粉质粘土地质隧道施工技术及控制要点

Construction technology and control points of Geological Tunnel with silty clay

隧道洞口施工中开挖是一项十分复杂地高难度的项目,隧道洞口的开挖难点在于软弱围岩浅埋段,开挖软弱围岩洞身的施工方法:必须严格按照"新奥法"的原则组织施工,应加强地表观测,施工过程中应严格控制开挖进尺,土质围岩"禁爆破",执行"管超前、即支护、短进尺、早封闭、勤监测、备预案";加强隧道的衬砌支护工作,采用信息化动态施工管理,根据施工监控量测数据掌握围岩动态和支护结构的工作状态,利用监控测量结果及时调整设计支护参数,及时正确的指导施工。本文结合已完工的青海省S102线大湟平公路工程静房隧道施工过程中实际情况作为依据,静房隧道进口段地质情况是穿越地层为粉质粘土、全风化砂砾岩和全风化-强风化泥质砂岩,其中,粉质粘土结构松散,胶结性差,含少量碎石颗粒;属于软质岩,局部呈现破碎状。在隧道开挖施工中极易出现坍塌、掉块等现象,甚至洞口成洞时顶部易出现冒顶,侧壁失稳,隧道进口基岩以全风化泥质砂岩和风化砂砾岩为主,均为透水性较好的透水层,在施工前期一定要做好坡面及隧道截排水措施,尤其是雨季时加强支护,并且要做好隧道仰拱施工开挖必须短距离进行成环,同时对地基进行加固处理,避免出现隧道整体下沉的发生;现将粉质粘土地质条件下隧道工程施工存在的问题进行分析,论述这种围岩情况下施工技术及控制要点,为同类型地质情况的隧道施工提供参考和借鉴。

Tunnel entrance excavation is a very complicated and difficult project.The difficulty of tunnel entrance excavation lies in the shallow buried section of weak surrounding rock.The construction method of excavating the tunnel body of weak surrounding rock must be strictly organized according to the principle of"NATM".Surface observation should be strengthened and excavation should be strictly controlled during construction.Blasting is forbidden around soil surrounding rock."Piling pipe before excavation,Shoring in time,Short footage,pouring soon,Enhanced monitoring and measurement and the safety construction plan"is carried out.To strengthen the lining support work of the tunnel,the information dynamic construction management is adopted,the dynamic state of the surrounding rock and the working state of the supporting structure are mastered according to the monitoring and measuring data,and the monitoring and measuring knot is used.Timely adjustment of design support parameters,timely and correct guidance of construction.Based on the actual construction situation of Jingfang Tunnel in Dahuangping Highway Project of S102 Line in Qinghai Province,the geological condition of Jingfang Tunnel entrance section is silty clay,fully weathered sandy conglomerate and fully weathered-strongly weathered argillaceous sandstone,in which silty clay has loose structure,poor cementation and a small amount of crushing.Stone particles belong to soft rocks,partly fractured.In tunnel excavation,collapse and block fall are very easy to occur,even the top of the tunnel is prone to collapse,side wall instability,the tunnel entrance bedrock is mainly weathered argillaceous sandstone and weathered sandy conglomerate,are good permeable layer,in the early construction must do a good job of slope and tunnel drainage measures,especially It is rainy season to strengthen the support,and to do a good job of tunnel inverted arch construction excavation must be short-distance cycling,while strengthening the foundation,to avoid the occurrence of tunnel subsidence as a whole.This paper analyzes the problems existing in tunnel construction under silty clay geological conditions,discusses the construction technology and control points under this surrounding rock condition,and provides reference for tunnel construction under similar geological conditions.