含水率对全风化红砂岩地层隧道围岩变形影响研究

Influence of Water Content on Deformation of Surrounding Rock in Weathered Red Sandstone Stratum Tunnel

全风化红砂岩胶结程度极差,水敏感性高,遇水易软化崩解,隧道开挖过程中极易产生大变形,探究含水率对该地层隧道施工影响极有必要。以蒙华铁路阳城隧道为依托,通过现场试验、室内试验及数值模拟对全风化红砂岩隧道在不同含水率下的变形特征进行研究,并针对性提出加密降水措施。研究结果发现:全风化红砂岩存在最优含水率,当围岩含水率在12.74%左右时,围岩岩性较好;数值模拟显示围岩处于最优含水率时,围岩变形最小。由天然含水率加密降水至最优含水率附近可有效减少围岩变形量,降低幅度可达40%~50%;现场采取加密降水后能有效控制围岩变形,实测值与数值模拟值拟合较好,最大偏差10%左右,证实数值模拟有相当可靠度。

The weathered red sandstone is characterized by extremely poor cementation degree and high water sensitivity. It is likely to soften and collapse when encountered with water, and tends to deform during tunnel excavation. It is necessary to explore the influence of water content on the tunnel construction of the formation. Based on the Menghua Railway Yangcheng Tunnel, this paper studies the deformation characteristics of the fully weathered red sandstone tunnel with different water content by means of field test, laboratory test and numerical simulation, and proposes infill precipitation measures. Research shows that fully weathered red sandstone has an optimal moisture content, and when the water content of the surrounding rock is close to 12.74%, the surrounding rock lithology is better. The numerical simulation shows that the surrounding rock has the smallest deformation when the surrounding rock is at the optimal water content, and the precipitation from the natural water content to the optimal water content can effectively reduce the deformation of the surrounding rock by up to 40%~50%. The site infill precipitation can effectively control the deformation of surrounding rock, the measured value is well fitted with the numerical simulation value with 10% maximum deviation, which proves that the numerical simulation has considerable reliability.