12:166, Zhang

Spring, 2002

Lecture on

Porosity, Specific Yield and Aquifer

· Porosity

V_V : the void volume r_b : the bulk density

V : the total volume r_d : the solid particle density

Factors affecting porosity

Particle shape and arrangement, Sorting, Compaction, Cementation, Fracturing, and Solution

Porosity of Various Sediments

· Effective (or Kinematic) Porosity

n_e : Percentage of interconnected pore space

· Void Ratio

Where V_s : the solid particle volume

Relationship between e and n: e=n/(1-n) or n=e/(1+e)

· Specific Yield

V_y: the volume of water drained under gravity

Specific Yield of sediments (Table 4.2)

· Specific Retention

V_r: the volume of water retained against gravity

Note: n=S_y + S_r

· Degree of Saturation

V_W: the volume of the contained water

· Aquifer and Aquitard

Aquifer) contains and transmits water at rates fast enough.

Unconfined or Water-Table Aquifer

Confined or Artesian Aquifer

Aquitard contains water but transmits it slowly.

Aquiclude contains water but does not transmit it.

Aquifuge neither contains nor transmits water.

Reading: Section 3.1 – 3.3 of the text (p. 66-81)

Optional homework is on the back. You will get some bonus if you submit it before next Fri., Feb. 8.

12:166, Zhang

Spring, 2002

Optional Homework

1. Based on the definition of porosity, i.e., n = V_v/V_T, derive n = 1- r_b/r_s.

2. Calculate porosity for the cubic packing and rhombohedral packing (Figure 3.1). Show your calculation step by step.

3. Provided that you have an oven and a balance or other weighting equipment, how would you measure the porosity of an alluvium sample in your kitchen? Describe your procedure step by step.

4. Do it in your kitchen.