求翻译：3.对于除险加固土石坝工程，防渗墙的深度除地基部分与新建土石坝相同外，还应根据防渗墙布置的轴线情况，加上穿过坝体部分的深度。二项之和为防渗墙的深度。是什么意思？

3. for the reinforcement of Earth-rock dam engineering, depth in addition to ground part of the cut-off wall outside the same as the new Earth-rock dam, also should be based on anti-seepage wall arrangement of axes, and through the depth of the part of the dam. And on the second item of cutoff wall