作用在基础上的外荷载之和一般均有偏心,基础基底反力一般为呈梯形分布的压应力(图1),属小偏心受压状态.当作用在基础上的外荷载偏心过大时,最小基底压应力σ_2将出现负值,即基底出现了拉应力,这在基底是认为不可能承受的, The sum of the external loads acting on the foundation is generally eccentric, and the basic base reaction force is generally a trapezoidal distributed compressive stress (Fig. 1), which is a state of small eccentric compression. When the external load acting on the foundation is eccentric, the eccentricity is too large. , The minimum base compressive stress σ_2 will appear negative, ie the base will have tensile stress, which is considered to be impossible to bear on the basement.