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In the design of bridge abutment should we use at-rest, active or passive pressure

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For rigid abutments such as abutments built with piling foundation, these type of abutments will experience no lateral movement, at-rest earth pressure shall be used to design this type of abutments.

Figure 1






for abutments with shallow foundations, during construction, this abutments will be subjected to at-rest earth pressure, then the soil will push the abutments forward until it reaches equilibrium points, for abutments where lateral movements occur active earth pressure developed. the state of equilibrium occurs when the rest earth pressure reduced to active earth pressure. for this type of abutments, at-rest earth pressure shall be used to assess structural stability and active earth pressure adopted for assessing structural adequacy.

Figure 2

passive earth pressure shall be investigated for the intergral abutment, where the expansion joints are not used to absorb the movement of the bridge deck, due to this movement abutment will be pushed back, the movement required to mobilize full passive earth pressure estimated to be 10 times movement required for active earth pressure. in general passive earth pressure assumed to be null and difficult to develop but in the event of soil removal behind the abutment wall due to any reason such as utility diversion, passive earth pressure should be considered and the soil contribution to stability is ignored.  





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