土石混合体介质具有高度非均质性、显著的结构效应与尺寸效应等特点,这使其物理力学特性及其复杂。本文针对土石混合体在剪切过程中剪切带的变形性状与影响因素,采用自主研发的RSM–1000型电机伺服控制大型土工抗剪强度试验系统,考虑不...土石混合体介质具有高度非均质性、显著的结构效应与尺寸效应等特点,这使其物理力学特性及其复杂。本文针对土石混合体在剪切过程中剪切带的变形性状与影响因素,采用自主研发的RSM–1000型电机伺服控制大型土工抗剪强度试验系统,考虑不同含石量(0,30%,50%,70%)、上覆压力(50,200,300,400 k Pa)、块石尺寸(L1,L2,L3)3个主要结构控制因素,进行土石混合体剪切变形试验,通过在试样内部钻孔设置铝丝与干灰的方法,监测剪切带特征变化规律。研究结果表明:当含石量小于30%时,块石对试样的变形影响较小,强度主要依赖于砂土强度;当含石量达到50%时,试样内已形成骨架结构,变形受块石的影响突显,强度由块石和砂土共同作用;当含石量达到70%时,试样内已形成块石架空结构。在高含石量与大粒径块石条件下,含贯穿剪切面的块石试样随剪切变形发展,块石发生挤压、翻转现象;剪切面附近分布块石的试样,随剪切变形发展,块石以剪胀作用为主,块石发生挤压、棱角剪断与错动重分布。试样的剪切变形现象可类比由后向前变形的推移式滑坡或由前后向中间变形的复合式滑坡的破坏特征,即后缘坡顶在主动土压力作用下产生裂隙,随之下沉挤密、失稳起滑;前缘坡脚蠕滑变形推移;坡中岩土体发生剪切错动至滑动面渐进扩展破坏,最终剪切面贯通,形成整体破坏。该研究成果对揭示土石混合体滑坡剪切带形成演化规律、破坏模式及土石混合体滑坡的防灾减灾具有重要意义。展开更多
Southeastern Tibet,which has complex topography and strong tectonic activity,is an important area for studying the subsurface deformation of the Tibetan Plateau.Through the two-station method on 10-year teleseismic Ra...Southeastern Tibet,which has complex topography and strong tectonic activity,is an important area for studying the subsurface deformation of the Tibetan Plateau.Through the two-station method on 10-year teleseismic Rayleigh wave data from 132 permanent stations in the southeastern Tibetan Plateau,which incorporates ambient noise data,we obtain the interstation phase velocity dispersion data in the period range of 5–150s.Then,we invert for the shear wave velocity of the crust and upper mantle through the direct 3-D inversion method.We find two low-velocity belts in the mid-lower crust.One belt is mainly in the SongPan-GangZi block and northwestern part of the Chuan-Dian diamond block,whereas the other belt is mainly in the Xiaojiang fault zone and its eastern part,the Yunnan-Guizhou Plateau.The low-velocity belt in the Xiaojiang fault zone is likely caused by plastic deformation or partial melting of felsic rocks due to crustal thickening.Moreover,the significant positive radial anisotropy(VSH>VSV)around the Xiaojiang fault zone further enhances the amplitude of low velocity anomaly in our VSVmodel.This crustal low-velocity zone also extends southward across the Red River fault and farther to northern Vietnam,which may be closely related to heat sources in the upper mantle.The two low-velocity belts are separated by a high-velocity zone near the Anninghe-Zemuhe fault system,which is exactly in the inner and intermediate zones of the Emeishan large igneous province(ELIP).We find an obvious high-velocity body situated in the crust of the inner zone of the ELIP,which may represent maficultramafic material that remained in the crust when the ELIP formed.In the upper mantle,there is a large-scale low-velocity anomaly in the Indochina and South China blocks south of the Red River fault.The low-velocity anomaly gradually extends northward along the Xiaojiang fault zone into the Yangtze Craton as depth increases.Through our velocity model,we think that southeastern Tibet is undergoing three different tectonic modes at t展开更多
文摘土石混合体介质具有高度非均质性、显著的结构效应与尺寸效应等特点,这使其物理力学特性及其复杂。本文针对土石混合体在剪切过程中剪切带的变形性状与影响因素,采用自主研发的RSM–1000型电机伺服控制大型土工抗剪强度试验系统,考虑不同含石量(0,30%,50%,70%)、上覆压力(50,200,300,400 k Pa)、块石尺寸(L1,L2,L3)3个主要结构控制因素,进行土石混合体剪切变形试验,通过在试样内部钻孔设置铝丝与干灰的方法,监测剪切带特征变化规律。研究结果表明:当含石量小于30%时,块石对试样的变形影响较小,强度主要依赖于砂土强度;当含石量达到50%时,试样内已形成骨架结构,变形受块石的影响突显,强度由块石和砂土共同作用;当含石量达到70%时,试样内已形成块石架空结构。在高含石量与大粒径块石条件下,含贯穿剪切面的块石试样随剪切变形发展,块石发生挤压、翻转现象;剪切面附近分布块石的试样,随剪切变形发展,块石以剪胀作用为主,块石发生挤压、棱角剪断与错动重分布。试样的剪切变形现象可类比由后向前变形的推移式滑坡或由前后向中间变形的复合式滑坡的破坏特征,即后缘坡顶在主动土压力作用下产生裂隙,随之下沉挤密、失稳起滑;前缘坡脚蠕滑变形推移;坡中岩土体发生剪切错动至滑动面渐进扩展破坏,最终剪切面贯通,形成整体破坏。该研究成果对揭示土石混合体滑坡剪切带形成演化规律、破坏模式及土石混合体滑坡的防灾减灾具有重要意义。
基金supported by Key Research and Development Project of the Ministry of Science and Technology(Grant No.2018YFC1503400)China Earthquake Science Experiment Project,China Earthquake Administration(Grant No.2018CSES0101)。
文摘Southeastern Tibet,which has complex topography and strong tectonic activity,is an important area for studying the subsurface deformation of the Tibetan Plateau.Through the two-station method on 10-year teleseismic Rayleigh wave data from 132 permanent stations in the southeastern Tibetan Plateau,which incorporates ambient noise data,we obtain the interstation phase velocity dispersion data in the period range of 5–150s.Then,we invert for the shear wave velocity of the crust and upper mantle through the direct 3-D inversion method.We find two low-velocity belts in the mid-lower crust.One belt is mainly in the SongPan-GangZi block and northwestern part of the Chuan-Dian diamond block,whereas the other belt is mainly in the Xiaojiang fault zone and its eastern part,the Yunnan-Guizhou Plateau.The low-velocity belt in the Xiaojiang fault zone is likely caused by plastic deformation or partial melting of felsic rocks due to crustal thickening.Moreover,the significant positive radial anisotropy(VSH>VSV)around the Xiaojiang fault zone further enhances the amplitude of low velocity anomaly in our VSVmodel.This crustal low-velocity zone also extends southward across the Red River fault and farther to northern Vietnam,which may be closely related to heat sources in the upper mantle.The two low-velocity belts are separated by a high-velocity zone near the Anninghe-Zemuhe fault system,which is exactly in the inner and intermediate zones of the Emeishan large igneous province(ELIP).We find an obvious high-velocity body situated in the crust of the inner zone of the ELIP,which may represent maficultramafic material that remained in the crust when the ELIP formed.In the upper mantle,there is a large-scale low-velocity anomaly in the Indochina and South China blocks south of the Red River fault.The low-velocity anomaly gradually extends northward along the Xiaojiang fault zone into the Yangtze Craton as depth increases.Through our velocity model,we think that southeastern Tibet is undergoing three different tectonic modes at t
