三峡库区易滑地层硬质岩石破坏模式的能量学分析

在易发生滑坡的地层内,硬质岩常构成滑坡抗滑段,其能量耗散和释放的过程决定了滑坡临界破坏时刻的特征。三峡库区常见顺层岩质滑坡的易滑地层有侏罗系中、下统和三叠系中统,采用能量学方法分析了三峡库区三组易滑地层中四类硬质岩石的变形破坏模式。该方法基于概化的顺层岩质滑坡地质力学模型,提出了岩石弱化(或损伤)-破坏过程的能量学解释,并通过四类硬质岩石的三轴循环加载试验,确定了两类破坏控制模式下岩石能量耗散和释放的规律,并将其应用于千将坪顺层岩质滑坡的启滑初速度预测。结果表明:①三峡库区侏罗系中统上沙溪庙组(J2s)的长石岩屑砂岩属应变控制型岩石(Ⅰ型),三叠系中统巴东组(T2b)的灰岩、泥灰岩和侏罗系下-中统聂家山组(J1-2n)的细砂岩属应力控制型岩石(Ⅱ型);②应变控制型岩石(Ⅰ型)随应力值增加其损伤系数增值明显,而应力控制型岩石(Ⅱ型)在破坏前无明显损伤,可储存大量弹性应变能并在破坏时释放;③千将坪滑坡前缘抗滑段岩石属于应力控制型岩石(Ⅱ型),其弹性应变能释放是导致滑坡剧烈启动的原因。易滑地层硬质岩石变形破坏模式的能量耗散分析是顺层岩质滑坡预测预报的关键,对滑坡抗滑段岩石的监测需根据岩石变形破坏模式来确定具体的监测目标。

Energetics Analysis of Hard Rock Failure Modes in Rockslides of the Three Gorges Reservoir Area

Hard rock acts as the resistance part of rockslide, for the energy dissipation and release controls the rockslide failure.Studying energy dissipation’s laws of hard rocks, this paper proposes an energy analysis of rock failure based on geological mechanics model of bedding rockslide. By the cyclic loading test of rock samples in three gorges area, the curve of stress and strain is obtained. The energy model is used to analyze the rocks’ failure types and to calculate the initial speed of the Qianjiangping landslide. It indicates that sandstone(from J2s) belongs to ‘strain control type’ and demonstrates obvious damage before the peak stress. However, limestone and marl(from T2b), and sandstones(from J1-2n) are rocks of ‘stress control type’ which can store great elastic energy released to develop failure at the post-peak stage. The rock of resistance part of Qianjiangping landslide is stress control type, which releases elastic energy leading to its rapid slide. Rock failure type is the key to make early warn of bedding rockslide and to determine the monitor parameter.