济广高速公路平远（粤赣界）至兴宁段南山隧道位于广东省最大的采煤矿区境内。煤系层发育，开采预留的巷道、采空区交错分布。隧道具有小间距，浅埋、偏压、围岩软弱、采空区分布等特点，因此地质情况及隧道特点给施工带来了较大难度。隧道掘进中通过采空区时出现地表开裂、初支变形、侵限二衬、掌子面流塌等隐患，为了防止初支再次出现变形，针对采空区段采用短台阶留核心土开挖、超前小导管强支护，加大预留沉降量，工艺改进，加强监测等措施克服了采空区不良地质，缩短了掘进工期，保证了工程质量，确保了施工安全。%Nanshan Tunnel of Pingyuan-Xingning Section of Ji-Guang Expressway is located in the largest coal mining area of Guangdong Province, with highly developed coal-bearing layers and interlocked distribution of reserved mining roadway and mined-out regions. The characteristics of this tunnel include small distances, weak rock, shallow buried, distribution of mined-out regions and so on, therefore, the geological conditions and the characteristics of the tunnel have brought great difficulties to the construction. The hidden dangers, such as surface cracking, deformation of the initial support, intruding into the clearance limit of the secondary lining, collapse of the working face may arise when going across the mined-out regions. In order to pre-vent the deformation of the initial support, a plenty of measures, such as short bench excavation, reinforced supporting with ad-vanced small pipe, increased settlement reservation, improved construction technology and strengthened monitoring have been carried out to overcome the adverse geological conditions, to shorten the tunneling time, to ensure the quality and safety of the construction and to provide references for future tunnel construction under the similar geological conditions.
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