721260_jurnal geolistrik

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Hindawi Publishing CorporationJournal o Geological ResearchVolume , Article ID ,pageshttp://dx.doi.org/.//

Research ArticleEffectiveness of Geoelectrical Resistivity Surveys forthe Detection of a Debris Flow Causative Water ConductingZone at KM 9, Gap-Frasers Hill Road (FT 148), Frasers Hill,Pahang, Malaysia

Mohamad Anuri Ghazali,1 Abd Ghani Rafek,1

Kadderi Md Desa,1 and Suhaimi Jamaluddin2

School of Environmental Sciences and Natural, Faculty of Science echnology, Universiti Kebangsaan Malaysia, Selangor, Bangi, Malaysia

Slope Engineering Branch, Public Works Department, Jalan Sultan Salahuddin, Kuala Lumpur, Malaysia

Correspondence should be addressed to Abd Ghani Raek; [email protected]

Received September ; Revised November ; Accepted November

Academic Editor: Karoly Nemeth

Copyright Mohamad Anuri Ghazali et al. Tis is an open access article distributed under the Creative CommonsAttribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work isproperly cited.

Tis study reports the ndings o resistivity surveys which were conducted at the initiation area o debris ow at KM , Frasers HillGap road (F). Te study involves three slope parallel survey lines and two lines perpendicular to the slope ace. Te parallellines are FH, FH, and FH, while the lines FH and FH are perpendicular. A granite body was detected at the central parto the east line and is nearest to the ground surace along FH. Te existence o low resistivity zones within the granite body isinterpreted as highly ractured, water conducting zones. Tese zones are continuous as they have been detected in both the east-west as well as the north-south lines. Te residual soil layer is relatively thin at zones where weathered granite dominates the slopeace o the ailure mass. Te weak layer is relatively thick with an estimated thickness o m and water ow occurs at the base oit. Te high water ow recorded rom the horizontal drains urther supports the possible existence o these highly ractured, waterconducting zones located within the granite. Te shallow racturedgranite is virtually oating above the water saturated zone andthereore is considered unstable.

1. Introduction

Te study area has experienced at least our debris owincidents, which are concentrated at an initiation zone. Oneo the debris ow triggering actors in the mountainousterrain o Peninsular Malaysia is highintensity rainall duringor beore the debris ow incident. At the time o occurrenceo the debris ows in the study area, the intensity o rainallrecorded was between mm/day to mm/day. Tis valueis not considered high or Malaysian condition. Te ndingis based on the current larger study on seven other sites inPeninsular Malaysia which showed that heavy rainall is amajor triggering actor. However, a Fraser Hill site, incidentso debris ow occurred during low o rainall intensity and at

the same time high water ow was observed. Tereore, the

source o this water ow needed to be established.A debris ow is one type o the natural disasters that

can be classied as landslides and can cause damage toproperty and loss o lie. Te rst denition o debris ow washighlighted by Stiny as a ood o mountain torrents, carryingsuspended load and transporting quantities o bedload [].Sharpe dened debris ow as a rapid ow o saturated or

viscous debris in a stream or channel []. According toHungr et al. a debris ow is dened as a very rapid toextremely rapid ow o saturated nonplastic debris in a steepchannel [,]. Te debris is loose unsorted material o lowplasticity such as that produced by mass wasting processes(colluvium), weathering (residual soil), glacial transport


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Journal o Geological Research

Site location

Km 90, Gap-Teranum road

Km 9, Frasers Hill Gap road

F : Location o the study area on the geological map o Peninsular Malaysia, with Google image o site area [].

(till or ice contact deposits), explosive volcanism (granularpyroclastic deposits), or human activity (e.g., mine spoil).Meanwhile, Jakob, considered sources o debris to includesoil blankets and veneers on steep slopes, colluvial gullylls, channel bedload material, zones o weathered or alteredrocks, residual soil, headwalls and side slopes o steep gullies,

talus deposits, man-made lls, and similar accumulations ounstable or erodible material []. Meanwhile, Iverson ocuseson widespread Coulomb ailure within a sloping soil, rockor sediment mass, pore-uid pressures, and conversion olandslide translational at debris source zones [].

Chiessi et al., showed that geoelectrical imaging can beemployed to conrm the variability o the characteristics oboth the cover material and the substratum, a variabilitywhich is also highlighted in seismic surveys by lateral vari-ations in velocity within the same layer []. Jongman andGarambois used the geoelectrical resistivity to determine thelocation o the vertical and lateral boundaries o the slidedebris and detection o water within the slide debris [].

Determination o groundwater ow has been reviewed byHubbard and Linde by combining Ground Penetration Radar(GPR) with seismic survey and geoelectricalresistivity survey[]. Results rom the application o geophysical methodsavailable, the case studies illustrate the use o hydrogeo-physical approaches to quantity subsurace architecture thatinuence ow (such as hydrostratigraphy and preerentialpathways), delineateanomalous subsurace uid bodies (suchcontaminant plumes), monitor hydrological process (suchas reshwater-seawater interace dynamics and ow throughractures), and estimate hydrological properties (such ashydraulic conductivity) and state variables (such as watercontent).

In addition, boreholescould also be used to determine thesoil properties and identiy type o material and strength othe soil. Te combination o these methods is very effectiveand costly. Unortunately, boreholes could not to be carriedout at the study site because drilling rigs are unable to accessthe extremely hilly terrain.

Te main purpose o this study is to determine theweak layer at the initiation zone using geoelectrical resistivityimaging.

.. Objective. Generally the scope o this work is to under-stand actors associated with debris ow incidents in Penin-sular Malaysia. Te main objective o this specic study wasto determine the main cause o the ormation o the debrisow mass within the initiation zone. Te existence o a highoutow o water at the toe o the slope suggested the possibleexistence o weak zones that are water conducting. Tereoregeoelectrical resistivity imaging was applied to identiy

(a) zones o soil or weathered rock with high watercontent,

(b) groundwater ow,

(c) weak zones o weathered and highly ractured rocks.

2. Background

Te study area is located at km , Gap-Frasers Hill road(F), and within the Raub-Bentong Suture zone as shownon the geological map o Peninsular Malaysia (Figure ).Landslides into the channel at this location occurred repeat-edly resulting in debris ow impacts to the Gap-ranum


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: (a) Chronology o landslides at km , Frasers Hill-Gap road (F). (b) Chronology o debris ows at km , Gap-ranum road(F ).

(a)

Date Description

(a) December , A landslide occurred at Kilometre -, F , New Gap road to Frasers Hill and the road was declared unsae

or all vehicles

(b) January , Te collapse o a new embankment occurred within the project site, causing some damage to equipment andmachinery and affected work in progress (Figure : photograph taken on January andFigure : viewnal landslide beore remediation)

(b)

Date Description

(a) November , Blockage occurred due to rubble, mud, and rock slide material.

Public Work Department (PWD) carried out cleaning work and the road was eventually opened

(b) February , Debris ow occurred again, resulting in the blockage due to mud, rock slides, and rock blocks. Road was closed

to all traffic users rom // to //.

(c) March , Clearing work carried out using explosives

(d) March , Route was reopened to all traffic

(e) March , Debris ow occurred again and caused the ow o mud and boulders to cover the road. Cleaning work carriedout and the road could be used by light vehicles

() March , Debris ow occurred with debris, boulders, and mud. Cleaning work carried out and road was opened to light

vehicles only

(g) March , Debris ow occurred. Cleaning work carried out and road was opened to light vehicles only

(h) March , Debris ow occurred resulting in mud and rock slides. Te road was closed. Cleaning could not be conducted

due to weather conditions that were hazardous to workers at the site

(i) March , Bridge collapsed causing structural breaks o the steel plate beam buckle

(j) March , Debris ow and the cliff road ailed and the road surace collapsed or over m (Figure shows this incident)

(k) June , Repairs completed and roads opened to vehicles

(l) July , Te collapse o new gabion retaining wall, destroyed by rock slides

(m) July , New debris ow resulting in mudslide. Road was closed

(n) July , Cleaning works carried out. Road reopened to all vehicles

road (F ). Repeated ailures occurring at km , Gap-Frasers Hill road (F), with debris ow were documentedon December , and January , and severalsubsequent incidents which were not recorded. Tis studylocation is the source o the debris ow ormation downthe channel that impacted the ranum-Gap road at km ,F (seeFigure or a simplied site location map). Telandslides occurred could be classied as regressive landslideo large scale. Te chronology o events at both roads isdocumented in ables(a) and(b).

3. Physiographic and Geologic Setting

Te granitic bedrock at Frasers Hill is a part o the itiwangsaMountain Range. Te porphyritic granite o the study area ismoderate to coarse grain and crossed by the Kuala Lumpurand Bukit inggi aults []. Tis area consists o porphyriticgranite, biotite granite, and sheared granite (protomilonite,ortomilonite, and ultramilonite) []. Te distance betweenthe initiation area (km , Gap-Frasers Hill road) o debrisow to the impact area (km , Gap-eranum road) is about m. Meanwhile, the catchment area at this location is.km2.

Km 9, Gap-Frasers Hill Gap (FT148)

Site location

Gap-Frasers Hill Gap (FT148)

Frasers Hill

Gap-Frasers Hill Gap (FT56)

Km 90, Gap-Teranum road

F : Simplied site location map.

Tere are two main streams owing down to the impactzone o debris ow. Te highest peak is Bukit Peninjua withan elevation o m. Overall the stream bed gradient is. and the average slope angle o the banks is to .Te outcrop o the ormation o the debris ow is weathered


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: Te main coordinates o the resistivity lines.

Name o resistivity line Location o rst electrode (A) Location o last electrode (B) Location o center o line (C)

FH N. N. N.

E. E. E.

FH N. N. N.

E

.

E

.

E

.

FH N. N. N.

E. E. E.

FH N. N. N.

E. E. E.

FH N. N. N.

E. E. E.

17

S1

3

tarek

Highly weathered granite(or residual soil)medium weathered graniteloosen blockoverhang port

FH05

FH04

FH03

FH02

FH01

S12, 13

86

B

B

B

MP 7B

C

C

C

C

MP 6

A

MP 5

MP 9

MP 8 MP 10

MP 11

A

A

A

B

MP 14a

MP 17

MP 16

MP 18

22

Fr o

m

ga

p

S14

S11A

B

MP 15

MP 12

MP 12

To

Fra

serHill

N

FH01-resistivity lineMP 5-Mackintosh Probe

Scale

0 m 50 m

F : Location o geoelectrical resistivity lines and Mackintosh Probe at initiation area.

granite with weathering grades between IV to V as well asresidual soil. Tere are also blocks o granite boulders looselysuspended within the ailure mass.

Figure below shows the location o ve meterresistivity lines. Tree resistivity lines are named as FH,FH, and FH which are parallel to each other and spaced m apart. Te other two-lines FH and FH are spaced m a part in north-south direction and are perpendicularto the above FH, FH, and FH lines (able ).

4. Materials and Methodology

.. Resistivity Survey. Te method employed in this studyis the standard method using Wenner array with resistivityline parallel and perpendicular to the slope ace. Te Wennerarray with a total prole length o m was employed withan estimated penetration depth o m to m below theground surace. Zones o high water content and weak zonescould be determined as low resistivity zones by using this


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Sequence of measurements to build up a pseudosection

Resistivity

Station 32

Station 18

Station 1

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20Data

Electrode number

C13a

P13a

P2 3aC2

C1 P1 P2 C2

C1 P1 P2 C2

2a 2a 2a

computer

Laptop

meter

levela a a

118

3243

5156

= 1 = 2

= 3

= 4 = 5

= 6

F : Te arrangement o electrodes or a D electrical survey and the sequence o measurements used to build up a pseudosection [].

method. Reraction or seismic survey could not be useddue to the limited space or seismic lines compared to theestimated target depth.

o determine the true subsurace resistivity, an inversiono the measured apparent resistivity values using a computerprogram was carried out.

One o the new developments in recent years is the use oD geoelectrical resistivity imaging or tomography surveys to

map areas with moderately complex geology [].Such surveys are usually carried out using a large number

o electrodes connected to a multicore cable. A modernresistivity meter together with an electrode selector systemis used to automatically select the relevant our electrodes oreach measurement.

Figure shows the typical setup or a D survey with anumber o electrodes along a straight line attached to a multi-core cable. Normally a constant spacing between adjacentelectrodes is used. Te multi-core cable is attached to anelectronic switching unit which is connected to a resistivitymeter or terrameter.

Te sequence o measurements to take, the type o array

to use, and other survey parameters (such the current touse) are normally entered into a text le which can beread by a built-in computer program in the resistivity meteror terrameter. Afer reading the control le, the computerprogram then automaticallyselects the appropriateelectrodesor each measurement.

Te terrameter or resistivity meter employed was anABEM SAS and ABEM LUND ES electrode selec-tor system. Tis system is connected to stainless steelelectrodes, which are laid out in a straight line with aconstant spacing via a multi-core cable (Figures and ).Te resistivity meter selects only our active electrodes to beused or each measurement.

F : Notepad window or correction o data.

.. Data Processing. Resistivity data was analyzed using adriven sofware RESDINV Ver .. (see Figure ) withnine usual options at the top o the screen (le, edit, changesettings, inversion, display, topography options, print, help,and quit). Te input data le must be in a le. Datormat. Te procedures below were steps ollowed during the

processing o resistivity data using the RESDINV sofware.

(a) Selected data le rom read menu.

(b) Exterminated bad datum points rom Edit menu. Anegative value or values which were too large wereedited using notepad or other text editor (Figure ). AFunction to exterminate bad datum points was usedto eliminate urther bad data value by clicking themouse when the cursor at the points o those was notin line (Figure ).

(c) Change menu was also used to modiy the resistivitydata by selecting the number o iterations o required


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5

10

15

20

30

40

6080

100

120

F : Procedure to remove bad data points. Red circles are datapoints removed.

Datum blockLevel block

F : Blocks datum and datum level rectangular building blocksto produce the geological model.

while the damping actor applications, mesh rene-ment, convergence limit, and the model resistivity

values set values depending on whether the data sethave a value that was too high or low.

(d) Next Inversion menu was selected to initiate datainversion process.

(e) Adjustment was made by smoothing the resistivitymodel using the robust inversion procedure rom themenu.

() RMSerrorstatistics menu wasselected to reduceRMS(Root Mean Square) error that affects the inversionprocess and the building o the model resistivity data.

Te resistivity data in the orm o rectangular blocks(Figure ) were modied and recalculated to pro-duce resistivity pseudosection. Tis process involvesa recalculation and observation o resistivity valuesbased on pseudocross-sectional eld beore gener-ating a pseudocount (calculated pseudosection) thatwas very similar to the actual eld data. Te inversemodel resistivity sections wereproduced rom pseudocount or the purpose o quantitative interpretation.

(g) Afer completing the inversion process, the show dis-play menu was selected to display the actual resistivitymodel (Figure ).

200 120 40 40 120

(m)

1.25

24

52.4

Inverse model resistivity section

0 5 10 25 75 150 200 2000

Depth

Unit electrode spacing 5 m.

39.4

12.4

terat on 15 s. error= .1

F : Actual resistivity model obtained rom the inversionprocess and ready or interpretation process.

Read

data

le

Exterminate

bad datum

point

Damping factor,convergencelimit, number ofiterations, nitemesh grid size,model resistivity

value check,includesmoothing ofmodel resistivityand Jacobianmatrixcalculation

F : Block diagram showing el data processing techniquesusing RESDINV sofware.

Interpretation o underground mass based on the ollow-

ings:

(i) uniorm the resistivity values or line survey becausethe line survey is in the same area;

(ii) underground mass is an electrical conductor whichwill produce a low resistivity values;

(iii) the completely weathered rock mass will produce lowresistivity values;

(iv) water saturated zone will produce low resistivityvalues.

Te data obtained rom the resistivity survey prole was

used to prepare an illustration model, a three-dimensionalsubsurace prole using AutoCAd () (Figure ).

Te rst stage was to build a three-dimensional topog-raphy o the initiation area, and the next stage was to builda subsurace prole in three-dimension. Data rom the velines o geoelectrical resistivity survey were combined toproduce an illustration three-dimensional model o the studyarea.

5. Results and Discussion

Based on the resistivity results, a subsurace prole could bedivided into our zones as shown inable below.


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: Attribute o various zones based on resistivity values.

Number Zoningsymbol

Description

aResistivity values above m, are the reshgranite rock mass

b Resistivity value between

m

m,granite slightly weathering and highly ractured

cResidual soil (IAEG, V-IV)( m, m)

d Water conducting zone or high water content

(5,000m)(b) weathered granite (3000 m5,000m)

(d) saturated soil (5000 m)(b) weathered granite and highly fractured

(3000 m5000m)

(d) water conducting (


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Horizontal scale is 33.97 pixels per unit spacing

Last electrode is located at 100 m

Model resistivity with topography

1 1 3 7. 8 1 30 4 45 1 52 9 5 2 50 18 02 6 6 18 94

CA BWestEast

Granite Weathered granite

5

Elevation

20

60

a a

c

c

cb b

Unit electrode spacing= 5m

Vertical exaggeration in model section display= 0.92

(a) granite (>5000 m)

(b) weathered granite and highly fractured

(3000 m5,000 m)

(c) residual soil (6000 m3000 m)

First electrode is located at 100 m

5

15

25

10060

20

Iteration10 RMS error= 4.4

Resistivity ( m)

F : Resistivity result at line FH.

1 1 3 4.7 1 10 3 46 1 09 3 3 45 0 1 08 91 3 43 82

155

Horizontal scale is 33.97 pixels per unit spacing

Last electrode is located at 100 m

20 60

Model resistivity with topography

Elevation

Iteration 10 RMS error 9

ab

c

bb

b d

Water saturated soil/water conducting

CSouth

North

ABWeathered granite

Granite

c

Vertical exaggeration in model section display= 0.92

(a) granite (>5000 m)


51525

100 60 20

Unit electrode spacing= 5 m


(1200 m5000 m)

(c) residual soil (100 m1200 m)(d) water conducting (5000 m)


51525

100 60 20

(c) residual soil (600m3000 m)


(3000 m5000 m)

(d) water conducting (


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Height(m)

80

0Main landslide, gunite surface

bridgeHighly fractured

Water conducting zone

Bedrock

Residual soil

In situ granite mass

Underground water flow

Water flow

Water conducting zone

F : Conceptual sketch showing the subsurace prole at the initiation area o the debris ow.

5

Water

conducting

FH03FH02

FH01

10

15

80

10

15

15 Granite

Water conducting

Highly

fracturedBedrock

10

15

20

Water ow

60

Residualsoil

Surface failuremass

In situ granite

Tofrase

rhill

4

19

Bridge

FH05

200 m

F : Postulated subsurace conditions at initiation zone o debris ow.

the water seepage along the boundary o the two differentgeologicalmaterials and a close view o the main ailure scarp,

exposing the unconormable contact between the overlyingresidual soil and the underlying weathered granite.Figure is an on-site view o initiation zone o the study area (seeFigure or a general view). A combination o suraceand subsurace geological data (geoelectrical resistivity) wereused to produce illustration in three-dimensional model asshown inFigure .

Tirteen () Mackintosh Probe tests were conductedin the initiation debris ow zones and ow paths zones.Mackintosh Probe resulted in that the residual soil wasbetween . meters to . meters thick with value o blows (able ). Tat location o Mackintosh probe tests isshown inFigure .

Tis method is suitable to determine the ow o thegroundwater in the initiation zone by the characteristics as

shown below:(i) initiation o a steep slope,

(ii) seepage at the slope surace and toe o the slope,

(iii) low intensity o rainall beore and during debris owincident,

(iv) material consisting o residual soils and weatheredrock.

6. Conclusion

Tis rock mass within the initiation zone o the debris owis a heterogeneous mass o resh, moderately weathered, and


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F : Te rst landslide, photo taken on Jan , , at FrasersHill Gap road (F ).

F : View o the nal landslide beore strengthening o slopewas carried out.

F :Te view oconditions atF , ranum-Gap road, neara Bailey Bridge on March , .

Boulder

Granite

F : General view o initiation zone during geoelectricalresistivity survey.

Batteries

Resistivity meter

ABEM LUND

F : Te ABEM SAS resistivity meter and ABEM LUNDES electrode selector system.

F : Boundary o residual soil and weathered granite at themain scarp.

Water ow

Bridge

Water ow out

Granite Mainfailure

scarp

F : View o main ailure scarp or initiation area o debrisow at Frasers Hill.

highly ractured granite with residual soil together with awater conducting zone at a depth below the in situ granite.Te geoelectrical resistivity proling revealed that the graniterock mass is virtually oating above the water conductingzone and is thereore highly unstable. In conclusion, thegroundwater ow is identied as a weak zone or a plane oweakness. Determination o the position o the groundwaterow and subsurace prole is very important in design-ing slope strengthening and reinorcement works in thisarea.


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: Mackintosh Probe result.

MP number Depth with blows Remarks

. Flow path

. Flow path

. Initiation zone

. Initiation zone

. Initiation zone

. Initiation zone

. Initiation zone

. Initiation zone

. Flow path

. Flow path

. Flow path

. Flow path

. Flow path

Acknowledgments

Te authors would like to thank Slopes Engineering Branch,Public Works Department, Malaysia, or the support in con-ducting this study and both reviewers or their constructivecomments.

References

[] J. Stiny, Die Muren, Verlag der Wagner Schen Universitaets-Buchhandlung, Innsbruck, Austria, , ranslated by M.Jakob and N. Skermer,Debris Flows, EBA Engineering Consul-tants, Vancouver, Canada, .

[] C. F. S. Sharpe, Landslides and Related Phenomena, Columbia

University Press, New York, NY, USA, .[] O. Hungr, S. G. Evans, M. J. Bovis, and J. N. Hutchinson,

A review o the classication o landslides o the ow type,Environmental and Engineering Geoscience, vol. , no. , pp. , .

[] O. Hungr, S. G. Evans, M. J. Bovis, and J. N. Hutchinson,A review o the classication o landslides o the ow type,Environmental and Engineering Geoscience, vol. , no. , pp. , .

[] M. Jakob, A size classication or debris ows, EngineeringGeology, vol. , no. -, pp. , .

[] R. M. Iverson, M. E. Reid, and R. G. LaHusen, Debris-owmobilization rom landslides, Annual Review of Earth andPlanetary Sciences, vol. , pp. , .

[] C. S. Hutchinson and D. N. K. an, Geology of Peninsu-lar Malaysia, Geological Society o Malaysia, Kuala Lumpur,Malaysia, .

[] V. Chiessi, M. DOrece, and S. Superbo, Geophysical survey-ing o slopes affected by debris ows: the case o S. Felice aCancello (Caserta, Southern Italy), Annals of Geophysics, vol., no. , pp. , .

[] D. Jongman and S. Garambois, Geophysical investigation olandslide: a review,Bulletin de la Societe Geologique de France ,vol. , no. , pp. , .

[] S. S. Hubbard and N. Linde, Hydrogeophysics, inreatise onWater Science, P. Wilderer, Ed., vol. , pp. , AcademicPress, Oxord, UK, .

[] D. H. Griffiths and R. D. Barker, wo-dimensional resistivityimaging and modelling in areas o complex geology,Journal ofApplied Geophysics, vol. , no. -, pp. , .

[] M. H. Marjani, Geology and engineering geology at FrasersHill, Pahang Darul Makmur [Tesis], Universiti KebangsaanMalaysia, .


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