Study On The Seismic Characteristics And Anti-seismic Strengthening Measures Of Stratiform Soft Rock Slope

―5.12‖Wenchuan earthquake has produced different degrees of shock and loosecrack damages to highway slope in the earthquake region. There formed a largenumber of potential unstable soil mass, which became the potential threats, as well asthe aftershock happened in the later stage, to the construction and later operation ofthe highway slope in the earthquake region. Guanggan highway which is located inthe earthquake region is under construction. Phyllite which has the transverseisotropic characteristics gives priority to the rocks of this highway. The low degree ofcementing and different solts of stratiform slope may be the reason for the damage ofthe slope when earthquake happens.The topic of this Master Dissertation is researched on the study of seismiccharacteristic and anti-seismic strengthening measures of stratiform soft rock slope.This paper will expound engineering geological conditions and summarize thecharacteristics of soft rock slope of Guanggan highway, which base on indoorphysical and mechanical test, engineering geological investigation data of soft rockslope. It will study seismic dynamic response through numerical simulation ofstratiform soft rock slope. Based on the results above,it will study the aseismicreinforcing mechanism of frame anchor structure. It will evaluate dynamic stabilityand verify the aseismic reinforcing mechanism of frame anchor structure, whichcombines with typical slope of Guanggan highway. It will proceed aseismic optimumto the original scheme combine with numerical simulation results and geologicalstructure of slope. The main researching achivements as follows:(1)On the basis of physical and mechanical test, we summarized the soft rockslope characteristics as follows: the lithology is thin stratiform sericite rock withthousand pieces, weak to strong weathering, rock quality are in Ⅳ~Ⅴ levels, shear strength test parameters and deformation parameters are in the low standard, and thewater softening effect is obvious; The strongly weathered rock section, in the effect ofjoints cutting, rock quality is in the condition of fractured structure; ground waterlevel is low; In the combination of the slope there is quartz hard rock, which does notaffect the stability; the failure of the slope are in these models: Local spalling, largearea collapse, small-scale sliding type damage and sliding-cut out front of destruction.We combined engineering geological analogy method, conclude the thousand piecesrock physical and mechanical parameters suggested values.(2)Analysed the distribution of principal stress of slope and shear stress of slopetoe, the horizontal earthquake dynamic action response characteristic of stratiformsoft rock slope was researched. Gentle dip, dip in the stratiform soft rock slope wasapt to slip along the level, vertical or steep slope in soft rock layer was easy to bendtoward the free surface, so the two types of slope under seismic slope in the tensilestress zone was wide distribution and shear were bigger, especially the steep inlayered rock slope, the trailing edge was easy to form the tensile stress through underthe action of earthquake; and under the seismic action, steep over-dip stratiform softrock slope has strong stability.(3)Anchor structure seismic effect was researched with weak plane angle andanchor angle cross combinations under the slope PGA amplification. On the basis ofthat, the frame anchor structure anti-seismic reinforcement mechanism was discussedcombined with the stratiform soft rock slope dynamic response characteristics andanchoring theory.Under the horizontal earthquake action, for corrosion dip layeredrock slope, anchor angle should be slow in horizontal direction with a larger force tobalance the horizontal seismic force, Thereby preventing slope along bedding plane;On the steep over-dip stratiform soft rock slope, anchor should be as far as possibleand orthogonal dimensions, the rock layer vertical tensile structure, to improve rocktensile strength perpendicular to the plane of rock mass, enhance the overall seismic;to rise steeply, tilt within the layered slope, prone to tipping and local relative bending,solid anchor angle should be relatively slow to provide a large horizontal force tobalance the horizontal seismic force, limiting rock bend toward the free surface. Onthe other hand, for the thin layer of rock anchor stack together to form the compositebeam, increasing the overall bending stiffness of rock mass.(4)Evaluated danymic stability on the high side slope of typical soft rock strataof Guangan road, the forth, fifth and sixth slops strongly weathered rock segments were prone to large areas of collapse damage or slump damage along the weatheringinterface under the disturbance of earthquake; By the control of schistosity plane, thefirst, second, third and forth slopes weakly weathered rock segments was prone tolocal collapse damage during the earthquake, and the other unfavorable rock massesformed by the local joint fractures and schistosity plane under the effects ofearthquake were shattered, relaxed and some scattered rock avalanched.(5)According the numerical simulation demonstration on support effects of theoriginal design under the earthquake dynamics, the forth, fifth and sixth slopesstrongly weathered rock segments in the original support scheme still had a largeslope displacement. On the basis of analysing previous anchor bar frame seismiceffect, and slop displacement distribution of numerical simulation combined with theslope geological structure, the origial scheme was optimized. The thesis analysedrelative components of anchor bar frame such as bolt, anchor cable and frame beams(6)Combined with dynamic parameters in security assessments of the area alongGuanggan road to synthetize artificial earthquake wave, and evaluated seismic on original supporting meassures, it showed that the seismic effect of original supporting meassures was good in the effect of synthetic seismic wave.