kajian terhadap amalan terbaik dalam rekabentuk jalan...

KAJIAN TERHADAP AMALAN

TERBAIK DALAM

REKABENTUK JALAN DI

KAWASAN BERBUKIT Dibentang oleh;

Ir. Dr. Mohamad Nor bin Omar

Unit Geo-Environmental & Rekabentuk Asas

Cawangan Kejuruteraan Jalan & Geoteknik

ISI KANDUNGAN

PENGENALAN

OBJEKTIF KAJIAN

HASIL PENEMUAN KAJIAN

KAJIAN KES : KEGAGALAN LIMA (5) CERUN DI

JALAN PERSEKUTUAN FT185 IAITU LOJING –

GUA MUSANG

AMALAN TERBAIK DALAM REKABENTUK

JALAN DI KAWASAN BERBUKIT

KESIMPULAN

PENGENALAN

Kajian ini merupakan kajian susulan daripada

kajian awalan kejadian kegagalan cerun di Jalan

Persekutuan FT185 iaitu Lojing – Gua Musang

di mana telah diarahkan oleh Y.B. Menteri Kerja

Raya bagi menjalankan kajian menyeluruh

terhadap kegagalan cerun tersebut dan

seterusnya menambahbaik garis panduan

rekabentuk dan penyelenggaraan cerun sediada.

OBJEKTIF KAJIAN

Mengkaji punca-punca kegagalan cerun di jalan

kawasan berbukit di seluruh Malaysia.

Mengkaji amalan terbaik dalam merekabentuk

jalan di kawasan berbukit.

Menambahbaik garis panduan merekabentuk

cerun yang sediada

KAJIAN KES : KEGAGALAN LIMA (5) CERUN DI JALAN

PERSEKUTUAN FT185 IAITU LOJING – GUA

MUSANG

Site Location

Failure Areas along FT 185

KM 83.3

KM 83.8

KM 84.6

KM 106

KM 134

1

2

3

4

5

LOCATION 1 (KM 83.3)

(Note: Reinforced soil wall not indicated in

asbuilt drawing)

N

Approximate Reinforced

Soil Wall alignment

X

X

X-X

To Gua

Musang

To Simpang

Pulai

Road Platform

Reinforced

Soil Wall Gabion

Facing

Cracks Line

Maximum

Settlement

Center Median

Pre-cast Drain

Cut Slope

Cut Slope

Location 1 (KM 83.3)

Broken

drain


Tension Crack

Broken Drain

Settlement

To Gua

Musang


Sagging of Gabion Cages


Geogrid exposed at the gap area

The gap measures 500mm

beneath the Gabion Cage

LiDAR Data (KM 83.3) N

Courtesy of JKR

Flow Accumulation (KM 83.3)

N

Reinforced Soil

Wall

To Gua Musang

To Simpang

Pulai

Surface runoff from the

pavement gather at the

failure area (collection

point)

(m2)

Reinforced

Soil Wall

Probable Failure Mechanism (KM 83.3)

Strain associated with the mobilisation of friction of tensar geogrid causing drain to break.

Suspect settlement had not fully ceased during drainage construction.

Water was allowed to infiltrate into the reinforced soil leading to loss of soil through the internal erosion beneath wall base.

No effective inspection and maintenance carried out to capture and repair the problem at an early stage.

Probable Cause(s) Failure (KM 83.3)

Location 2 (KM83.8)

N

Location 2 (KM83.8)

X

To Gua

Musang

To Simpang

Pulai

Center Median

Drain

Cut Slope

X

X-X

Eroded Gully

Road Platform Eroded

Gully

Location 2 (KM83.8)

Eroded Gully

Broken Drain

To Gua

Musang

Location 2 (KM83.8)

Exposed Gully –

Texture indicates

original soil

Location 2 (KM83.8)

Toe of Failed Slope

– Accumulation of

Debris

LiDAR Data (KM 83.8) N

Courtesy of JKR


Failure

Location

>11.1 acres catchment

area. Here too, the

surface water gathers

from the paved area

N To Gua Musang

To Simpang

Pulai

(m2)

Discharge outlet may not have been properly designed

and constructed which led to uncontrolled water flow

on the slope.

Erosion took place at toe / mid slope which was left

unattended for a long period of time.

No effective inspection and maintenance carried out to

capture and repair the problem at an early stage.


Location 3 (KM84.6)

N

Location 3 (KM84.6)

X

To Gua

Musang

To Simpang

Pulai

Center Median

Drain

Cut Slope

X

X-X

Eroded Gully

Road Platform

Eroded

Gully

Location 3 (KM84.6)

Exposed Gully –

Texture indicate

Original Soil

To Simpang

Pulai

Subsoil drain

Location 3 (KM84.6)

Eroded Gully

To Gua

Musang

No subsoil

drain

Deterioration of Gully (KM84.6)

10th August 2010

10th November 2010

2nd December 2010

LiDAR Data(KM 84.6)

N

Courtesy of JKR


N

To Gua Musang

>7.04 acres

catchment area

Failure

Location

(m2)

To Simpang

Pulai

Drainage system may not have been properly designed

and constructed

(Note: discharge outlet and details of subsoil drain are

not shown in as-built drawings)

Erosion took place (may have been triggered by poor

drainage design) and was left unattended for a long

period of time.

No effective inspection and maintenance carried out to

capture and repair the problem at an early stage.


Location 4 (KM 106)

N

Location 4 (KM106)

X

To Gua

Musang

To Simpang

Pulai

Center Median

Drain

Cut Slope

X

X-X

Road Platform

Fill Slope

Natural Slope

Crack Line

Cracks + Settlement

Crack Line Road Platform

Fill Slope

Natural Slope

Failure at Location 4 (KM 106)

Crack and

Settlement

To Simpang

Pulai


Minor Depression and

Crack extends beyond

the road median

To Gua Musang


Large Upper Catchment

To Simpang

Pulai


Flat Ground at

embankment toe may be

soft deposits / water logged


To Gua Musang

~500mm drop of

berm drain

LiDAR Data (KM 106) N

Courtesy of JKR

Flow Accumulation (KM 106)

N

Failure

Location

To Gua Musang To Simpang

Pulai

>50 acres

catchment area

(m2)

Accumulation of surface and subsurface water into

embankment due to concave catchment.

Possible clogging of sand blanket.

Pore water pressure is much higher than hydrostatic.

Probable Cause(s) Failure (KM 106)


N

Location 5 (KM 134) To Gua

Musang

To Simpang

Pulai

Eroded

Gully Eroded

Gully

Drai

n

Drai

n

Failure at Location 5 (KM 134) - RHS

Broken Drain

To Simpang

Pulai

Failure at Location 5 (KM 134) - RHS To Gua Musang

Potential

secondary slip

Failure at Location 5 (KM 134) - RHS

Embankment

(gentler failed

slope)

Cut Slope

(steeper

failed slope)

Failure at Location 5 (KM 134) - LHS

To Gua Musang

LiDAR Data (KM 134) N

Courtesy of JKR

Flow Accumulation (KM 134)

N

Failure

Location

To Gua Musang

To Simpang

Pulai

>7.91 acres

catchment area

(m2)

>11.86 acres

catchment area

Drain built across the original and fill ground suffered

differential settlement.

Broken drain led to erosion of slope.

Splashing of water at the drainage junction led to soil

erosion.

Erosion took place was left unattended for a long

period of time.

No effective inspection and maintenance carried out.

Probable Cause(s) Failure (KM 134)

AMALAN TERBAIK DALAM

REKABENTUK JALAN DI

KAWASAN BERBUKIT PENAMBAHBAIKAN GARIS PANDUAN

PROCUREMENT

53

PROCUREMENT [1]

Key Lessons Learnt Proposed Improvement Measures

Qualification of

Design

Consultants,

Independent

Design Checkers

and Contractors to

be clearly defined.

To include qualification requirements

of Design Consultant, Independent

Design Checker and Contractor with a

more systematic and stringent criteria.

Requirements on

qualifications and

capacity of

Independent

Checker shall be

reviewed.

Independent Checkers should not be an

individual considering the scale of works

and responsibilities involved. He shall be

attached with an Engineering

Consultancy Firm that has a staff size

of at least 1/3 of the staff

requirements for a Design Consultant.

54

PROCUREMENT [2]


Appropriate

professional staff to

be specified.

- The right professional staff needs to be

deployed. For major slope works, there

shall be input from both the

Geotechnical Engineers and

Engineering Geologists.

- The need for Engineering Geologists

with appropriate training and

experience on slope engineering

shall be included together with his roles

and responsibilities specified.

55

PROCUREMENT [3]


Appointment of

Independent

Geotechnical

Checkers (IGC) for

Design & Build

projects.

The Independent Geotechnical Checker

shall be employed directly by JKR

instead of the Contractor, and he shall

report directly to JKR. For consistency,

the terms “IGC” shall be revised to

Independent Checker (Geotechnical).

Sub-consultancy

shall be critically

reviewed and made

more stringent.

Sub-consultancy shall be discouraged

and if unavoidable, be limited to only area

requiring specific specialist input. Any

sub-consultancy shall not be more than

25% of the total scope.

56

PROCUREMENT [4]


Lack of necessary

information for

procurement.

It is strongly recommended that the

feasibility study shall be carried out to

provide the following necessary

information for procurement:

- Provide project background and

baseline information

- Identify the specific technical

requirements for Consultant

appointment

- Identify specialists needed for the

project

- Propose the work schedule for design

development

57

PLANNING

58

PLANNING [1]


Proper planning of

road projects.

To emphasize the importance of proper

planning of road alignment, desk study

& preliminary geotechnical

assessment, site investigation,

hydrological / catchment study and

time frame for site investigation and

design works.

Right of Way

(ROW) to consider

extent of drainage

downslope.

To emphasize the need of proper planning

particularly the geotechnical and

drainage aspects during Feasibility

Study Stage and before finalising the

road alignment.

59

PLANNING [2]


Sufficient time

frame for design

and site

investigation

works.

- Suggested minimum time frame for

design stages:

o Feasibility study: 6 to 12 months

o Preliminary design: 9 months

o Detailed design: 6 months

- Time frame for preliminary and detailed

site investigation and design is

dependent on the scale and

complexity of the project. This shall be

proposed by the Design Consultant

after studying the project details during

the Feasibility Study Stage.

60

PLANNING [3]


Geotechnical and

drainage

assessments to be

carried out by using

advance tools.

Modern technological survey methods

such as LiDAR or better technique to

obtain the detail ground topography and

profile.

Importance of

proper desk study

and geotechnical &

geological

assessments.

Emphasis on importance of proper desk

study to include aerial photo

interpretation, site reconnaissance,

site history and geotechnical &

geological assessments such as

geological mapping of rock slopes and

previous landslide scars.

61

PLANNING [4]


Proper planning of

subsurface

investigation works.

- Budgeting cost of subsurface investigation

shall be at least 0.5% of the project

cost to ensure proper SI are carried out.

- Site investigation boreholes shall be

planned in clusters (more for high slopes

and where there are adverse geological

conditions). It is suggested to have three

boreholes over a slope section (at

slope crest, mid and toe) for soil

stratification, weathering profile

monitoring of groundwater fluctuation

and ground movements.

- To require site investigation to be fully

supervised by the Design Consultant.

Separate budget shall be allocated for

supervision fee. 62

DESIGN

63

DESIGN [1]


Slope classification

and design safety

factors.

- Change of the slope classification into

existing and engineered slopes,

instead of treated/ untreated or

reinforced/ unreinforced slopes

- The recommended safety factors for low

and high risk slopes respectively are;

a) For existing slopes: 1.1 and 1.2

b) For engineered slopes: 1.2 and 1.4

Proper drainage

details to be

included.

Proper analyses, design and detailing of

drainage including catch pits, energy

breakers and reinforcement are needed.

64

DESIGN [2]


Drainage design

with differential

settlement problem

to be properly

assessed.

- Avoid precast drains.

Reinforcements to be used for drains

where the drains are susceptible to

differential ground settlement.

- More conservative design to

accommodate unforeseen differential

settlement is needed at interface

between cut and fill.

Requirements for

Geological Mapping

not specified.

Requirements and standard format for

geological mapping of soil and rock

slopes to be specified. The mapping shall

be carried out by a qualified Engineering

Geologist with relevant experience in

slope engineering.

65

DESIGN [3]


Proper procedure

and presentation of

rock characteristics.

- Further elaboration on rock

characteristics in addition to

weathering grade to determine the

rock cut slope angles. These parameters

may include rock mass classifications

and rock joints properties.

- Guidelines and standards on rock

mapping procedures and record sheets

be included.

66

CONSTRUCTION

67

CONSTRUCTION [1]


Lack of quality

control of site

works.

Quality control of site works shall be

emphasized. Supervision by experienced

and qualified staff from Contractor is

required.

Supervision of site

works and design

verification by the

Design Consultant

during construction

shall be made

mandatory.

- Design Consultant to supervise the

works during the construction stage.

Separate budget shall be allocated for

supervision fee.

- Design Consultant to verify design

assumptions made especially with the

actual ground conditions.

- Design Consultant to check and verify

design changes made on site.

68

CONSTRUCTION [2]


Insufficient

information and

lack of verification

in as-built

drawings.

- Design Consultant to check and verify

the as-built drawings submitted by

the Contractor and ensure that the

drawings reflect actual work

constructed on site.

- Design Consultant to produce a

summary of all Variation Order (VO)

made and ensure that these have been

incorporated into the as-built drawings.

- The Independent Checker shall review

the adequacy of the as-built

drawings for submission.

- To proposed a checklist of as-built

drawing for geotechnical work to be

incorporated in JKR-SPK 69

CONSTRUCTION [3]


Proper and

systematic keeping

of construction

records and as-built

drawings.

Proper and systematic keeping of

construction records and as-built drawings

shall be maintained and strengthened. The

Design Consultant shall produce a

monthly summary with plots (figure)

of the site works and testing results.

This shall form as part of the as-built

records.

70

MAINTENANCE

71

MAINTENANCE [1]


A standardised

routine

maintenance

inspection and

procedure is

required.

Inventory of slopes and geotechnical

features are needed. A standardised

inspection procedure shall be

introduced and followed.

(see attached flow chart)

Slope height

exceeding six berms

are not allowed in

current JKR

guideline mainly

due to concerns on

safety and

maintenance cost.

Slopes exceeding six berms may be

considered and allowed subject to design

assessments and whole life cycle costing

compared to other engineering solutions

such as tunneling.

72

MAINTENANCE [2]


Access for

maintenance works

is required.

Provision of maintenance access including

staircase and guardrails during design

stage shall be included.

Budget allocation

for maintenance.

Sufficient budget shall be allowed for

routine and engineer inspections of slopes

at appropriate time interval to ensure

long-term safety of slopes.

73

KESIMPULAN

74

1. KAJIAN KES

Proper discharge outlet of surface / subsurface

drainage to be incorporated in the design.

Sufficient land acquisition for discharge outlet.

To include method statement for drainage

construction.

Application of LiDAR data and aerial

photography in desk study.

Hydrological study of proposed development.

Effective implementation of routine inspection

and maintenance.

To improve future as-built drawings.

2. AMALAN TERBAIK DALAM

REKABENTUK JALAN DI KAWASAN

BERBUKIT

Suggestions for improvement as a result of this

study should be noted in order to improve

the existing guidelines, particularly guidelines

provided by;

Cawangan Kerja Cerun,

Cawangan Jalan,

Bahagian Senggara Fasiliti Jalan dan

Cawangan Kejuruteraan Jalan & Geoteknik

TERIMA KASIH

77

QUALIFICATIONS OF SENIOR

DESIGN CONSULTANT

(GEOTECHNICAL)

- Registered Professional Engineers with Board of

Engineers, Malaysia (BEM) with minimum of five

years of relevant design experience. Suggestions on

nurturing of Malaysian sustainable Design

Consultants are described by Gue et al. (2011).

- The roles and responsibilities of the Design

Consultant should be clearly stated during the

appointment stage. One important requirement is

that the Consultant has a separate and

independent team to carry out in-house

checking and review of the designs. 78

QUALIFICATIONS OF INDEPENDENT

CHECKERS (GEOTECHNICAL)

1a. Must be a registered Professional Engineer

with experience relevant to type of critical

works

1b. Minimum 10 years relevant design

experience, or 8 years for PhD holders

1c. Minimum 5 years experience in

Geotechnical Engineering

1d. Minimum 3 years experience in slope design

with at least 1 year in Malaysia

or

2. An Accredited Checker (Geotechnical) of

Board of Engineers Malaysia (BEM)

79

QUALIFICATIONS OF CONTRACTOR

The Contractor’s team shall include a

responsible person who is a Professional

Engineer and has at least 10 years of

relevant experience to oversee

construction of the entire road works

80

Carry out technical assessment on existing conditions and stability of slopes

RECOMMENDED SLOPE INSPECTION

REQUIREMENTS FOR ROADS IN HILLY

TERRAIN Maintenance Inspections

Monthly Inspection by Maintenance/Inspection Team

Immediate inspection by Qualified Personnel

Carry out remedial works (if necessary)

Routine Non-routine

Inspection Once Every 2 Years by Qualified Personnel

Inspection Once Every 5 Years by Qualified Geotechnical Engineer

Verify records by Maintenance/Inspection Team

Verify records

Immediate inspection by Qualified Geotechnical

Engineer

Records of blockage, cracks, slips and chainage

If defects are found

81

If minor defects

Carry out repair works

If major slip or recurring cracks

kajian terhadap amalan terbaik dalam rekabentuk jalan...

Documents