Overview
- TEXTBOOK : Lab13 and Lab14 in 9th, Lab 10 in 8th
- Objectives : learn how to determine the coefficient of permeability of a given soil sample by constant-head and falling-head permeability test.
- The rate of flow of water through a soil specimen of cross-sectional area A can be determined as
? = ??? where q = flow in unit time, k=coefficient of permeability, i = hydraulic gradient
- The permeability coefficient, k is defined as a measure of material’s capacity to transmit water
- k can be determined in the lab by Constant head test (for coarse grain) or by Falling head test (for coarse or fine grain soils)
You will find more information with Virtual Labs of PermeabilityTest http://smfe-iiith.vlabs.ac.in/exp6/Introduction.html?domain=Civil%20Engineering&lab=Soil%20Mechanics%20Lab
UVA TTA, Virginia's LTAP, (2014, Jan 7). Hydraulic Conductivity [Video]. Youtube
Submit a lab report based on the video above and using experimental data given in Table 6-1 and 6-2.
Table 6-1. Constant Permeability Test
ItemTest No.123Average Flow, Q(cm3)489534560Time of collection, t(s)606060Temperature of water, T(?)19.919.919.9Head Difference, h(cm)74.586.594.5Diameter of specimen, D(cm)7.1377.1377.137Length of specimen, L(cm)101010Area of specimen, [Image unavailable: LaTeX: A=\frac{\pi}{4}D^2\left(cm^2\right)]A=?4D2(cm2)[Image unavailable: LaTeX: k=\frac{QL}{Aht}\:\:\left(cm/s\right)]k=QLAht(cm/s)Average k (cm/s)
Table 6-2. Falling-head Permeability Test
ItemTest No.123Diameter of specimen, D(cm)7.1377.1377.137Length of specimen, L(cm)101010Area of specimen, [Image unavailable: LaTeX: A=\frac{\pi}{4}D^2\left(cm^2\right)]A=?4D2(cm2) Beginning head difference, h1(cm)888576Ending head difference, h2(cm)557145Tiest duration, t(s)8.23.29.5Volume of water flow through specimen, Vw(cm3)53.52451[Image unavailable: LaTeX: k=\frac{2.303V_wL}{\left(h_1-h_2\right)tA}\log\left(\frac{h_1}{h_2}\right)\:\left(cm/s\right)]k=2.303VwL(h1?h2)tAlog?(h1h2)(cm/s)Average k (cm/s)
Lab Report should
- Write down the procedures described in the video(UVA TTA, Virginia's LTAP,2014). Ignore the measurements shown in the video.
- Include completed data tables 6-1 and 6-2, and sample calculations for both tests.
- Assuming that the same soil sample was used in the two tests, discuss the variation of k between two test methods. Also, discuss possible source of errors if conducting the test.