p–ISSN: 2723 - 6609 e-ISSN: 2745-5254

Vol. 5, No. 12 December 2024 http://jist.publikasiindonesia.id/

Jurnal Indonesia Social Teknologi, Vol. 5, No. 12, December 2024 6383

Analysis of Liquefaction Potential in The Youtefa Bay Area,

Jayapura City

Emilyano Joel O. Wayangkau1*, Duha Awaluddin Kurniatullah2, Dewi Ana

Rusim3, Alfian Adie Chandra4, Helen Gianditha Wayangkau5

Universitas Cenderawasih, Indonesia

Email: titincivil@gmail.com1*, duhaawaluddin@gmail.com2, dewianarusi[email protected]3,

alfiansipiluncen@gmail.com4, helenwayangkau97@gmail.com5

*Correspondence

ABSTRACT

Keywords: Cyclic

Resistance Ratio (CRR)

Value; Cyclic Stress Ratio

(CSR); Liquefaction

The distribution of soil in Jayapura City, especially the Youtefa

Bay area, consists of three dominant soil types that then form the

stratigraphy of the local soil layer, namely allifial deposits, silt

silt/silt clay, and fine, uniformly grained sand. Soil conditions like

this have great potential for liquefaction, especially since this area

is mostly passed by fault lines that have the potential to cause

earthquakes. The groundwater table factor that is very close to the

surface soil is also an important factor in the occurrence of

liquifaction. There are 2 ways to analyze the potential for

liquifaction, namely by laboratory test and from field test data.

The approach to calculating field test data is CPT (Cone

Penetration Test) testing. The results obtained were the Cyclic

Stress Ratio (CSR) value and the Cyclic Resistance Ratio (CRR)

value obtained by simulating seismic data using an earthquake

strength of 6.5 on the riter scale and a pic ground acceleration

value (0.3), then based on the results of the cone penetration test

(CPT)/Sondir showed a maximum value of CRR 2.88, a minimum

value of 0.21, a maximum CSR value of 3.70, a minimum value

of 2.25. The maximum value of FS is 0.97, the minimum value is

0.07. There are 6 points at the research location that have the

potential for liquefaction (Very High), namely points S1, S2, S5,

S7, S8, S10, while 3 points with medium potential (High), namely

points S3, S4, S9 for those with low potential (Low) S6.

Introduction

The Jayapura City area often experiences earthquake disasters, this is because the

structure of the tectonic order is in tune with the tectonic structure of the Papua region as

a whole.

The vulnerability of the Jayapura City area to earthquakes with a risk level of

small to large risk can cause a failure due to loss of soil stability (failure of the lower

structure) (Kumar et al., 2023). The failure of this soil structure is caused by the amount

of energy released by the epicenter (hypocenter) in the form of vibrations that propagate

on the earth's surface. One of the damages to the soil structure due to the earthquake is

liquefaction.

Emilyano Joel O. Wayangkau, Duha Awaluddin Kurniatullah, Dewi Ana Rusim, Alfian Adie Chandra,

Helen Gianditha Wayangkau

Jurnal Indonesia Social Teknologi, Vol. 5, No. 12, December 2024 6384

Liquefaction is more likely to occur in unconsolidated water-saturated soils with

low porosity, such as sandy loam or fine sand and gravel. During an earthquake, the

unconsolidated sand layer will tend to shrink in volume. At the same time, there is an

increase in water pressure in the pores of the rock and causes a decrease in the shear

strength of the rock, namely a reduction in effective stress. Liquefaction results in the

collapse of bearing capacity, lateral soil movement, and different subductions in

buildings.

In general, the distribution of soil in Jayapura City, especially the Youtefa Bay

area, consists of three dominant soil types that then form the stratigraphy of the local soil

layer. These three types of layers include (alluvial deposits, silt clay/silt clay, fine sand

with uniform grains). Soil conditions like this have great potential for liquefaction, then

based on the geological distribution map of the location of Jayapura City, Keerom

Regency and Sarmi Regency are often passed by fault lines that have the potential to

cause earthquakes so that it has the potential to cause liquefaction. The groundwater table

factor that is very close to the surface soil is also an important factor that can result in the

potential for liquifaction. However, it is necessary to conduct research to prove the

potential for liquefaction in Jayapura City, especially the Youtefa Bay area, (Holtekamp).

Method

This study uses a quantitative approach with field survey methods and laboratory

testing. Primary data was obtained through Cone Penetration Test (CPT) testing at 10 test

points in the Youtefa Bay area, Jayapura City. This test was carried out to obtain the value

of conus tip resistance (qc), the number of adhesive resistance (JHP), and the value of

Fraction Ratio (FR). This data is then used to calculate key parameters such as Cyclic

Resistance Ratio (CRR), Cyclic Stress Ratio (CSR), and Safety Factor (FS).

1. Research Design

This study uses a field experimental design to evaluate liquefaction potential

based on seismic data simulations with a magnitude of 6.5 on the Richter scale and a peak

soil acceleration (PGA) value of 0.3g. This simulation was carried out to calculate seismic

parameters and soil resistance to cyclic pressure due to earthquakes.

2. Data Collection Techniques,

Data collected through:

• Field Testing: CPT testing is carried out at each test point to obtain soil parameter

data.

• Seismic Data Simulation: Using geotechnical data processing software to

calculate CRR, CSR, FS, and liquefaction potential index (LPI) values.

3. Data Analysis

Data analysis is carried out in the following stages:

• CPT Data Processing: The data from the CPT test results is analyzed to determine

the qc, FR, and soil content weight values.

• CRR and CSR calculations: The calculations were performed using a formula

from Seed & Idriss (1971) which was updated by Idriss & Boulanger (2008).

Analysis of Liquefaction Potential in The Youtefa Bay Area, Jayapura City

Jurnal Indonesia Social Teknologi, Vol. 5, No. 12, December 2024 6385

• Safety Factor Determination (FS): The FS value is calculated as the ratio between

CRR and CSR. If the FS value is < 1, then the liquefaction potential is declared

high.

• Evaluation of the Liquefaction Potential Index (LPI): The calculation of the LPI

is carried out by considering the depth and severity of the liquefaction potential at

each test point.

4. Result Validation

The results of the tests and calculations are compared with international standards

and related geotechnical literature to validate their level of accuracy and reliability.

With this research method, the liquefaction potential in the Youtefa Bay area can

be comprehensively analyzed based on seismic parameters and local geotechnical

conditions obtained through field surveys and seismic data simulations.

Results and Discussion

The results of the CPT/Sondir test provide the value of the conus end resistance (qc)

and the number of adhesive resistance (JHP), the difference in the reading results shows

the value of "Fraction Ratio" (FR). This result, after plotting into a graph, will provide

information on the Soil Type and Contents Weight Value, which can then be used to

calculate the CRR value which represents the value of soil resistance to repeated loads

due to earthquakes (CSR).

The Liquifaction Potential Index can be calculated and funded using sondir/CPT data.

According to Iwasaki et al. in 1982, it was divided into several categories. Starting from

Very Low to Very High. The LPI calculation itself uses a formulation where z is the depth

of the midpoint of the soil layer (0-20 m) and dz is the difference in depth increase. Weight

factor w(z), and severity factor F (z).

For the calculation of the potential liquidation index, it can be calculated with the formula

above and can be formulated using Microsoft Exel Software as seen in the table

Data

- z : 1 m

- SF : 0.83

a. Calculating the value of F (z))

- F(z) = 1-SF

= 1-0,83

= 0,17

b. Calculating the value of w (z)

- w(z) = 10-(0,5.z)

=10-(0,5.1)

= 9.5

c. Calculating the LPI value

- LPI = LPI depth 0 to depth 20 m

= 67,95 (Very High)

The results of the calculation of CRR, CSR, FS, and Liquifaction Potential Weighting

values that have been carried out with the number of tests of 10 CPT/Sondir test points are then

expressed in the form of tables and maps of liquifaction potential.

Emilyano Joel O. Wayangkau, Duha Awaluddin Kurniatullah, Dewi Ana Rusim, Alfian Adie Chandra,

Helen Gianditha Wayangkau

Jurnal Indonesia Social Teknologi, Vol. 5, No. 12, December 2024 6386

Table 1. Table Recapitulation Results of Calculation of CRR, CSR, FS, LPI Sondir 10

The Cyclic Stress Ratio (CSR) value and Cyclic Resistance Ratio (CRR) values

obtained by simulating seismic data using an earthquake strength of 6.5 on the riter scale

and a pic ground acceleration value (0.3), based on the results of the cone penetration test

(CPT)/Sondir test, the maximum CRR value is 2.88, the minimum value is 0.21, the

maximum CSR value is 3.70, and the minimum value is 2.25. The Cyclic Stress Ratio

(CSR) value and Cyclic Resistance Ratio (CRR) value were obtained based on the results

of the cone penetration test (CPT)/sondir and earthquake zoning to obtain the "Pic

Ground Acceleration" (PGA) value. Sondir testing is carried out to obtain the conus tip

resistance value (qc) and "fraction ratio" (FR) which will be used to obtain the type of

soil, the weight value of soil content and the value of "n" based on the soil type per depth

of 0.00-20 m, the results of this analysis are then used to calculate the behavior of total

Analysis of Liquefaction Potential in The Youtefa Bay Area, Jayapura City

Jurnal Indonesia Social Teknologi, Vol. 5, No. 12, December 2024 6387

soil stress, pore water pressure and effective stress due to the influence of pore water

pressure that occurs below the groundwater surface due to the influence of earthquakes

which result in The total tension of the soil has the potential to experience a reduction in

its strength value. By combining several other variables such as the normalization value

of conus resistance (qcIN), cyclic voltage reduction (RD), CRR and CSR values can be

calculated.

The "Factor Savety" (FS) value obtained based on the results of the cone

penetration test (CPT)/Sondir showed a maximum value of FS 0.97, a minimum value of

0.07. The value of the "Safety Factor" (FR) is obtained from the quotient of CRR and

CSR values. If the CRR value is less than the CSR value, it can be assumed that

liquifaction has the potential to occur.

The evaluation results of the "Liquifaction Potential Index" (LPI) were obtained

from the calculation of the FS value and the depth of the CPT test, where the calculation

results showed that the liquifaction potential consisted of very high, high, low (high,

medium). Low). The results of the LPI analysis from each test point showed that the

research location was dominated by a very high potential for liquifaction. The results of

the calculation show that there are 6 points at the research location that have a very high

potential for liquifaction (Very High), namely points S1, S2, S5, S7, S8, S10, while 3

points with medium potential (High), namely points S3, S4, S9 for those with low

potential (Low) S6

Conclusion

The results obtained were the Cyclic Stress Ratio (CSR) value and the Cyclic

Resistance Ratio (CRR) value obtained by simulating seismic data using an earthquake

strength of 6.5 on the riter scale and a pic ground acceleration value (0.3), then based on

the results of the cone penetration test (CPT)/Sondir showed a maximum value of CRR

2.88, a minimum value of 0.21, a maximum CSR value of 3.70, a minimum value of 2.25.

The maximum value of FS is 0.97, the minimum value is 0.07. There are 6 points at the

research location that have the potential for liquifaction (Very High), namely points S1,

S2, S5, S7, S8, S10, while 3 points with medium potential (High), namely points S3, S4,

S9 for those with low potential (Low) S6.

Bibliography

Badan Standarisasi Nasional. (2002). Tata cara perencanaan ketahanan gempa untuk bangunan

gedung (SNI 03-1726-2002). Yayasan Penerbit PU.

Badan Nasional Penanggulangan Bencana (BNPB). (2013). Informasi kebencana bulanan

teraktual (Edisi Desember 2013). BNPB.

Das, B. M. (1993). Mekanika tanah (prinsip-prinsip rekayasa geoteknis) (Jilid 1). Erlangga.

Idriss, I. M., & Boulanger, R. W. (2008). Soil liquefaction during earthquakes. Earthquake

Engineering Research Institute (EERI).

Idriss, I. M. (1999). An update to the Seed-Idriss simplified procedure for evaluating liquefaction

potential. Proc. TRB Workshop on New Approaches to Liquefaction (Publ. No. FHWA-RD-

99-165). Federal Highway Administration.

Emilyano Joel O. Wayangkau, Duha Awaluddin Kurniatullah, Dewi Ana Rusim, Alfian Adie Chandra,

Helen Gianditha Wayangkau

Jurnal Indonesia Social Teknologi, Vol. 5, No. 12, December 2024 6388

Irmasanti, I., Isnaniati, I., & Farichah, H. (n.d.). Melakukan analisis potensi likuifaksi dengan data

CPT (Cone Penetration Test): Studi kasus Proyek-X di Surabaya Pusat menggunakan

metode evaluasi Youd-Idriss (1996) dan metode Cetin (2004).

John, T. H., & Yohannes, L. (n.d.). Evaluasi potensi pencairan tanah (liquefaction) akibat gempa.

Kumar, D. R., Samui, P., & Burman, A. (2023). Suitability assessment of the best liquefaction

analysis procedure based on SPT data. Multiscale and Multidisciplinary Modeling,

Experiments and Design, 6(2), 319–329. https://doi.org/10.1007/s41939-023-00148-x

Liao, S. S. C., & Whitman, R. V. (1986). Catalogue of liquefaction and non-liquefaction

occurrences during earthquakes. Research Report, Department of Civil Engineering,

Massachusetts Institute of Technology.

Rismatriandys, M. S., Idasrioktaviana, I., & Irdhiani, I. (n.d.). Studi potensi likuifaksi pada sekitar

Jalan Jamur Kelurahan Balaroa Kota Palu, dilakukan dengan cara melakukan uji Cone

Penetration Test (CPT).

Sarlina, L., Minarto, E., & Mantiri, S. Y. Y. (2015). Pemetaan tingkat risiko gempa bumi di sekitar

wilayah Kota Jayapura berdasarkan pengukuran mikrotremor. Vol. 16, No 1, Juni.

Seed, H. B., & Idriss, I. M. (1971). Simplified procedure for evaluating soil liquefaction potential.

Journal of the Soil Mechanics and Foundations Division, ASCE, 97(SM9), 1249–1273.

Seed, H. B., Idriss, I. M., & Arango, I. (1975). Summary report on the influence of seismic history

on the liquefaction characteristics of sands. Earthquake Engineering Research Institute

(EERC Report No. 75-25). Berkeley, California.

Tim Pusat Studi Gempa Nasional. (2017). Peta sumber dan bahaya gempa Indonesia tahun 2017.

Kementerian Pekerjaan Umum dan Perumahan Rakyat.

Towhata, I. (2008). Geotechnical earthquake engineering. Springer, Verlag, Berlin Heidelberg.

Widodo, P. (2012). Seismologi teknik dan rekayasa kegempaan. Pustaka Pelajar.

Youd, T. L., Idriss, I. M., et al. (2001). Liquefaction resistance of soils: Summary report from the

Geotechnical and Geoenvironmental Engineering. ASCE, 127(10), 817–833.Wira Buana,

T., Hermawan, W., Rahdiana, R. N., Widyaningrum, R., Wahyudin, G., Hasibuan, G.,

Wiyono, W., & Sollu, W. P. (n.d.). Penerbit: Badan Geologi, Kementerian dan Sumber Daya

Mineral.