公路隧道下穿煤层采空区开挖过程相似模型试验  

Similarity model test of highway tunnel excavation beneath mined-out area

作　　者：方勇[1] 符亚鹏[1] 杨志浩[1] 杨斌[1,2] 

机构地区：[1]西南交通大学交通隧道工程教育部重点实验室,四川成都610031 [2]云南省交通规划设计研究院,云南昆明650011

出　　处：《土木工程学报》2015年第2期125-134,共10页China Civil Engineering Journal

基　　金：国家自然科学基金(51278422);国家科技支撑计划课题(2012BAG05B03);四川省青年科技基金(2012JQ0021);中央高校基本科研业务费专项资金(SWJTU11ZT33)

摘　　要：隧道下穿煤层采空区施工将不可避免地对采空区地层产生扰动,破坏其原有的平衡状态,使既有采空区"活化",进而影响隧道围岩及初期支护的稳定性。开展隧道下穿煤层采空区开挖的室内相似模型试验分析,考虑隧道与采空区不同间距的影响。通过埋设位移计、土压力计及电阻应变计,研究隧道开挖过程中采空区及洞周地层的移动和初期支护的内力特征。测试结果表明,隧道开挖引起的采空区地层移动受采空区与隧道间距的影响显著,间距越小,采空区地层沉降越大、沉降槽曲线越窄、越陡,上台阶开挖引起的地层沉降占总沉降的比例越高,而初支闭合后收敛越快。当间距小于1D时,采空区地层大致处于隧道开挖引起的松动范围以内,并使松动范围进一步扩大,从而增大初期支护上的荷载。钢拱架最大弯矩主要发生在拱脚处,当间距很小时,钢拱架拱脚处弯矩显著增大,同时轴力水平降低、偏心距增大,大大增加了初期支护的失稳风险。试验揭示了隧道下穿煤层采空区开挖过程中地层的移动规律和初期支护受力特征,对指导类似工程施工具有积极意义。Tunnel construction beneath mined-out area may inevitably disturb the ground and affect the stability of surrounding rocks and preliminary support structure. With the distance between the tunnel and mined-out area considered,an indoor similarity model test of tunnel excavation was carried out. By embedding the displacement meter,soil pressure gauge and electric resistance strain gauge,the ground movement and internal forces in preliminary support structure in mined-out area and surrounding stratum of cavity were measured in the test. The results show that the distance between mined-out area and tunnel has significant effects on the displacement of mined-out area and internal force in preliminary support structure. The shorter the distance is,the greater the mined-out area settlement will be. The narrower and the steeper the settlement trough is,the higher proportion of the settlement caused by the upper-step excavation in the total settlement will be and the faster the convergence can be attained after the closure of preliminary support structure. When the distance is less than 1D( D is the span of tunnel),the mined-out area is almost located within the loosed zone which may be further expanded,so that the loads on preliminary support may be increased correspondingly. It is also shown that the maximum bending moment of the steel arch may mainly occur at the arch foot.When the distance is small,the bending moment at the arch foot may increases remarkably. In the meanwhile,the axial force may decrease and the eccentric distance may increase,which could dramatically increase the risk of instability in the preliminary support. Based on the model test,the discipline of ground movement and the stress characteristics in preliminary support during the tunnel excavation process beneath the mined-out area may be disclosed,which may provide a valuable guideline for future identical constructions.

关 键 词：公路隧道 采空区 模型试验 初期支护 地层移动 

分 类 号：U451.5[建筑科学—桥梁与隧道工程]