Study On Instability Mechanism And Prevention Countermeasures Of A Strongly Weathered Rock Slope On G239 Line

Under the disturbance of excavation,the structure of highway slope in strongly weathered clastic rock is easy to be damaged due to external disturbance.After excavation,slope instability is very easy to occur,which not only affects the construction progress,but also brings great loss of life and property.High and steep slopes are mostly excavated by stages.After excavation,the slope surface becomes steeper,the lower part appears free face,and the lower support reduces,resulting in the risk of sliding.When encountering weak rock mass,it is easy to cause local failure at the bench,and then the rock and soil mass at the back of the bench will be damaged.Based on the reconstruction project of dongfangcheng daciyao section of G239 line,this paper studies the multi-stage excavation failure mechanism and treatment method of highway slope in strongly weathered clastic rock.Based on the analysis of the existing data,large-scale horizontal push shear tests were carried out in the field,and related laboratory tests were carried out.Finally,parameters inversion was carried out by using large-scale horizontal push shear test data combined with numerical simulation,and the physical and mechanical parameters of rock and soil were obtained.The finite difference software is used to simulate the excavation process of the slope and analyze its deformation and failure mechanism.Then according to the deformation and failure mechanism,different excavation methods are designed for comparative analysis,and an optimal scheme is selected to ensure the temporary stability after excavation.The characteristics of slope deformation after excavation are analyzed,and targeted support schemes are adopted.Finally,numerical simulation is used to verify the results.The main research work and achievements are as follows(1)The field test and laboratory test are carried out,and the numerical simulation is used to carry out the parameter inversion work.The physical and mechanical parameters of rock and soil are obtained comprehensively,which provides accurate physical and mechanical parameters for the follow-up research.At the same time,it also verifies the effectiveness of field test combined with parameter inversion in obtaining the parameters of strongly weathered clastic rock,which provides an effective research method for obtaining the mechanical parameters of strongly weathered clastic rock.(2)The typical section of slope failure after excavation is selected to establish the numerical calculation model,and the excavation simulation is carried out according to the field construction.According to the comprehensive analysis of its deformation characteristics,plastic zone distribution characteristics,maximum shear strain increment distribution and stability coefficient change,the instability mode is obtained,which is the traction landslide caused by excavation,and provides the basis for the follow-up study of slope control countermeasures.(3)According to the failure mechanism,the excavation method is optimized.The slope should be increased appropriately for the lower part of moderately weathered clastic rock with good quality,and the slope toe should be gentle for the upper part of weakly weathered clastic rock and loess.The stability coefficients of different schemes are calculated.Finally,it is determined that the first to third steps shall be excavated according to 1:0.90,and the fourth step shall be excavated according to 1:0.50,so as to ensure the temporary stability during and after excavation.The characteristics of deformation after excavation are analyzed,and the bolt is designed to reinforce the weak rock mass of the slope,so as to ensure the long-term stability after excavation.