FO UNDA TIONS. 22$ 



The size of the grains of sand may increase from very fine 

 particles to coarse gravel; the coarser the grain, the better 

 the foundation as a rule. Gravel and sand, when incorpo- 

 rated with a binder of clay, are cemented together to an 

 extent which makes such a soil but little less valuable as a 

 bearing material to the softer grades of rock, but where the 

 grains of sand are fine, having no cohesion, the mass, when 

 saturated with water, becomes semi-fluid, and is subject to 

 hydraulic principles. Owing to its porosity and suscepti- 

 bility to moisture, sand, like clay, is subject to the disin^ 

 tegrating effects of frost, and the foundation-pits should 

 therefore be excavated below the liability of such exposure. 

 Also like clay, having a capillary attraction for fluids, in sand 

 foundations, springs are frequently encountered which should 

 be treated as above suggested in the absence of more definite 

 knowledge and experience. The same methods would apply 

 for a weak clay foundation, such as spreading concrete over 

 the area uncovered, is advisable to assist and to augment its 

 bearing-surface, but frequently in such soils, as well as upon 

 the clay variety, the bearing values are increased by remov- 

 ing a portion of the soft material and driving or jetting down 

 short piles upon which stringers of wood are spiked, the 

 spaces between rows being filled with concrete; sometimes 

 the use of the stringers alone will be found sufficient in addi- 

 tion to the use of the concrete, which is compacted flush 

 with the tops of the sills. Such construction is called "gril- 

 lage," and is frequently used. Since timbers covered by 

 water and removed from atmospheric oxidation have been 

 proven to last for indefinite periods, such a foundation, where 

 completely subject to saturation, is very effective and safe. 

 In very soft sand, clay, or alluvial soils these methods are 

 found effective, and in addition planking, making a floor for 

 the foundations to be started upon, is spiked transversely 



