冲击劈裂下隧洞岩石损伤特性与爆破原位裂隙扩展机理

稳定围岩为隧道爆破提供了重要的环境保障。为探究长距离隧道在周期性爆炸荷载下的围岩损伤特征与破裂机理,以下穿高速引水隧洞原位围岩及岩样为研究对象,借助SHPB(分离式霍普金森压杆)试验系统开展冲击劈裂试验,揭示了岩体力学行为和能量演化特征,并引入矿井巷道4D超高清成像技术,进一步分析了周期性爆炸荷载下隧道围岩的原位裂隙扩展机理。结果表明:①冲击劈裂下花岗岩和凝灰岩的劈裂应力-压缩应变曲线不同于通常冲击压缩“应力屈服”特征,而是具有“应力残余”特征,峰值应力和动力增长因子均呈正线性增长趋势;应变-时间曲线未出现通常冲击压缩“后期减小”变形特征,而是作为弹脆性材料表现出“后期稳定”变形特征。②岩体冲击能量-时间曲线历经“初始缓慢增长-快速线性增长-后期稳定”演化阶段,且同一冲击能级下岩体能量转化比率满足:反射能比率>耗散能比率>透射能比率;岩体损伤破坏整体表现出“中部劈裂+加载端部破碎→中部劈裂+加载端部破碎+半圆断裂→整体破碎”状态特征。③提出以“少域多测”与“多域少测”结合的窥孔成像试验,原位围岩孔壁裂隙扩展特征主要表现为“微裂纹发育→裂隙扩展→扩展放缓→停止延伸”演变阶段,未显现对围岩影响较大的破碎片脱落现象和继续向内延伸迹象。④综合山下顶管隧洞D1观测孔、山茶检修隧洞D2观测孔结果验证了良好的控界爆破效果,对现场爆破施工起到了显著的实际指导作用,同时取自隧道原位的岩样冲击劈裂结果为爆前钻孔与爆破方案设计提供了有效的理论依据和参考。

水岩循环对变质砂岩微观结构损伤与宏观力学劣化影响机理研究

为研究水岩循环过程中变质砂岩矿物成分及微观结构变化对宏观物理力学参数弱化的影响,通过水岩循环试验,对变质砂岩微观矿物成分、结构在水岩循环过程中的演化机制及其与宏观物理力学参数相互关系开展了研究。研究结果表明,岩石各项物理力学指标随着水岩循环次数的增加而不断衰减,其衰减速率随循环次数增加而减缓。水岩循环后岩石抗压强度试验表明,应力-应变曲线中初始裂隙压密阶段随着循环次数的增加而出现并且变得明显,岩石试样破坏特征有随着循环次数的增加由剪切破坏向拉张破坏转变的趋势。结合XRD和SEM试验手段对矿物成分及微观孔隙平面面积的变化进行了统计,分析认为绿泥石、云母、斜长石等矿物的水化溶蚀作用以及微观孔隙的水化扩展,是造成岩石损伤的主要原因。因此,提出利用矿物成分劣化度D_(m)和微观结构劣化度D_(c)的概念来表达岩石水岩循环微观损伤量化指标,并建立了水岩循环作用下受矿物成分及微观结构影响下的岩石物理力学参数弱化的回归模型。该模型的提出能够为水岩循环下相关物理力学参数的选取提供参考。

CT IDENTIFICATION OF THE MECHANIC CHARACTERISTICS OF DAMAGE PROPAGATION OF ROCK

The computerized tomography technique is applied to study the damage propagation of rock for the first time in this paper. CT values and their distribution regularity of damage propaga-tion of rock are analyzed in detail. The relation between CT values and stresses (strains) of the damage propagation of rock is then discussed. This provides the foundation for establishing the constitutive relation of damage propagation of rock.

Analysis of the mechanic characteristics of the damage propagation of rock under triaxial stress condition

The advanced computerized tomography is applied to study the damage propagation of rock. The real time CT scanning is carried out to the damage propagation of rock under triaxial stress condition. The damage propagation constitutive relation of rock under triaxial stress condition is analyzed at last.

STUDY ON THE DAMAGE CONSTITUTIVE RELATION OF ROCK UNDER UNIAXIAL STRESS CONDITION

The damage propagation constitutive relation of rock under uniaxial stress condition is studied by CT scanning in this paper. Damage variables of rock are calculated using CT scanning method and Lemaitre’s equivalent strain hypothesis respecively, the damage propagation constitutive relation of rock is discussed.