水平岩层隧道超挖原因及合理超挖数量分析

摘要

研究目的:蒙华铁路蒙陕段存在水平岩层,多为粉砂岩夹薄层泥岩,层状构造,层间结合差,节理裂隙发育.水平岩层段隧道施工时拱部水平节理岩隙处易发生掉块剥落,开挖找顶、排险作业后常表现为不规则矩形或平顶;仰拱开挖后基底清理时顺水平节理剥离,岩块脱落较严重,开挖轮廓墙脚“弧形位置”处超挖严重.现场实测超挖量远超规范允许值,导致隧道开挖、出渣运输及超挖回填等数量不同程度增加,因此有必要针对水平岩层段隧道超挖回填的合理数量进行分析研究.研究结论:(1)水平岩层隧道的超挖与爆破作业扰动、开挖应力释放、地下水影响、隧道不同部位、洞身围岩强度及施工方法等均有关;(2)结合大量现场写实与测量数据,采用数理统计分析方法,遵循实事求是原则,扣除施工误差影响,得到了隧道在Ⅱ～Ⅴ级围岩拱部/边墙/仰拱(底板)各部位、有水/无水工况条件下,更加贴近现场实际的、合理的超挖及回填数量;(3)本研究结果可为水平岩层条件下隧道设计、现场施工、验工计价等提供一定的借鉴和指导,也可为同类型地质条件下隧道施工定额的研究提供参考.%Research purposes:The horizontal rock stratum of Inner Mongolia and Shaanxi paragraph of West Inner Mongolia-Central China Railway exists,most of which is siltstone clipping thin layer mudstone,with stratiform structure,poor interlayer bonding,and joint and fracture development.The block and spalling is easy to happen in the tunnel arch horizontal joint fissure under construction,often expressed as irregular rectangle and fiat roof after excavation and excluding risk.The horizontal joint stripped when basilar cleaning after inverted arch excavation,rock mass shedding is more serious,the overbreaking in the tunnel wall arc position is serious.The excess excavation of field measurement is far beyond specification permissible value,which causes tunnel excavation,dregs transportation and overbreaking backfill quantity also increase in different degrees.It is necessary to analyze and research the reasonable quantity of horizontal rock stratum tunnel overbreaking and backfill.Research conclusions:(1) The overbreaking of horizontal rock stratum tunnel is relate to the blasting operation disturbance,stress release of excavation,influence of groundwater,different parts of tunnel,strength of surrounding rock,construction methods and so on.(2) Combining with a large number of field measured data,using mathematical statistics analysis method,following principle of seek truth from facts,deducting the influence of construction error,the field practical and reasonable overbreaking and backfill quantity of arch,side wall and inverted arch is got under the conditions of various parts of Ⅱ ～ Ⅴ class surrounding rock tunnel with and without water.(3) The research achievements could provide guidance for tunnel design,construction and inspection price,and provide reference for the research of tunnel construction quota under the similar geological conditions.