

Pawinihan avalanches and avalanche areas Sijembung happened

recently. The area was chosen because of the presence of the

perfect profile associated levels of weathering on the Quaternary

volcanic breccia Rogojembangan (QJo), so

different rock. One target is a homage to the identification of the

type of land movement quickly with considerable intensity. The

method used is the Schlumberger geoelectric method and analysis

of test pit. The results obtained are on a sliding surface weathering

zone 4 with ground material calibration result of weathering of

volcanic breccias. Value resistifitas sliding plane zone is from

153.23 to 1291.27 M Ohm at a depth of 0-396 m. After correlated

with test pit and engineering geological observations along the

sliding surface is got sliding surface occurred in the weathering of

volcanic breccia zone 4 with a depth of ± 8.9 m and shaped sliding

surface is rotational sliding. Identification of the sliding surface on

lithology breccias on the location of the village Prendengan

avalanches can be used as a validation positioning on the sliding

surface breccias in the area of Mount Pawiniahan.

that the geoelectric data correlate with weathering profiles can be

validated properly. This correlation is important to know the

position of sliding surface. Prendengan avalanches in the area and

can be used as a validation of the sliding surface of avalanches in

the area of Mount Pawinihan which is an avalanche by the number

of victims is quite a lot, as many as 80 people died. Identification

of the sliding surface with geoelectric methods need to be

developed in each of the

Keywords : landslide , volcanic breccia , sliding surface ,

rotational sliding , resistivity

Introduction

Landslides are natural process caused by the decline of

material from the top of a hill due to gravity (Varnes, 1978),

this natural phenomenon can be considered dangerous if it

has to interact with human life. Natural disasters avalanches

quite a lot happening in Indonesia, BNPB data (2012) noted

the incidence of avalanches in Indonesia reached 1,000

events with the number of fatalities around 34,000 people

died during the 1815-2012 disaster casualties are frequently

the result is pretty much as it did in avalanches Mount

Pawinihan , Banjarnegara. An avalanche has left an estimated

more than 80 people died (Permanajati et al., 2006). This

phenomenon can not be left unchallenged, to avoid the

number of casualties will be more and more.

Scientist efforts to minimize the impact of disasters can be

done with his research on the mechanism of avalanches. It is

expected to understand the concept of landslide prevention

advice will be sought. From geological studies one of which

discusses the influence of internal land is on the condition of

soil and rock. According Sudarmo and Purnomo (1997) one

of the internal factors that influence soil is rock weathering.

In general weathering is the process of soil formation of

rocks. Expression attempted weathering zone delineated by

the geoelectric and well test equipment on a profile that is a

landslide.

In regional areas of research went into the Quaternary rocks

Rogojembangan composed by breccias. Pyroclastic breccias

in the research area has weathering. The spread of volcanic

breccias almost uniformly in the area of Mount Pawinihan.

This assessment is more focused search for zones where the

sliding plane happens to be the weathering of volcanic

breccias. Correlation between geoelectric and weathering

profiles can be used as a model in deleniasi geoelectric which

have been adapted to the profile of the test wells fresh rock to

soil residues at the very top.

Location of research is in the area of Mount Pawinihan,

Sijeruk Village, District Banjarmangu, Banjarnegara (Figure

1). The research location can be reached by four wheel and

two wheels at the distance of about half an hour from the

town of Banjarnegara to the north. The research location is

the location where the avalanche in the village prendengan

location close to the highway Sijeruk-Prendengan. Landslides

are natural disasters caused by the decline of material from

the top of a hill due to gravity (Varnes, 1978), this natural

phenomenon can be considered dangerous if it has to interact

with human life. Natural disasters avalanches quite a lot

happening in Indonesia, BNPB data (2012) noted the

incidence of avalanches in Indonesia reached 1,000 events

with the number of fatalities around 34,000 people died

during the 1815-2012 disaster casualties are frequently the

result is pretty much as it did in avalanches Mount Pawinihan

Banjarnegara. An avalanche has left an estimated more than

PROCEEDINGS

Jogja Earthquake in Reflection 2016

24–26 May 2016

80 people died (Permanajati et al., 2006). This phenomenon

can not be left unchallenged, sehngga the number of

casualties will be more and more.

Man's efforts to minimize the impact of disasters can be done

with his research on the mechanism of avalanches. It is

expected to understand the concept of landslide prevention

advice will be sought. From geological studies one of which

discusses the influence of internal land is on the condition of

soil and rock. According Sudarmo and Purnomo (1997) one

of the internal factors that influence soil is rock weathering.

In general weathering is the process of soil formation of

rocks. Expression attempted weathering zone delineated by

the geoelectric and well test equipment on a profile that is a

landslide.

In regional areas of research went into the Quaternary rocks

Rogojembangan composed by breccia lithology piroklasik.

Pyroclastic breccias in the research area has weathering. The

spread of volcanic breccias almost uniformly in the area of

Mount Pawinihan. This assessment is more focused search

for zones where the sliding plane happens to be the

weathering of volcanic breccias. Correlation between

geoelectric and weathering profiles can be used as a model in

deleniasi geoelectric which have been adapted to the profile

of the test wells fresh rock to soil residues at the very top.

Location of research is in the area of Mount Pawinihan,

Sijeruk Village, District Banjarmangu, Banjarnegara (Figure

1). The research location can be reached by four wheel and

two wheels at the distance of about half an hour from the

town of Banjarnegara to the north. The research location is

the location where the avalanche in the village prendengan

location close to the highway Sijeruk-Prendengan.

Methodology

The study was conducted in the following order. The first to

do is to classify the level of weathering by the method of

British Standard BS EN ISO 14689-1 for the material is not

uniform (Source: Price, 2009) at the location of avalanches.

This classification to divide zones of weathering. Then

conduct geoelectric the avalanche cut him so diharakan soil

profile on location avalanches can be observed well. Next to

the correlation determines the position of sliding plane.

Table 1. Classification of degree of weathering by British

Standard BS EN ISO 14689-1 for the heterogen material

(Source: Price, 2009)

Results and Discussion

The location is in the Prendengan landslide with coordinates:

07 ° 18 '41.7 ", 109 ° 41' 52.4". The locations were right lane-

Prendengan Sijeruk of Banjarnegara. Based on the

weathering profile measurement obtained the degree of

weathering of rock is 2 to 6. The pyroclastic breccias

Figure 2. The observation of the soil profile at the location of

the Prendengan landslide

Research area

Figure 1. Map of research area

PROCEEDINGS

Jogja Earthquake in Reflection 2016

24–26 May 2016

Based on observations in the field, is the result of breccia

formed in volcanic activity, which is a product of pyroclastic

fall. It is characterized by grain and uniformity has sorting

either the large grains are graded (gradded bedding).

According to Lockwood and Hazlett (2010) declared the

formation of pyroclastic breccia with a uniform grading

showed formed as pyroclastic activity dropping, then changes

the gradation on pyroclastic breccias in the field fining

upward showing a decline in volcanic activity (Figure 3).

Based on the measurement results obtained geoelectric soil

profile and distribution of soil and rock (Figure 4). Land

obtained at a depth of 0 to 3.96 m, and then beneath the

breccia with a depth of 3.96 to 6.9 m, then 6.9 m - 62.82 m

are sandstones, silty sandstones further below and clay.

Figure 3. Profile weathering of pyroclastic breccias in the

village of Prendengan show structure of gradded bedding.

Figure 4. Figure geoelectric log results in Prendengan

landslide

Based on the results of correlation of test wells and

geoelectric and validation sliding plane can be obtained

through sliding plane are at a depth of 8.9 m based on

measurements of the soil profile and there is a limit on the

degree of weathering 3 and 4, and based on the data of

geoelectric there is a layer of sandstone. So from the

geoelectric observations contained in some layers of

sandstone. It is clear that for this kind of observation with

geoelectric avalanches in the breccia is not easy but it needs

to be supported by the observation of the weathering profile

and approach the degree of weathering. Avalanche of events

in Prendengan can be concluded that there is a sliding plane

on weathering boundaries 3 and 4

Conclusion

There sliding surface at a depth of 8.9 m, which are at the

limit of weathering weathering 3 and 4. Level 3 is

characterized byTheir composition fragments that still shows

the composition of rocks compared to the matrix. Then the

rate of weathering 4 is characterized by the presence of

fragments, but the fragility of the material matrix of control.

The weathering rate limit is often difficult because of the

differences observed with geoelectric boundaries of

weathering is graded material.

Slip Surface

Slip surface

PROCEEDINGS

Jogja Earthquake in Reflection 2016

24–26 May 2016

Reference

BNPB.(2012): Data Informasi Bencana Indonesia,

http://www.bnpb.go.id/website/asp/index.asp,

diunduh tanggal 20 Juli 2012

Lockwood, J.P and Hazlett, R.W. (2010): Volcanoes Global

Perspective, John Wiley & Sons Ltd, The

Atrium, Southern Gate, Chichester, West Sussex,

PO19 8SQ, UK.

Permanajati, I., Waluyo,G., Suwardi., dan Setijadi, R.,

(2006): Longsoran Gunung Pawinihan, Desa

Sijeruk, Kecamatan Banjarmangu, Banjarnegara,

Prosiding Lokakarya DAS Serayu Hulu, Unsoed,

pp. 1-4.

Soedarmo, G.D. dan Purnomo, S. J. (1997): Mekanika Tanah

2, Kanisius, Yogyakarta.

Varnes, D.J. (1978): Slope Movement Type and Processes in

Landslide Analysis and Control, Trasportation

Research Board, National Academy of Science.