Marscraft Keystone Silicone Sandfilled Sacs

3d Printed silicone ( similar material that maintains shape) sacs that would be filled with sand in Mars to create buildng blocks.
Part of the building would be dug into the earth as chambers (Trenches) of different sizes. A reusable printed structure would be used to build the Arcs with the Keystones and then repeated until the desired length is attained.
Communication between Chambers can be done via tunnel or a slim Trench depending on the distance.
A 3d printed thin tube ( or sheet tha