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Parameter Akuifer

Irwan Iskandar, PhD KK Eksplorasi Sumberdaya Bumi

Teknik Pertambangan

Fakultas Teknik Pertambangan dan Perminyakan ITB

Parameter Kuantitatif

Besaran (vektor ataupun) skalar yang dapat dihitung / diukur dari pengujian di lapangan (field test) ataupun di laboratorium (laboratory test) e.g.

• Permeabilitas/konduktivitas hidraulik (Transmisivitas)

• Storativitas (specific yield, specific storage, specific retention)

• Porositas, porositas efektif

Pengujian Laboratorium

Pengujian sifat intrinsik batuan (dari intact rock)

• Porositas

• Specific yield

• Ukuran butir (hazen test)

• Permeabilitas

Permeabilitas (k) dalam kuliah ini

Konduktivitas hidraulik (K)

5

Sketsa Alat Uji constant head permeameter

Pengujian Permeabilitas di Laboratorium

6


Sketsa Alat Uji Falling Head permeameter

7

Hazen Test Approximation

D10 : effective size dari partikel, diambil nilai 10% ukuran partikel terkecil


Pengujian Permeabilitas di Laboratorium Wall permeameter (dengan tekanan) ASTM D-5084

Phone: 022 250 2239 Fax: 022 250 4209

Sample Code : KPC-9

Description : soil unconsolidated material even compacted

Grain Size : clay - silt

Date of Test :

Tested by :

Checked by :

Sample Length (cm) : 6.67

Sample Diameter (cm) : 5.5

Area of Section (cm2) : 23.74625

Constant Pressure (kg/cm3) : 0.2

Head (cm) : 200

Record of Test

Vol. Coloumn Time dV dT Q

(cm3) (sec) (cm3) (sec) (cm3/sec)

50 0 0

49.5 60 0.5 60

48.95 120 0.55 60

48.4 180 0.55 60

47.9 240 0.5 60 K :

47.55 300 0.35 60

47.15 360 0.4 60

46.7 420 0.45 60 8.19252E-06 cm/sec

46.3 480 0.4 60 8.19252E-08 m/sec

45.95 540 0.35 60 0.00583333

45.6 600 0.35 60

45.25 660 0.35 60

Dr. Irwan Iskandar ST, MT.

Hydraulic Conductivity (K)

Laboratory of Hydrogeology

Mining Engineering Department, ITBAddress: Gedung Teknik Pertambangan ITB, Labtek IV, Jl. Ganesha No. 10 Bandung,

Laboratory Test of Hydraulic Conductivity ASTM Standard D-5084

25 Januari 2012 - 10 Februari 2012

00.10.20.30.40.50.6

0 100 200 300 400 500 600 700

dV

(cm

3)

Time (sec)

Calculation of K (Hydraulic Conductivity)

tHA

LqK

..

.

Dimana;

K: Konduktivitas Hidraulik (cm/det) atau

(m/det)

q: Volume minimum rata-rata (cm3)

L: Panjang conto yang diuji (cm)

A: Luas penampang conto yang diuji (cm2) DH: Tinggi tekan/ Head (cm)

Dt Waktu pengujian (det)

• Transmisivitas : Permeabilitas x zona jenuh

T = K x b*

b* dalam uji lapangan, merupakan tebal zona pengujian

Pengujian Permeabilitas (Transmisivitas) di Lapangan

• Metode Uji e.g.:

•Pumping Test, (mendapatkan nilai T (K), S, Radius pengaruh, efisiensi sumur, debit optimum)

• Packer Test, (nilai T, dan K pada zona spesifik)

•Slug test, (Nilai T (K))

Pengujian Permeabilitas (Transmisivitas) di Lapangan – Pumping Test

Pengujian Permeabilitas (Transmisivitas) di Lapangan – Packer Test

Permeability in Fractured Rocks

• Dual ‘porosity’

• Secondary porosity as ‘main actor’

• Rock defects/Fracture/gouge

• Connectivity?

• Heterogeneity

• Isotropy / anisotropy

• K value from field/lab. test?

• Dual Porosity

-100 m

-110 m


Depth

• Connectivity

• heterogeneity

-100 m

-110 m

-120 m

K105 : high

Depth Connected

K115 : low

Not Connected

• Anisotropy

West East


-100 m

-110 m


Laboratory test from core

NOT RELIABLE High K value (rock mass)

K is very low impermeable

Pumping Test

Result

• Transmisivity (Permeability)

• Storativity

• Radius of Influence

Limitation and Problem

• Need construction, observation well (obs. well),

• Sometimes obs. well not at ‘right’ position


25 m

100 m Pumping well

Observation well 1

Observation well 2

No drawdown

5 meter drawdown



• Packer test

• Can be test at an interval depth

• No need well construction, nor obs. well

• Suitable in fracture rocks

Result

• Transmisivity (Permeability)

• Type of rock defects (filled, blocked, open)

Packer Test

-100 m

-110 m

-120 m

K105

K115

Water enter rock formation ‘’easily”

K >>>

Packer Test

-100 m

-110 m

-120 m

K105

K115

Very limited number of water can enter the rock formation

K <<<

Packer Test

Pengujian Permeabilitas (Transmisivitas) di Lapangan – Slug Test

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