垃

Left earth radical - the indexing element, a pictograph of a clod of soil. Here the meaning slides from clean earth to dirty earth: 垃 only appears in the compound 垃圾 ('garbage'), where the dirt-on-the-ground sense became extended into household refuse and trash. The radical anchors the modern meaning in its grimy, dusty source.

Right 立 supplies the sound - lì drifting to lā through tone and vowel shift. 立 pictures a person standing firm on the ground; for 垃 it functions purely as a sound-marker carrying the reading. The character is essentially bound: 垃 by itself is almost never used - it lives inside the compound 垃圾, the everyday word for garbage.