Does The Pressure Increase Under The Soil? Why?

Yes, Soil pressure enhances with depth due to the overburden or self-weight of the soil and because of loads imposed upon the soil.

I agree with Mrs Woofter, Mr Alex and Mr Tartir.

Yes, due to self weight of the soil and due to loads imposed upon the soil.

For example, the pressure variation below the depth of soil is linear and the relation is given by pressure = unit wt * depth. As depth increases, there will be a linear increase in the soil pressure.         

Yes, Pressure will increase. Self soil weight and external weight

We treat soil sort of like a fluid, like water,the pressure it exerts increases linearly with depth in the downward direction, but unlike water in that it exerts less pressure horizontally than vertically. You've got a density. Convert that to a unit weight - density is mass/volume, multiply by gravity to get weight/volume. Now draw a diagram of your wall. The pressure at the top of the soil is zero. As you go down, it increases linearly pressure = unit weight * depth

I agree with Alex.

yes, soil pressure increases with depth, due to compression of the soil or water is lost in that depth

Liquefaction is a phenomenon in which the strength and stiffness of a soil is ... However, earthquake shaking can cause the water pressure to increase to the point ... a potential disaster of flooding of the heavily populated areas below the dam.

en.wikipedia.org/wiki/Pore_water_pressure

Pore water pressure (sometimes abbreviated to pwp) refers to the pressure of groundwater held within a soil or rock, in gaps between particles (pores). Pore water pressures in below the phreatic level (see also groundwater) are measured inpiezometers. The vertical pore water pressure distribution in aquifers can generally be assumed to be close to hydrostatic.

In the unsaturated zone, the pore pressure is determined by capillarity and is also referred to as tension, suction, or matric pressure. Pore water pressures under unsaturated conditions (vadose zone) are measured in with tensiometers. Tensiometers operate by allowing the pore water to come into equlibrium with a reference pressure indicator through a permeable ceramic cup placed in contact with the soil.

Pore water pressure is vital in calculating the stress state in the ground soil mechanics, from Terzaghi's expression for theeffective stress of a soil.

Yes, pressure will increase deeper in the soil due to the weight of the above layers.