中文摘要：

不同围岩条件下浅埋偏压小净距隧道的围岩稳定性相差很大,特别是半软半硬岩层隧道,由于软硬交界面的存在,其施工力学特性更加复杂。使用FLAC3D模拟不同净距下均质硬岩、均质软岩和竖向半软半硬岩隧道施工15种工况,对比分析中岩墙、拱顶上部围岩、仰拱处围岩和边坡的围岩稳定性。结果表明：隧道开挖引起均质围岩中岩墙上部水平位移最大,而半软半硬岩中部水平位移最大,中岩墙上部围岩稳定性最差;0.6B净距可以作为半软半硬岩偏压小净距隧道的临界值;半软半硬围岩隧道开挖引起拱顶沉降量和硬岩隧道比较接近,远小于软弱围岩隧道拱顶沉降;隧道开挖引起软岩侧洞室上覆盖层围岩稳定性变差;隧道开挖引起拱顶上部围岩破裂面整体呈＂W＂形,仰拱部围岩破裂面呈＂M＂形。

英文摘要：

The surrounding rock stability of bias small-interval tunnels in different rock strata are quite different. Especially in half-soft and half-hard rock,for the interface of hard and soft rock,the mechanical properties of tunnels are distinct from that in homogeneous conditions. Tunnel excavations in 15 different conditions were simulated with finite difference software FLAC 3D. General conclusions of surrounding rock stability of bias small-interval tunnel in different strata were obtained through analyzing the vault displacement and plastic zone of middle wall,crown,invert and side slope rocks. Results show that the largest horizontal displacement caused by tunneling in middle rock walls,the upper in homogeneous rock,but the middle in half-soft and half-hard rock,and the stability of upper rock in middle wall worst; 0. 6B spacing can be used as the critical distance of half-soft and half-hard rock small interval tunnel bias; the excavation vault settlement of half-soft and half-hard rock tunnel and hard rock tunnel vault relatively close,far less than the weak rock tunnel; half-soft and half-hard rock tunnel excavation cause side cavern overlying rock stability deteriorates, even tunnel collapses; tunnel excavation face caused by broken rock the whole upper vault was＂W＂shaped, invert appear before the Ministry of broken rock ＂M＂shape.