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1、上游: (1)平坦地带上游沟床加固问题不大,按以前的“标准铺砌”即可。 (2)陡坡地带,往往需开挖上游沟岸。沟壁开挖后更易坍塌,将导致沟床与涵洞堵塞。故应尽量少挖沟壁,或挖动后加以铺砌。加固沟床要接上原沟床。 (3)只要涵内流速不超过允许值,陡坡涵洞入口处可不作绥流井,但要避免上游水流飞冲路基。 2、下游: 缺路修建后、水流汇集,一般小桥涵处的水深与流速均较天然状况增大。涵管出口水流将使地面或河床发生或加大冲刷。设计时应考虑①出口水流应不危及居民房舍与农田水利;②冲刷应不危及桥涵与路基。
1, the upstream: (1) flat belt upstream ditch reinforcement is not a problem, according to the previous “standard paving” can be. (2) steep slopes, often to dig upstream ditches. After the ditch excavation more easily collapsed, will lead to ditch bed and culverts blocked. Therefore, it is advisable to dig the trench walls as little as possible or to dig after the excavation. Strengthen the ditch to connect the original ditch bed. (3) As long as the culvert flow rate does not exceed the allowable value, the Sui River can be avoided at the entrance of steep slope culvert, but the upstream water flow should be avoided to fly the subgrade. 2, the downstream: After the completion of the lack of construction, water flow together, the general small bridges and culverts of the water depth and velocity are more natural conditions. Culvert exit flow will cause the ground or river bed to occur or increase scouring. Design should be considered ① outlet flow should not endanger residential buildings and farmland water conservancy; ② erosion should not endanger the bridge culvert and roadbed.