Also, the crack extension time decreases with the increase of material creep index and the loading of overlying strata rock while it increases with the increase of tensile strength of roof rock.

断裂孕育时间随材料的蠕变指数、上覆岩层压力的增大而减小；裂隙扩展时间也随材料的蠕变指数、上覆岩层压力的增大而减小，但随岩石的抗拉强度增大而增加。

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Due to the distinct difference in tensile and compressive properties, the position and deformation curvature of curved neutral layer will change with time for the! Strata in a creep state.

由于岩石材料抗拉与抗压性能的明显差异，使岩层受蠕变作用时，其弯曲中性层位置及变形曲率都将随时间变化。

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