RULES FOR PIPE CULVERTS BASED ON THE MINISTRY OF SURFACE TRANSPORT, UNDER DEEP FILLS

LOADS ON PIPES UNDER HEAVY FILLS :-- The exact amount and the nature of load under heavy fills still remains a disputed point and depends upon many factors. It is not like the arc action of masonry walls as taken for lintels. According to the results of some research taken by the American standard, it is considered that :(1) In the case of conduits laid in cuts or the linings of tunnels, no further increase in pressure on the pipe conduit is to be expected if the depth of trench exceeds nine times it's width. (2) For culverts under heavy filling the earth pressure is less than the total weight of the material over the pipe if the pipe inflexible and the top of the pipe deflects more than the adjacent soil. If the pipe is rigid, the total load coming on the pipe is more than the weight of the earth prism over the pipe depending on the stiffness of the pipe, the type of it's bedding and the amount of compaction of the fill around it. Another point to be considered is the dispersion of the live load under the heavy fills. All pipes and tubes with less than 0.91 metre of cover in fields or 1.22 metres of cover in roads to be surrounded with at least 15 cm of concrete. Every culvert under a highway should be so laid that the minimum distance from the finished surface of the road bed to the top of the pipe is not less than one half the diameter of the pipe. Under rules for construction of the pipe culverts with deep fills based on the ministry of surface transport all pipes and tubes with 6 meters of cover to be surrounded with at least 15 cm of concrete, subject to over 4.27 metres of cover to be bedded on and haunched with at least 15 cm of concrete to a height of atleast half of the external diameter of the pipe. Any splaying of the concrete to be above the level.