大型机组蜗壳通常采用保压、垫层、直埋3种埋设方式，结合向家坝地下电站工程实际，通过不同蜗壳埋设方式对比计算分析，给出了一种适合该地下电站机组特点的直埋、垫层组合埋设方案。计算结果表明：组合方案具有混凝土应力分布均匀、拉应力值不大，能够充分发挥混凝土联合承载作用等优点，可作为推荐方案。

The spiral case of large hydraulic unit usually adopts three different embedding types including pressure preservation，cushion layer and direct embedment. In combination with the project of Xiangjiaba Underground Power Station，a combining scheme of the embedded directly spiral case with a cushion layer is given，which can be fit in features of this hydraulic unit. The results showed that the combining scheme can be recommended，which have the advantages of more uniform distribution of stress，less tensile stress and jointly bearing load with concrete.