How do pit toilets work?
Pit latrine
A "partially lined" pit latrine is one where the upper part of the hole in the ground is lined. Pit lining materials can include brick, rot-resistant timber, concrete, stones, or mortar plastered onto the soil.[7] This partial lining is recommended for those pit latrine used by a great number of people — such as a public restroom in rural areas,  or in a woodland park or busy lay-by, rest stop or other similarly busy location — or where the soils are unstable in order to increase permanence and allow emptying of the pit without it collapsing easily. The bottom of the pit should remain unlined to allow for the infiltration of liquids out of the pit.