砂卵石地层盾构下穿高速公路加固方案研究

Study on Reinforcement Schemes of Shield Tunneling through Highway in Sandy Pebble Stratum

成都地铁17号线九江北站~白佛桥站盾构区间侧穿绕城高速江安立交桥台并下穿高速公路路基,在砂卵石地层中大直径盾构隧道掘进易导致地层沉降,若沉降过大会威胁到高速公路的安全运营,故有必要对盾构隧道洞内加固方案开展研究。采用三维数值方法对隧道洞顶不同范围内的地层进行洞内注浆加固模拟,以高速公路路基沉降、管片内力及邻近桩基水平位移为主要评价指标,研究不同加固方案对地表沉降及邻近桩基横向位移的控制效果。结果表明:(1)当对隧道拱部120°和180°及径向3 m范围土体进行注浆加固时,路基沉降及管片内力均满足控制标准要求;(2)各方案加固效果对比发现,增加径向注浆厚度相较于增大环向注浆范围对地表沉降的控制效果更明显;(3)加固前后管片内力均满足控制标准要求;(4)隧道洞内注浆加固对侧穿的桩基变形影响较小,各加固工况下其水平变形均满足控制标准要求。

The shield section from Jiujiang north station to Baifoqiao station of Chengdu metro line 17 passes alongside the Jiang’an overpass abutment of the ring expressway and crosses underneath the roadbed of the ring expressway.The large-diameter shield tunnel in the sandy pebble stratum is easy to cause the formation settlement.If the settlement is too large,it will threaten the safe operation of the expressway.So it is necessary to carry out research on the reinforcement plan of the shield tunnel.The three-dimensional numerical method is used to simulate the grouting reinforcement in different areas of the shield tunnel roof.The settlement of the highway subgrade,the internal force of the segment and the horizontal displacement of the adjacent pile foundation are used as the main evaluation indicators to study the control effect of the ground settlement and the lateral displacement of adjacent pile foundation in different reinforcement schemes.The results show that:(1)When the soil at 120°and 180°of the tunnel arch and 3 m in the radial direction is reinforced by grouting,the settlement of the roadbed and the internal force of the segment meet the requirements of the control standard;(2)The comparison results about the reinforcement effect of each plan show that increasing the radial grouting thickness has a more obvious control effect on surface settlement than increasing the circumferential grouting range;(3)The internal forces of the segments before and after reinforcement meet the control standard requirements,indicating that the internal forces are not controlled;(4)The grouting reinforcement in the tunnel has little effect on the deformation of the side-crossing pile foundation,and the horizontal deformation under each reinforcement condition meets the requirements of the control standard.