Evaluation Method For Dynamic Stability Of Landslide Stabilizing Pile System With Different Evolution Modes

The landslide shows different deformation evolution modes under the action of internal and external dynamic factors,and each mode has a corresponding engineering geological condition and a specific deformation evolution process.The geomechanical model of landslide deformation is an important basis for stability evaluation and prevention of landslide,which is directly related to the safety and control effect of stabilizing pile engineering.It is vital to investigate into evaluation method for dynamic stability and thrust calculation method of landslide stabilizing pile system with different evolution modes.The importance of the study is of practical significance to stability control of landslide and control effect evaluation of stabilizing pile especially.It is an expansive issue in the landslide hazard research that different evolution modes is considered in the evaluation method for dynamic stability of landslide stabilizing pile system.This issue relates to numerous aspects like the intrinsic law and macroscopic characteristics of landslide evolution process,landslide deformation behavior and mechanical characteristics,main control factors of landslide stability,landslide dynamic stability evaluation method,dynamic stability evaluation method of landslide stabilizing pile system,landslide thrust calculation method and landslide control method,etc.The paper presents a systematic research on this issue,combining the geotechnical investigation,in-site monitoring,theoretical study,etc.The study and achievements are mainly as follows.(1)Based on the system study of the landslide,the intrinsic laws and macrodeformation characteristics of different types of landslide corresponding to the evolution process are constructed,and the evolution laws of different types of landslides are revealed.Based on the classification of reservoir landslides,the forming conditions,stress states and deformation failure modes of different types of landslides are analyzed,and the geomechanical models of different types of landslides are established.A landslide stability factor-deformation rate-slip surface crack propagation-time model was proposed to describe the internal evolution law of different types of landslides,and to further improve and establish the fracture supporting system for different types of landslides at different evolution stages.(2)The typical reservoir landslide in Three Gorges Reservoir area is selected as the research object.Based on the engineering geological survey and in-site monitoring data,the main control factors for the stability of landslide deformation development process were analyzed.The research indicates that the landslide deformation has obvious characteristics of stage deformation,which is a typical retrogressive landslide,and its deformation occurred first at the front part of the landslide and progressed upslope due to drawdown of reservoir water level and heavy rainfall.Landslide deformation response to reservoir water level fluctuation and rainfall intensity was examined using the grey relational model.The deformation of landslide at different stages has a strong correlation with the control factors.With the evolution of landslide,the main control factors of landslide stability are not invariable,and will change with the deformation evolution.The main control factors of the front part are converted from the reservoir water level drawdown to the combined effect of the reservoir water level drawdown and rainfall.The main control factors of the middle and back parts are converted from the rainfall to the combined effect of the reservoir water level drawdown and rainfall.Finally,the main control factor of all the parts was the combined effect of rainfall and water level drawdown,which indicated that the deformation of entire sliding mass exhibited an acceleration trend,making the landslide relatively dangerous.(3)Based on the strain softening characteristics of rock and soil and the progressive failure theory,the law of stability change of different types of landslides during the gradual evolution are analyzed.Different types of landslides show different deformation characteristics and mechanical behaviors in the progressive evolution process.The distinguish criterion of sliding block of critical state is proposed based on the unbalanced thrust method and progressive evolution process of different types of landslides.The calculation model and calculation formula of stability of progressive failure of landslides are established and the parameter value method of sliding zone is proposed,and the process to achieve stability calculation of the progressive failure is described.Moreover,the progressive failure and stability variation for three typical examples of landslides are analyzed.The results show that the law of reduce speed of retrogressive landslide and complex landslide is from large to small to large,and the law of reduce speed of loadcaused landslide is from small to large.In addition,the different part of landslide plays a different role on stability in the progressive failure process of three types of landslides,and the deformation regularity of different types of landslides is verified.(4)Based on the study of the evolution laws of different types of landslides,the macro-deformation characteristics of different types of landslide-stabilizing pile system in the evolution process are discussed.The equivalence principle was introduced to determine the expressions of various parameters of the composite block,and an evaluation model for the stability of the landslide-stabilizing pile system was established.The quantitative relationship between the pile position,the pile width and the pile spacing ratio and the stability of the landslide-stabilizing pile system is analyzed.The research indicates: After the piles are installed,the overall stability of the landslide is improved accordingly,and the stability of the landslide-stabilizing pile system presents a gradual decreasing trend with evolution process,and different pile positions have different effects on the stability of different types of landslide-stabilizing pile system.The research results reflect the optimal reinforcement position of the retrogressive landslide in the front part,the optimal reinforcement position of the load-caused landslide in the back part,the comprehensive optimal reinforcement position of the complex landslide in the front part.In addition,the stability of the l landslide-stabilizing pile system gradually decreases,and finally it tends to the law of landslide stability change with the decrease of a.The results show that the law of percentage reduce speed of the stability coefficient of the landslidestabilizing pile system is from large to small to large,and finally tends to a stable law.(5)Based on the principle of time series analysis and the principle of damage mechanics,a mathematical model for landslide displacement decomposition and a quantitative relation between landslide deformation and stability coefficient are established.The dynamic stability evaluation method of landslide-stabilizing pile system based on displacement time curve is proposed.Taking the Majiagou landslide-stabilizing pile system as an example,the response characteristics of the stability of landslidestabilizing pile system and rainfall and reservoir water level are evaluated from a quantitative point of view.The research indicates that the stability of the different parts gradually decreases and the stability coefficient of the landslide in the creep deformation state at the present stage tends to be 1.0.The stability coefficient fluctuates in the external influence factors(rainfall and reservoir water level),that is to say,the rainfall and reservoir water level drawdown has accelerated the deformation of landslide-stabilizing pile system and reduced its stability.The rise of reservoir water level can properly restrain the deformation of landslide-stabilizing pile system and increase its stability.(6)Considering the progressive failure process and the deformation evolution model of landslide,the thrust calculation methods of different types of landslide are proposed.The research indicates that the thrust of retrogressive landslide,load-caused landslide and complex landslide are 4100,4980 and 3150 kN/m,respectively,when different types of landslides gradually destroyed to the fifth state,which is proved that the difference of thrust between different modes and the importance of determining the types of landslide.In addition,the reinforcement method is put forward for different types of landslides based on the deformation and failure mode of landslide.The main idea of reinforcement method is to control the active deformation area and to ensure the stability of the passive deformation area.The different area uses different safety factor to control.And through the calculation and analysis of three typical examples of landslide,a scientific quantitative determination method is provided for the calculation of the design thrust of different types of landslides.Meanwhile,the identification,information monitoring,information feedback and dynamic evaluation of different types of landslides in each deformation stage are discussed.Control method of different types of landslide which is to control the active deformation sliding body in the initial deformation stage and to implement process control according to deformation evolution characteristics is proposed.The research results plays the important guiding role for landslide stability evaluation and landslide control.The main innovations in this article are summed up as follows:(1)The dynamic stability evaluation method of different types of landslides is proposed.The distinguish criterion of sliding block of critical state is proposed based on the unbalanced thrust method and progressive evolution process of different types of landslides.The calculation model and calculation formula of stability of progressive failure of landslides are established and the temporal and spatial distribution of landslide parameters was determined.In view of this,the dynamic stability evaluation method of different types of landslides is proposed,which lays the foundation for the stability evaluation of landslide-stabilizing pile system.(2)The dynamic stability evaluation method of different types of landslide stabilizing pile system is proposed.The macro-deformation characteristics of different types of landslide-stabilizing pile system in the evolution process are discussed.The equivalence principle was introduced to determine the expressions of various parameters of the composite block,and an evaluation model for the stability of the landslide-stabilizing pile system was established.The quantitative relationship between the pile position,the pile width and the pile spacing ratio and the stability of the landslide-stabilizing pile system is analyzed.The layout method of stabilizing pile under different evolution modes is quantified combined with local and integral coordination deformation.Based on the dynamic stability evaluation method of displacement-time curve,the stability evolution of landslide-stabilizing pile system with rainfall and reservoir water level fluctuation was evaluated from a quantitative point of view,which provided the basis for the proposed anti-sliding structure design method.(3)The thrust calculation method of landslide based on different evolution modes is proposed.Considering the progressive failure process of the landslide,the thrust calculation method for the progressive failure process of different types of landslides is proposed.In addition,the different area of different types of landslides uses different safety factor to control.The main idea of reinforcement method is to control the active deformation area and to ensure the stability of the passive deformation area.In view of this,the thrust calculation method is put forward for different types of landslides based on the deformation and evolution mode of landslide,which provide a scientific quantitative determination method for the calculation of the design thrust of different types of landslides.