我国红层分布特征及主要工程地质问题

我国中新生代红层分布总面积约826 389km2,是工程建设中不可避免的岩土体。南方地区红层约占红层总面积的60%,以西南、中南地区红层分布较广,多为裸露型红层,受降雨等因素影响滑坡、风化等问题突出;北方地区红层约占40%,以甘肃以及蒙宁晋陕交界红层分布相对较多,多为埋藏型红层,工程地质问题具有隐蔽性。红层分布受控于分布区的区域断裂带,岩体结构破碎,水文网络发育,渗流、软化等问题突出。由于砂岩、泥岩、页岩、蒸发岩、杂色岩等多种软硬岩层互层结构和工程活动等因素的影响,沿着软弱结构面易发生滑坡、差异风化等工程地质问题。由于时代较新,岩土体的胶结性差,物理力学性能相对较差,岩石多属于软岩类别。稳定性差,易崩解软化。蒸发岩和红层岩土体中可溶成份在水作用下,容易发生岩溶、腐蚀、渗流等物理化学问题。建议在工程建设中将红层作为特殊岩体对待。

Red beds distribution and engineering geological problem in China

The total area of the Mesozoic and Cenozoic red beds in China is(826 389km~2),since the red beds are an inevitable mass in civil engineering.The percent of south is 60%,and the problems,such as weathering and landslide,are often found in southwest and central south red beds for rainfall.The percent of north is 40%,the red beds are often covered by the Quaternary sediments,and the problems are easy to neglect.The red beds distribution is closely controlled by regional tectonics.The interbedding natures exist not only between red sandstone,mudstone and shale but also between red beds with coal seam,magmatite,evaporite and varied rock,respectively.The problems,such as landslide and differential weathering,will happen along with the weak structure plane with engineering disturbances.It is belonging to soft rock because of short geological age,low cementation and low strength.The water stability of red beds is poor due to more clay mineral in red beds and low cementation.The chemical stability of red beds is not good for the dissolvable chemical composition of red beds and evaporite.The red beds should be regarded as a special mass according to the engineering geological properties.