| Based on the disaster geological survey project in the southern Qinling Mountains,this paper carried out on-site landslide disaster geological investigation and research in Mian County,Lueyang County,and Ningqiang County in the southern Qinling Mountains.The intersection of the suture zone has complicated geological structure,frequent and prone to geological hazards;many high and steep slopes are the main areas that breed large geological disasters and engineering slope instability,especially the layered soft metamorphic rock mass area with a wide distribution area The rock masses on the bank slopes and excavations are dumped and deformed,and the problems of pregnancy and disasters are more prominent.According to the on-site investigation,the anti-dumping and deformation landslide of the rapeseed dam soft metamorphic rock in the study area was selected as a typical landslide,and a systematic analysis study was carried out through investigation,test,simulation,analysis and other means;based on carrying out indoor rock and soil mechanical tests,the soft metamorphic rock in the study area was revealed The physical and mechanical characteristics of water-rock interaction;and based on large-scale physical model tests,summarizing the instability and failure mode of the toppling deformation landslide ultimately serves to predict and prevent the anti-dumping deformation landslide of soft metamorphic rock in the study area.Its main work and results are as follows:(1)Through data collection,on-site investigation and comprehensive analysis,summarize the structural characteristics of the slope where the toppling deformation and failure occurred in the study area: the rock layer is soft rock,the slope foot> 40 °,the rock layer dip angle> 60 ° and the rock layer thickness is small;the slope body is made of It consists of thin layered to medium thick layered slate,phyllite and schist.The Caiziba landslide was selected as the research object.The landslide was affected by the overall tectonic activities in the area.The rock body of the Silurian Diebuyan Formation in the study area was mainly squeezed by the north-south in-situ stress and distributed in strips.Extension;due to the development of joint fissures and weathering,the landslide body is broken,and a large amount of strongly weathered phyllite fragments are accumulated in the lower part;the front edge of the landslide is empty,and it will be dumped and deformed under the action of gravity.(2)Collect representative soft metamorphic rock and soil samples,carry out routine physical and mechanical properties tests,obtain rock mass material composition,structural characteristics and physical mechanical parameters,reveal the soft metamorphic rock water-rock interaction mechanism and aging deformation mechanical behavior;With the increase of the immersion time,the parameters of the rock(cohesive force,internal friction angle,peak strength,etc.)gradually deteriorate,showing obvious timeliness and non-average;from the microstructure,with the increase of the immersion time,the internal The minerals changed from the face-to-face contact with close connection to edge-to-edge and corner-to-edge contact,and the structure tended to be loose and porous.(3)According to the basic principle of the centrifugal model test and the three theorems of similarity,the similarity constant of the model test is determined,and the material selection and proportion test of the model are carried out.The optimal similar material and corresponding mix ratio of the model test are selected by comparison,Quartz sand:gypsum:cement:2% aqueous solution of borax=20:16:1:9.(4)A large-scale physical model test based on the similarity theory was carried out to study the time-lapse process of typical soft metamorphic rock anti-dip slope dumping deformation,and reveal the instability mechanism and deformation failure mode of this type of landslide.That is,this kind of slope is under the action of its own gravity,the trailing edge sinks and produces tensile cracks,the leading edge undergoes shear creep,the plane bends toward the free surface,and a break zone is formed in the slope body,when the nearby shear stress When the shear strength is exceeded,the slope body will collapse(5)Combined with the two-dimensional scattered element software UDEC,the deformation process of the anti-dipping layered slope was reversed.The results of the numerical simulation of the model test and the results of the centrifuge model test were basically consistent with the field investigation phenomenon;using UDEC software to deform the model The displacement field of each stage in the process was analyzed. |
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