huangyhg

underground sanitary tank - lid attachment & joint spacing
i am designing an underground sanitary tank. what would be the best way to connect the lid (either cast on the ground and craned on top or pre-stressed craned on top) to the walls to give walls stability to resist deflection from backfill loads?
i was thinking of dowelling and epoxy into the top of the walls thru holes in the lid and epoxy to seal - what do you think?
regarding contraction joints; 60 feet is maximum length of wall recommended without joints with 30 to 50 feet being more common, would you consider that length measured along each wall or measured along the tank length?
for example: sanitary tank 60 feet long x 15 feet wide with 4 compartments of various sizes.
do you add the perimeter dimensions to determine the need for joints in this case 150' or just go by the tank length of 60' and that would not require any joints?
no joints needed. if used, put waterstop at center of wall thickness.
am i pushing the envelope if i do not use any joints?
which presents the most risk; installing a joint that may leak or not installing any joints and the cracks that develop may leak??
joints will almost always leak no matter how careful you are. cracking will occur, but as long as it is controlled to small crack widths by adequate crack control reinforcement, it may not leak. even if it does leak, autogeneous healing will help.
if you don't ever need to remove the lid, cast prestressing ducts into the top of the wall and into the edge of the lid. insert dowels and grout.
if you need a removable lid, cast the lid thicker inside the wall to create a bearing lug.

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