Draw compaction curve with features

A compaction curve plots dry unit weight ($\gamma_d$) against water content ($w$) for a fixed compaction effort. The dry unit weight rises with $w$ up to a peak, then falls.

 gd
  |                    ZAV line
  |         MDD  .-"-.  .
  |  . - - - - -/     \   .
  |            /       \    .
  |          /          \
  |  dry   /      wet     \
  | side  /       side
  +------+----------------------- w
       OMC

Features:

• Maximum dry density (MDD): the peak value of $\gamma_d$ at the top of the curve.
• Optimum water content (OWC or OMC): the water content corresponding to the MDD.
• Dry side of optimum: the part left of the peak, where $w <$ OMC. The soil is stiff and has a flocculated structure.
• Wet side of optimum: the part right of the peak, where $w >$ OMC. The soil has a dispersed structure and lower strength; the curve approaches the ZAV line.
• Zero air void (ZAV) line: $\gamma_d = G\gamma_w/(1+wG)$ for $S = 100\%$; the compaction curve always lies below and to the left of it.

The ZAV line is drawn using the specific gravity of the solids; it lies above the compaction curve because some air always remains in the soil.