2. Excavate a foundation pit laterally beneath the bottom of the original foundation, with the same width as the foundation and a depth reaching the design bearing stratum;

　　3. The pit body beneath the foundation shall be filled with cast-in-place concrete, and pouring shall stop at 80 mm from the bottom of the original foundation. After curing for one day, fill the gap at the base with dry, stiff cement mortar mixed with an expansive agent and an accelerator, then strike wooden strips with a hammer and compact the filled mortar.