kaedah pengukuran utility suvey

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Kaedah Pengukuran/ Perolehan

Data untuk Pemetaan Utiliti

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Peralatan Pengesanan dan

Penentududukan

PCL GPR

Total Station GNSS

Mengapa pepasangan utiliti bawah

tanah perlu dikesan?

Bagi mengelakkan kemalangan yang melibatkan nyawa dan kemusnahan aset

utiliti sedia ada.

Bagi mengelakkan pertambahan kossemasa kerja-kerja pengorekkan jalan.

Sebagai maklumat awalan sebelumkerja-kerja pengorekkan

Bagi memenuhi kewajiban pihakkontraktor.

Maklumat-maklumat yang

diperlukan sebelum kerja-kerja

pengorekkan dilaksanakan

1. Apakah maklumat utiliti yang tertanam di kawasan

itu?

(jenis, pemilik, material bahan, saiz dll)

2. Dimanakah kedudukan pepasangan utiliti

tersebut?

(alignment, direction)

3. Berapakah kedalaman pepasangan utiliti

tersebut?

(kedalaman utiliti ditanam)

Persediaan yang perlu sebelum memulakan

kerja-kerja pengesanan utiliti

1.Dapatkan peta atau pelan utiliti bagi

kawasan tersebut (maklumat awalan)

2.Perhatikan keadaan tempat semasa

(keadaan tanah (basah/kering), pili bomba,

gas valve dll)

3.Menilai keberkesanan pelbagai teknik

pengesanan bagi mengesan pepasangan

utiliti. JANGAN bergantung kepada satu

teknik pengesanan sahaja.

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Bagaimana Data Utiliti Diperoleh

PengesananUntuk pepasangan (installation) sudah ditanam

Ukuran TerusUntuk pepasangan baru yang belum ditanam

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PengesananUntuk pepasangan (installation) sudah ditanam


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Teknik Perolehan Geofizik

Secara Pengesanan

Untuk pepasangan (installation) sudah ditanam

Libatkan pengesanan utiliti di bawah tanah secara non-invasive

Menggunakan kaedah pengesanan geofizikal e.g PCL dan GPR

Libatkan pengukuran tanda di permukaan

diukur menggunakan peralatan ukur konvensional

atau GNSS

Hasil ukuran tahap Kualiti B

Peralatan utama yang digunapakai

bagi mengesan pepasangan utiliti

bawah tanah:

Electromagnetic Locater (Pipe and cable locater)

Ground Penetrating Radar (GPR)

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Pengesanan Menggunakan

Pipe and Cable Locator (PCL)

Mengandungi 2 komponen utama Pemancar (transmitter) Penerima (receiver)

Terdapat pelbagai jenis PCL dengan berbagai saiz dan bentuk serta frekuensi boleh diperoleh dipasaran. Julat frekuensi yang biasa digunakan : 50 Hz ke 480 kHz

PCL berupaya mengesan pada ketepatan 10cm dan kedalaman pada 5% daripada nilai sebenar

Teknik pengesanan menggunakan prinsip

radio detection

Menggunakan prinsip elektomagnetic untuk mengesan utiliti bawah tanah.Arus elektrik yang mengalir pada bahan konduktor

mengeluarkan medan magnet bulat di kelilingkonduktor.

Koil penerima boleh digunakan untuk mengesanamplitud medan magnetAmplitud berubah bergantung kepada kedudukan dan

arah penerima dalam medan magnet

Amplitud paling tinggi apabila penerima berada tepatdiatas bahan konduktor

Digunakan untuk kesan bahan logam yang boleh mengeluarkan gelombang elektromagnet

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Prinsip Asas Operasi PCL

Pemancar Penerima

Medan magnet

Pemancar keluarkan isyarat gelombang

Isyarat gelombang jana medan magnetik

Medan magnetik mengarahkan isyarat ke dalam penderia penerima

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Pengendalian PCL

Adakah pengukurtersebut sedang

mengesan kabel?

Apakah yang sebenarnya dikesan?

?

.yang sebenarnya dikesan adalahmedan magnet (magnetic fields)

Apakah itu Medan Magnet?

Medan magnet adalah arus yang dipancarkan oleh

konduktor yang membawa arus.

Terdapat 2 kaedah bagi mengesan

medan magnet iaitu secara;

1. Peak and

2. Null

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Peak Response Peak Response

Null Response Null Response

Null Response LOCATING

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Locating Pipe or Cable Direction

Pipe or Cable Direction

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Marking

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BAGAIMANA

MEMILIH

FREKUENSI

YANG SESUAI?

Frequency

Frequency vs Range Frequency = Range

(Capacitance Effect)

Radiodetection

Low frequency = long range (minimum capacitance signal loss to ground).

This frequency is better for connection and locating longer metal pipes or cables.

Which Frequency ?

Higher frequency = shorter range (greater capacitive signal loss to ground).

This frequency is better for induction onto small or short length conductors, such as telephone drops, CATV cables or street light cables.

Which Frequency ?

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Pipe = Surface Area = Range

Pipe = Surface Area = RangeGround Moisture

Low Frequency Better Identification Higher Frequency, Broader Peak

High Frequency Signal Coupling Higher Frequency

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APPLICATIONPassive

ActiveThere are two methods of signal detection.

1. Radio Signal

2. Power signal

Two types of Passive Signal

Passive Signal - Radio

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Passive Signal - Power 50/60Hz Passive Sweep

Passive

ActiveThere are two methods of signal detection.

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DIRECT CONNECTION

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Direct Connection Direct Connection

mA

mA

A successful connection to the metallic pipe or cable will be indicated by a change in the transmitter audio or visual indicator. Always make the best possible connection for reliable signal.

ConnectionDirect Connection

Direct Connection Direct Connection

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SIGNAL CLAMP

Signal Clamp

Signal Clamp Signal Clamp

Signal Clamp Higher Frequency

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INDUCTION

Induction Induction

Induction Induction - Signal Strength

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Induction - Identification Active Sweep

Induction - IdentificationInduction - Never Locate Near To

The Transmitter.

Min 10 paces away from the

transmitter.Check the signal with the receiver.

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Induction : Re-Bar Interference

During excavation, keep checking in the trench. This may show smaller conductors which were not detectable at ground level.

General Locating

GENERAL LOCATION

Problems Solving

Locate A Death End Pipe, But NOT

Pot End Cable!Locate A Bend

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Locate A Submerge Pipe or Cable. Locate A Tee.

Locate Problem: Re-bar

Remote ground = better range, less signal transfer.

Connection

Badly positioned remote ground causes more signal transfer.

Always place ground rod away from adjacent utilities.

Connection

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Ground stake too close to target conductor: Less range, some signal transfer.

Connection

Metal fences may seem a convenient ground point, but might produce interfering signals.

Always use an independent ground such as a screwdriver or ground stake.

Grounding to a structure which is also grounded can produce multiple signals.

Connection

LOCATOR LIMITATIONS

SIGNAL

DISTORTION

Peak

Null

1

3

This distortion varies depending upon the direction and magnitude of the current flow, causing a discrepancy between the peak and null aerial responses.

Distortion

Current on one line may induce 'stray' signals to nearby conductors.

Distortion

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Distorted field may appear to come from a different point.

DistortionUnique Features For Cable Identification

DEPTH MEASUREMENT

CURRENTMEASUREMENT(CM)

CURRENT DIRECTION(CD)

HOW TO TAKE DEPTH

MEASUREMENT?

Depth Measurement

Depth Measurement Depth Measurement

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Peak

Null

d

Peak

Null

d

Distortion and Depth

When there is a discrepancy between the aerial responses the following must be observed.

1. The Peak response will always be more accurate.

2. Push button depth estimation should not be used until the two responses agree.

Depth Measurement

Depth Measurement Current Measurement(CM)

Low Frequency Better IdentificationSignal Coupling: How to identify?

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Current Measurement(CM) Current Measurement(CM)

Current Measurement(CM) Current Measurement(CM)

Current Measurement(CM)

CURRENT DIRECTION(CD)

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The target line is

identifiable by

Current Direction.

Expected current direction indications and return signal path.

Current Direction (CD) Current Direction(CD)

Current Direction(CD) Current Direction(CD)

Possible current direction indication on

conductors.

Current Direction (CD)

Penentuan lokasi

Menggunakan Alat penerima Global Navigation Satellite System

(GNSS) latest boleh menerima isyarat dari 3 system GNSS GPS, GLONASS dan Galileo

untuk menentukan lokasi.

Teknik pengesan utiliti tidak boleh position cuma detect kedudukan

Pengesan akan tanda dengan tepat kedudukan utiliti dan

kemudian di ukur menggunakan

GPS dan total station

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Ground Penetrating Radar

GPR can be defined as a radar which able

to detect buried

objects and to

characterize the

subsurface structure

and properties in a

wide variety of

applications.

Basic concept of GPR

The GPR is a device used for non-invasive

scanning and precise

detection of

underground utilities.

GPR is composed of

a receiver and

transmitter antenna, a

control unit, battery

supply and a survey

cart


Generally, when the survey cart moves on the site surface the transmitting antenna send polarized, high frequency electromagnetic

(EM) waves in the ground. Because of different existing

inhomogenities in the ground, e.g. soil layers, underground utilities,

stones, gravel, cavities and other anomalies, part of the EM waves

is reflected from the dielectric boundary between different materials

and other part is refracted and goes to the deeper layer


GPR image Frequency selected

General character of EM field phase velocity and

attenuation with

frequency illustrating the GPR plateau(Annan, 2002)

0.001 10001

Attenuation,

Frequency (MHz)

GPR Plateau

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GPR Limitations

The factors affecting the GPR performance and should be consider are the design of a

GPR (hardware), target types, material of

the target and the surrounding

(environment)

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Teknik Pengesanan menggunakan

Pengesanan Menggunakan Ground

Penetratin/Probing Radar (GPR) Teknik radio detection tidak boleh digunakan untuk

kesan bukan metalik termasuk paip air dan gas plastik,

paip di perbuat dari tanahliat dan cable gentian.

GPR berfungsi dengan menghantar microwave kedalam tanah dan proses pantulan balik dari pelbagai lapisan

yang diterima oleh akan menghasilkan imej dalam

bentuk hyperbola.

Imej perlu dibuat interpretasi

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Teknik Pengesanan menggunakan

Pengesanan Menggunakan Ground

Penetrating/Probing Radar (GPR)

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Operasi Pengesanan

PCL

BM GPR Mula

GPR Mula

GPR Mula

GPR Henti

GPR Henti

GPR Henti

1

2

4

3

5

6(x3 , y3)

(x1 , y1) (x4 , y4)

(x2 , y2)

(x5 , y5)

(x6 , y6)

Tanda Cat (GPR) Stesen Kawalan

(xA , yA)

(xB ,yB)

Elektrik

TelekomunikasiAir

Tanda Cat (PCL)A

B

Laluan PCL

10 11 12(x10 , y10)

(x11 , y11) (x12 , y12)

Kabel (sedang dipasang)

La

lua

n G

PR

La

lua

n G

PR

La

lua

n G

PR

LubangUjian

Jarak Selang Pengesanan

Kesan setiap 20m

Garis Rentas

Garis lintang

Arah pergerakan

Lihat muka 11 garis panduan

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Pelbagai Jenis Antena GPR

Dari kiri ke kanan: Sistem Antenna GPR.1,500, 900, 550, 400, 300, 200, 120, 100, 80 MHz

Kelas Antena

Frekuensi

Antena

Kedalaman

Pengesanan

Frekuensi Tinggi > 1000 MHz < 0.5 m

Frekuensi Sederhana

Tinggi

400 600 MHz 0.5 m 1.5 m

Frekuensi Sederhana

Rendah

200 400 MHz 1.5 m 2.0 m

Frekuensi Rendah < 200 MHz 2.0 m 3.0 m

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PengesananUntuk pepasangan sudah ditanam


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Kaedah Ukuran Terus

Libatkan pengukurankepada utiliti yang terdedah

Menggunakan peralatan ukur konvensional

Ukuran lubang ujian

Ukuran terus sebelum pepasangan utiliti ditimbus

Hasil ukuran data utiliti pada tahap Kualiti A

Lubang ujian

Backoe

Penggalian menggunakan alat asas

Ekskavasi hampagas

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Peralatan Ukuran Terus

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Perbandingan Pengesanan & Pengukuran Terus

Sesuai mulakan pemetaan utiliti secepat mungkin

Penggunaan kaedah pengukuran terus terbaik bagi pepasangan baru

Penggunaan kaedah pengesanan kaedah terbaik untuk pepasangan sedia ada

Kaedah Kegunaan Tahap Kualiti Peralatan Ketepatan

(relatif) Kos (relatif)

Masa Perolehan

Data (relatif)

Pengesanan Pepasangan Tertanam

B PCL GPR

Total Station GNSS

Rendah Tinggi Lama

Pengukuran Terus

Pepasangan baru belum

ditanam

A Total Station GNSS

Tinggi Rendah Cepat

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kaedah pengukuran utility suvey

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