冰碛层围岩稳定性及亚分级研究

依托拉林铁路藏噶隧道,采用现场取样、室内土工试验和数值模拟的方法,选取密实程度、含石量和含水率3个主要影响因素,对冰碛层围岩稳定性及亚分级展开研究。结果表明:冰碛层围岩的抗剪强度随密实程度和含石量的增大逐渐增大,随含水率的增大逐渐减小;冰碛层围岩塌方过程分为3类,分别为"局部塌方、小塌方、中~大塌方""局部失稳、中~大塌方"和"大塌方";冰碛层围岩亚分级可分为Ⅳ2,Ⅴ1和Ⅴ2共3个亚级,分级指标为密实程度、含石量和含水率。依据藏噶隧道冰碛层段"三台阶"施工方法,推荐Ⅳ2亚级围岩采用型钢钢架和管棚支护;Ⅴ1亚级围岩采用"管棚+小导管"超前加固、型钢钢架和管棚支护;Ⅴ2亚级围岩采用"帷幕注浆、管棚+小导管"超前加固、型钢钢架和管棚支护。现场采用对应的加固措施后,最大沉降小于100 mm,满足隧道施工要求。

Study on the Stability and Sub-Classification of Moraine Surrounding Rock

Based on the method of field sampling,indoor geotechnical test and numerical simulation for Zangga tunnel of Lhasa-Linzhi Railway,the stability and sub-classification of the moraine surrounding rock were studied by selecting three factors:compactness,stone content and water content.Results show that the shear strength of the moraine surrounding rock increases gradually with the increase of compactness and stone content,and decreases gradually with the increase of the water content.The collapse process of the moraine surrounding rock is divided into three modes,which are"local landslide,small landslide,medium to large landslide","local instability,medium to large landslide"and"large landslide".The sub-classification of the moraine surrounding rock can be divided into three sub-classes:Ⅳ2,Ⅴ1 andⅤ2.The classification indicators are compactness,stone content and water content.Based on the construction method of"three-step"in the moraine surrounding rock section of Zangga tunnel,it is recommended that the subclassⅣ2 surrounding rock be supported by profile steel frame and pipe shed.The subclassⅤ1 surrounding rock can be reinforced with"pipe shed+small duct"in advance,and be supported by profile steel frame and pipe shed.The subclassⅤ2 surrounding rock can be reinforced in advance with"curtain grouting,pipe shed+small duct",and be supported by profile steel frame and pipe shed.After the corresponding reinforcement measures are adopted on site,the maximum settlement is less than 100 mm,which meets the requirements of tunnel construction.