某行车道路(地面坡度为5‰)上合流制排水管段设计流量如图示,排水管采用钢筋混凝土管,节点1处管顶覆土深度0.7m。设计管段1~2和管段2~3的管径d和敷设坡度i应为下列何项? (A)d1-2=200mm,i1-2=5.2‰;d2-3=250mm,i2-3=5.0‰; (B)d1-2=200mm,i1-2=4.1‰;d2-3=250mm,i2-3=4.6‰; (C)d1-2=300mm,i1-2=5.0‰;d2-3=300mm,i2-3=5.0‰; (D)d1-2=300mm,i1-2=2.9‰;d2-3=300mm,i2-3=2.9‰
某行车道路(地面坡度为5‰)上合流制排水管段设计流量如图示,排水管采用钢筋混凝土管,节点1处管顶覆土深度0.7m。设计管段1~2和管段2~3的管径d和敷设坡度i应为下列何项? (A)d1-2=200mm,i1-2=5.2‰;d2-3=250mm,i2-3=5.0‰; (B)d1-2=200mm,i1-2=4.1‰;d2-3=250mm,i2-3=4.6‰; (C)d1-2=300mm,i1-2=5.0‰;d2-3=300mm,i2-3=5.0‰; (D)d1-2=300mm,i1-2=2.9‰;d2-3=300mm,i2-3=2.9‰