PEESSURE OF EARTH AGAINST WALLS. 



To find the pressure of the different kinds of earths, filling, 

 &c., against walls, it is necessary first to ascertain the line or 

 angle of rupture, or natural slope, the earth would assume 

 but for the resistance of the wall. This natural slope differs 

 with the different kinds of earths. Assuming that the earth 

 is level with the top of the wall, the line of rupture for the 

 different kinds of earths, filling, &c., will be as follows : 



A bank of vegetable earth will rupture on the surface at a 

 distance from the top of the wall of three-fifths the height 

 of the wall. 



A bank of sand will rupture at two-thirds the height of 

 the wall. 



A bank of unhewn stone, at one-seventh the height of the 

 wall. 



A bank of rubble at two-fifths the height of the wall. 



A bank of brick, with a bank of vegetable earth behind 

 it, will rupture at a distance of about one-sixth the height 

 of the wall. 



A bank of clay, well rammed, will rupture at a distance 

 of three-sixteenths the height of the wall. 



The strongest horizontal stress against the wall is at half 

 the angle which the natural slope makes with it ; hence : 



