Allow blocked content for a specific uri

With this irule you should have what you want :

when ASM_REQUEST_BLOCKING
{

  set x [ASM::violation_data]

   if {([lindex $x 0] contains "VIOLATION_ATTACK_SIGNATURE_DETECTED")}
   {
      if {[IP::client_addr] equals your_IP}{
        if {ASM::payload contains "your_expression"} {
              ASM::disable  
        }
      }
   }  
}