10th Asian Regional Conference of IAEG (2015)

Seismic Bearing Capacity of Jatinangor Education Area, Bandung, Indonesia
Twin H. W. KRISTYANTO(1), Dicky MUSLIM(3), Zufialdi ZAKARIA(3), J. I. Mendes(4),Arif R. DARANA (2,3), and Yukni ARIFIANTI(5)(1)Department of Geology, Faculty of Mathematics and Natural Science, Universitas Indonesia
E-mail: twin.hosea@hotmail.com(2) Geotetra Research Group, Bandung, Indonesia(3) Faculty of Geology, Padjadjaran University, Indonesia(4) Ministry of Energy and Mineral Resources, East Timor,(5) Centre for Volcanology and Geo-Hazard Mitigation, Geological Agency, Indonesia
Abstract
Jatinangor is education area in eastern Bandung, Indonesia. It had been prepared as
education area since 1980’s with concept of the Project Development Area of Great
Bandung, West Java, Indonesia. It caused research area experienced physical changes
between 1970 until early 1980’s. Rapid physical changing occurred preceding theestablishment of 4 universities there.
According to earthquake vulnerability map of West Java Province, research area islocated in area with high vulnerability of earthquake effects. Even earthquake occurred withepicentre in Tanjungsari (15 km east part of research area) in 1972 and in Cicalengka (18km west part of research area) in 2000. While in north part of research area, lays a popular
active fault named Lembang Fault that could increase the peak ground acceleration ofresearch area. Therefore, it is important to calculate the relationship between those seismic
factors with bearing capacity to prevent undesired failure or settlement of buildings whenearthquake happen. So, the aims of this research are to calculate how much the reducing of
the seismic bearing capacity value from static bearing capacity value.
Methods that were used in this research are: (1) field study such as: engineering
geological mapping, soil and rock sampling from either outcrops or 20 bore holes; andgeophysics analysis to get information of soil thickness, (2) laboratory analysis method forgaining information about angle of friction, cohesion, and unit weight, and (3) officemethod be in the form of analysis of engineering geological map, static bearing capacity(Terzhagi’s Formula), seismic bearing capacity (Kharni, 1993), and geostatistic analysis forzoning the location based on the value of either static or seismic bearing capacity.
The results show that: seismic factors in research area reduce the bearing capacity
about 8% - 20% for depht of footing 1 m. Geostatistic analysis shows that research area has
wider area of low bearing capacity when seismic factors are calculated in bearing capacity
calculation.
Keywords: Seismic bearing capacity, PGA, soil thickness, earthquake.
1.

planned. It can be seen from the construction ofhouses/buildings irregular, dense housing, irregularity
boarding houses, slums, and narrow streets and proneto misfire, the build-up of waste that until now there
is no solution. Uncontrolled land clearing the name ofdevelopment resulted in Jatinangor be uncomfortableand prone to some geological constraints such as
flooding, soil movement, and the air is hot. In the dry
season, Jatinangor experiencing water shortage due toforest conservation area has been damaged(Anonymous, 2009).
Meanwhile, according to earthquake vulnerability
map of West Java, research area is located in areas ofIntroduction

Jatinangor is education area in eastern Bandung,Indonesia. It had been prepared as education area
since 1980’s with concept of the Project
Development Area of Great Bandung, West Java,Indonesia. It caused research area experienced
physical changes between 1970 until early 1980’s.
Rapid physical changing occurred preceding theestablishment of 4 universities there (Anonyms,2009).
Environmental conditions of Jatinangor at thistime to be degraded by development that is not well1

10th Asian Regional Conference of IAEG (2015)high earthquake vulnerability. Even once anearthquake with epicentre in Tanjungsari in 1972 andthe earthquake centred on Cicalengka in 2000. The
study area is also close to the fault area dent locatedin northwest. In addition, the study area is also
traversed by several faults which are indicated by thelineament (Syahbana et al., 2010).
According Kharni (1993) an area with highseismic vulnerability is not enough supportability
analysed using static bearing capacity equation.
However, the necessary analysis of seismic bearing
capacity taking into accounts the seismic coefficientof horizontal and /or vertical. To that end, the rapid
physical development of the research sites, such as
the construction of housing, apartments, college
territorial expansion (ITB and Unpad), and thedevelopment of road infrastructure should pay
attention to the threat of geological disasters,
especially earthquakes. So we need a study on thebearing capacity of the land in the study area thattakes attention the effect of earthquakes.
Through those backgrounds, this research aims todetermine how much influence the seismicity factor
to the decline in the value of the soil bearing capacity.
1.1 Static Bearing Capacity
Bearing capacity is ability of soil for holdingback pressure or load of building above it withoutcause shear failure and excessive settlement. The
ability is depending on soil shear strength (Bowles,1984) (See Figure 1).

Fig. 1 Bearing Capacity (Bowles, 1984)
Terzhagi in Zakaria (2006) discuss the influenceof foundation shape toward value of ultimate bearing
capacity. The influence is analysed based oncontinuous foundation that applied for the othershapes of foundation.
Continuous footing also known as generalequation of bearing capacity, i.e:(1)qu = c . Nc + γ Df . Nq + 0.5 γ. B.N γ
Which:= Ultimate bearing capacity, (kN/m2)
quB= Wide of foundation (m)= Depth of foundation (m)Dfγ= Unit weight (kN/m2)
c= Cohesion (kN/m2)
Nc, Nq, Nγ = Bearing capacity factor
φ= Angle friction (0)equilibrium value that will result in failure or collapse
if it is passed over. Therefore the value of allowablebearing capacity (qa) must be lower than ultimate
bearing capacity.
Allowable bearing capacity depends on how
great the chosen safety factor (F). In general, value ofsafety factor that is chosen is in range of 2-5. The
formula of allowable bearing capacity is:

Terzhagi in Zakaria (2006) presented a bearing
capacity formula which was calculated in ultimate
bearing capacity condition (qult). It means an

1.2 Seismic Bearing Capacity
Seismic vibrations such as earthquakes canreduce the bearing capacity of the soil and can lead to(2)Which:
qa = allowable bearing capacity (kN/m2)
qu = ultimate bearing capacity (kN/m2)
F = Safety factor.

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10th Asian Regional Conference of IAEG (2015)

excessive reduction or collapse of the foundation.
Therefore, it is important to calculate the seismic
bearing capacity. The analysis was developed using
horizontal and vertical seismic coefficient obtained
from the data of peak ground acceleration (PGA)
which is caused by the earthquake (Al-Karni, 1993).
Seismic bearing capacity factors that offered by
Al-Karni (1993) can be used to modify the existing
equations of static bearing capacity (Terzhagi, 1973;
Meyerhof, 1963, Hansen, 1970, Vesic, 1973). For
example, soil bearing capacity equation Meyerhof(1963) for the vertical load can be modified into a
general equation to include the effects of theearthquake as follows:

Cicalengka, about 5km from research area). The
study area is also close to the fault area dent locatedin northwest. In addition, the study area is also
traversed by several faults are indicated by thelineament (Syahbana et al., 2010).
For comparison in Bandung basin area, based on
the results of the seismic risk analysis, the maximum
PGA values at the bedrock is about 0.09 g. Aftertaking account of the soil, it was found that themaximum PGA is about 0.17 g in the north-west andincrease gradually until 0.35 g in the south-east(Suharman, 2000). Research area is in the eastern partof the Bandung Basin. The soil materials of it consistof local Cibiru volcano (Silitonga, 1973). Engineering
geological characteristics of the study area have thesame soil with Cibiru region i.e, silty clay and sandy
clay with a thickness of 2-20 meters and low –moderate allowed bearing capacity (Djadja andHemawan, 1996). So that the average value of PGA(3)
Which:

quE= ultimate seismic bearing capacity (kN/m2)
B= Wide of foundation (m)= Depth of foundation (m)Dfγ= Unit weight (kN/m2)
c= Cohesion (kN/m2)
Nc, Nq, Nγ = Bearing capacity factor
φ= Angle friction (0)s and d = shape and depth factors
ec, eq, and eγ = seismic factors of Al-Karni (1993),
the equation is as follows:(peak ground acceleration) maximum in the study
area is approximately from 0.34 to 0.35 g.
2.

Methodology

This research used three methods, they are: (1)field sampling of soils and engineering geologicalmapping; (2) Laboratory analysis method, for getting
data cohesion (c), angle of friction (φ), and unit
weight (γ); and (3) studio analysis method for getting
value of both static and seismic bearing capacity,
geostatic analysis to show the zone of bearing
capacity (static and seismic), and statistics analysis toshow how different between seismic and static
bearing capacity values.

(4)
(5)

3.

Results and Discussions

3.1 Static Bearing Capacity(6)

Table 1 Static Bearing Capacity of Research Area

Which,
kh = horizontal seismic coefficient
kv = vertical seismic coefficient = ½.kh
kh = PGA/g
with:
PGA = Peak Ground Accelerationg = acceleration due to gravity ( 10m /s2)
1.3 Seismicity of Research Area
According to the earthquake
disastervulnerability map of West Java, study area is locatedin the area of high earthquake vulnerability. Evenearthquakes have occurred around the site area in1972 (its epicenter was in Tanungsari about 10 km
from research area) and 2000 (its epicenter was in

Calculation of static bearing capacity in research310th Asian Regional Conference of IAEG (2015)

area was done based on data of soil mechanics from20 boreholes, places of taking undisturbed sample.
The type of failure in this research is assumed as local
shear failure (due to plastic soil in research area) withwide of foundation 2 m and depth of foundation are 1
m. The results of bearing capacity calculation are
shown in table 1.

Surfer v.10 with geostatistics methods (Kriging).
4. Conclusion
Based on static bearing capacity analyses, seismic
bearing capacity analyses, and statistical analyses(with significance level 0.05), it is concluded thatseismicity factors reduce the value of bearing
capacity in research area. The average reduction of
the values is about 3.013 Ton/m3 or 19.12%.
Geostatistical analyses also show that there is
reduction of the bearing capacity in research area. It
is represented by wide spreading of smaller bearing
capacity value when seismicity is calculated on
bearing capacity formula.

3.2 Seismic Bearing Capacity
Calculation of seismic bearing capacity inresearch area was done based on data of soil
mechanics from 20 boreholes, places of taking
undisturbed sample. The type of failure in thisresearch is assumed as local shear failure (due toplastic soil in research area) with wide of foundation
2 m and depth of foundation are 1 m. The results ofbearing capacity calculation are shown in table 2.

Acknowledgements
The authors would like to thanks to Padjadjaran
University, East Timor Government, and GeologicalAgency who have provided funding for authors topresent this research in international forum.

Table 2 Seismic Bearing Capacity of Research Area

References
Al-Karni, Awad Ali (1993): Seismic Bearing
Capacity of Shallow Footing on Cohesionless Soil,
University of Ariszona, pp. 70-95.
Anonymous (2009): Report of Feasibility Study ofJatinangor Area for City Area Planning, Region
Development Agency of Sumedang Regency, pp.
1-4.
Bowles, Joseph E. (1984): Geotechnical and Physical
Properties of Soil, Second Edition, pp. 32-40.
Djadja and Hermawan (1996): Engineering
Geological Map of Bandung Basin, West Java,Geological Agency.
Silitonga (1973): Regional Geological Map ofBandung Basin, West Java, Geological Agency.
Syahbana, Devy K. and Solikhin, Ahmad (2010):
Earthquake Vulnerability Map of West Java,
Indonesia, Geological Agency.
Zakaria, Zulfialdi (2006): Bearing Capacity ofShallow Foundation, Engineering Geological
Laboratory Padjadjaran University, pp. 1-11.

3.3 Reduction of Bearing Capacity Value Due To
Seismicity
Calculations of static and seismic bearing capacity
indicate reduction. The average reduction of thebearing capacity of the soil is about 3,013 Ton/m2 orabout 19.12%. Based on statistical analysis, t-test, thevalues of the static and seismic bearing capacity
indicates that the values of both of them are different.
This statistical test used a significance level of 0.05.
Zone of static and seismic bearing capacity can beseen in figure 2 and figure 3 on page 5 and 6. The
pictures show that areas with smaller value of bearing
capacity are more widespread in seismic bearing
capacity map. It indicates that there is change ofbearing capacity value after calculating the seismicity
factors (i.e. peak ground acceleration) into bearingcapacity formula. Zoning is done using the software

410th Asian Regional Conference of IAEG (2015)

GRADUATE PROGRAMFACULTY OF GEOLOGYPADJADJARAN UNIVERSITY

2015
STATIC BEARING CAPACITY ZONE
AREAS OFPADJADJARAN UNIVERSITY
JATINANGOR, INDONESIA
N00

By:
Color

600 m

T. H. W. Kristyanto

Index(Ton/m2):

Campus Building
Sampling Location
RoadContour, Interval 1Ton/m2
RiversCampus Area(Padjadjaran University)

Fig. 2 Zoning Map of Static Bearing Capacity of Research Area

5

10th Asian Regional Conference of IAEG (2015)

GRADUATE PROGRAMFACULTY OF GEOLOGYPADJADJARAN UNIVERSITY

2015
SEISMIC BEARING CAPACITY ZONE
AREAS OFPADJADJARAN UNIVERSITY
JATINANGOR, INDONESIA
N

By:

600 m

T. H. W. Kristyanto

Color Index(Ton/m2):

Campus Building
Sampling
Location
RoadContour,Interval

1

Ton/m2
RiversCampus Area
(Padjadjaran University)

Fig. 3 Zoning Map of Seismic Bearing Capacity of Research Area

6