For the power station with medium-low water head and long-distance diversion tunnel ,and when there are no available geologic exploration tunnel and transport hole to be reformed near the surge shaft ,the engineering quantity is large when using cavern-typed upper-chamber for the surge shaft ,so it is not suitable to use the conventional upper-chamber as the cavern-typed surge shaft .When the upper-chamber could not reach the hole condition ,and the surge shaft is located in the conditions of gentle topogrophy and good geology ,the open-air upper-chamber-typed surge shaft could be used .The open-air upper-chamber-typed surge shaft has such advantages as limiting water level rise ,storing waste water .Also ,it needs small water hammer pressure to operate safely and it could be constructed safely .Furthermore it is suitable for slip-form construction .Therefor it is a prior-selecting type of the surge shaft .Through the comparison and selection for three types of the surge-shaft such as the simple cylindrical type ,impeded-hole type and open-air upper-chamber type ,it is shown that the open-air upper-chamber-typed surge shaft is more rational because of its smaller height ,less engineering quantity and less investment expenses .%对于中低水头长距离引水隧洞的电站，当调压井附近没有可利用的地质探洞、交通洞等加以改造作为调压井的上室时，采用洞室型式上室工程量大，不宜选用常规上室为洞室式的调压井。在上室达不到成洞条件，调压井处地形平缓，地质较好时，可采用露天上室式调压井。因露天上室式调压井具有限制水位继续上升，弃水储存功能，运行水锤压力小，运行安全，施工安全、滑模施工方便的优点，是调压井优先选用的型式。通过简单圆筒式、阻抗孔式、露天上室式三种型式的调压井比选，结果表明：在调压井高度较小，工程量较少，投资量较少，选用露天上室式更合理。
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