城市地铁隧盾构法施工地表沉降分析1.docVIP

武汉工程大学本科毕业论文日城市地铁隧道盾构法施工地表沉降分析Cities metro shield tunneling surface subsidence analysis 学生姓名 指导教师 PAGE \* MERGEFORMAT PAGE \* MERGEFORMAT IV摘 要浅埋暗挖隧道上覆地层己无自承载能力，荷载应全部由隧道支护结构来承担，但实际上，不但是土层，即使是干砂，地层仍能形成自然载拱。大量资料表明，随着地基土层压缩模量的增加，地面沉降逐渐减小。在土层压缩模量较小时，地面沉降和水平位移受模量的变化影响很大，随着盾构外径的增大，则由盾构施工引起的单位长度的地层损失就随着增大，在相同地面沉降槽宽度的情况下，最大地面沉降也随着增大；而隧道覆土厚度越大，则最大地面沉降值就会越小，但地面沉降槽宽度会越大。最大地面沉降随覆土厚度与盾构外径的比值即H／D的增大而减小。土压舱压力过大，则地面隆起，压力过小，则地面产生沉降。盾构推进过程中，盾构纠偏、叩头、抬头、曲线推进等造成的超挖都会使得实际开挖面大于设计开挖面，从而引起多余的地层损失。在盾构暂停推进时，千斤顶漏油回缩而可能引起盾构后退，使开挖面土体坍落或松动，造成地层损失。由于盾构壳具有一定的厚度，为了便于管片的拼装及盾构的纠偏而在盾构壳与衬砌之间保留有一定的空隙。千斤顶推动盾构机前行时，在盾尾衬砌管片外围形成了建筑空隙，使得周围土层要填充建筑空隙而发生涌向隧道的位移而引起地面沉降。关键词：盾构; 沉降; 有限元 AbstractShallow Tunnels overlying strata had no self-load capacity, the load should all by tunnel supporting structure to bear, but in fact, not only the soil, even dry sand, formation can still form a natural arch out. Large amounts of data showed that with the foundation soil compression modulus increases, land subsidence decreases. In the soil compression modulus is small, ground subsidence and horizontal displacement modulus changes by a great impact, with the shield diameter increases, caused by shield construction unit length increases as ground loss on in the same slot width of land subsidence in the case, along with the maximum ground subsidence increases; while the tunnel Futuhoudu larger, the smaller the maximum value of ground subsidence, but the ground subsidence trough width is greater. Maximum ground subsidence with Futuhoudu shield diameter ratio with that of H / D increases. Earth pressure tank pressure is too large, ground uplift, the pressure is too small, ground settlement produced. Shield forward process, shield correction, kowtow, rise, curve propulsion caused overbreak will make more than the actual design of the excavation face excavation face, causing excess ground loss. Shield pause in advance, the jack may cause retraction spill shield back, so that the