Experiment 5 Part b Permeability By Falling Head

Experiment # 5 Part b Permeability By Falling Head Method Soil Mechanics Lab CE 350 1

Objective u To determine the coefficient of permeability of fine sand, silts or clays. Soil Mechanics Lab CE 350 2

REQUIRED APPARATUS Permeameter cylinder u Perforated metal or plastic disks u Filter materials such as Ottawa sand u Deaired water u Timer (stop watch). u Centigrade thermometer, range 0 to 50 C. u Balance, sensitive to 0. 1 g. u Oven. u Scale, graduated in centimeter. u Soil Mechanics Lab CE 350 3

Rate of Flow Soil Mechanics Lab CE 350 4

REQUIRED MEASUREMENTS u u u u u Wet weight of soil specimen, Wwet. Moisture content of soil specimen, w. Diameter of soil specimen, D. Length of soil specimen, L. Cross-sectional area of standpipe, a. Height to water surface in standpipe at start of test, H 0. Height to water surface in standpipe at end of test, H 1. Time at start of test, t 0. Temperature of test water, T. Time at end of test, t 1. Soil Mechanics Lab CE 350 5

Void Ratio Determination Wt. of dry soil + can Diameter of specimen, D Wt. of can Area of specimen, A Wt. of dry soil Ws Initial height of specimen, L Sp. Gravity, Gs Initial volume of specimen, V Vol. of solid (Vs = Ws/Gs) Initial void ratio, e Soil Mechanics Lab CE 350 6

Coefficient of Permeability Test No. Initial height of specimen Void ratio, e = (AL – Vs)/Vs Initial time, t 1 Final time, t 2 Elapsed time, t = t 1 – t 2 Initial head, h 1 Final head, h 2 Area of standpipe, a Water temperature, C Viscosity correction factor, R T Coefficient of permeability, K 20 Soil Mechanics Lab CE 350 7

Correction Factor, RT, for Viscosity of Water Soil Mechanics Lab CE 350 8

Sample Preparation u Undisturbed Ø Ø Sample Tube Sample Block Sample u Remolded Sample Soil Mechanics Lab CE 350 9

Typical Values of Permeability Coefficient Soil Type k (cm/sec) Clean Gravel 100 -1. 0 Coarse Sand 1. 0 -0. 01 Fine Sand 0. 01 -0. 001 Silt 0. 001 -0. 00001 Clay Less than 0. 000001 Soil Mechanics Lab CE 350 10

Applications Excavation in soil bearing ground water u Earth Dam u Drainage Filters u Soil Mechanics Lab CE 350 11