建立了渗透变形初期的完整井和非完整井理想模型，通过有限元计算描述了渗透变形的发展过程。完整井模型中的涌砂在平面上可以是不连续的，除涌水口附近的区域外，近河床处在一定范围也可发生渗透变形。涌砂主要来自于涌水口的临河侧，随着砂的不断涌出，渗透变形的发展呈条带状向堤岸方向扩展，在一定条件下可与近河床处的渗透变形区相连通形成集中渗漏通道。非完整井模型中涌砂向深部的扩展是趋缓的，并最终将停止。因此，完整井模型中的涌砂是发展性的，而非完整井模型中的涌砂是非发展性的。

Two ideal models, i.e. a perfect well model and an imperfect well model, used for calculating deformation initial period, are set up, and their development processes are reprerented by FEM. The computed results obtained from the perfect well model indicate that: the distribution of piping in plane is not in succession; in addition to the near area of the well, the percolation deformation near the riverbed may also occur within a certain extent; and drift sands chiefly come from one side near river, with the continuous driftage of sands, the percolation deformation will develop as a long narrow strip, and may connect with the percolation deformation near river bed to form a concentrated percolation passage under certain conditions. In the imperfect well model, the expansion of drift sands in depth is slowly and ultimatly stops. So, drift sands in the perfect well modol are of developmental property, but these in the imporrfect well model aren't of this property.