Research On The Influence Of Excavation Disturbance On The Stability Of Bedding Cataclastic Rock High Slope With With Multi-Layer Muddied Interlayer

Influenced by the mutual collision and extrusion of the Indian Ocean plate,Eurasian plate,and Pacific plate,the crustal dynamics background in the western region of China is active and the geological tectonic movement is strong,and many bedding cataclastic rock slopes containing multi-layered muddied interlayer have been formed in the long geological history process.The mechanical properties of the muddied interlayer and fractured rock body itself are very poor,and the muddied interlayer is very thin and has strong concealment,The stability of bedding slope formed by its fabric is very poor.With the deepening of the western development strategy and the"Belt and Road" initiative,there are more and more engineering construction activities in the western mountainous areas,such as highways,railroads,water conservancy and hydropower,power plants,open-pit mining,and large-scale urban construction,and the scale is increasing,such as Sichuan-Tibet Railway,Yunnan-Tibet Railway,Yunnan-China Water Diversion Project,etc.In mountainous areas with complex geological conditions and active tectonic movements,human engineering construction activities will inevitably form a large number of excavation slopes,and excavation disturbance is one of the important precipitating factors affecting slope stability.For example,the high slope of Yunnan Province has been unstable three times during excavation and support.Therefore,based on the actual excavation high slope project,this thesis investigates the influence of excavation disturbance on the stability of excavated high slope containing bedding cataclastic rock with multi-layered muddied interlayer and slope reinforcement technology by using a combination of site investigation,engineering geological survey,borehole television,onsite large-scale direct shear test,observation and fine measurement of typical excavation profile,indoor analysis test,and numerical simulation technology The main research results are summarized as follows:(1)The high slope is distributed with multi-layer muddied interlayer,which is approximately parallel to each other as a whole,with a spacing of 5～50 cm,an average dip direction of 194.4°±4.87°,and an average dip angle of 22.3°±2.15°;the thickness of the muddied interlayer is less than 3 cm,and the thickness of the muddied interlayer in different horizontal positions of the same horizon and the different horizon is different;the clay content of the muddied interlayer is up to 78%,belonging to the argillaceous(full argillaceous)muddied interlayer,which has the characteristics of high liquid limit,high plastic limit,high plasticity index,high dry density,high water content,and low shear strength);the dolomite rock mass on the upper and lower plates of the interlayer is generally very fragmented.(2)The stability of the bedding cataclastic rock slope with a muddied interlayer is lower than that without the interlayer,and the muddied interlayer through the toe of the slope has a key control effect on the stability of the slope;With the increase of the height or buried depth of the single layer of the muddied interlayer,the number of muddied interlayer decreases,the cohesion and internal friction angle increase,and the stability of the slope increases.The height of the muddied interlayer exceeds 0.7H or the burial depth exceeds 0.8H,H is the slope height,and its influence on the stability of the bedding cataclastic rock slope can be ignored.The dip angle of the muddied interlayer increases from 0° to 90°,and the slope stability safety factor decreases first,then increases,and then decreases.When the slope angle is 30°,45° and 60° respectively,the dip angle of the minimum safety factor is 20°,30° and 40° in turn;the vertically layered slope is more stable than the horizontally layered slope,and the stability of-steep bedding slope is weaker than that of gentle bedding slope.The stability of the slope decreases when the slope angle increases.(3)The potential sliding surface of the cataclastic rock slope without a muddied interlayer is circular,and the potential instability mode is tractive landslide;the bedding cataclastic rock slope with multiple layers of muddied interlayer has multiple layers of sliding along the interlayer,and the instability mode is related to the dip angle and slope angle of rock stratum;when the slope angle is 45°,with the increase of the dip angle of the rock stratum,the slope deformation and failure modes are compression and shear failure,traction-slip failure,traction-slipping-bending and shear failure,flexural deformation,bend-breaking-collapse failure.(4)-When excavating the bedding cataclastic rock high slope with multiple layers of muddied interlayer in layers,the slope stability will gradually decrease,especially when the muddied interlayer is exposed on the slope surface,and the slope stability should be highly valued after the muddied interlayer is exposed;the mode of slope instability induced by excavation is bending uplift-multi-layer shear slip-trailing edge tension fracture;the slope should be supported immediately after excavation;Numerical simulation of the effect of excavation on the stability of bedding cataclastic rock slopes with multi-layer muddied interlayer requires comprehensive consideration of slope morphology change,unloading,and geotechnical parameter deterioration to obtain realistic simulation results.(5)For the multi-stage bedding cataclastic rock high slopes with multi-layer muddied interlayer,it is more appropriate to set the anti-slip piles in the middle and lower part of the slope;slope stability is enhanced with the increase of pile length,but there is a critical length;the reinforcement effect of anti-slide piles with rectangular section is better than that of piles with square and circular section;The diameter of the anti-slide pile increases and the stability of the slope is slightly enhanced when the distance to diameter ratio remains unchanged;the distance-todiameter ratio of anti-slide piles increases,the soil arch effect and pile group effect weaken,and the slope stability decreases;the pile group and shadow effect of double-row piles are obvious,and the plume-shaped arrangement cannot weaken the shadow effect.(6)The reinforcement should be enhanced in the nodes of the lattice beam and middle of the longitudinal beam,but not in the middle of the cross beam;With the increase of the cross section size of the lattice beam,the slope stability is not significantly enhanced,but the internal force of lattice beam decreases gradually and evenly;The spacing of lattice beams is not the smaller or the larger the reasonable;the internal force of lattice beam with cantilever is smaller and even than that without cantilever,but with the increase of cantilever length,the internal force increases and is uneven)the proposed anchorage angle β is calculated according to β=45°+Φ/2-α,φ is the internal friction angle of the muddied interlayer,α is the dip angle of the muddied interlayer;the stability of the slope increases with the increase of the anchor cable length,but there exists a critical length;it is suggested to use pre-stressed anchor cable anti-slide piles at the lower part of the slope and discontinuous composite support of lattice anchor structure at the upper part of the slope to strengthen the slope.