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 Being introduced to investigate seismic pattern, crustal buckling can explain many earthquake precursor phenomena according to the layered structure of crust. After a discussion on crustal buckling, whether the continental crust has possession of producing buckling condition and the relationship between crustal buckling and earthquake, we conclude thin layer in crust will be bended at first due to its low critical yield stress and there arises small shocks and seismic anomalies, which results from tbe intensification... Being introduced to investigate seismic pattern, crustal buckling can explain many earthquake precursor phenomena according to the layered structure of crust. After a discussion on crustal buckling, whether the continental crust has possession of producing buckling condition and the relationship between crustal buckling and earthquake, we conclude thin layer in crust will be bended at first due to its low critical yield stress and there arises small shocks and seismic anomalies, which results from tbe intensification of the regional crustal movment and is named regional precursors. A considerable mediumlong term precursors likely belong to the sets. Thick layer in crust corresponding to large quakes possesses higher critical yield stress, so it influences late upon the precursor field (excluding dilatancy). For that reason, the remarkable precursors from source of a large quake mainly are the one of short and immediate term. Linking with the relationship of precursor field and earthquake source, we can see that crustal buckling causes seismicity to grow big from being small before a large quake. It is identical with the RT figure of regional small quake befores Tangshan earthquake of magnitude 7.8.There are two significant points which crustal buckling gives rise to earthquake precursors,1).Instability will provide the basic background for variation of precursor field and instable fracture;2) .Jumping, initiation and development of buckling will be reflected intensively in precursor observations. In addition, jumping, external cause modulation and triggers of quake all have relation of it. Therefore crustal buckling is one of the mechanics basis of earthquake precursor.  研究地震活动图象而引入的地壳屈曲,从地壳为一层状结构物的基本事实出发,对很多地震前兆现象可做出自己的解释。本文对屈曲的特点、大陆地壳是否具备产生屈曲的条件、地壳屈曲与地震的关系等讨论后得到,当地块加强运动时,由于地壳中薄岩层屈曲的临界应小,将首先屈曲并出现小震活动和异常,它们是区域运动加强的反映,称为“区域前兆”。相当部分的中长期前兆似属此例。与较大地震相应的厚岩层临界应力大,对前兆场明显影响较晚(扩容除外),故来自大震震源的突出前兆主要将为短临。联系场源关系,地壳屈曲给出大震前区域地震活动有一由小变大的增强过程,这与唐山7.8级震前区域小震活动的R—t图吻合。 地壳屈曲对前兆的意义主要有两点:①失稳性,为前兆场变化、失稳破裂提供了重要背景。②突变性,屈曲的发生、发展将强烈地反映于前兆观测中,突跳现象,外因调制,触发等与此有关。故地壳屈曲是地震前兆的力学基础之一。  σ3effect is mainly expresed as two kinds of landslide phenomena.1.Buckling landslide in anaclinal bedded rocksThe test results of the long strip test piece in rigid channel shows that there exists the second principal stress σ2 along the channel walls of both sides .which are opposite in direction and equal in effects to limit the lateral expansion of test samples due to axial stress σ1; the least principal stress σ3 would be formed while the channel bottom is upward,and it would push up the samples to occur... σ3effect is mainly expresed as two kinds of landslide phenomena.1.Buckling landslide in anaclinal bedded rocksThe test results of the long strip test piece in rigid channel shows that there exists the second principal stress σ2 along the channel walls of both sides .which are opposite in direction and equal in effects to limit the lateral expansion of test samples due to axial stress σ1; the least principal stress σ3 would be formed while the channel bottom is upward,and it would push up the samples to occur deflection and bendingmoment while the axial stress σ1 deviates the axis of the test samples.and a upward yieldbending phenomenon will be formed.The field investigation results;on the long slope,while the dip angle of the thin and anaclinal bedded rocks equals or approximates to the slope angle of the slope surf ace, and the dipping direction of bedded rock equsls basically to the slope direction, there occur yieldbending deformation and even buckling landslide at the foot of the slope because oveffects exists.2.Crushing landslide in the horizontal bedded rocksOn the border of the slope,the differential unit rock and earth bodies(clay or soft rock)could expande freely to outside, which is freeing, while it is pressured uniformly by the gravity from the upper hard rocks of the slope, e. i. σ3 = 0. There exists the lateral stress while the expansion is limits at the internal side.e. i. σ3≠0.Thus,a stress difference ( stress gradient) forms between the two sides of the unit rock and earth bodies. Under the action of the stress gradient, the unit rock and earth bodies are slowly crushed to outside and the upper hard rocks,as a mass,creep with the unit rock and earth bodies to form crushing landslide.  斜坡发育过程中,正倾岩层的屈曲变形和水平岩层的塑性流动,受坡体内存在的最小主应力σ_3梯度作用而成。σ_3效应主要呈现有:屈曲滑坡和挤出型块体滑坡。  According to rheological behavior for surrounding rock with slabrent and quasislabrent structure, the buckling model of viscoelasticity rock strata is built. The relaxation module of rock plate described creep behavior of surrounding rock is derived. And the critical load curves for buckling and postbuckling behavior of viscoelasticity rock plate are given in the load. Some researches and calculations show that upon condition that compression stress is added up to subcritical buckling, the bifurcation... According to rheological behavior for surrounding rock with slabrent and quasislabrent structure, the buckling model of viscoelasticity rock strata is built. The relaxation module of rock plate described creep behavior of surrounding rock is derived. And the critical load curves for buckling and postbuckling behavior of viscoelasticity rock plate are given in the load. Some researches and calculations show that upon condition that compression stress is added up to subcritical buckling, the bifurcation buckling of rock strata will be caused owing to creep behavior of rock mass, the postbuckling failure of surrounding rock will be occurred, that postbuckling mode amplitude can work as displacement and time criteria of a fracturing rock stratum.  针对板裂和似板裂介质结构围岩体的流变特性,建立了粘弹性围岩岩层的屈曲模型,给出了可描述巷道围岩蠕变特征的岩板松弛模数,及在一定载荷作用下粘弹性岩板的屈曲和后屈曲临界载荷特性曲线。分析计算表明,当岩板的压应力水平增大到亚临界屈曲状态时,由于材料的非稳定蠕变特征将引起岩层的分岔失稳,围岩发生后屈曲破坏。后屈曲模态幅值可作为岩层破坏的位移判据及时间判据。   << 更多相关文摘 
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