| The construction of mountain city is restricted by the red line of construction land and the need for building high buildings.It often forms a steep slope near the building.Once the slope is obviously deformed or unstable,the damage will lead to serious disasters.Therefore,the stability of the high slope of the urban construction has become a major engineering geological problem for the further development of the mountain city.Guan Jing district located in Guanjing base which is in charge of 114 geological team,which is located in Guanjing road,Honghuagang District,Zunyi city,Guizhou Province.The slope height is from 13 to 45 m,the slope is 70~90 degrees and the safety grade of slope engineering is grade one.In September 18,2015(lower excavation to 877 m elevation),it is found that segment IV and adjacent to segment IIIoccurred sliding deformation obviously along the clay inter-layer,the head of upper part of anchors of segment IV appeared cracks,which indicated the segment IV exists significant security hidden trouble.Therefore,under the condition of the field excavation had not been completed,changing the supporting design scheme and pointedly Strengthening supporting are needed urgently.Based on the academic thought of geological process mechanism analysis--quantitative evaluation,the slope stability and the support optimization scheme are studied.And the main research contents and results are as follows:(1)Field engineering geological survey shows that the rock layer in the range of excavation slope is dominated by mudstone and sandstone,and can be divided into 17 sub layers.Theslope excavation for dip interbed inclined outward high slope,thin mudstone interlayer multilayer sandstone and mudstone in development for interlayer,even for the local development of clay interlayer.The main adverse weak side effects of a strong weathered clay interlayer and upper slope slope toe of seventh layered IV segment development in the zone(fifth layer).(2)Based on the evolution mechanism of conceptual model of deformation of the slope,the slope deformation evolution is divided into three stages: natural slope evolution,stress concentrated area,slope slip stage layer bedding;in the process of unloading rebound deformation stage excavation the slope;the deep slope,slope bedding "pressure arch formation" stage.According to the Platts theory,the pressure arch arch is about 12~16m high.This range is basically consistent with the slope deformation and failure scope of the IV section.(3)Through the test of interlayer and rock mechanics,combined with the classification of rock mass quality of slope,the physical and mechanical parameters of rock mass of slope rock mass are put forward.(4)The three-dimensional numerical analysis of slope evolution is carried out by using FLAC3 D software:(1)During the excavation of the slope,the consequent pressure arch structure which is beneficial to the overall stability of the slope is gradually formed in the IV section slope,which is mainly distributed above 7 layers,and the supporting slope isstable as a whole.The maximum range of relaxation rock mass in pressure arch is 22~24m,in which the strong relaxation rock mass range is 12~16m.The strength of rock mass outside arch is calculated by strength reduction method.Without consideration of supporting action and completion of excavation,the safety factor of slope is 1.03 under saturated condition,and the slope is under steady state.(2)By analyzing the indexes of the maximum principal stress,the minimum principal stress and displacement,the plastic zone distribution,the safety degree of each layer and the safety factor of the points,the parameters of anti slide support of the slope are determined:(a)Anti sliding piles arranged in a hierarchical 7 potential sliding surface,whenthe 7 layered depth is large enough,it depends on the depth of the layer 5;distributed in the IV section of the slope on both sides of the arch,the right side V distribution in the range of 50 ~ 55 m,20,anchor pile length 6~7m,anchoring force in the C52~C54 section of 4525.67KN/m,C55~C56 for 2712KN/m,C57~C58 for 2121KN/m;the left distribution in the III side,11 root anchorage pile length 5~7m,anchor in C31~C33 between 2454.67KN/m,C34~C41 in section 2195KN/m.(b)Anti deformation pile in IV section and III section on the right side of the slope in the range of 16 m,the main is to suppress the potential sliding surface of slope deformation and the local damage,7 root anchorage pile length is about 4m,C41~C44 anchor in section 2399KN/m,C45~C51 section 4846.5KN/m.(c)Anti deformation and anti sliding pile pile with large section round pile,pile diameter between 2 ~ 2.5m;V segment of the right in the range of 30 m,the residual sliding force,recommend the use of double row anti slide piles to reinforce retaining piles,can adopt the round section pile and rectangular section pile.It is suggested that the length of anchorage section of anti slide pile should be 1/4 ~ 1/3 of the total length of pile.(5)Using two-dimensional limit equilibrium method to calculate the pressure arch rock mass stability,without considering the spatial effect and stability of the existing support,with 7 layered bottom sliding surface when the arch coefficient of rock mass stability storm conditions is 0.39 to 5;layered bottom sliding surface when the arch rock stability coefficient of storm conditions is 0.81.The calculated residual sliding force is between 1551.28~1988.67KN/m.(6)The simulation of support after excavation of slope section of V FLAC3 D softwarw,based on the displacement,support and the plastic zone,the shear strain increment characteristic analysis shows that,under the supporting conditions,improve the supporting role of V slope abutment,after the completion of the site excavation,slope deformation control 1.32,the safety factor of the slope,the slope is in stable state. |
