隧道震裂岩体围岩分级方法初探

汶川地震产生了大量的震裂松动山体,为合理评价在这些震裂山体中新建隧道的围岩级别,通过极震区在建隧道现场震裂岩体调查,对震裂岩体特征及其对围岩稳定性的影响进行了分析。震裂岩体是一种受强烈地震波作用后,岩体结构面更加发育,层间结合更差的一种岩体;并且硬质岩和软质岩的震裂特征不同,硬质震裂岩体易产生集中式张裂缝和松动,软质震裂岩体易产生体积式松弛变形。在此基础上,提出了岩体震裂等级,划分为轻微、中等、强烈三种级别,并建立了震裂岩体围岩分级的修正方案,即:轻微震裂岩体对围岩稳定性影响不大,可不考虑降低围岩级别,或者降低0.5级;中等震裂岩体对围岩稳定性有不利影响,围岩级别降低0.5～1级;强烈震裂岩体对围岩稳定性影响极为不利,围岩级别降低1～1.5级。

Discussion of Surrounding Rock Classification for Tunnels in Shattered Rock Masses

A lot of shattering loose rock masses were created by the Wenchuan earthquake.In order to rationally evaluate the classification of the surrounding rock of newly built tunnels in these mountain areas,this paper analyzes,by way of site investigation,the features of shattered rock masses and their effects on the stability of surrounding rock.The shattered rock,which exhibits a more developed structural plane and poorer joining of interlamination after the effects of an intense seismic wave,has different features concerning hard rock and soft rock.The shattered hard rock is prone to centralized tension fissures and loosening,and the soft rock is prone to the volumetric deformation of loosening.Based on this,a three-level classification of shattered rock masses is proposed,e.g.slight,moderate and intense.In addition,a revision program is presented in which the level of the classification is not lowered or only lowered by 0.5 for the slight shattered rock mass since it has little impact on the stability of the surrounding rock;the level of the classification is lowered by 0.5 to 1 for the moderate shattered rock mass since it has adverse effects on the stability of the surrounding rock;and the level of classification is lowered by 1 to 1.5 for the intense shattered rock mass since it has extremely adverse effects on the stability of the surrounding rock.