Three variables are considered: critical buckling position, and neutralplane, the fiber buckling half-wavelength.
引入三个变量：临界屈曲位置、中性面位置和纤维屈曲半波长。
2
As the size of coal pillar increases, the width of neutralplane area increases. However, the speeding-up of neutralplane area occupying the width of coal pillar decreases and becomes stable.
随煤柱尺寸增加，中性面区域的宽度逐渐增大，但其占煤柱宽度比例增速降低并逐渐趋于稳定。
3
This plane is therefore called the neutral surface of the beam.