ON THE COMPARATIVE NECESSITY FOR 

 THE DRAINAGE OF DRAYROADS AND 

 RAILROADS. 



By GEORGE PHILLIPS, C.E., 



(LATE INSPECTING SURVEYOR, QUEENSLAND RAILWAYS). 



[Ilriiil hefnre tin- I!ni/,(f Sucii'ti/ of Qucgnslfind, June llt/i, 1S9'^.] 



Put in as few words as possible, tlie duty of a drayroad is 

 to ciirrii ronrcnt rated loads nt a coiiipaiativehi loir speed, whilst the 

 dut\ of a railroad is precisely the reverse, namely, to ntrri/ 

 distriliKted loads at a C(.iiijiaratii-eJi/ /ii(/li sjicid. 



In detail, the duty of a drayroad is to sustain on any 

 portion of its comparatively wide surface, without undue crush- 

 ing, grinding, or displacement, concentrated loads of about 1100 

 pounds per square inch ; whereas on railroads the loads are so 

 distributed that those parts of the road that correspond in 

 strength with the component parts of a drayroad are only 

 called upon to sustain without displacement an ultimate pres- 

 sure below the sleepers of from pounds to 10 pounds per 

 square inch. 



AVell compressed dry earth can sustain a weight of many 

 tons per square foot without serious displacement, but when 

 surface soils are moistened by long-continued rain the particles 

 tend to slide one upon another, and become displaced under 

 comparatively small jnx'ssure — the amount of displacement being 

 pretty well in proportion to the amount of pressure, provided 

 the pressure is applied in the same manner. 



