When the force can not contact drill string with one side of the borehole wall, the stiffness of drill string can influence the contact force.

当外力不足以使钻柱紧贴于井壁的一侧时，钻柱的刚度对钻柱与井壁之间的接触力有影响。

youdao

Elements of stonework excavation: Use down-hole drill assisted with hammer drill drilling. Control blasting loosely and side slope molding smoothing wall blasting.

石方开挖施工要点：采用潜孔钻机配以凿岩机钻眼，松动控制爆破和边坡成型光面爆破。

youdao