遗留煤柱群链式失稳会引发覆岩垮落、地表塌陷、动载矿压、瓦斯外逸或水体下泄等灾害。揭示遗留煤柱群链式失稳的核心机理是精准防控的基本前提。本文从链式失稳的源头出发，提出了遗留煤柱群的最弱失稳致灾模式，界定了关键柱的基本概念，分析了关键柱的主要特征，研发了关键柱判别的技术方法，揭示了关键柱局部失稳的诱灾机理，形成了遗留煤柱群链式失稳的关键柱理论，并对其潜在的应用范围与领域进行了展望。研究结果表明:① 遗留煤柱内在物理力学性质和外在环境因素等的差异性，导致采场遗留煤柱群呈现出最弱失稳致灾模式——遗留煤柱群体系中任一失稳致灾模式发生时，最弱失稳致灾模式必然已经发生，即遗留煤柱群体系发生链式失稳时，稳定性最弱的遗留煤柱必然发生了失稳。② 关键柱是指采空区中最先可能发生局部失稳的遗留煤柱;“关键柱”之所以“关键”，是因为唯有采空区“关键柱”发生局部失稳，邻近区域稳定性稍强的遗留煤柱的失稳破坏才可能被活化，采场遗留煤柱群的链式失稳也才可能发生。③ 安全系数最小的遗留煤柱可以判别为煤柱群体系中的“关键柱”，在进行关键柱判别的时候需要遵循区域性、相对性、动态性和复合性等四大原则。④ 关键柱局部失稳的诱灾机理体现在:关键柱载荷的逐渐减小使得最邻近遗留煤柱承担的载荷线性增大，即关键柱的局部失稳会引发覆岩载荷向最邻近的遗留煤柱中转移与扩散，导致进一步的失稳破坏，并最终可能引发遗留煤柱群体系的“多米诺”链式失稳与破坏。⑤ 关键柱理论不仅可以应用于柱采区邻近煤层开采、强矿压控制、煤柱留设、充填开采、瓦斯抽采和水害防治等技术领域，还能推广应用于非煤矿山资源开采矿柱群的失稳防控等领域。遗留煤柱群链式失稳的关键柱理论的提出有望促进我国煤炭资源绿色开采理论与技术的发展。

Chain instability of residual coal pillars can lead to the dynamic disaster,such as the overburden caving,surface collapse,dynamic shock,gas leaking and water releasing.Revealing the chain failure mechanism of residual coal pillars is the basic prerequisite for its accurate control.Starting from the chain instability source,the weakest failure model of residual coal pillars was firstly proposed.The basic concept of key pillar was defined and its characteristics was analyzed.The determining method of key pillar were developed and the chain failure of residual coal pillars was revealed.Then,the key pillar theory in the instability of residual coal pillars was formed.At last,the potential application scope and field of key pillar theory was discussed.Results show that ① the differences in the internal physical-mechanical properties and external environmental factors have led to the weakest instability model of residual coal pillars.When any form of instability models appears in the residual coal pillar system,the weakest instability model must have occurred.That is,the coal pillar with the weakest stability factor fails inevitably when the chain instability of pillar system occurs.② The key pillar refers to the pillar that the local instability occurs earliest in the pillar system.Only the local failure of key pillar appears,the collapse of adjacent coal pillars with stronger stability can be activated.And the chain failure of residual pillar system can occur.③ The pillar with the smallest safety factor can be determined as the key pillar in the pillar system.Four principles of regionality,relativity,dynamics,and compound should be followed in determining the position of key pillar.④ Linear increase of load for the nearest adjacent coal pillar is triggered by the gradual reduction of load for key pillar.That is,the local instability of key pillar will cause the shift of overburden stress,which will transfer to the nearest coal pillars and lead to further instability and damage.Eventually,the chain failure and destruction of residual pillar system may also be caused.⑤ The key pillar theory can be used in the fields,such as the adjacent seams mining in the pillar areas,the strong pressure behavior controlling,the coal pillar designing,the backfilling mining,the gas extraction and the water disaster prevention.It can also be applied to the controlling of rock pillars in the non-coal resources mining.The key pillar theory in the instability of residual coal pillars is expected to promote the development of the theories and technologies of Chinese green mining.