TOPIC 2 STEADY STATE FLOW THROUGH SOIL Course: S0705 – Soil Mechanic Year: 2008

Bina Nusantara CONTENT PERMEABILITY / CAPILARITY (SESSION 7 : F2F) SEEPAGE (SESSION 8 : F2F) FLOW NET / JARINGAN ALIRAN (SESSION 9 – 10 : F2F)

Bina Nusantara SESSION 7 PERMEABILITY / CAPILARITY

Bina Nusantara INTRODUCTION DEFINITION : THE VELOCITY OR THE CAPABILITY OF WATER/FLUDI PASS THROUGH POROUS MEDIA NOTATION : k UNIT : m/s, cm/s PURPOSE : –To evaluate the seepage through dam –To evaluate the uplift force or seepage force under hydraulic structure for stability analysis –To control seepage velocity –To determine the consolidation time rate

Bina Nusantara –LABORATORY CONSTANT HEAD (TINGGI KONSTAN) FALLING HEAD (TINGGI JATUH) –FIELD UNCONFINED AQUIFER (AKIFER BEBAS) CONFINED AQUIFER (AKIFER TERKEKANG ) INCONSTANT WATER HEIGHT (TINGGI AIR TIDAK TETAP) DETERMINATION OF PERMEABILITY COEFFICIENT

Bina Nusantara CONSTANT HEAD (TINGGI KONSTAN) –SUITABLE FOR SANDY SOIL, SAND OR GRAVEL WHICH HAVE BIG VOID RATIO VALUE –BASIC EQUATION :

Bina Nusantara FALLING HEAD (TINGGI JATUH) –MORE ECONOMICAL FOR LONG TERM TEST –BASIC EQUATION :

Bina Nusantara UNCONFINED AQUIFER (AKIFER BEBAS)

Bina Nusantara UNCONFINED AQUIFER (AKIFER BEBAS) Q

Bina Nusantara CONFINED AQUIFER (AKIFER TERKEKANG )

Bina Nusantara CONFINED AQUIFER (AKIFER TERKEKANG )

Bina Nusantara INCONSTANT WATER HEIGHT (TINGGI AIR TIDAK TETAP) 2r yy L y

Bina Nusantara RANGE OF k VALUE Cm/s

Bina Nusantara RANGE OF k VALUE C is coefficient of soil roughness (published by Hazen), the value range from 40 to 150 i.e. as follow : CSand (one or all of the next characteristics) 40-80Very fine, well graded or contain some fine particle Rather rough, poor graded or clean, rough and well graded Very rough, very poor graded, contain gravel and clean

Bina Nusantara EQUIVALENT COEFFICIENT OF PERMEABILITY OF LAYERED SOIL –Equivalent Coefficient of Vertical Permeability (kv’) –Equivalent Coefficient of Horizontal Permeability (kh’)

Bina Nusantara Equivalent Coefficient of Vertical Permeability (kv’) Basic Concept –q in = q out –v constant

Bina Nusantara Equivalent Coefficient of Vertical Permeability (kv’)

Bina Nusantara EXAMPLE 1 Question : Find the permeability coefficient of sand in ft/min q = 1 ft 3 /hr

Bina Nusantara EXAMPLE 1 SECTION 1 SECTION 2 TOTAL

Bina Nusantara EXAMPLE 1 k = 4 ft/hour = 6,67x10 -2 ft/min

Bina Nusantara EXAMPLE 2 q Questions : - determine h - determine q in cc/sec Section 1 Section 2

Bina Nusantara EXAMPLE 2 Section 1 Section 2 h = cm Determination of h

Bina Nusantara EXAMPLE 2 Determination of water flow rate or q = 0.15 cc/s

Bina Nusantara SESSION 8 SEEPAGE

Bina Nusantara INTRODUCTION DEFINITION VOLUME OF WATER/FLUID FLOW IN OR FLOW OUT AT A MEDIA OR CERTAIN SOIL MASS PURPOSE –TO DETERMINE THE INFLUENCE OF SEEPAGE TO THE STABILITY OF STRUCTURE OR DAM –TO ESTIMATE THE FLOW VELOCITY AND FLOW RATE AT DEWATERING WORK

Bina Nusantara WATER FLOW EQUATION –BASIC OF THEORY DARCY LAW BERNOULLI LAW CONTINUITY EQUATION = constant energy

Bina Nusantara WATER FLOW EQUATION Inflow water per time unit: Outflow water per time unit:

Bina Nusantara WATER FLOW EQUATION q inflow = q outflow CONTINUITY EQUATION

Bina Nusantara WATER FLOW EQUATION STEADY STATE CONDITION: WATER FLOW VELOCITY :

Bina Nusantara WATER FLOW EQUATION HOMOGEN SOIL k constant at x,y,z direction ISOTROPY SOIL k x = k y = k z = k LAPLACE EQUATION TWO DIMENSION

Bina Nusantara WATER FLOW EQUATION SEEPAGE SOLUTION –CLOSED FORM SOLUTION –MODEL SOLUTIONS –APPROXIMATE SOLUTIONS NUMERICAL SOLUTIONS GRAPHICAL SOLUTIONS  FLOW NET

Bina Nusantara SESSION 9-10 FLOW NET / JARINGAN ALIRAN

Bina Nusantara DEFINITION Combination of 2 line group which perpendicular each other i.e. : –Flow Line A bundle of line or points which defined flow direction –Equipotential Line The position of point which have same total head

Bina Nusantara FLOW NET / JARINGAN ALIRAN

Bina Nusantara FLOW NET / JARINGAN ALIRAN

Bina Nusantara FLOW NET / JARINGAN ALIRAN

Bina Nusantara FLOW NET / JARINGAN ALIRAN

Bina Nusantara FLOW NET / JARINGAN ALIRAN GUIDANCE OF FLOW NET DRAWING –The water surface of upper stream and lower stream is equipotential line –The interface line of water and soil is equipotential line –The flow line perpendicular with equipotential line –The impermeable surface of boundary line is flow line –The shape area formed by flow line and equipotential line is square

Bina Nusantara FLOW NET / JARINGAN ALIRAN

Bina Nusantara FLOW NET / JARINGAN ALIRAN

Bina Nusantara FLOW NET / JARINGAN ALIRAN

Bina Nusantara FLOW NET / JARINGAN ALIRAN a = b h h+h qq a b

Bina Nusantara EXAMPLE 3 4,50 m 8,60 m A B C D E Datum Sheet Piling 6,0 m 0,5 m k = 1,5 x m/s

Bina Nusantara EXAMPLE 3

Bina Nusantara EXAMPLE 3 N d = 12 N f = 4,3 H = 4,0 m

Bina Nusantara EXAMPLE 3

Bina Nusantara EXAMPLE 4 k = 2,5 x m/s 5 m 15 m 12 m

Bina Nusantara EXAMPLE 4 N d = 15 N f = 4,7 H = 4,0 m

Bina Nusantara EXAMPLE 4

Bina Nusantara SEEPAGE FORCE / GAYA REMBESAN Hh2LHh2L h1h1

Bina Nusantara SEEPAGE FORCE / GAYA REMBESAN TOTAL FORCE BODY FORCE (GAYA BADAN) L Soil weight =  t.L.A  w. h 2. A  w. h 1. A

Bina Nusantara SEEPAGE FORCE / GAYA REMBESAN SEEPAGE BODY FORCE (j)= CRITICAL CONDITION  bouyancy =  t -  w Hh2LHh2L h1h1

Bina Nusantara EXAMPLE 5 k = 1x10 -3 cm/s n = 0.67 Questions : 1.Water Flow Rate 2.Flow Velocity 3.Seepage Velocity 4.Seepage Force at point A

Bina Nusantara EXAMPLE 5 Water Flow Rate Flow Velocity

Bina Nusantara EXAMPLE 5 Seepage Velocity Seepage Force